US20210016096A1

US20210016096A1 - Method and device for verifying atrial activity oversensing consistency on his sensing channel

Info

Publication number: US20210016096A1
Application number: US17/023,725
Authority: US
Inventors: Yun QIAO; Wenwen Li; Jan O. Mangual-Soto; Luke C. McSpadden
Original assignee: Pacesetter Inc
Current assignee: Pacesetter Inc
Priority date: 2019-07-18
Filing date: 2020-09-17
Publication date: 2021-01-21
Also published as: US11730967B2; US20210393967A1

Abstract

Methods and systems are provided herein and include an HIS electrode configured to be located proximate to a HIS bundle and to at least partially define a HIS sensing channel. The system includes memory to store cardiac activity (CA) signals obtained over the HIS sensing channel, the memory to store program instructions; and one or more processors that, when executing the program instructions, are configured for utilizing an atrial oversensing (AO) process to analyze the CA signals, obtained over the HIS sensing channel during an AO avoidance (AOA) window, for an atrial activity (AA) component to identify AA beats. The system applies a consistency criteria to the AA beats to determine a number of the AA beats that are indicative of consistent AO. Based on the consistency criteria and the number of AA beats indicative of consistent AO, the system performs at least one of adjusting an AO parameter utilized by the AO process or disabling the AO process and manages HIS bundle pacing based on a ventricular event.

Description

RELATED APPLICATION DATA

The present applications relates to, and claims priority, from: U.S. Provisional Application 62/948,047, Titled “AUTOMATIC PACING IMPULSE CALIBRATION USING PACING RESPONSE TRANSITIONS” (Docket 13653USL1), filed Dec. 13, 2019; is a continuation application of U.S. application Ser. No. 16/904,837, Titled “SYSTEMS AND METHODS FOR IMPROVED HIS BUNDLE AND BACKUP PACING TIMING”, (Docket 13936US01) (13-0392US1), filed Jun. 18, 2020; and is a continuation application of U.S. application Ser. No. 16/871,166, Titled “SYSTEMS AND METHODS FOR IMPROVED HIS BUNDLE AND BACKUP PACING TIMING” (Docket 13845US01) (13-0381US01), filed May 11, 2020, which claims priority to: U.S. Provisional Application 62/875,863, Titled “SYSTEMS AND METHODS FOR IMPROVED HIS BUNDLE AND BACKUP PACING TIMING” (Docket 13652USL1), filed Jul. 18, 2019, and to U.S. Provisional Application 62/948,047, Titled “AUTOMATIC PACING IMPULSE CALIBRATION USING PACING RESPONSE TRANSITIONS” (Docket 13653USL1), filed Dec. 13, 2019, the complete subject matter of which are expressly incorporated herein by reference in their entireties.

BACKGROUND

Embodiments of the present disclosure generally relate to HIS bundle pacing and more specifically, to avoid atrial activity over sensing and to automatic pacing impulse calibration using pacing response transitions.
In a normal human heart, the sinus node, generally located near the junction of the superior vena cava and the right atrium, constitutes the primary natural pacemaker initiating rhythmic electrical excitation of the heart chambers. The cardiac impulse arising from the sinus node is transmitted to the two atrial chambers, causing a depolarization known as a P-wave and the resulting atrial chamber contractions. The excitation pulse is further transmitted to and through the ventricles via the atrioventricular (AV) node and a ventricular conduction system comprised of the bundle of HIS (also referred to as the HIS bundle), the left and right bundle branches, and the Purkinje fibers, causing a depolarization and the resulting ventricular chamber contractions. The depolarization of the interventricular septum and ventricles is generally referred to as a QRS complex and is observed and measured through the use of electrocardiograms (ECGs) and similar equipment for measuring electrical activity of the heart.
Disruption of this natural pace-making and conduction system as a result of aging or disease can be successfully treated by artificial cardiac pacing using implantable cardiac stimulation devices, including pacemakers and implantable defibrillators, which deliver rhythmic electrical pulses or other anti-arrhythmia therapies to the heart, via electrodes implanted in contact with the heart tissue, at a desired energy and rate. To the extent the electrical pulses are sufficient to induce depolarization of the associated heart tissue, the heart tissue is said to be captured and the minimum electrical pulse resulting in capture is generally referred to as the capture threshold.
In the majority of individuals, the most effective heartbeat is triggered by the patient's own natural pacing physiology. Implantable cardiac stimulation devices are intended to fill in when the natural pacing functionality of the patient's heart falls or acts inefficiently (such as in cases of sinus arrest and symptomatic bradycardia, respectively) or when the heart's conduction system fails or acts inefficiently (such as in cases of third-degree and second-degree (i.e., Mobitz II) AV blocks, respectively). In a large number of heart failure patients, natural conduction through the AV node and the HIS bundle are intact and disruption of ventricular rhythm is the result of conduction disorders residing in the left and/or right bundle branches. Dilatation of the heart due to congestive heart failure (CNF) has been associated with delayed conduction through the ventricles. This delayed conduction leads to reduced hemodynamic efficiency of the failing heart because of the resulting poor synchronization of the heart chambers.
Direct stimulation of the HIS bundle has been found to provide hemodynamic improvement for various patients including those suffering from dilated cardiomyopathy but having normal ventricular activation. Other examples of patients that may benefit from direct stimulation of the HIS bundle include those with atrioventricular junction (AVJ) ablation or third-degree AV block that require permanent ventricular pacing. Accordingly, the natural conduction system, when intact, can provide hemodynamically optimal depolarization timing of the heart chambers.
However, an opportunity remains to improve upon HIS bundle pacing methods and systems. For example, IMDs that include a HIS bundle pacing (HBP) lead also have a HIS bundle sensing channel that utilizes one or more electrodes on the HIS bundle pacing lead to sense atrial and ventricular activity. Systems, that utilize HIS bundle pacing, experience oversensing of atrial signals over the HIS sensing channel. Heretofore, clinicians have attempted to avoid over sensing by manually programming parameters associated with the HIS sensing channel, such as to lower sensitivity and to extend a ventricular blanking period.
The close proximity of the HIS bundle to the basal-septal atrial myocardium, atrioventricular (AV) node, and basal-septal ventricular myocardium presents unique challenges to physicians during the implant process, especially those new to HIS implanting. AV node capture or simultaneous HIS and atrial capture may not be immediately apparent during implant without performing additional testing. In cases with successful HIS capture, the multi-component (one or more of atrial, HIS, and ventricular) signal in the HIS intracardiac electrograms (IEGM) could also disrupt implantable device logic and effect normal functionality. For example, a large atrial signal, that is present on the HIS bipolar or unipolar IEGM, can cause atrial oversensing (AO) and have undesirable consequences.
Algorithms have been proposed for automated measurement of HIS capture type and threshold based on the bipolar and unipolar evoked responses. A large atrial signal or unintended atrial and AV node capture may cause unreliable sensing of the HBP evoked response thus rendering the algorithm inaccurate.
A need remains for methods and devices that overcome the foregoing and other disadvantages of conventional approaches. For example, a need remains for methods and systems that provide a consistency verification, after identifying AO, to assure true AO is identified.
Further, HBP could have the following responses: loss of capture (LOC), RV/myocardial capture, non-selective HIS bundle (HB) capture, and selective HB capture. Currently, the HBP capture types and thresholds are being diagnosed in clinics by healthcare professionals using 12-lead surface ECG. Various device-based algorithms have been proposed to automatically diagnose HBP capture types and thresholds. Notwithstanding, a large safety margin is commonly used when programming the HBP output. An opportunity remains to provide improved device-based algorithms for automatic measurement and programming of HIS capture threshold, in order to maximize HIS pacing while improving battery longevity.
Heretofore, HIS capture threshold test algorithms have been proposed that identify HBP thresholds based on changes in evoked response (ER) following a train of HBP at decremental amplitudes. The HBP at decremental amplitudes is proposed to be performed in DDD mode with short AV delay or in WI mode with overdrive pacing. It is desirable to minimize the test duration to reduce any patient discomfort. However, the HIS capture threshold test, utilizing decremental HBP amplitudes, has experienced certain limitations. In particular, an effect is experienced during the HIS capture threshold test, in which capture thresholds measured, in response to successive HBP at decrementing amplitudes, are usually slightly lower as compared to capture thresholds that are measured, in response to successive HBP at incrementing amplitudes.
A need remains for methods and systems that limit or avoid the effect on capture thresholds resulting from the nature of the changes in the amplitude (e.g., incrementing or decrementing) of the successive HBP pulses, while minimizing test duration without sacrificing accuracy when determining HBP capture type.

SUMMARY

In accordance with embodiments herein, an AO setup test is provided to detect AO using the atrial timing on the atrial channel and the time separation of atrial and ventricular signals on the HIS channel during intrinsic AV conduction. The AO setup test is generally applied when the device is in DDD mode as the AO setup test utilizes the atrial sensed or paced event to initiate the search (AOA) window for the atrial signal on the HIS channel. In accordance with one implementation, the AO setup test measures both atrial and ventricular (if available) signal amplitude on the HIS channel during the AO setup test.
In accordance with embodiments herein, methods and systems are described that automatically verifies AO consistency from the HIS IEGM to ensure true AO is identified. The methods and systems may further comprise a sequential step by step verification of the AO identified.
In accordance with embodiments herein, methods and systems are described that provide a nonsequential threshold search that includes successive HBP pulses delivered at rough amplitude steps over a first (e.g., large) range of pacing amplitudes, followed by fine amplitude steps over a second (e.g., small) range of pacing amplitudes. For example, the rough amplitude steps may be utilized while decrementing amplitude between successive HBP pulses over the first range, while the fine amplitude steps are utilized while incrementing amplitudes between successive HBP pulses over the second range. The nonsequential threshold search is managed in a manner that seeks to limit/minimize test duration and to limit/minimize a Wedensky effect without sacrificing accuracy.
In one aspect of the present disclosure, a method of identifying pacing thresholds and programming a stimulation device for HIS bundle pacing is provided. The stimulation device includes a pulse generator, a stimulating electrode in proximity to a HIS bundle of a patient heart, at least one sensing electrode adapted to sense electrical activity of the patient heart, a processor, and a memory. The method includes applying, using the pulse generator and stimulating electrode, a first pacing impulse having a first pacing impulse energy to the HIS bundle and, in response to applying the first pacing impulse, collecting first response data using the at least one sensing electrode. The method further includes applying, using the pulse generator and stimulating electrode, a second pacing impulse having a second pacing impulse energy to the HIS bundle, the second pacing impulse energy being different than the first pacing impulse energy and, in response to applying the second pacing impulse, collecting second response data using the at least one sensing electrode. The method also includes identifying a change in one or more response characteristics between the first response data and the second response data, the response characteristics indicative of a change from a first capture type for the first pacing impulse energy and a second capture type for the second pacing impulse energy and, in response to identifying the change in the one or more response characteristics, setting a pacing impulse energy setting of the stimulation device to the first pacing impulse energy.
In certain implementations, the first response data includes a first unipolar electrogram (EGM) and the second response data includes a second unipolar EGM. In such implementations, the response characteristics may include unipolar stim-to-onset time and unipolar width. In other implementations, the first response data includes a first bipolar EGM and the second response data includes a second bipolar EGM. In still other implementations, wherein the first response data includes each of a first unipolar electrogram (EGM) and a first bipolar EGM, the second response data includes each of a second unipolar EGM and a second bipolar EGM, and the response characteristics include each of bipolar stim-to-peak and unipolar width. In yet other implementations, the response characteristics include at least one of bipolar stim-to-peak, unipolar width, unipolar stim-to-onset time, and unipolar maximum positive slope. In other implementations, the response characteristics include a first response characteristic corresponding to total ventricular activation time and a second response characteristic corresponding to time between pacing and activation. In certain implementations, the first capture type indicates capture of the HIS bundle and the second capture type indicates a loss of capture of the HIS bundle. In still other implementations, the first capture type indicates correction of a branch bundle block and the second capture type indicates a loss of branch bundle block correction.
In another aspect of the present disclosure, a cardiac stimulation system adapted to deliver impulses for pacing the HIS bundle of a patient heart is provided. The system includes a pulse generator adapted to generate electrical impulses, a processor communicatively coupled to the pulse generator and adapted to measure responses of the patient heart using at least one sensing electrode, and a memory communicatively coupled to the processor including instructions executable by the processor. The instructions cause the processor to apply, using the pulse generator and a stimulating electrode, a first pacing impulse having a first pacing impulse energy to the HIS bundle and, in response to applying the first pacing impulse, to collect first response data using a sensing electrode. The instructions further cause the process to apply, using the pulse generator and the stimulating electrode, a second pacing impulse having second pacing impulse energy to the HIS bundle, the second pacing impulse energy being different than the first pacing impulse energy and, in response to applying the second pacing impulse, to collect second response data using the at least one sensing electrode. The instructions also cause the processor to identify a change in one or more response characteristics between the first response data and the second response data, the response characteristics indicative of a change from a first capture type for the first pacing impulse energy and a second capture type for the second pacing impulse energy. The instructions further cause the process to set a pacing impulse energy setting of the stimulation device to the first pacing impulse energy in response to identifying the change in the one or more response characteristics.
In certain implementations, the first response data includes a first unipolar electrogram (EGM) and the second response data includes a second unipolar EGM. In other implementations, the first response data includes a first bipolar EGM and the second response data includes a second bipolar EGM. In still other implementations, the response characteristics include at least one of bipolar stim-to-peak, unipolar width, unipolar stim-to-onset time, and unipolar maximum positive slope. In other implementations, the response characteristics include a first response characteristic corresponding to total ventricular activation time and a second response characteristic corresponding to time between pacing and activation. In still other implementation, the first capture type indicates capture of the HIS bundle and the second capture type indicates a loss of capture of the HIS bundle. In other implementations, the first capture type indicates correction of a branch bundle block and the second capture type indicates a loss of branch bundle block correction.
In yet another aspect of the present disclosure, a method of identifying pacing thresholds and programming a stimulation device for HIS bundle pacing is provided. The stimulation device includes a pulse generator, a stimulating electrode in proximity to a HIS bundle of a patient heart, and at least one sensing electrode adapted to sense electrical activity of the patient heart. The method includes collecting a first response data set for a first pacing impulse energy. Collecting the first response data set includes applying, using the pulse generator and stimulating electrode, a plurality of first pacing impulses having the first pacing impulse energy to the HIS bundle and measuring a response to each of the plurality of first pacing impulses using the at least one sensing electrode. The method further includes collecting a second response data set for a second pacing impulse energy different than the first pacing impulse energy. Collecting the second response data set includes applying, using the pulse generator and stimulating electrode, a plurality of second pacing impulses having the second pacing impulse energy to the HIS bundle and measuring a response to each of the plurality of second pacing impulses using the at least one sensing electrode. Subsequent to determining a variance of the responses of the first response data set is below a variance value, the method includes identifying a change in one or more response characteristics between the first set of response data and the second set of response data, the response characteristics indicative of a change from a first capture type for the first pacing impulse energy and a second capture type for the second pacing impulse energy. The method further includes, in response to identifying the change in the one or more response characteristic, setting a pacing impulse energy setting of the stimulation device to the first pacing impulse energy.
In certain implementations, each response of the first response data set and each response of the second response data set includes a unipolar electrogram (EGM). In other implementations, each response of the first response data set and each response of the second response data set includes a unipolar electrogram (EGM). In still other implementations, the one or more response characteristics include a first response characteristic corresponding to total ventricular activation time and a second response characteristic corresponding to time between pacing and activation.
In accordance with another aspect herein, a method is provided for identifying pacing thresholds and programming a stimulation device for His bundle pacing (HBP), the stimulation device including a pulse generator, a stimulating electrode in proximity to a His bundle of a patient heart, and at least one sensing electrode adapted to sense electrical activity of the patient heart. The method comprises: applying, using the pulse generator and stimulating electrode, a HBP pulse having an impulse energy to the His bundle; in response to the applying a first pacing impulse, measuring response data for a corresponding evoked response using the at least one sensing electrode; determining a response characteristic based on the response data; adjusting the impulse energy and repeating the applying, measuring and determining, wherein the impulse energy is adjusted in a non-sequential manner between HBP pulses; identifying a change in the response characteristic indicative of a change from a first capture type and a second capture type; and setting one or more parameters of a HBP therapy based on the change in the response characteristic.
In accordance with other aspects herein, the repeating the applying, measuring, determining and adjusting obtains a collection of response characteristics for a collection of HBP pulses at corresponding different impulse energies. Additionally or alternatively, the adjusting in the non-sequential manner includes at least one rough energy adjustment between first and second HBP pulses and at least one fine energy adjustment between third and fourth HBP pulses. Additionally or alternatively, the at least one rough energy adjustment includes a voltage step-up of at least 1.0V between the first and second HBP pulses and the at least one fine energy adjustment includes a voltage step-down of no more than 0.25V between the third and fourth HBP pulses. Additionally or alternatively, the adjusting applies the at least one rough energy adjustment during a rough HBP test between upper and lower rough limits and applies the at least one fine energy adjustment during a fine HBP test between upper and lower fine limits, the upper and lower fine limits defined based on a transition point identified during the rough HBP test. Additionally or alternatively, the identifying further comprises identifying a rough transition point based on the response characteristic associated with the first and second HBP pulses separated by the at least one rough energy adjustment and refining the rough transition point to a fine transition point based on the response characteristic associated with the third and fourth HBP pulses separated by the at least one fine energy adjustment.
In accordance with new and unique aspects herein, a system is provided. The system comprises: a HIS electrode configured to be located proximate to the HIS bundle and to at least partially define a HIS sensing channel; memory to store cardiac activity (CA) signals obtained over the HIS sensing channel, the memory to store program instructions; and one or more processors that, when executing the program instructions, are configured for: applying, using a pulse generator and a stimulating electrode, a HBP pulse having an impulse energy to the His bundle; in response to applying a first pacing impulse, measuring response data for a corresponding evoked response using at least one sensing electrode; determining a response characteristic based on the response data; adjusting the impulse energy and repeating the applying, measuring and determining, wherein the impulse energy is adjusted in a non-sequential manner between HBP pulses; identifying a change in the response characteristic indicative of a change from a first capture type and a second capture type; and setting one or more parameters of a HBP therapy based on the change in the response characteristic.
Additionally or alternatively, the one or more processors repeat the applying, measuring, determining, and adjusting to obtain a collection of response characteristics for a collection of HBP pulses at corresponding different impulse energies. Additionally or alternatively, the adjusting in the non-sequential manner includes at least one rough energy adjustment between first and second HBP pulses and at least one fine energy adjustment between third and fourth HBP pulses. Additionally or alternatively, the at least one rough energy adjustment includes a voltage step-up of at least 1.0V between the first and second HBP pulses and the at least one fine energy adjustment includes a voltage step-down of no more than 0.25V between the third and fourth HBP pulses. Additionally or alternatively, the adjusting applies the at least one rough energy adjustment during a rough HBP test between upper and lower rough limits and applies the at least one fine energy adjustment during a fine HBP test between upper and lower fine limits, the upper and lower fine limits defined based on a transition point identified during the rough HBP test. Additionally or alternatively, the identifying further comprises identifying a rough transition point based on the response characteristic associated with the first and second HBP pulses separated by the at least one rough energy adjustment and refining the rough transition point to a fine transition point based on the response characteristic associated with the third and fourth HBP pulses separated by the at least one fine energy adjustment.
In accordance with embodiments herein, a system is provided. The system includes an HIS electrode configured to be located proximate to a HIS bundle and to at least partially define a HIS sensing channel. The system includes memory to store cardiac activity (CA) signals obtained over the HIS sensing channel, the memory to store program instructions; and one or more processors that, when executing the program instructions, are configured for utilizing an atrial oversensing (AO) process to analyze the CA signals, obtained over the HIS sensing channel during an AO avoidance (AOA) window, for an atrial activity (AA) component to identify AA beats. The system applies a consistency criteria to the AA beats to determine a number of the AA beats that are indicative of consistent AO. Based on the consistency criteria and the number of AA beats indicative of consistent AO, the system performs at least one of adjusting an AO parameter utilized by the AO process or disabling the AO process and manages HIS bundle pacing based on a ventricular event.
Optionally, the one or more processors may be further configured to determine, for at least a portion of the AA beats, an interval between a paced or sensed atrial (A) event and a characteristic of interest (COI) within the AA component (A/AA interval) of the corresponding AA beat. The applying the consistency criteria may include identifying a subset of the AA beats, for which the A/AA interval is within a first connection criteria. The one or more processors may be further configured to determine, for at least a portion of the AA beats, a peak of the AA component (AA peak) of the corresponding AA beat. The applying the consistency criteria may include identifying a subset of the AA beats, for which the AA peak is within a second connection criteria. The one or more processors may be further configured to identify first and second subsets of the AA beats, for which first and second characteristics of interest (COI) of the AA components fall within the corresponding first and second limits and may determine whether a number of beats in the first and second subsets of the AA beats is indicative of consistent AO.
Optionally, the consistency criteria may correspond to limits about first and second median values for corresponding first and second COI. The one or more processors may be further configured to utilize the consistency criteria to distinguish between candidate AA beats and outlier AA beats. The one or more processors may be further configured to adjust an AO parameter utilized by the AO process when the number of AA beats indicative of AO exceed a threshold. The AO parameter may represent at least one of i) a start time for the AOA window, a duration for the AOA window, or an AO sensitivity profile utilized to analyze the CA signals over the HIS sensing channel during the AOA window. The one or more processors may be further configured to disable the AO process when the number of AA beats indicative of AO fall below a threshold. The one or more processors may be further configured to manage the HIS pacing by lowering a sensitivity level of a ventricular event (VE) sensitivity profile for the HIS sensing channel. The one or more processors may be further configured to maintain a count of a number of AA components over a series of beats and, based on the count, determine whether to maintain or change current settings for the length of the AOA window and/or sensitivity profile. The AOA window may represent a time window enclosing atrial component activity components.
In accordance with embodiments herein, a method for pacing a HIS bundle of a patient heart using an implantable medical device (IMD) is provided. The method obtains cardiac activity (CA) signals over a HIS sensing channel. The HIS sensing channel utilizes a HIS electrode and utilizes an atrial oversensing (AO) process to analyze the CA signals, obtained over the HIS sensing channel during an AO avoidance (AOA) window, for an atrial activity (AA) component to identify AA beats. The method applies a consistency criteria to the AA beats to determine a number of the AA beats that are indicative of consistent AO. Based on the consistency criteria and the number of AA beats indicative of consistent AO, the method performs at least one of adjusting an AO parameter utilized by the AO process or disabling the AO process and manages HIS bundle pacing based on a ventricular event.
The method may determine for at least a portion of the AA beats, an interval between a paced or sensed atrial (A) event and a characteristic of interest (COI) within the AA component (A/AA interval) of the corresponding AA beat. The applying the consistency criteria may include identifying a subset of the AA beats, for which the A/AA interval may be within a first connection criteria. The method may determine, for at least a portion of the AA beats, a peak of the AA component (AA peak) of the corresponding AA beat. The applying the consistency criteria may include identifying a subset of the AA beats, for which the AA peak is within a second connection criteria. The applying the consistency criteria may further comprise identifying first and second subsets of the AA beats, for which first and second characteristics of interest (COI) of the AA components fall within the corresponding first and second limits; and may determine whether a number of beats in the first and second subsets of the AA beats is indicative of consistent AO. The consistency criteria may correspond to limits about first and second median values for corresponding first and second COI. The method may further comprise utilizing the consistency criteria to distinguish between candidate AA beats and outlier AA beats.
Optionally, the performing may include adjusting an AO parameter utilized by the AO process when the number of AA beats indicative of AO exceed a threshold. The AO parameter may represent at least one of i) a start time for the AOA window, a duration for the AOA window, or an AO sensitivity profile utilized to analyze the CA signals over the HIS sensing channel during the AOA window. The performing may include disabling the AO process when the number of AA beats indicative of AO fall below a threshold. The managing the HIS pacing may include lowering a sensitivity level of a ventricular event (VE) sensitivity profile for the HIS sensing channel. The method may maintain a count of a number of AA components over a series of beats and based on the count, determining whether to maintain or change current settings for the length of the AOA window and/or sensitivity profile. The AOA window may represent a time window enclosing atrial component activity components.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a stimulation device in electrical communication with a patient's heart by way of one or more of four leads and suitable for delivering multi-chamber stimulation and shock therapy in accordance with embodiments herein.

FIG. 2 illustrates a dual chamber stimulation device in communication with one atrium, one ventricle, and the HIS bundle in accordance with embodiments herein.

FIG. 3 illustrates a simplified block diagram of the multi-chamber implantable stimulation device of FIG. 1, which is capable of treating both fast and slow arrhythmias with stimulation therapy, including cardioversion, defibrillation, and pacing stimulation in accordance with embodiments herein.

FIG. 4A illustrates a process for implementing an atrial over sensing (AOS) set up test in accordance with embodiments herein.

FIG. 4B illustrates example CA signals collected over atrial and HIS sensing channels and analyzed in accordance with embodiments herein.

FIG. 4C illustrates example CA signals collected over atrial and HIS sensing channels and analyzed in accordance with embodiments herein.

FIG. 5 illustrates a process for implementing an AO consistency check in accordance with embodiments herein.

FIG. 6 illustrates a first method in which pacing impulses are applied at different energies and corresponding responses are measured and recorded.

FIG. 7 illustrates a second method in which the results, such as those obtained from the method of FIG. 6, are analyzed and classified to determine pacing settings for the stimulation device.

FIG. 8, for example, is a flow chart illustrating a method that combines collection and analysis of response data to configure pacing settings of a stimulation device.

FIG. 9 is a flow chart illustrating a method for collecting multiple sets of response data for each of a range of pacing impulse voltages.

FIG. 10 is a flow chart illustrating a method in which the results obtained from the method of FIG. 9, are analyzed and classified to determine pacing settings for the stimulation device.

FIG. 11 illustrates a process for implementing a nonsequential capture threshold test in accordance with embodiments herein.

DETAILED DESCRIPTION

It will be readily understood that the components of the embodiments as generally described and illustrated in the figures herein, may be arranged and designed in a wide variety of different configurations in addition to the described example embodiments. Thus, the following more detailed description of the example embodiments, as represented in the figures, is not intended to limit the scope of the embodiments, as claimed, but is merely representative of example embodiments.
Reference throughout this specification to “one embodiment” or “an embodiment” (or the like) means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” or the like in various places throughout this specification are not necessarily all referring to the same embodiment.
Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a thorough understanding of embodiments. One skilled in the relevant art will recognize, however, that the various embodiments can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obfuscation. The following description is intended only by way of example, and simply illustrates certain example embodiments.
The methods described herein may employ structures or aspects of various embodiments (e.g., systems and/or methods) discussed herein. In various embodiments, certain operations may be omitted or added, certain operations may be combined, certain operations may be performed simultaneously, certain operations may be performed concurrently, certain operations may be split into multiple operations, certain operations may be performed in a different order, or certain operations or series of operations may be re-performed in an iterative fashion. It should be noted that, other methods may be used, in accordance with an embodiment herein. Further, wherein indicated, the methods may be fully or partially implemented by one or more processors of one or more devices or systems. By way of example, one or more operations of each method described herein may be implemented by one or more processors or circuitry of an implantable medical device, while one or more other operations of the methods described herein may be implemented by one or more processors of an external device, such as a local external device, clinician programmer and/or a remote server. While the operations of some methods may be described as performed by the processor(s) of one device, additionally, some or all of such operations may be performed by the processor(s) of another device described herein.
The terms “atrial activity component” and “AA component” shall mean atrial pacing spikes or atrial evoked propagation or spontaneous intrinsic atrial propagation sensed at HIS lead.
The terms “consistency” and “consistent,” when used in connection with describing AA beats an atrial over sensing, shall mean that one or more characteristics of interest (COI) do not change beyond a defined limit or range over a defined interval or defined number of beats and that the one or more COI appear in the same manner over the time. For example, consistency criteria shall mean criteria utilized to determine whether AA beats exhibit one or more characteristics that remain unchanged or within a defined range over a collection of beats. As another example, consistent AO shall mean that atrial over sensing was detected over the defined interval or defined number of beats.
The term “intrinsic atrial-HIS delay” or “intrinsic AH delay” shall mean conduction delay from the time of As or Ap event in RA channel to the time HIS signal sensed at HIS lead electrodes. Practically it can be derived from time delay of As or AP to sensed ventricular depolarization (A-Vs)-the delay from pacing HIS to V sense (HVs)+pacing latency at HIS. The peak means the max peak in the specified window with either rectified or the absolute values.
The term “outlier”, when used in connection with AA beats, A/AA intervals, AA peaks and the like, is used relative to a mathematical reference or range to refer to items outside of or at an outer boundary of the mathematical reference (e.g., mean, average) or range.
The terms “rough” and “fine” are used, relative to one another, to describe a general degree or level of amplitude change between successive HBP pulses. As nonlimiting examples, a “rough” amplitude change may correspond to steps of 1-5 V (and more preferably between 0.5 V and 2 V) between successive HBP pulses, while a “fine” amplitude change may correspond to steps of 0.1-0.5 V (and more preferably between 0.1 V and 0.25 V) between successive HBP pulses. As another nonlimiting example, a fine amplitude change may be a percentage (e.g., between 10% and 25%) of a rough amplitude change.
The term “obtain” or “obtaining”, as used in connection with data, signals, information and the like, includes at least one of i) accessing memory of an external device or remote server where the data, signals, information, etc. are stored, ii) receiving the data, signals, information, etc. over a wireless communications link between the IMD and a local external device, and/or iii) receiving the data, signals, information, etc. at a remote server over a network connection. The obtaining operation, when from the perspective of an IMD, may include sensing new signals in real time, and/or accessing memory to read stored data, signals, information, etc. from memory within the IMD. The obtaining operation, when from the perspective of a local external device, includes receiving the data, signals, information, etc. at a transceiver of the local external device where the data, signals, information, etc. are transmitted from an IMD and/or a remote server. The obtaining operation may be from the perspective of a remote server, such as when receiving the data, signals, information, etc. at a network interface from a local external device and/or directly from an IMD. The remote server may also obtain the data, signals, information, etc. from local memory and/or from other memory, such as within a cloud storage environment and/or from the memory of a workstation or clinician external programmer.
The obtaining operation, when from the perspective of an IMD, may include sensing new signals in real time, and/or accessing memory to read stored data, signals, information, etc. from memory within the IMD. The obtaining operation, when from the perspective of a local external device, includes receiving the data, signals, information, etc. at a transceiver of the local external device where the data, signals, information, etc. are transmitted from an IMD and/or a remote server. The obtaining operation may be from the perspective of a remote server, such as when receiving the data, signals, information, etc. at a network interface from a local external device and/or directly from the IMD. The remote server may also obtain the data, signals, information, etc. from local memory and/or from other memory, such as within a cloud storage environment and/or from the memory of a workstation or clinician external programmer.
Embodiments may be implemented in connection with one or more implantable medical devices (IMDs). Non-limiting examples of IMDs include one or more of a cardiac monitoring device, pacemaker, cardioverter, cardiac rhythm management device, defibrillator, neurostimulator, leadless monitoring device, leadless pacemaker, and the like. For example, embodiments herein may be implemented by, or in connection with, the systems and methods described in U.S. Patent Application 2019/0022378, titled “SYSTEMS AND METHODS FOR AUTOMATED CAPTURE THRESHOLD TESTING AND ASSOCIATED HIS BUNDLE PACING”, published Jan. 24, 2019, and/or U.S. patent application Ser. No. 15/973,351, titled “METHOD AND SYSTEM TO DETECT R-WAVES IN CARDIAC ARRHYTHMIC PATTERNS” the complete subject matter of which is incorporated herein by reference in its entirety.
Additionally or alternatively, embodiments may be implemented in connection with a transvenous IMD and/or one or more leadless implantable medical device (LIMD) that include one or more structural and/or functional aspects of the device(s) described in U.S. Pat. No. 9,216,285 “Leadless Implantable Medical Device Having Removable And Fixed Components” and U.S. Pat. No. 8,831,747 “LEADLESS NEUROSTIMULATION DEVICE AND METHOD INCLUDING THE SAME”, which are hereby incorporated by reference. Additionally or alternatively, the IMD may include one or more structural and/or functional aspects of the device(s) described in U.S. Pat. No. 8,391,980 “METHOD AND SYSTEM FOR IDENTIFYING A POTENTIAL LEAD FAILURE IN AN IMPLANTABLE MEDICAL DEVICE” and U.S. Pat. No. 9,232,485 “System And Method For Selectively Communicating With An Implantable Medical Device”, which are hereby incorporated by reference. The LIMD may communicate with one another to practice the methods and systems described herein. Additionally or alternatively, a transvenous IMD may communicate with one or more LIMD to practice the methods and systems described herein.
Additionally or alternatively, embodiments may be implemented in connection with a transvenous or leadless IMD and a subcutaneous IMD that includes one or more structural and/or functional aspects of the device(s) described in U.S. application Ser. No. 15/973,195, titled “Subcutaneous Implantation Medical Device With Multiple Parasternal-Anterior Electrodes” and filed May 7, 2018; U.S. application Ser. No. 15/973,219, titled “IMPLANTABLE MEDICAL SYSTEMS AND METHODS INCLUDING PULSE GENERATORS AND LEADS” filed May 7, 2018; U.S. application Ser. No. 15/973,249, titled “SINGLE SITE IMPLANTATION METHODS FOR MEDICAL DEVICES HAVING MULTIPLE LEADS”, filed May 7, 2018, which are hereby incorporated by reference in their entireties. Further, one or more combinations of IMDs may be utilized from the above incorporated patents and applications in accordance with embodiments herein.
Additionally or alternatively, embodiments herein may be implemented by, and/or in connection with, the systems and methods described in: U.S. Patent Application 2019/0022378, titled “SYSTEMS AND METHODS FOR AUTOMATED CAPTURE THRESHOLD TESTING AND ASSOCIATED HIS BUNDLE PACING”, published Jan. 24, 2019, and/or U.S. patent application Ser. No. 15/973,351, titled “METHOD AND SYSTEM TO DETECT R-WAVES IN CARDIAC ARRHYTHMIC PATTERNS”; U.S. application Ser. No. 16/904,837, filed Jun. 18, 2020, titled “SYSTEMS AND METHODS FOR IMPROVED HIS BUNDLE AND BACKUP PACING TIMING”; U.S. Provisional Application No. 62/902,698, Titled “METHOD AND DEVICE FOR AVOIDING ATRIAL ACTIVITY OVERSENSING ON HIS SENSING CHANNEL,” on Sep. 19, 2019, the complete subject matter of which are incorporated herein by reference in their entireties.
Additionally or alternatively, embodiments herein may be implemented by, and/or in connection with, the systems and methods described in: U.S. application Ser. No. 16/904,837, Titled “SYSTEMS AND METHODS FOR IMPROVED HIS BUNDLE AND BACKUP PACING TIMING”, (Docket 13936US01) (13-0392US1), filed Jun. 18, 2020; U.S. application Ser. No. 16/871,166, Titled “SYSTEMS AND METHODS FOR IMPROVED HIS BUNDLE AND BACKUP PACING TIMING” (Docket 13845US01) (13-0381US01), filed May 11, 2020; U.S. Provisional Application 62/875,863, Titled “SYSTEMS AND METHODS FOR IMPROVED HIS BUNDLE AND BACKUP PACING TIMING” (Docket 13652USL1), filed Jul. 18, 2019; U.S. application Ser. No. 16/181,234, Titled “AUTOMATED OPTIMIZATION OF HIS BUNDLE PACING FOR CARDIAC RESYNCHRONIZATION THERAPY” (Docket 13217US01) (13-0375US01), filed Nov. 5, 2018; U.S. application Ser. No. 16/138,766, Titled “SYSTEMS AND METHODS FOR AUTOMATED CAPTURE THRESHOLD TESTING AND ASSOCIATED HIS BUNDLE PACING” (Docket 13349US01) (13-0373US01), filed Sep. 21, 2018; U.S. application Ser. No. 15/653,357, Titled “SYSTEMS AND METHODS FOR AUTOMATED CAPTURE THRESHOLD TESTING AND ASSOCIATED HIS BUNDLE PACING” (Docket A17P1011) (13-0371US01), filed Jul. 18, 2017; U.S. Provisional Application 62/948,047, Titled “AUTOMATIC PACING IMPULSE CALIBRATION USING PACING RESPONSE TRANSITIONS” (Docket 13653USL1), filed Dec. 13, 2019, the complete subject matter of which are incorporated herein by reference in their entireties.
Embodiments herein provide a consistency check for processes that seek to avoid atrial over sensing (AO). As described in one or more of the applications and/or patents referenced and incorporated herein, AO avoidance processes may utilize P-wave duration (PWD), intrinsic atrial-HIS (AH) delay and/or intrinsic atrial conduction delay (IACD) to estimate a risk of oversensing atrial activity and to automatically adjust a length of a post atrial ventricular period (PAVP), which in some imitations may be referred to as an atrial oversensing avoidance (AOA) window. The AO avoidance processes may further adjust a maximum sensitivity setting with ventricular safety pacing. PAVP is an initial time window for the purpose of including atrial components and processing the signals such as the peak and its location etc. The term PAVP may be used to represent a subset of implementations for an AOA window. For example, the term PAVP may be utilized to refer to implementations in which the corresponding period is used as a device refractory period, whereas the term “AOA window” is more generally used to refer to a PAVP as well as implementations in which the corresponding window period is not limited to only device refractory periods, such as when a sense refractory period could have other functions or features that are not used in connection herewith.
The AO avoidance processes address the challenges that arise when a HIS sensing channel is utilized to monitor for RV activity. When the HIS electrode is located in the RA, the HIS sensing channel detects RV activity as a low amplitude component of the CA signal because the ventricular activity is occurring in the far field and exhibits a low-frequency content which is filtered by the HIS sense amplifier. Given that the HIS sensing channel is configured to detect low amplitude, low frequency far field RV signals, the potential arises that the IMD may over sense atrial or HIS activity over the HIS sensing channel. The potential also exists to over sense atrial activity when the HIS electrode is located in the RV.
Embodiments of the present disclosure may be implemented in either a dual chamber or multi-chamber cardiac stimulation device. For example, the present disclosure may be implemented in a rate-responsive multi-chamber cardiac stimulation device. Certain cardiac pacemakers and defibrillators incorporate a pacing lead in the right ventricle and may also include a second lead in the right atrium. High-burden right ventricle pacing may contribute to the development of pacing-induced cardiomyopathy and symptoms associated with heart failure (HF). Several pathophysiologic mechanisms have been implicated in the development of pacing-induced HF, each of which likely stems from non-physiological electrical and mechanical activation patterns produced by right ventricle pacing. HIS bundle pacing (HBP) may restore physiological activation patterns by utilizing a patient's intrinsic conduction system and may do so even in the presence of bundle branch block. HBP has also been shown to provide significant QRS narrowing, with improved ejection fraction.
Another possible clinical application of HBP is cardiac resynchronization therapy (CRT). Conventional CRT systems include pacing from both a right ventricular and a left ventricular lead, and have been shown most effective for patients exhibiting a wide QRS complex and left bundle branch block. HBP has also been shown to be effective at narrowing the QRS complex in patients with left bundle branch block, likely due to the anatomy of the HIS bundle, which includes right and left bundle fibers that are longitudinally dissociated. Therefore, what is thought of as left bundle branch block, can be a result of a proximal blockage within the HIS bundle that eventually branches to the left bundle. As a result, by pacing the HIS bundle distal to the blockage, a normalized QRS complex can be achieved in some patients. Theoretically, this pacing mode may provide even better results than known CRT treatments, as activation propagates rapidly through natural conduction pathways.
FIG. 1 illustrates a stimulation device 10 in electrical communication with a patient's heart 12 by way of one or more of four leads, 20, 21, 24, and 30 and suitable for delivering multi-chamber stimulation and shock therapy. To sense atrial cardiac signals and to provide right atrial chamber stimulation therapy, the stimulation device 10 is coupled to an implantable right atrial lead 20 having at least an atrial tip electrode 22, which typically is implanted in the patient's right atrial appendage or atrial septum. To sense left atrial and ventricular cardiac signals and to provide left chamber pacing therapy, the stimulation device 10 is coupled to a “coronary sinus” lead 24 designed for placement in the “coronary sinus region” via the coronary sinus ostium for positioning a distal electrode within the coronary veins overlying the left ventricle and/or additional electrode(s) adjacent to the left atrium. As used herein, the phrase “coronary sinus region” refers to the vasculature of the left ventricle, including any portion of the coronary sinus, great cardiac vein, left marginal vein, left posterior ventricular vein, middle cardiac vein, and/or small cardiac vein or any other cardiac vein accessible by the coronary sinus which overlies the left ventricle. Accordingly, an exemplary coronary sinus lead 24 is designed to receive atrial and ventricular cardiac signals and to deliver left ventricular pacing therapy using at least a left ventricular tip electrode 26, left atrial pacing therapy using at least a left atrial ring electrode 27, and shocking therapy using at least a left atrial coil electrode 28. In another embodiment, an additional electrode for providing left ventricular defibrillation shocking therapy may be included in the portion of the lead overlying the left ventricle, adjacent to the ring electrode 25. The stimulation device 10 is also shown in electrical communication with the patient's heart 12 by way of an implantable right ventricular lead 30 having, in this embodiment, a right ventricular tip electrode 32, a right ventricular ring electrode 34, a right ventricular coil electrode 36, and a superior vena cava (SVC) coil electrode 38. Typically, the right ventricular lead 30 is transvenously inserted into the heart 12 so as to place the right ventricular tip electrode 32 in the right ventricular apex so that the right ventricular coil electrode 36 will be positioned in the right ventricle and the SVC coil electrode 38 will be positioned in the superior vena cava. Accordingly, the right ventricular lead 30 is capable of receiving cardiac signals and delivering stimulation in the form of pacing and shock therapy to the right ventricle.
The stimulation device 10 is further connected to a HIS bundle lead 21 having a HIS tip electrode 16, such as a helical active fixation device, and a HIS ring electrode 19 located proximal from the HIS tip electrode 16. In certain implementations, the HIS ring electrode 19 is located approximately 10 mm proximal the HIS tip electrode 16. The HIS bundle lead 21 may be transvenously inserted into the heart 12 so that the HIS tip electrode 16 is positioned in the tissue of the HIS bundle. The HIS bundle lead 21 may be located proximate the HIS bundle in the RA or in the RV. Accordingly, the HIS bundle lead 21 is capable of receiving depolarization signals propagated in the HIS bundle or delivering stimulation to the HIS bundle, creating a depolarization that can be propagated through the lower conductive pathways of the right and left ventricles (i.e., the right and left bundle branches and Purkinje fibers).
An alternative embodiment of the present disclosure is shown in FIG. 2 in which a dual chamber stimulation device 210 is in communication with one atrium, one ventricle, and the HIS bundle. Though not explicitly illustrated in FIG. 2, a right atrial lead 20 can be optionally included. In such implementations, the stimulation device 210 maintains communication with the right atrium of the heart 12 via a right atrial lead 20 having at least an atrial tip electrode 22 and an atrial ring electrode 23, and an SVC coil electrode 239. A HIS bundle lead 221, having a HIS tip electrode 216 and a HIS ring electrode 219, is positioned such that the HIS tip electrode 216 is proximate the HIS bundle tissue. The stimulation device 210 is shown in FIG. 2 in electrical communication with the patient's heart 12 by way of a right ventricular lead 230 including a right ventricular tip electrode 232, a right ventricular ring electrode 234, and a right ventricular coil electrode 236.
Optionally, the distal end of the HIS bundle lead 21 is further provided with a non-traumatic conductive surface (also referred to herein interchangeably as a mapping collar). The non-traumatic conductive surface is advantageously used to make electrical measurements that indicate the location of the HIS bundle without having to anchor the HIS bundle tip electrode 16 into the endocardial tissue. The non-traumatic conductive surface and the HIS bundle tip electrode 16 are electrically coupled within the lead body of the HIS bundle lead 21 and together form one conductive element for the purposes of sensing, stimulation, and impedance measurements. Drugs, for example an acute anti-arrhythmic drug such as lidocaine and/or an anti-inflammatory agent such as dexamethasone sodium phosphate, can be stored, for example, within a reservoir (not shown) at the base of the HIS bundle tip electrode 16 for local dispensation.
The HIS bundle lead 21 is also provided with a HIS ring electrode 19. The HIS ring electrode 19 is preferably spaced between approximately 2 mm and 30 mm, but preferably 10 mm, from the HIS tip electrode 16. The HIS ring electrode 19 may function as the return electrode during bipolar sensing, stimulation, or impedance measurement operations.
The HIS tip electrode 16 and the HIS ring electrode 19 are each connected to flexible conductors respectively, which may run the entire length of the HIS bundle lead 21. The flexible conductor is connected to the HIS tip electrode 16 and is electrically insulated from the flexible conductor by a layer of insulation. The conductor is connected to the HIS ring electrode 19. The flexible conductors serve to electrically couple the HIS ring electrode 19 and the HIS tip electrode 16 to the HIS ring electrode terminal 51 and the HIS tip electrode terminal 50, respectively. One embodiment of the HIS bundle lead 21 is available from St. Jude Medical CRMD as lead model No. 1488T.
Optionally, the HIS lead may be implanted in the RV with the HIS tip electrode (16 or 216) located proximate the HIS bundle along the septum wall. As a further option, the HIS tip electrode may be configured as and/or provided on, a helical screw at the distal end of the HIS lead, such that the HIS electrode is screwed into the septum wall of the RV proximate the HIS bundle.
FIG. 3 illustrates a simplified block diagram of the multi-chamber implantable stimulation device 10 of FIG. 1, which is capable of treating both fast and slow arrhythmias with stimulation therapy, including cardioversion, defibrillation, and pacing stimulation. While a particular multi-chamber device is shown, this is for illustration purposes only, and one of skill in the art could readily duplicate, eliminate or disable the appropriate circuitry in any desired combination to provide a device capable of treating the appropriate chambers) with cardioversion, defibrillation and pacing stimulation. The housing 40 for the stimulation device 10, shown schematically in FIG. 3, is often referred to as the “can”, “case” or “case electrode” and may be programmably selected to act as the return electrode for all “unipolar” modes. The housing 40 may further be used as a return electrode alone or in combination with one or more of the coil electrodes 28, 36, and 38 (shown in FIG. 1) for shocking purposes. The housing 40 further includes a connector (not shown) having a plurality of terminals 42, 44, 46, 48, 50-52, 54, 56, and 58 (shown schematically and, for convenience, next to the names of the electrodes to which they are connected). As such, to achieve right atrial sensing and pacing, the connector includes at least a right atrial tip terminal (AR TIP) 42 adapted for connection to the atrial tip electrode 22 (shown in FIG. 1).
To achieve left chamber sensing, pacing and shocking, the connector includes at least a left ventricular tip terminal (V.sub.L TIP) 44, a left atrial ring terminal (A.sub.L RING) 46, and a left atrial shocking terminal (A.sub.L COIL) 48, which are adapted for connection to the left ventricular tip electrode 26, the left atrial ring electrode 27, and the left atrial coil electrode 28, respectively (each shown in FIG. 1). To support right chamber sensing, pacing and shocking, the connector further includes a right ventricular tip terminal (V.sub.R TIP) 52, a right ventricular ring terminal (V.sub.R RING) 54, a right ventricular shocking terminal (RV COIL) 56, and an SVC shocking terminal (SVC COIL) 58, which are adapted for connection to the right ventricular tip electrode 32, right ventricular ring electrode 34, the right ventricular coil electrode 36, and the SVC coil electrode 38, respectively (each shown in FIG. 1). To achieve HIS bundle sensing, or sensing and stimulation, the connector further includes a HIS bundle lead tip terminal 50 and a HIS bundle lead ring terminal 51 which are adapted for connection to the HIS tip electrode 16 and the HIS ring electrode 19, respectively (each shown in FIG. 1).
At the core of the stimulation device 10 is a programmable microcontroller 60 which controls the various modes of stimulation therapy. The microcontroller 60 includes a microprocessor, or equivalent control circuitry, designed specifically for controlling the delivery of stimulation therapy and may further include RAM or ROM memory, logic and timing circuitry, state machine circuitry, and I/O circuitry. Typically, the microcontroller 60 includes the ability to process or monitor input signals (data) as controlled by a program code stored in a designated block of memory. The details of the design and operation of the microcontroller 60 are not critical to the present disclosure. Rather, any suitable microcontroller 60 may be used that carries out the functions described herein.
As shown in FIG. 3, an atrial pulse generator 70 and a ventricular pulse generator 72 generate pacing stimulation pulses for delivery by the right atrial lead 20, the right ventricular lead 30, the coronary sinus lead 24, and/or the HIS bundle lead 21 via an electrode configuration switch 74. It is understood that in order to provide stimulation therapy in each of the four chambers of the heart, the atrial and ventricular pulse generators 70, 72 may include dedicated, independent pulse generators, multiplexed pulse generators, or shared pulse generators. The pulse generators 70, 72 are controlled by the microcontroller 60 via appropriate control signals 76, 78, respectively, to trigger or inhibit the stimulation pulses. As used herein, the shape of the stimulation pulses is not limited to an exact square or rectangular shape, but may assume any one of a plurality of shapes which is adequate for the delivery of an energy pulse, packet, or stimulus.
The microcontroller 60 further includes timing control circuitry 79 which is used to control the timing of such stimulation pulses (e.g., pacing rate) as well as to keep track of the timing of refractory periods, blanking intervals, noise detection windows, evoked response windows, alert intervals, marker channel timing, etc., which is well known in the art. According to one embodiment of the present disclosure, timing control circuitry 79 also controls the onset and duration of a HIS signal sensing window during which a depolarization signal conducted through the AV node to the HIS bundle can be detected. Timing control circuitry 79 also controls a timing delay provided after a detected HIS signal detection, prior to the delivery of a right and/or left ventricular stimulation pulse. The switch 74 includes a plurality of switches for connecting the desired electrodes to the appropriate I/O circuits, thereby providing complete electrode programmability. Accordingly, the switch 74, in response to a control signal 80 from the microcontroller 60, determines the polarity of the stimulation pulses (e.g., unipolar, bipolar, cross-chamber, etc.) by selectively closing the appropriate combination of switches (not shown) as is known in the art.
Atrial sensing circuits 82 and ventricular sensing circuits 84 may also be selectively coupled to the right atrial lead 20, coronary sinus lead 24, and the right ventricular lead 30, through the switch 74 for detecting the presence of cardiac activity in each of the four chambers of the heart. Accordingly, the atrial (ATR. SENSE) and ventricular (VTR. SENSE) sensing circuits 82, 84 may include dedicated sense amplifiers, multiplexed amplifiers, or shared amplifiers. The switch 74 determines the “sensing polarity” of the cardiac signal by selectively closing the appropriate switches, as is also known in the art. In this way, the clinician may program the sensing polarity independent of the stimulation polarity.
According to one embodiment of the present disclosure, a HIS sensing circuit 83 is selectively coupled to the HIS bundle lead 21 (shown in FIG. 1) for detecting the presence of a conducted depolarization arising in the atria and conducted to the HIS bundle via the AV node. As used herein, each of the atrial sensing circuit 82, the ventricular sensing circuit 84, and the HIS sensing circuit 83, includes a discriminator, which is a circuit that senses and can indicate or discriminate the origin of a cardiac signal in each of the cardiac chambers. Each sensing circuit 82-84 preferably employs one or more low power, precision amplifiers with programmable gain and/or automatic gain control, bandpass filtering, and a threshold detection circuit to selectively sense the cardiac signal of interest. The automatic gain control enables the device 10 to deal effectively with the difficult problem of sensing the low amplitude signal characteristics of atrial or ventricular fibrillation. The outputs of the sensing circuits 82-84 are connected to the microcontroller 60 which, in turn, is able to trigger or inhibit the atrial and ventricular pulse generators 70, 72, respectively, in a demand fashion in response to the absence or presence of cardiac activity in the appropriate chambers of the heart. The atrial and ventricular sensing circuits 82, 84, in turn, receive control signals ever signal lines 86, 88, from the microcontroller 60 for purposes of controlling the gain, threshold, polarization charge removal circuitry (not shown), and the timing of any blocking circuitry (not shown) coupled to the inputs of the sensing circuits 82, 84.
For arrhythmia detection, the stimulation device 10 includes an arrhythmia detector 77 that utilizes the atrial and ventricular sensing circuits 82, 84, to sense cardiac signals to determine whether a rhythm is physiologic or pathologic. As used herein “sensing” is reserved for the noting of an electrical signal, and “detection” is the processing of these sensed signals and noting the presence of an arrhythmia. The timing intervals between sensed events (e.g., P-waves, R-waves, and depolarization signals associated with fibrillation) are then classified by the microcontroller 60 by comparing them to a predefined rate zone limit (i.e., bradycardia, normal, low rate VT, high rate VT, and fibrillation rate zones) and various other characteristics (e.g., sudden onset, stability, physiologic sensors, and morphology, etc.) in order to determine the type of remedial therapy that is needed (e.g., bradycardia pacing, anti-tachycardia pacing, cardioversion shocks or defibrillation shocks, collectively referred to as “tiered therapy”).
Cardiac signals are also applied to the inputs of an analog-to-digital (ND) data acquisition system 90 represented by an ND converter. The data acquisition system 90 is configured to acquire intracardiac electrogram signals, convert the raw analog data into a digital signal, and store the digital signals for later processing and/or telemetric transmission to an external device 102. The data acquisition system 90 is coupled to the right atrial lead 20, the HIS bundle lead 21, the coronary sinus lead 24, and the right ventricular lead 30 through the switch 74 to sample cardiac signals across any pair of desired electrodes.
In one embodiment, the data acquisition system 90 is coupled to microcontroller 60, or to other detection circuitry, for detecting a desired feature of the HIS bundle signal. In one embodiment, an averager is used to determine a sliding average of the HIS bundle signal during a HIS signal sensing window using known or available signal averaging techniques.
Advantageously, the data acquisition system 90 may be coupled to the microcontroller 60, or other detection circuitry, for detecting an evoked response from the heart 12 in response to an applied stimulus, thereby aiding in the detection of capture. The microcontroller 60 detects a depolarization signal during a window following a stimulation pulse, the presence of which indicates that capture has occurred. The microcontroller 60 enables capture detection by triggering the ventricular pulse generator 72 to generate a stimulation pulse, starting a capture detection window using the timing control circuitry 79 within the microcontroller 60, and enabling the data acquisition system 90 via control signal 92 to sample the cardiac signal that falls in the capture detection window and, based on the amplitude, determines if capture has occurred.
The microcontroller 60 is further coupled to a memory 94 by a suitable data/address bus 96, wherein the programmable operating parameters used by the microcontroller 60 are stored and modified, as required, in order to customize the operation of the stimulation device 10 to suit the needs of a particular patient. Such operating parameters define, for example, pacing pulse amplitude, pulse duration, electrode polarity, rate, sensitivity, automatic features, arrhythmia detection criteria, and the amplitude, waveshape and vector of each shocking pulse to be delivered to the patient's heart 12 within each respective tier of therapy.
The HIS sensing circuit 83 is connected to one or more HIS electrodes, to collectively define the HIS sensing channel that collects at least a portion of the CA signals. The atrial sensing circuit 82 is connected to one or more RA electrodes, to collectively define an RA sensing channel. The memory 94 is configured to store the CA signals obtained over the RA sensing channel and over the HIS sensing channel. The memory also is configured to store program instructions.
The microcontroller 60 is configured, when executing the program instructions, for: utilizing an atrial oversensing (AO) process to analyze the CA signals, obtained over the HIS sensing channel during an AO avoidance (AOA) window, for an atrial activity (AA) component to identify AA beats; applying a consistency criteria to the AA beats to determining a number of the AA beats that are indicative of consistent AO; based on the consistency criteria and the number of AA beats indicative of consistent AO, performing at least one of adjusting an AO parameter utilized by the AO process or disabling the AO process; and managing HIS bundle pacing based on the ventricular event.
Additionally or alternatively, the microcontroller 60 be configured to determine, for at least a portion of the AA beats, an interval between a paced or sensed atrial (A) event and a characteristic of interest (COI) within the AA component (A/AA interval) of the corresponding AA beat, the applying the consistency criteria including identifying a subset of the AA beats, for which the A/AA interval is within a first connection criteria. Additionally or alternatively, the microcontroller 60 be configured to determine, for at least a portion of the AA beats, a peak of the AA component (AA peak) of the corresponding AA beat, the applying the consistency criteria including identifying a subset of the AA beats, for which the AA peak is within a second connection criteria. Additionally or alternatively, the microcontroller 60 be configured to identify first and second subsets of the AA beats, for which first and second characteristics of interest (COI) of the AA components fall within the corresponding first and second limits; and determining whether a number of beats in the first and second subsets of the AA beats is indicative of consistent AO. Additionally or alternatively, the first and second criteria correspond to limits about first and second median values for corresponding first and second COI, the one or more processors further configured to utilize the first and second criteria to distinguish between candidate AA beats and outlier AA beats.
Additionally or alternatively, the microcontroller 60 be configured to adjust an AO parameter utilized by the AO process when the number of AA beats indicative of AO exceed a threshold, the AO parameter representing at least one of i) a start time for the AOA window, a duration for the AOA window, or an AO sensitivity profile utilized to analyze the CA signals over the his sensing channel during the AOA window. Additionally or alternatively, the microcontroller 60 be configured to disable the AO process when the number of AA beats indicative of AO fall below a threshold. Additionally or alternatively, the microcontroller 60 be configured to manage the HIS pacing by lowering a sensitivity level of the VE sensitivity profile for the HIS sensing channel.
Additionally or alternatively, the microcontroller 60 be configured to maintain a count of a number of AA components over a series of beats and based on the count, determine whether to maintain or change current settings for the length of the AOA window and/or sensitivity profile. Additionally or alternatively, the AOA window represents a time window enclosing atrial component activity components.
Further, in accordance with aspects herein, the microcontroller 60 may be configured to apply, using the pulse generator and stimulating electrode, a HBP pulse having an impulse energy to the His bundle; in response to applying the first pacing impulse, measure response data for a corresponding evoked response using the at least one sensing electrode; determine a response characteristic based on the response data; adjust the impulse energy and repeating the applying, measuring and determining, wherein the impulse energy is adjusted in a non-sequential manner between the HBP pulses; identify a change in the response characteristic indicative of a change from a first capture type and a second capture type; and set one or more parameters of a HBP therapy based on the change in the response characteristic.
Additionally or alternatively, the microcontroller 60 may be configured to repeat the applying, measuring, determining, and adjusting to obtain a collection of response characteristics for a collection of HBP pulses at corresponding different impulse energies. Additionally or alternatively, the adjusting in the non-sequential manner includes at least one rough energy adjustment between first and second HBP pulses and at least one fine energy adjustment between third and fourth HBP pulses. As explained herein, at least one rough energy adjustment includes a voltage step-up of at least 1.0V between the first and second HBP pulses and the at least one fine energy adjustment includes a voltage step-down of no more than 0.25V between the third and fourth HBP pulses. Additionally or alternatively, the microcontroller 60 may be further configured to apply the at least one rough energy adjustment during a rough HBP test between upper and lower rough limits and applies the at least one fine energy adjustment during a fine HBP test between upper and lower fine limits, the upper and lower fine limits defined based on a transition point identified during the rough HBP test. Additionally or alternatively, the microcontroller 60 may be configured to identify a rough transition point based on the response characteristic associated with the first and second HBP pulses separated by the at least one rough energy adjustment and refine the rough transition point to a fine transition point based on the response characteristic associated with the third and fourth HBP pulses separated by the at least one fine energy adjustment.
In the present example, the above operations are performed by an implantable medical device having a housing that includes the memory and the one or more processors, the housing configured to be coupled to the RA electrode and HRIS electrode. Optionally, the IMD may have at least a portion of the one or more processors, while an external device has at least a portion of the one or more processors. The IMD and external device both perform at least a portion of the identifying, calculating, analyzing, adjusting, monitoring, and managing operations.
Advantageously, the operating parameters of the implantable device 10 may be non-invasively programmed into the memory 94 through a telemetry circuit 100 in telemetric communication with the external device 102, such as a programmer, trans-telephonic transceiver, or a diagnostic system analyzer. The telemetry circuit 100 is activated by the microcontroller 60 by a control signal 106. The telemetry circuit 100 advantageously allows intracardiac electrograms and status information relating to the operation of the device 10 (as contained in the microcontroller 60 or memory 94) to be sent to the external device 102 through an established communication link 104.
In the preferred embodiment, the stimulation device 10 further includes a physiologic sensor 108, commonly referred to as a “rate-responsive” sensor because it is typically used to adjust pacing stimulation rate according to the exercise state of the patient. However, the physiologic sensor 108 may further be used to detect changes in cardiac output, changes in the physiological condition of the heart, or diurnal changes in activity (e.g., detecting sleep and wake states). Accordingly, the microcontroller 60 responds by adjusting the various pacing parameters (such as rate, stimulation delays, etc.) at which the atrial and ventricular pulse generators 70, 72 generate stimulation pulses.
A common type of rate responsive sensor is an activity sensor, such as an accelerometer or a piezoelectric crystal, which is mounted within the housing 40 of the stimulation device 10. Other types of physiologic sensors are also known, for example, sensors which sense the oxygen content of blood, respiration rate and/or minute ventilation, pH of blood, ventricular gradient, etc. However, any suitable sensor may be used which is capable of sensing a physiological parameter which corresponds to the exercise state of the patient. The type of sensor used is not critical to the present disclosure and is shown only for completeness.
The stimulation device 10 additionally includes a battery 110 which provides operating power to all of the circuits shown in FIG. 3. For the stimulation device 10, which employs shocking therapy, the battery 110 must be capable of operating at low current drains for long periods of time, and then be capable of providing high-current pulses (for capacitor charging) when the patient requires a shock pulse. The battery 110 must also have a predictable discharge characteristic so that elective replacement time can be detected. Accordingly, the device 10 preferably employs lithium/silver vanadium oxide batteries, as is true for most (if not all) current devices.
The device 10 is shown in FIG. 3 as having an impedance measuring circuit 112 which is enabled by the microcontroller 60 via a control signal 114. The known uses for an impedance measuring circuit 112 include, but are not limited to, lead impedance surveillance during the acute and chronic phases for detecting proper lead positioning or dislodgement; detecting operable electrodes and conductors; and automatically switching to an operable pair if dislodgement or electrical disruption occurs; measuring respiration or minute ventilation; measuring thoracic impedance for determining shock thresholds; detecting when the device has been implanted; measuring stroke volume; and detecting the opening of heart valves, etc. The impedance measuring circuit 112 is advantageously coupled to the switch 74 so that any desired electrode may be used.
In the case where the stimulation device 10 is intended to operate as an implantable cardioverter/defibrillator (ICD) device, it must detect the occurrence of an arrhythmia, and automatically apply an appropriate electrical shock therapy to the heart aimed at terminating the detected arrhythmia. To this end, the microcontroller 60 further controls a shocking circuit 116 by way of a control signal 118. The shocking circuit 116 generates shocking pulses of low (for example, up to 0.5 joules), moderate (for example, 0.5-10 joules), or high energy (for example, 11-40 joules), as controlled by the microcontroller 60. Such shocking pulses are applied to the patient's heart 12 through at least two shocking electrodes, and as shown in this embodiment, selected from the left atrial coil electrode 28, the right ventricular coil electrode 36, and the SVC coil electrode 38. As noted above, the housing 40 may act as an active electrode in combination with the right ventricular electrode 36, or as part of a split electrical vector using the SVC coil electrode 38 or the left atrial coil electrode 28 (i.e., using the right ventricular electrode 36 as a common electrode).
Cardioversion shocks are generally considered to be of low to moderate energy level (so as to minimize pain felt by the patient), and/or synchronized with an R-wave and/or pertaining to the treatment of tachycardia. Defibrillation shocks are generally of moderate to high energy level (i.e., corresponding to thresholds in the range of 5-40 joules), delivered asynchronously (since R-waves may be too disorganized), and pertaining exclusively to the treatment of fibrillation. Accordingly, the microcontroller 60 is capable of controlling the synchronous or asynchronous delivery of the shocking pulses.
The device 10 includes two separate connection terminals, one for each of the two flexible conductors that are further connected to switch 74. The two flexible conductors can then be selectively connected as desired to the HIS sensing circuit 83, ventricular pulse generator 72, or impedance measuring circuit 112 for sensing, stimulating, and measuring tissue impedance at the site of the HIS bundle. Using the lead 21, it is possible to effect stimulation with the HIS tip electrode 16 and the HIS ring electrode 19, and to effect sensing with the conductive surfaces. According to another design, the sensing is affected by the conductive surfaces and stimulation is affected by means of the leads other than the HIS lead, for example the right atrial lead 20. For more details regarding a heart electrode equipped with multiple conductive surfaces, reference is made to U.S. Pat. Nos. 5,306,292 and 5,645,580, which are incorporated herein by reference. The HIS tip electrode 16 may be secured in the HIS bundle thereby anchoring the HIS tip electrode 16 in contact with the HIS bundle tissue. The electrogram signal arising from the HIS bundle can then be received by the HIS sensing circuit 83. A bypass filter (not shown) that allows signals ranging from 30-200 Hz to be received may be used to block the high frequency alternating current excitation signals.

Methods and Systems to Avoid Over Sensing Atrial Activity Components

Various embodiments are described hereafter for avoiding oversensing of atrial activity components. It should be recognized that the various embodiments may be implemented dynamically within an external or implantable medical device. Embodiments may be implemented continuously and/or based on predetermined criteria in an automatic manner by an IMD. Additionally or alternatively, an external programmer may instruct an IMD to initiate the measurements and calculations described herein. Additionally or alternatively, various embodiments may be implemented entirely, or in part, by an IMD, a local external device, a programmer and/or remote server. For example, an IMD may receive an instruction from a local external device, a programmer and/or remote server to initiate collecting CA signals and/or other information calculated from the CA signals as described herein. The CA signals and/or subsequent calculations may be streamed to a local external device, server and/or programmer. The data streamed from the IMD may be processed on a local external device, programmer, and/or remote server to automatically set HBP parameter settings, including but not limited to the component sensitivity profile, VE sensitivity profile, AOA window length, PAVP window length and the like.
In the following discussion of the methods for managing sensing, at least some operations are described with respect to CA signals generally. It is understood that the corresponding operations may be performed on a beat by beat basis and/or may be performed utilizing an ensemble of a predetermined number of beats. Additionally or alternatively, the operations described herein may be performed over multiple beats during one respiration cycle (e.g., 8-10 beats) or more than one respiration cycles. By utilizing an ensemble of beats over a respiration cycle, embodiments account for variations between beats at different phases in the respiration cycle.
FIG. 4A illustrates a process for implementing an atrial over sensing (AOS) set up test in accordance with embodiments herein. At 402, the one or more processors initiate an AOS set up test. The AOS set up test is configured to detect AOS using atrial timing on an RA sensing channel and the time separation of atrial and ventricular events as detected over the HIS sensing channel during an intrinsic AV conduction. The AOS set up test is generally run while the IMD is operating in a DDD mode as the test utilizes atrial sensed or atrial paced events to initiate the AOA window for which the CA signals received over the HIS sensing channel are analyzed for AA components. As described hereafter in connection with the operations of FIG. 4A, during the AOS set up test, atrial and ventricular event amplitudes are measured over the HIS sensing channel.
At 404, the one or more processors extend the sensed/paced atrioventricular delay (AVD) by a preprogrammed or automatically determined amount to allow intrinsic ventricular activation without intervention of a HIS pacing event. For example, the AVD may be extended up to 300 ms following an atrial sensed event or the AV delay may be extended up to 350 ms following an atrial paced event. If an intrinsic AV conduction is not detected, HIS pacing is delivered when the AVD times out. At 404, the one or more processors further set the sensitivity for the HIS sensing channel to have a high sensitivity level (e.g., 0.5 mV).
At 406, the one or more processors initiate a beat counter (e.g., n=1). The beat counter is utilized to keep track of a total number of beats, from which a subset may be declared to be AA beats.
At 408, the one or more processors detect an atrial sensed or paced event over the RA sensing channel and initiate an AOA window. The one or more processors search the CA signals obtained over the HIS sensing channel during the AOA window for an AA component. As a nonlimiting example, the AOA window may be set to 100 ms when the atrial event represents an atrial sensed event, and the AOA window may be set to 160 ms when the atrial event represents an atrial paced event. Additionally or alternatively, different durations may be programmed for the AOA window duration, such as in connection with different sensing configurations (e.g., bipolar versus unipolar sensing).
At 410, the one or more processors determine whether an AA component was detected over the HIS sensing channel during the AOA window. For example, the presence of an AA component may be declared when an amplitude of the CA signals, sensed over the HIS sensing channel, cross a sensitivity profile (referred to herein as a “component sensitivity profile”, or “AO sensitivity profile”) that is defined for the HIS sensing channel during the AOA window. By way of example, the component sensitivity profile may represent a preprogrammed sensitivity threshold that is not change over time. For example, the AO sensitivity profile may be set to a constant AO sensitivity threshold that corresponds to a percentage (e.g., 150%) of a maximum prior measured AA peak.
Additionally or alternatively, the component sensitivity profile may vary over time, such as described in the '351 application which describes various parameters that may be adjusted to define a sensitivity profile. As a nonlimiting example, an AA component may be declared when the CA signal exhibits an amplitude that exceeds a component sensitivity profile/threshold of 0.5 mV during the AOA window. It is recognized that the operation to detect an AA component during an AOA window is separate and distinct from the operation of detecting ventricular events over the HIS sensing channel.
Detection of ventricular events is based on CA signals that follow the AOA window and is based on a VE sensitivity profile which may be the same as or different from the AO sensitivity profile utilized to search for AA components during the AOA window. For example, the VE sensitivity profile may be manually programmed to 0.5 mV or another value based on a peak of prior detective ventricular events.
When an AA component is detected to exceed the AO sensitivity profile, the process declares an AO event to have occurred, and flow moves to 412. When an amplitude of the CA signals during the AOA window does not exceed the AO sensing profile, the process determines that an AA component is not detected, and flow moves to 414.
At 412, the one or more processors determine and record a A/AA interval between the paced or sensed event (as denoted by an atrial marker) and a COI within the AA component. For example, the A/AA interval may be between onset or a peak of the atrial paced or sensed event (as denoted by an atrial marker) and onset, peak or termination of the AA component. Additionally or alternatively, an A/AA period may be measured as the time delay from the atrial marker to the end of the AA component. At 412, the one or more processors further identify an amplitude of the AA component as a second COI (e.g., the peak amplitude of the AA component). As explained hereafter, the A/AA interval and the AA peak are recorded in connection with each AA component identified at 410 and subsequently used in connection with the consistency check of FIG. 5. The operations of FIG. 4A are repeated to build a set of AA beats with corresponding A/AA intervals and AA peaks. At the end of the operations of FIG. 4A, the AA beats represent candidate AO beats as the AA beats have not yet been analyzed for consistency and determined to represent resultant AO beats.
In accordance with new and unique aspects herein, it has been recognized that the delay from an atrial paced or sensed event to a COI within the AA component (e.g., the peak of an AO event is very consistent beat by beat). Accordingly, at 412, for each AA beat, the A/AA interval is measured and subsequently checked for consistency (in accordance with the operations of FIG. 5). As explained below in connection with FIG. 5, erroneously detected AA beats or outlier AA beats are excluded. A nonlimiting example of outlier AA beats may arise due to premature ventricular contractions (PVCs) a risk of atrial over sensing is confirmed when a desired number (e.g., two or more) effective atrial over sensed the beats are detected over one or more atrial over sensed beats are detected where the amplitude of the AA component is within a defined window (e.g., 0.5 mV to 1.0 mV).
At 414, the one or more processors record a characteristic of interest from the ventricular event, such as the amplitude of the ventricular event following the AOA window.
At 416, the one or more processors determine whether a desired number of beats have been analyzed for AA components (e.g., five beats). If not, flow moves to 418 where the count of the number of beats is incremented (e.g., n+n+1). Next flow moves to 408 where the AOA window is reset in connection with the next sensed or paced atrial event. The operations at 408-416 are repeated for desired number of beats, after which flow moves to 420. As one example, the operations at 408-416 may be repeated to collect information concerning a number of atrial sensed beats in order to characterize characteristics of interest in the AA components following atrial sensed beats. As another example, the operations at 408-416 may be repeated to collect information concerning a number of atrial paced beats in order to characterize characteristics of interest in the AA components following atrial paced beats.
At 420, the one or more processors determine whether atrial over sensing has been identified. For example, the one or more processors may merely determine if, for any or a select number of the beats, the process detected an AA component during the AOA window. Additionally or alternatively, the one or more processors may implement the various operations and processes described in the patent applications and patents referenced and incorporated herein to determine whether atrial over sensing has been identified. When atrial over sensing is not identified at 420, flow moves to 422.
At 422, the one or more processors determined that atrial oversensing has not been identified utilizing the present set of AO parameters. In response thereto, the AO process may be disabled. Additionally or alternatively, the parameters of the AO process may be modified and the operations of FIG. 4A repeated. For example, when the AO process is disabled, the VE sensitivity profile may revert to a user programmed VE sensitivity profile (e.g., such is set to a minimum allowed sensitivity, 0.5 mV and the like).
At 420, when an atrial over sensing is identified, flow moves to 424.
At 424, the one or more processors perform an AO consistency check, as explained herein in accordance with embodiments herein. Depending on the outcome at 424, flow moves to either 426 or returns to 422.
At 426, the one or more processors identify AO parameters to be utilized by the AO process. For example, the AOA window may be set to have a duration that is a function of one or more prior measured a/AA intervals. For example, the AOA window following an atrial sensed event, may be set to have a duration corresponding to the longest prior interval from an atrial sensed event to an AA component (AS/AA interval) times a multiple (e.g., 1.25). As another example, the AOA window following an atrial paced, may be set to have a duration corresponding to the longest prior interval from an atrial paced event to an AA component (AP/AA interval) times a multiple (e.g., 1.25). For example, the AO sensitivity profile may be set to a constant AO sensitivity threshold that corresponds to a percentage (e.g., 150%) of a maximum prior measured AA peak. For example, the VE sensitivity profile may be manually programmed to 0.5 mV or another value based on a peak of prior detective ventricular events.
Among other things, the one or more processors apply one or more consistency criteria to the AA beats to determining a number of the AA beats that are indicative of consistent AO. Based on the number of AA beats indicative of consistent AO, the one or more processors perform at least one of an adjustment of an AO parameter utilized by the AO process (at 426) or disabling the AO process (at 422). Thereafter, the one or more processors continue to manage HIS bundle pacing based on the ventricular event.
It is desirable to utilize the AO avoidance process when a set up test detects a risk of atrial over sensing. Optionally, the AA peaks and the A/AA intervals associated with effective AA beats may be displayed to a user may be utilized to program parameters of the AO process automatically. Additionally or alternatively, when atrial over sensing occurs, amplitudes of the ventricular signal and the V/AA amplitude ratio may be displayed to the user. When no atrial over sensing beats are detected, the AO process may be disabled and the VE sensitivity may be programmed by the user.
FIG. 4B illustrates example CA signals collected over atrial and HIS sensing channels and analyzed in accordance with embodiments herein. The atrial EGM 450 represents the CA signals collected over the atrial sensing channel, while the HIS EGM 452 represents the CA signals collected over the HIS sensing channel. An atrial sensed (AS) or atrial paced (AP) event 454 is denoted at the marker “AS or AP” 456 (over a marker channel 458) corresponding to the vertical dashed line. The AS or AP event 454 is detected at 402 (FIG. 4A), followed by the start of the AOA window at 408. During the AOA window, the HIS EGM 452 is analyzed based on an AO a sensitivity profile 460 to detect AA component 462 (at 410). At 412, the one or more processors record an A/AA interval 464 between an onset of the AS/AP event 454 and an end of the AA component 462. At 412, the one or more processors also record an AA peak (as denoted at 466 in connection with the next AA component 468.
The AA components 462, 468 are followed by ventricular events 470, 472 within the HIS EGM. The ventricular events 470, 472 are detected and assigned markers VS at 478, 479. FIG. 4B further illustrates, within the atrial EGM 450, examples of the ventricular event components 474, 476 that appear over the atrial sensing channel.
The CA signals, such as atrial and HIS EGM 450, 452, are obtained for multiple beats over atrial and HIS sensing channels utilizing corresponding electrodes located in the RA and proximate to the HIS. The atrial over sensing process of FIG. 4A analyzes the atrial and HIS EGM 450, 452 over the series of beats during a corresponding AOA windows following AS or AP events in search of AA components to identify AA beats.
Optionally, the process of FIG. 4A may be implemented without extending the AVD at 404. Instead, a normal AV delay may be utilized, and only atrial signal amplitude is measured over the HIS channel. For example, the process would measure atrial signal amplitude in the HIS channel, such as within either the 100/160 ms after an atrial sensed/paced event search window, or before the programmed AV delay, whichever of these two is smallest. In the present example, the process would not measure the atrial oversensing signal on the HIS channel delay, given that pacing by the programmed AV delay could overlap with the end of the atrial signal delay. The ventricular signal amplitude may be measured over the HIS channel during normal ventricular sensing with the AOA process enabled or disabled.
FIG. 4C illustrates example CA signals collected over atrial and HIS sensing channels and analyzed in accordance with embodiments herein. The atrial EGM 480 represents the CA signals collected over the atrial sensing channel, while the HIS EGM 42 represents the CA signals collected over the HIS sensing channel. An atrial sensed (AS) or atrial paced (AP) event 484 is denoted at the marker “AS or AP” (over a marker channel) corresponding to the vertical dashed line. The AS or AP event is detected at 402 (FIG. 4A), followed by the start of the AOA window 486 at 408.
The AOA process (as described further in the above referenced and incorporated patents and applications) may be implemented utilizing a reduced sensitivity profile when searching for AA components over the HIS channel during the AOA window. As explained herein and elsewhere, reducing the AO sensitivity profile is utilized to avoid atrial over sensing and ensure proper ventricular sensing on the HIS channel. For example, during the AOA window 486, the HIS EGM 42 is analyzed based on an AO sensitivity profile 488 to detect AA component 490 (at 410). At 412, the one or more processors record an AA peak for the corresponding AA beat. Following the AOA window 486, the sensitivity profile is shifted from the AO sensitivity profile 488 to a VE sensitivity profile 492. The VE sensitivity profile 492 is utilized to identify ventricular events 496. The AO sensitivity profile 488 utilizes a sensitivity threshold that is set to a higher level, relative to a sensitivity threshold utilized during the VE sensitivity profile 492.
Optionally, the AO sensitivity and AOA window may be programmed manually by the user or automatically using the measurements from prior detection of atrial over sensing.
FIG. 5 illustrates a process for implementing an AO consistency check in accordance with embodiments herein. For example, the AO consistency check may be implemented at 424 in FIG. 4. At 502, the one or more processors determine whether a number of detected AA beats exceeds a predetermined criteria, such as a desired percentage of the total number of beats tested. For example, the one or more processors may determine whether a percent of the tested beats were initially declared to represent AA beats that are potentially indicative of AO. When the number of AA beats relative to the total number of tested beats exceeds the threshold, flow moves 504. Alternatively, when the number of AA beats, relative to the total number of beats, falls below the threshold, flow moves to 514.
At 504-508, the one or more processors apply a consistency criteria to the AA beats to determine a number of the AA beats that are indicative of consistent AO.
At 504, the one or more processors identifies the AA beats, from at least a portion of the AA beats determined in connection with FIG. 4A, that have an A/AA interval that satisfies a first consistency criteria. For example, the one or more processors may determine a mathematical combination (e.g., median or mean) for the A/AA intervals for the set of AA beats. Based on the mathematical combination, the one or more processors determine limits or a desired range to distinguish acceptable AA beats from outlier AA beats. The one or more processors identify a first subset of the AA beats that have an A/AA interval that meets a first consistency criteria, namely the number of AA beats that have an A/AA interval that falls within a desired range or limits of a reference level. For example, the one or more processors may identify the first subset of the AA beats that have an A/AA interval that is within 0.5 to 1.5 of a median A/AA interval. The median A/AA interval may be preprogrammed or automatically determined from the operations at FIG. 4A. The first subset of beats within the desired range/limits of the A/AA interval median are maintained as a first count of candidate AA beats.
At 506, the one or more processors identify the AA beats, from at least a portion of the AA beats determined in connection with FIG. 4a , that have a peak of the AA component (AA peak) that satisfies a second consistency criteria. For example, the one or more processors apply the consistency criteria to identify a subset of the AA beats, for which the AA peak is within the second connection criteria. For example, the one or more processors may determine a mathematical combination (e.g., median or mean) for the AA peaks for the set of AA beats. Based on the mathematical combination, the one or more processors determine limits or a desired range to distinguish acceptable AA beats from outlier AA beats. The one or more processors identify a second subset of the AA beats that have an AA peak that meets a second consistency criteria, namely the number of AA beats that have an AA peak that falls within a desired range or limits of a reference level. For example, the one or more processors may identify the second subset of the AA beats that have an AA peak that is within 0.25 to 1.75 of the median AA peak. The median AA peak amplitude may correspond to the median of the peaks for all of the AA beats. The median AA peak may be preprogrammed or automatically determined from the operations at FIG. 4A. The second subset of beats within the desired range/limits of the AA peak median are maintained as a second count of candidate AA beats.
At 508, the one or more processors count the number of beats in the first subset and the second subset that satisfy the first and second criteria. When the number of beats that satisfy one or both of the first and second criteria exceeds a threshold (e.g., two or more beats), flow moves to 512. Alternatively, when the number of beats that satisfy the one or both of the first and second criteria for below the threshold, flow moves 510.
At 512, the one or more processors declare the current AO process to be operating in an effective manner and sets the parameters of the AO process (utilized in connection with FIG. 4) to be the resultant AO process parameters. For example, the one or more processors may adjust an AO parameter for at least one of i) a start time for the AOA window, a duration for the AOA window, or an AO sensitivity profile utilized to analyze the CA signals over the HIS sensing channel during the AOA window. At 510, the one or more processors determined declare the current AO process to be operating in an inconsistent manner and accordingly disables the AO process from further use until adjustments are made or for a predetermined period of time.
Returning to 502, when the number of detected AA beats falls below the threshold, flow moves to 514. At 514, the one or more processors analyze the peaks of the AA beats. At 514, the one or more processors compare the peaks to a predetermined range, such as 0.5 mV to 1.0 mV. At 516, the one or more processors determine whether the number of AA beats that have an AA peak within the predetermined range satisfy a criteria (e.g., greater than or equal to one). When a sufficient number of the number of AA beats have an AA peak within the predetermined range, flow moves to 512 (where the present AO parameters are utilized). Alternatively, when too few AA beats have AA peaks within the predetermined range, flow moves 510 (where the AO process is disabled).
In accordance with the foregoing, the operations at 502-516 apply consistency criteria to the AA beats to determine a number of the AE beats that are indicative of consistent AO. The operations at 504, 506 and 514, identify a subset of the AA beats, for which one or more characteristic of interest of the AA components fall within limits. At 504, the limits represent a range surrounding a mathematical combination (e.g., mean value) for the A/AA interval for the set of AA beats. At 506, the limits represent a range surrounding a mathematical combination (e.g., mean value) for the AA peaks for the set of AA beats. At 514, the limits represent a predetermined range for the AA peak. At 508 and 516, the process determines whether a number of beats in the subset of the AA beats is indicative of consistent AO.

Automatic Pacing Threshold Testing

New and unique aspects herein relate to stimulation devices and corresponding methods related to HIS bundle pacing. Among other things, the present methods and devices provide for automatic determination of HIS bundle capture thresholds, for configuring stimulation devices based on determined capture thresholds, for identifying different capture types in response to application of pacing impulses of varying energies, and other related features and functions. Aspects may be implemented in any suitable stimulation device including, but not limited to, implantable dual chamber and multi-chamber cardiac stimulation devices as well as external programming units for such stimulation devices. Certain cardiac pacemakers and defibrillators incorporate a pacing lead in the right ventricle and may also include a second lead in the right atrium. High-burden right ventricle apical pacing may contribute to the development of pacing-induced cardiomyopathy and symptoms associated with heart failure (HF). Several pathophysiologic mechanisms have been implicated in the development of pacing-induced HF, each of which likely stems from non-physiological electrical and mechanical activation patterns produced by right ventricle pacing. HIS bundle pacing (HBP) has been shown to restore physiological activation patterns by utilizing a patient's intrinsic conduction system, even in the presence of bundle branch block. HBP has also been shown to provide significant QRS narrowing, with improved ejection fraction.
Another possible clinical application of HBP is cardiac resynchronization therapy (CRT). Conventional CRT systems include pacing from both a right ventricular and a left ventricular lead and have been shown to be most effective for patients exhibiting a wide QRS complex and left bundle branch block. HBP has also been shown to be effective at narrowing the QRS complex in patients with left bundle branch block, likely due to restoration of conduction through the Purkinje fibers, which include right and left bundle fibers that are longitudinally dissociated. Therefore, what is thought of as left bundle branch block, can be a result of a proximal blockage within the HIS bundle that eventually branches to the left bundle. By pacing the HIS bundle distal to the blockage, a normalized QRS complex can be achieved in some patients. Theoretically, this pacing mode may provide even better results than known CRT treatments, as activation propagates rapidly through natural conduction pathways.
Depending on electrode position, pacing output, patient physiology, and other factors, pacing impulses delivered to the HIS bundle may result in capture of different cardiac tissue. As used herein, the term “capture” refers to when a pacing impulse has sufficient energy to depolarize cardiac tissue, thereby causing the depolarized cardiac tissue to contract. In the context of HBP, pacing of the HIS bundle will generally result in one of four capture scenarios: non-selective HIS bundle capture, selective HIS bundle capture, myocardium-only capture, or loss of capture (or non-capture). Non-selective capture refers to when a pacing impulse results in capture of both the HIS bundle and the local myocardium surrounding the HIS bundle. Because of the simultaneous depolarization of the HIS bundle and myocardium, non-selective HIS bundle capture generally results in a combined or condensed electrical response as compared to normal heart activity in which the HIS bundle and myocardium are depolarized sequentially, Accordingly, non-selective HIS bundle capture may be characterized by a shortened delay between application of the pacing impulse and ventricular depolarization (e.g., on the order of 20 ms) because the myocardial depolarization propagates immediately without exclusively traveling through the HIS-Purkinje system. Nevertheless, because the HIS bundle is stimulated and captured, the QRS duration is similar to the native QRS duration but may be slightly longer due to the myocardial excitation (e.g., 70-120 ms). In contrast, selective HIS bundle capture refers to exclusive capture of the HIS bundle without depolarization of the surrounding myocardial tissue. With selective HIS bundle capture, the stimulus to ventricular depolarization interval is virtually the same as the native delay between HIS bundle activation and subsequent ventricular depolarization and the QRS duration is essentially identical to the native QRS duration. In myocardium-only capture, the tissue surrounding the HIS bundle is captured without capturing the HIS bundle itself, resulting in slow or delayed signal conduction and activation. Finally, loss of capture generally refers to circumstances in which the applied stimulus is insufficient or otherwise unable to elicit a response. In such cases, backup pacing may be applied. For patients with branch bundle block or similar conduction disorders, the foregoing capture types may be further characterized by whether they result in correction of the conduction disorder. For example, a pacing impulse may result in any of non-selective HIS bundle capture with correction, non-selective HIS bundle capture without correction, selective HIS bundle capture with correction, or selective HIS bundle capture without correction.
While both selective and non-selective HIS bundle capture may be used to improve cardiac function, selective HIS bundle capture is generally preferred as the corresponding response more closely approximates natural heart function. However, due to the complexity and dynamic nature of certain cardiomyopathies and cardiac anatomies, selective HIS bundle capture may not be possible or, if possible, at one time, may no longer be possible as a patient's condition changes over time. Moreover, a patient's condition may also progress such that HIS bundle capture (whether selective or non-selective) may become unavailable and, as a result, direct ventricular pacing may be required.
In light of the foregoing, this methods and apparatuses are directed to optimizing HBP. More specifically, this disclosure describes stimulation devices capable of HBP and processes that may be implemented by such stimulation devices to initialize device settings. To do so, stimulation devices or a programming unit in communication with the stimulation device executes a capture threshold test in which response data is collected for a range of pacing impulse energies (e.g., a range of pacing impulse voltages, pacing impulse pulse widths, or combinations thereof). In certain implementations, the response data may include unipolar, bipolar, or both unipolar and bipolar responses (e.g., electrograms) recorded and stored by the stimulation device or programming unit. Transitions between capture types are then identified by analyzing changes in response characteristics for the various pacing impulse energy settings that were tested. Based on the number of observed transitions, the nature of the changes indicating the transitions (e.g., how the particular response characteristics change), an initial capture type, and/or other similar factors, the capture pacing impulse energies may then be assigned a capture type. The stimulation device or programming unit may then identify capture thresholds based on the pacing impulse energies at which transitions between different capture types occur and calibrate or adjust stimulation device settings to the best available pacing impulse energy (e.g., the lowest energy (the lowest voltage, pulse width, or combination thereof) for which HBP capture is achieved) according to the assigned capture types and/or identified capture thresholds. By relying on response data obtained from the patient, the settings of the stimulation device are specifically tailored to the individual patient and, as a result, improve both pacing reliability and overall life and function of the stimulation device.
Permanent HIS bundle pacing (HBP) has been proven feasible by delivering pacing stimuli at the HIS bundle with an implantable pacing lead and pacemaker. HBP activates the heart through the native HIS-Purkinje conduction system, thus offering the most physiologic pacing approach to correcting electrical dyssynchrony, among other things. HBP has also emerged as a safe alternative to conventional pacemaker therapy by exhibiting a range of clinical and electrophysiological advantages over conventional pacemaker therapy.
In conventional right ventricle (RV) pacing applications, implantable pacemakers may execute algorithms that automatically measure capture thresholds and apply a small safety margin to ensure RV capture. Such pacemakers may also include algorithms that automatically detect loss of capture (LOC). Among other things, such algorithms may provide backup pacing, adjust pacing output to ensure capture, or trigger automatic capture threshold searching when LOC recovery pacing output is too high.
However, conventional pacemaker-based algorithms are generally inappropriate and not readily adaptable for use in HBP applications due to differences in the response of the HIS bundle and local surrounding myocardium to pacing (as compared to other cardiac tissue) and other related complexities associated with HBP. Therefore, existing automatic capture threshold testing approaches implemented in RV pacing applications generally do not work for HBP applications. Accordingly, a new capture management approach is required for HBP applications. Such an approach should preferably result in HBP with minimal pacing output to improve overall battery and device life, among other things.
Pacing of the HIS bundle may result in a range of capture scenarios depending on various factors including, among other things, the physiology of the heart, the energy of the pacing impulse, whether the patient has any cardiac conditions affecting conduction, and the like. For example and as previously discussed, for patients with healthy conduction system (e.g., as exhibited by a narrow/normal QRS width), pacing of the HIS bundle may result in one of four general scenarios. First, selective capture may occur in which only the HIS bundle is captured. By capturing only the HIS bundle, subsequent conduction along the HIS/Purkinje system is the same or substantially similar to normal sinus beats. Second, non-selective capture may occur in which both the HIS bundle and local myocardium are captured. The resulting ventricular conduction is substantially similar to normal sinus beats but capture of the local myocardium activation adds a small delta wave prior to the main QRS complex. However, because the conduction speed of HIS-Purkinje system is much faster than that of the myocardium, there is little to no difference in clinical outcome between selective and non-selective HIS bundle capture. Third, myocardium-only capture may occur in which the myocardium is captured without capturing this HIS bundle, resulting in relatively slow/delayed activation of the ventricles. Finally, a loss of capture may occur in which neither the myocardium nor the HIS bundle is captured. For patients with bundle branch block (BBB) or other similar conduction-related issues (e.g., as exhibited by a wide/long QRS duration), each of the selective and non-selective cases may be further classified as resulting in a response with or without correction of the BBB.
Conventionally, the HBP responses discussed above and the corresponding capture thresholds are identified and diagnosed in-clinic by healthcare professionals using relatively complicated electrocardiogram systems, such as 12-lead surface ECGs. HBP pacing devices are then configured to implement HBP according to the capture thresholds identified during such testing. In addition to such approaches being time-consuming and complicated, if subsequent adjustments to a device's settings are required, a patient typically has to revisit the clinic for the healthcare professional to repeat the capture threshold test. Moreover, to account for changes that may occur between such visits, healthcare professionals may set pacing settings to include a large safety margin, e.g., by adjusting impulse energy settings well above that required to achieve a desired capture result. While such safety margins may be sufficient to account for changes when they occur, such over-stimulation is otherwise inefficient, leading to reduced battery and device life.
Devices and methods are provided herein to address the various issues identified above, among others. More specifically, the present disclosure is directed to methods of performing automatic capture threshold testing for determining efficient settings for stimulation devices for implementing HBP. In certain implementations, the automatic capture threshold testing methods described herein may be executed by the stimulation device itself. Notably, such a device-based approach eliminates or reduces the need for a patient to revisit a clinic or healthcare professional to adjust settings of their stimulation device. Moreover, the device-based approach enables the device to execute the capture threshold test itself (e.g., periodically, in response to a loss or change in capture, etc.) and to dynamically adjust the settings of the stimulation device between clinic visits. By doing so, the need for a significant safety margin is reduced and the stimulation device may be operated in a more efficient manner as compared to conventional pacing approaches.
While the example implementations of the present disclosure focus primarily on implementation in stimulation devices and implementation in the stimulation device carries certain advantages, it should be appreciated that the methods discussed herein may also be implemented by devices capable of communicating with a stimulation device. For example, the process methods of performing automatic capture threshold testing discussed herein may be implemented in programmers or similar devices adapted to monitor, receive data from, and configure stimulation devices.
Systems and methods according to the present disclosure leverage observed changes in the heart's response to different pacing impulse energies resulting to identify capture thresholds and corresponding pacing settings. For example, in one implementation, pacing impulses are applied using a range of pacing impulse energies and one or both of a unipolar and bipolar electrogram (EGM) are measured after each impulse using the HIS bundle lead. The collected response data is then analyzed to determine changes in characteristics of the measured responses indicative of a change in capture type between pacing impulse energy settings. The stimulation device may then be automatically configured based on the results of the analysis to achieve the best available capture scenario using the lowest pacing impulse energy.
For example, in one implementation, the stimulation device may apply pacing impulses at different energies (e.g., starting at maximum pacing impulse energy and gradually decrementing the pacing impulse energy until a loss of capture occurs) and may record one or both of a unipolar and a bipolar EGM for each pacing impulse energy. The stimulation device may then analyze the data to determine when changes in certain characteristics of the unipolar and bipolar responses have occurred. For example, in one implementation, each of a unipolar width and a bipolar stim-to-peak time (as measured from the unipolar and bipolar EGMs, respectively) may be measured and changes (e.g., a relative change exceeding about 10%) in one or both of the unipolar width and the stim-to-bipolar peak time may be used to identify when a transition between capture types has occurred. As discussed below in further detail, in at least certain implementations of the present disclosure, a capture type may then be associated with each pacing impulse energy based on the number of identified transitions, an initial capture type (e.g., a capture type achievable using a relatively high pacing impulse energy), known information regarding the patient (e.g., whether the patient has a branch bundle block or similar conduction-related condition), and other information. The stimulation system may then select a preferred pacing impulse energy which, in certain cases, is the minimum pacing impulse energy resulting in a particular capture type (e.g., selective capture, if possible, in patients with normal conduction or selective capture with correction in patients exhibiting branch bundle block or similar conduction-related conditions).
Although unipolar width and bipolar stim-to-peak time are used as examples, it should be appreciated that other characteristics of the response may be used to identify transitions between capture types. For example, and without limitation, unipolar width may be substituted with another response characteristic indicative of total ventricular activation time. Similarly, bipolar peak-to-stim time may be substituted with any suitable response characteristic indicative of the local activation time relative to pacing of the HIS bundle. For example, the bipolar peak-to-stim time may be substituted with a metric for stim-to-onset time, such as unipolar stim-to-onset time. Moreover, either of unipolar or bipolar response data may be used for each response characteristic.
Pacing impulse energy is generally used herein to describe the energy of a given pacing impulse. Pacing impulse energy may be determined as a function of the voltage and the duration (e.g., the pulse width) of the pacing impulse. Accordingly, to the extent the present disclosure discusses modifying pacing impulse energy, such modifications can be made by changing one or both of the voltage or the duration of the pacing impulse. For example, in certain implementations, decreasing the pacing impulse energy of the stimulation device may include reducing a pacing impulse voltage setting while maintaining a pulse width setting. Alternatively, decreasing the pacing impulse energy may instead include reducing the pulse width setting while maintaining a constant pacing impulse voltage. In still other implementations, reducing the pacing impulse energy may include reducing both the voltage and pulse width settings of the stimulation device simultaneously, in an alternating fashion (e.g., reducing voltage for a first set of one or more pacing impulses then reducing duration for a second set of one or more pacing impulses), or in any other suitable sequence.
Notably, in conventional approaches to capture threshold testing, empirical/historical data collected from a wide range of patients is often used to generate templates, determine ranges for response characteristics, or otherwise determine capture type for a given pacing impulse energy. Such approaches inherently rely on some universal cutoff applicable to all patients. In contrast, the approaches described herein rely on relative changes exhibited by a specific patient in response to application of pacing impulses of varying energies. As a result, the disclosed approach may be used to identify the best possible pacing settings for a specific patient, taking into account any abnormalities or idiosyncrasies of the patient that may not be fully reflected in available empirical data and that may cause the patient to deviate from any sort of general standard.
The approaches to capture threshold testing and device configuration described herein generally rely on the principle that patients exhibit only a limited number of capture sequences as pacing impulse energy is decreased. In other words, a patient will generally exhibit a first capture type at relatively high pacing impulse energy and will transition to one or more capture types (including loss of capture) as pacing impulse energy is decreased.
For patients with substantially intact conduction systems (e.g., patients exhibiting narrow/normal QRS widths), such transitions are summarized below in Tables 1a and 1b. For purposes of Tables 1a and 1b, nonselective capture is indicated as “NS”, selective is indicated as “S”, myocardium-only capture is indicated as “M”, and loss of capture is indicated as “LOC”.

TABLE 1a

Capture Type Transitions for Normal
Conduction (Single Transition Cases)

	Starting Capture Type	After Transition

1.	NS	LOC
2.	S	LOC
3.	M	LOC

TABLE 1b

Capture Type Transitions for Normal
Conduction (Two-Transition Cases)

	Starting Capture Type	After 1^stTransition	After 2^nd Transition

1.	NS	M	LOC
2.	NS	S	LOC

As illustrated in Table 1 a, the single transition cases generally include transitioning from one capture type (non-selective, selective, or myocardium-only) to a loss of capture. In contrast, the two-transition cases are only applicable for patients for which non-selective capture is possible, as each of selective and myocardium-only capture necessarily transition to loss of capture only as pacing impulse energy is decreased. As indicated in Table 1 b, the transitions in such cases include transitioning from non-selective capture to one of myocardium-only or selective capture and then subsequently transitioning to loss of capture.
Tables 2a-2c, below, provides a similar summary of possible transitions for patients with conduction issues, such as branch bundle block. In contrast to Tables 1a and 1b, Tables 2a-2c further indicate whether non-selective and selective capture is with or without correction (“w/corr.” or “w/o corr.”, respectively).

TABLE 2a

Capture Type Transitions for BBB Patients
(Single Transition Cases)

		Starting Capture Type	After Transition

1.	S	(w/corr.)	LOC
2.	S	(w/o corr.)	LOC
3.	NS	(w/corr.)	LOC
4.	NS	(w/o corr.)	LOC

	5.		M	LOC

TABLE 2b

Capture Type Transitions for BBB Patients (Two-Transition Cases)

Starting Capture	After 1^st	After 2^nd
Type	Transition	Transition

1.	S	(w/corr.)	S	(w/o corr.)	LOC
2.	NS	(w/corr.)	S	(w/corr.)	LOC
3.	NS	(w/corr.)	NS	(w/o corr.)	LOC
4.	NS	(w/corr.)	S	(w/o corr.)	LOC

5.

NS

(w/corr.)

M

LOC

6.

NS

(w/o corr.)

S

(w/o corr.)

LOC

	7.	NS	(w/o corr.)	M	LOC

TABLE 2c

Capture Type Transitions for BBB
Patients (Three-Transition Cases)

Starting	After 1^st	After 2^nd	After 3^rd
Capture Type	Transition	Transition	Transition

1.	NS (w/corr.)	S	(w/corr.)	S (w/o corr.)	LOC
2.	NS (w/corr.)	NS	(w/o corr.)	S (w/o corr.)	LOC
3.	NS (w/corr.)	NS	(w/o corr.)	M	LOC

Similar to Table 1a, the single transitions possible in cases where patients have a conduction-related issue generally include transitioning from one type of capture to a loss of capture. As indicated in Tables 2a and 2b, additional cases in which correction is lost arise in the context of patients with conduction related issues. Notably, once correction is lost, it is generally not regained as pacing impulse energy is further decreased.
With the foregoing in mind, FIGS. 6 and 7 are flow charts that illustrate methods that may be implemented together to configure a stimulation device for purposes of providing HIS bundle pacing. More specifically, FIG. 6 illustrates a first method 600 in which pacing impulses are applied at different energies and corresponding responses are measured and recorded. FIG. 7 illustrates a second method 700 in which the results, such as those obtained from the method 600 of FIG. 6, are analyzed and classified to determine pacing settings for the stimulation device.
Referring first to FIG. 6, the method 600 generally begins with initializing the pacing impulse energy setting of the stimulation device (operation 602). Although the initial pacing impulse energy setting may vary, in at least certain implementations of the present disclosure, the initial pacing impulse energy setting is the maximum output energy of the stimulation device. For purposes of the following example, pacing impulse energy is controlled based on voltage alone (e.g., by maintaining a constant pulse width) and the initial voltage is assumed to be 7.5V; however, in other implementations and for different devices, the initial pacing impulse energy setting value may differ. In certain implementations, initializing the pacing impulse energy setting of the stimulation device may also include setting an operational mode of the stimulation device. Although specific modes and settings for particular applications may vary, in at least one example implementation, the stimulation device may be set a DDD operational mode with a short A-H delay. In another example implementation, the stimulation device may be set to a WI mode with ventricular overdrive pacing (i.e., pacing of the ventricle occurring at a higher than intrinsic rate).
At operation 604 a pacing impulse is applied to the HIS bundle at the current pacing impulse energy setting and a corresponding response is recorded (operation 606). As indicated in FIG. 6, in at least certain implementations the response includes each of a unipolar and bipolar response, which may be recorded and analyzed as an electrogram (EGM) or similar response data format.
Although the response in FIG. 6 includes both a unipolar and bipolar EGM, in other implementations of the present disclosure, the response data may instead include only one of a unipolar or bipolar response. As discussed below in further detail, subsequent analysis and classification of the response obtained in operation 604 may vary depending on whether bipolar, unipolar, or both bipolar and unipolar data is available.
During recordation of the unipolar and bipolar responses, the stimulation device may generally monitor for a response to the applied pacing impulse (operation 608). In certain implementations, detecting the response may include, among other things, detecting the onset of the local myocardium activation resulting from application of the pacing impulse. Such monitoring may continue until either a response is detected, or a response timeout occurs (operation 610).
When a response is detected, the measured response data is stored, e.g., in memory of the stimulation device (operation 612). If a minimum pacing impulse energy has not yet been reached (operation 614), the pacing impulse energy of the stimulation device is decreased (operation 616). For example and without limitation, decreasing the pacing impulse energy may include one or both of reducing the pacing impulse voltage (e.g., by 0.25V or some other predetermined amount), changing the pacing impulse pulse width, or a combination thereof. After decreasing the pacing impulse energy, a subsequent pacing impulse is applied at the new pacing impulse energy, and the foregoing process of detecting and recording each of a unipolar and bipolar response are repeated. If, on the other hand, a response is obtained for a minimum pacing impulse energy (which may be a minimum pacing voltage, a minimum pulse width, minimum combination of voltage and pulse width, or minimum for any other parameter associated with pacing impulse energy for purposes of the capture threshold test), the stimulation device may proceed to analyzing the results of the test (operation 618).
As previously noted, a timeout may occur when monitoring a response to the pacing impulse applied in operation 604. In other words, a response to the applied pacing impulse may not be detected within a predetermined period of time. If such a timeout occurs, a backup impulse with higher pacing impulse energy may be applied to ensure a heartbeat (operation 620) and the current pacing impulse energy may be classified as resulting in loss of capture (operation 622). In certain implementations, the test may then be terminated, and the stimulation device may proceed to analysis of the test results (operation 618) as further reductions in the pacing impulse energy would be unlikely to result in anything but loss of capture. In other implementations, the test may be terminated in response to detecting loss of capture for a predetermined number of pacing impulse energy settings, e.g., loss of capture for two or more consecutive pacing impulse energy settings.
Analysis of test results, such as those obtained via the method 600 of FIG. 6, can be conducted in various ways; however, FIG. 7 illustrates one example approach 700 to analyzing such results to identify and implement patient-specific settings for a stimulation device. In general, the method 700 is based on an implementation in which the response data includes each of a unipolar and a bipolar response and in which analysis of the response data involves comparing each of the unipolar and bipolar EGM response data for a current pacing impulse energy to those of a next higher pacing impulse energy. If the device identifies a change in one or both of the unipolar or bipolar responses between the different pacing impulse energies, a capture type transition is identified. After such analysis is conducted for each pacing impulse energy, the system classifies each of the pacing impulse energies as resulting in a particular capture type. As discussed below in further detail, such classification may be based on the number of transitions identified, the particular changes indicating the occurrence of the transitions, an initial capture type, and the like. The device may then configure its pacing settings based on the classifications. For example, assuming that one or more pacing impulse energies resulted in selective capture, the device may set its pacing impulse energy to be the lowest energy for which selective capture was achieved.
Referring now to FIG. 7, the method 700 generally assumes that a collection of pacing response data is available for analysis. As previously discussed in the context of FIG. 6, such data may generally include a range of pacing impulse energies and, for each pacing impulse energy, each of unipolar and bipolar EGM response data. However, in other implementations, the response data may include only one of unipolar or bipolar EGM response data. With such response data available, the method 700 generally includes initializing an index for purposes of traversing the data (operation 702). Although other approaches may be implemented, in the specific example of FIG. 7, the index is assumed to be initialized to the second entry of the response data, which in certain implementations may be, the entry corresponding to a pacing impulse energy that is one step below the maximum energy (e.g., the maximum voltage) of the device or a maximum impulse energy used when collecting response data.
At operation 704, the unipolar and bipolar EGM data for the current pacing energy is compared to that of the next highest energy (e.g., by comparing the unipolar and bipolar EGM data for the current index value to that of the previous index).
At operation 706, an analysis is conducted to determine whether a change indicative of a transition is reflected by the two sets of unipolar and bipolar EGM data. More specifically, one or more characteristics of the unipolar response data and one or more characteristics of the bipolar response data are compared between the two sets to see if the different pacing impulse energies elicited substantially different responses. In at least certain implementations, the response characteristics may include the activation time of the local ventricular myocardium in the neighborhood of the HIS bundle and an estimate of the total activation time of the ventricles. Various approaches may be used to measure these characteristics from the collected response data. For example and without limitation, the local activation time of the ventricular myocardium may be measured from any of bipolar stimulation-to-peak time (BSP), bipolar stimulation-to-onset, or unipolar stimulation-to-onset. Similarly and without limitation, total ventricular activation time may be estimated using unipolar width (UW) or differentiated using unipolar maximum positive slope (dv/dt). For purposes of the current example, however, BSP and UW are used as the primary response characteristics for distinguishing between capture types. Nevertheless, it should be appreciated that other implementations of the present disclosure may rely on other response characteristics for distinguishing between capture types, including, but not limited to, any of the other response characteristics noted above or otherwise discussed herein.
The threshold for determining whether a change has occurred in the responses between successive pacing impulse energies may vary between applications and may vary based on the specific response characteristics being compared. The threshold for determining a change may be relative (e.g., a percentage change) or absolute between the responses. Also, depending on the characteristics of interest, a change may be based on any of an increase in the characteristic, a decrease in the characteristic, or any other suitable change.
In at least one specific implementation, a change is considered to have occurred if at least one response characteristic of interest changes between pacing impulse energies by at least about 10% (or an absolute equivalent for the response characteristics of interest). So, for example, in the current example in which BSP and UW are the characteristics of interest, a change of at least about 10% between responses is considered to indicate a change. During testing in conjunction with development of the concepts herein, it was observed that as pacing impulse energies change, BSP either increases or stays relatively constant (e.g., does not change by more than about 10%) while UW may increase, decrease, or stay constant. Accordingly, for the purposes of the current example, a change in response characteristics is considered to have occurred when BSP increases by at least about 10% between responses and/or if UW either increases or decreases by at least about 10% between responses.
Referring back to FIG. 7, if a change is measured, a transition is noted, and the observed change may be stored (operation 708). For example, the stimulation device may generate a flag, record, or similar indicator for purposes of noting that the current pacing impulse energy resulted in a change in one or more response characteristics. The stimulation device may also store data or measurements describing the change in the response characteristics. For example, the stimulation device may generate a record that indicates that the current pacing impulse energy resulted in a change and that includes related information such as the characteristic that changed, the direction of the change (e.g., increase or decrease), the magnitude of the change (measured in absolute or relative terms), or any other aspect of the change that may be used in further characterizing the change.
The foregoing method may be repeated for each pacing impulse energy for which a response was recorded. For example, in one implementation, the stimulation device determines if the current index is the maximum index (e.g., the index corresponding to the lowest tests pacing impulse energy) (operation 710). If not, the index is incremented (operation 712) and the process of comparing the response for the pacing impulse energy associated with the current index with the response of the next highest pacing impulse energy and determining whether a change has occurred is repeated.
If, on the other hand, the maximum index is reached, the stimulation device determines the capture type for each pacing impulse energy (operation 714). As previously discussed, capture types for ranges of pacing impulse energies generally follow a predetermined pattern. In other words, particular capture types tend to transition along a limited number of known transition sequences. As a result, by knowing the number of transitions that occurred, the change in characteristics associated with the transitions, and, in some cases, an initial capture type (e.g., a capture type associated with a relatively high pacing impulse voltage), capture types may be readily assigned to pacing impulse energies.
The following tables provide different transition paths and the various indications by which they may be identified when UW and BSP are the response characteristics of interest. Tables 3a and 3b provide transitions and indications for patients with substantially normal conduction and for which correction is not required. Tables 4a-4c provide transitions and indications for patients with conduction issues, such as branch bundle block. In each of the tables, the capture types include selective capture (S), non-selective capture (NS), myocardium-only capture (M), and loss of capture (LOC). For each of selective and non-selective capture, Tables 4a-4c further indicate whether the given capture type includes correction (“w/corr.”) or lacks correction (“w/o corr.”). As previously noted, the current example generally relies on bipolar stim-to-peak time (BSP) and unipolar width (UW) as the primary characteristics for identifying transitions. Accordingly, for each of BSP and UW, each transition listed in the tables further includes whether the transition is indicated by each of BSP and UW increasing (+), decreasing (−), or remaining unchanged (=). As previously discussed, an increase or a decrease may, in certain implementations, correspond to a change of at least about 10% in a response characteristic; however, the specific threshold used in identifying a change may vary between applications and patients. In general, it should be understood that for purposes of the present disclosure a characteristic being “unchanged” generally means that any changes to the characteristic fall below the threshold for indicating a change. For example, if a 10% threshold is implemented, any change less than 10% would be considered “unchanged”.

TABLE 3a

Transition Indications for Normal Conduction
(Single Transition Cases)

	Transition	Indication

1.	NS → LOC	BSP + UW−
2.	S → LOC	BSP + UW=
3.	M → LOC	BSP + UW−

TABLE 3b

Transition Indications for Normal
Conduction (Two-Transition Cases)

Transition	1^st	2^nd
Progression	Indication	Indication

1.	NS → M → LOC	BSP = UW+	BSP + UW−
2.	NS → S → LOC	BSP + UW−	BSP + UW=

TABLE 4a

Transition Indications for BBB Patients (Single Transition Cases)

	Transition	Indication

1.	S (w/corr.) → LOC	BSP + UW+
2.	S (w/o corr.) → LOC	BSP + UW=
3.	NS (w/corr.) → LOC	BSP + UW+
4.	NS (w/o corr.) → LOC	BSP + UW−
5.	M → LOC	BSP + UW−

TABLE 4b

Transition Indications for BBB Patients (Two-Transition Cases)

	1^st	2^nd
Transition Progression	Indication	Indication

1.	S (w/corr.) → S (w/o corr.) → LOC	BSP = UW+	BSP + UW=
2.	NS (w/corr.) → S (w/corr.) → LOC	BSP + UW−	BSP + UW+
3.	NS (w/corr.) → NS (w/o corr.) → LOC	BSP = UW+	BSP + UW−
4.	NS (w/corr.) → S (w/o corr.) → LOC	BSP + UW+	BSP + UW=
5.	NS (w/corr.) → M → LOC	BSP = UW+	BSP + UW−
6.	NS (w/o corr.) → S (w/o corr.) → LOC	BSP + UW−	BSP + UW=
7.	NS (w/o corr.) → M → LOC	BSP = UW+	BSP + UW−

TABLE 4c

Transition Indications for BBB Patients (Three-Transition Cases)

	1^st	2^nd	3^rd
Transition Progression	Indication	Indication	Indication

1.	NS (w/corr.) → S (w/corr.) → S (w/o corr.) → LOC	BSP + UW−	BSP + UW+	BSP + UW=
2.	NS (w/corr.) → NS (w/o corr.) → S (w/o corr.) → LOC	BSP = UW+	BSP + UW−	BSP + UW=
3.	NS (w/corr.) → NS (w/o corr.) → M → LOC	BSP = UW+	BSP = UW+	BSP + UW−

Referring to Tables 3a-4c, the process of determining capture types for each pacing impulse voltage (operation 714) may be conducted by first determining the type of patient conduction (e.g., normal or BBB) and determining which table is applicable based on the number of transitions observed during analysis of the response data. For example, if a patient has substantially normal conduction and two transitions were identified during analysis of the response data, the transition and indication information for Table 3b would apply. As another example, if three transitions were identified in a patient known to have BBB, the information in Table 4c would apply.
The specific characteristics of the identified transitions would then be analyzed to determine which transition sequence is applicable. For example, referring to Table 3b, if the transition resulted in an increase in each of BSP and UW, then the transition sequence is most likely NS S LOC. Accordingly, all pacing impulse energies above the pacing impulse energy identified as the first transition would be classified as resulting in non-selective capture, all pacing impulse energies from the first transition pacing impulse energy to the second pacing impulse energy would be classified as resulting in selective capture, and all remaining pacing impulse energies would be classified as resulting in loss of capture.
In certain cases, such as the foregoing example, only one transition needs to be analyzed in order to determine the capture types for each pacing impulse energy. However, in other scenarios, analysis of multiple transitions may be required to determine the applicable transition sequence. For example, each of the NS (w/corr.) S (w/corr.) LOC sequence and the NS (w/o corr.) S (w/o corr.) LOC sequence included in Table 4b share a common indication for their first transition (namely, an increase in BSP and a decrease in UW), but differ in the indication for their second transition (namely, an increase in both BSP and UW for the former and an increase in BSP only for the latter). Accordingly, analysis of multiple transitions may be required to determine the applicable transition sequence.
Certain transition sequences may share all indications and, as a result, may be indistinguishable from each on the basis of the identified transitions alone. In such cases, additional information regarding the patient may be required to determine the applicable transition sequence. For example, in at least one implementation, the capture type corresponding to the maximum pacing impulse energy (or other high pacing impulse energy) may first be identified using any suitable technique. This initial capture type may then be used to identify the correct transition sequence.
In one alternative implementation, the initial capture type may be determined automatically by the stimulation device by conducting a test in which the response elicited by applying the maximum pacing impulse energy (or other high pacing impulse energy) is analyzed in detail, such as by measuring certain characteristics or comparing the response to one or more stored templates to determine its corresponding capture type. Based on this initial capture type, the stimulation device may then be able to distinguish between transition sequences having otherwise similar indications.
In still other instances, neither the transition sequence nor the initial capture type may distinguish between transition sequences. For example, as indicated in Table 4b, the transition sequences NS (w/corr.)→NS (w/o corr.)→LOC and NS (w/corr.)→M→LOC have the same transition indicators and the same initial capture type. In certain implementations, such a result may be addressed by classifying pacing impulse energies between the first and second transitions as resulting in an indeterminate capture type.
Following classification of the pacing impulse energies, the stimulation device identifies a preferred pacing impulse energy setting and sets its pacing settings accordingly (operation 716). Selection of a pacing impulse energy setting may include identifying the lowest pacing impulse energy resulting in the “best” available capture type. In patients with intact conduction systems, the stimulation device may identify the lowers pacing impulse energy for which selective or non-selective capture was achieved and program the stimulation device's pacing settings accordingly. In patients with branch bundle block or similar conduction issues, corrective results are generally preferred over non-corrective results. Therefore, the stimulation device may identify the lowest pacing energy that leads to capture (either selective or non-selective) and correction and program the stimulation device's pacing settings accordingly.
In certain implementations, a margin of safety may be applied to the selected pacing impulse energy. To do so, the pacing impulse energy setting of the stimulation device may be set higher (e.g., 10-20% higher) than the optimal pacing impulse energy identified based on the response data (e.g., by increasing the voltage and/or the pulse width over that corresponding to the selected pacing impulse energy). In certain implementations, such a margin of safety may be applied when a beat-by-beat capture management mode of the stimulation device is subsequently activated in which pacing is applied and monitored continuously. In general, however, the foregoing approach results in the identification and implementation of pacing settings for optimal heart function for the specific patient while improving overall life and functionality of the stimulation device and its battery by avoiding unnecessary overstimulation.
The foregoing capture threshold test can be run manually in-clinic or periodically out-of-clinic. In certain implementations, the response data and/or any particular response characteristics for each capture type obtained during the capture threshold test may be stored as one or more patient-specific templates. Such templates may then be used when the stimulation device actively provides beat-by-beat pacing and capture management. In one specific implementation, during beat-by-beat pacing and capture management, the stimulation device collects response data (e.g., EGM response data) following application of pacing impulses and analyzes the collected response data.
In one implementation, the stimulation device analyzes the response data collected during beat-by-beat pacing by comparing the collected response data to data collected during the capture threshold test. For example, as noted above, as part of the capture threshold test, the stimulation device may determine and store values or ranges of values of response characteristics that indicate particular capture types. The stimulation device may then compare the response data collected during beat-by-beat pacing to the values identified during the capture threshold test to classify the pacing response, to determine when HIS bundle capture has been lost (e.g., when myocardium only capture has occurred), and/or when there has been a loss of capture. To the extent a loss of HIS bundle capture or total loss of capture occurs, the stimulation device may take appropriate recovery actions. Such recovery actions may include, without limitation, increasing the pacing impulse energy to regain capture or delivering one or more back-up pacing impulses.
In one specific example, following initial calibration of a stimulation device, the stimulation device may continuously or periodically measure unipolar and/or bipolar responses resulting from applied pacing impulses. The stimulation device may further determine the resulting capture type for each pacing impulse. If the stimulation device identifies a change in capture type (e.g., from selective or non-selective capture to myocardium only capture of loss of capture), the stimulation device may execute the capture threshold test describe above to identify new pacing impulse energy settings to regain capture. The stimulation device may also be configured to execute the capture threshold test in response to identifying a loss of capture (or predetermined number of loss of capture events).
The example method discussed above generally relies on the use of both unipolar and bipolar EGM characteristics to identify transitions between capture types. More specifically and as illustrated in Tables 3a-4c, the foregoing example relies on changes in unipolar width (UW) and bipolar stim-to-peak time (BSP) to detect changes in capture type. However, as previously discussed, other characteristics may be used to detect changes in capture type.
In certain implementations, capture threshold tests according to the present disclosure may instead rely on characteristics of a unipolar response (e.g., a unipolar EGM) only instead of on a combination of a unipolar and bipolar response. For example and without limitation, instead of BSP and UW, the method may instead be based on unipolar stim-to-onset time (USO) and unipolar width (UW). Similar to Tables 3a-4c, tables 5a-6c list the indications for each transition for a method using USO and UPS

TABLE 5a

Transition Indications for Normal Conduction
(Single Transition Cases)

	Transition	Indication

1.	NS → LOC	USO + UW−
2.	S → LOC	USO + UW=
3.	M → LOC	USO + UW−

TABLE 5b

Transition Indications for Normal
Conduction (Two-Transition Cases)

Transition	1^st	2^nd
Progression	Indication	Indication

1.	NS → M → LOC	USO = UW+	USO + UW−
2.	NS → S → LOC	USO + UW−	USO + UW=

TABLE 6a

Transition Indications for BBB Patients (Single Transition Cases)

	Transition	Indication

1.	S (w/corr.) → LOC	USO + UW+
2.	S (w/o corr.) → LOC	USO + UW=
3.	NS (w/corr.) → LOC	USO + UW+
4.	NS (w/o corr.) → LOC	USO + UW−
5.	M → LOC	USO + UW−

TABLE 6b

Transition Indications for BBB Patients (Two-Transition Cases)

	1^st	2^nd
Transition Progression	Indication	Indication

1.	S (w/corr.) → S (w/o corr.) → LOC	USO = UW+	USO + UW=
2.	NS (w/corr.) → S (w/corr.) → LOC	USO + UW−	USO + UW+
3.	NS (w/corr.) → NS (w/o corr.) → LOC	USO = UW+	USO + UW−
4.	NS (w/corr.) → S (w/o corr.) → LOC	USO + UW+	USO + UW=
5.	NS (w/corr.) → M → LOC	USO = UW+	USO + UW−
6.	NS (w/o corr.) → S (w/o corr.) → LOC	USO + UW−	USO + UW=
7.	NS (w/o corr.) → M → LOC	USO = UW+	USO + UW−

TABLE 6c

Transition Indications for BBB Patients (Three-Transition Cases)

	1^st	2^nd	3^rd
Transition Progression	Indication	Indication	Indication

1.	NS (w/corr.) → S (w/corr.) → S (w/o corr.) → LOC	USO + UW−	USO + UW+	USO + UW=
2.	NS (w/corr.) → NS (w/o corr.) → S (w/o corr.) → LOC	USO = UW+	USO + UW−	USO + UW=
3.	NS (w/corr.) → NS (w/o corr.) → M → LOC	USO = UW+	USO = UW	USO + UW−

The methods 600 of FIGS. 6 and 700 of FIG. 7 provide a relatively complete analysis of pacing impulse energy settings and their respective responses. More specifically, the methods 600 and 700 identify the capture type for each pacing impulse energy setting and all transitions between capture types. Nevertheless, it should be appreciated that in certain instances, it may only be necessary to identify a particular transition and to configure the pacing impulse energy settings of the pacing device based on the particular threshold.
In applications for patients with narrow QRS, for example, the systems and methods disclosed herein may be modified to identify the minimum pacing impulse energy below which capture of the HIS bundle has been lost and to configure the pacing device to deliver pacing impulses at that minimum pacing impulse energy. In other words, the systems and methods may identify the threshold at which the capture type transitions from either of selective or non-selective capture to either of myocardium-only capture or loss of capture and then set the pacing impulse energy of the stimulation device above the energy at which capture of the HIS bundle is lost. In applications for patients with wide QRS, the systems and methods disclosed herein may be modified to identify the minimum pacing impulse energy below which BBB correction is lost and to configure the pacing device to deliver pacing impulses at that minimum pacing impulse energy. In other words, the systems and methods may identify the threshold at which the capture type transitions from either selective or non-selective capture with correction to a capture type without correction (including any of selective or non-selective capture without correction, myocardium only capture, or loss of capture) and then set the pacing impulse energy of the stimulation device above the energy at which correction is lost.
It should also be understood that while the method 700 is generally described as occurring after the method 600, in certain applications, the two methods may be combined. More specifically, in the foregoing example, the unipolar and/or bipolar response data for multiple pacing impulse energies are first collected using the method 600 of FIG. 6. That response data is then processed to identify transitions using the method 700 of FIG. 7. In other implementations, certain operations of the method 700 of FIG. 7 may be performed as pacing impulse response data is collected such that the process of collecting, analyzing, and classifying the response data may be combined.
FIG. 8, for example, is a flow chart illustrating a method 800 that combines collection and analysis of response data to configure pacing settings of a stimulation device. Similar to the method 600 of FIG. 6, the method 800 of FIG. 8 begins by initializing the pacing energy setting (operation 802), applying a pacing impulse to the HIS bundle (operation 804), and recording corresponding response data (operation 806), the response data including one or both of unipolar and bipolar responses to the pacing impulse. The method 800 also similarly includes monitoring for a response to the applied pacing impulse (operation 808) and determining whether a timeout has occurred (operation 810). In the event of a timeout (e.g., a timeout caused by a loss of capture), the method includes applying a backup impulse (operation 822) before terminating the test process (operation 824). Termination of the test process is discussed below in further detail.
Assuming loss of capture has not occurred and if the pacing impulse applied at operation 804 is the first pacing impulse of the test (operation 818), the pacing impulse energy is decreased (operation 814, e.g., by decreasing the duration and/or amplitude of the impulse as previously discussed in the context of operation 616). A subsequent pacing impulse is then delivered and the process of recording and identifying a response or identifying loss of capture is repeated such that two sets of response data are available, each corresponding to a respective pacing impulse energy.
If response data is available for two consecutive pacing impulse energies, the response data for the pacing impulses is compared (operation 818) to determine whether a capture threshold has been identified (operation 820). The process of comparing consecutive sets of response data generally includes comparing the response data to identify changes indicative of a change in capture type and, more specifically, whether a change in one or more response characteristics between the two response data sets is indicative of a transition between capture types. As discussed in the context of operation 704 of FIG. 7, in certain implementations, the response data for each pacing impulse energy may include both unipolar and bipolar response data. In such implementations, the response characteristics may include, for example and without limitation, each of bipolar stim-to-peak time and unipolar width. In implementations in which only unipolar response data is collected, the response characteristics may include, for example and without limitation, unipolar stim-to-onset time, and unipolar width.
The process of comparing the sets of response data in operation 816 aims to determine whether a capture threshold has been crossed between the two different pacing impulse energies corresponding to the sets of response data. In applications for patients with narrow QRS, for example, the comparison of operation 816 may determine whether a loss of HIS bundle capture occurred between the pacing impulses. To do so, the comparison may include determining whether the response characteristics indicate a transition from either of selective or non-selective capture to myocardium-only or loss of capture occurred in response to reducing the pacing impulse energy (as listed, e.g., in Tables 3a-b for applications including unipolar and bipolar response data or Tables 5a-b for application including unipolar response data only). In applications for patients with BBB, the comparison of operation 816 may determine whether a loss of BBB correction has occurred. For example, the comparison may include determining whether the response characteristics indicate a transition from a corrective response to a non-corrective response in response to reducing the pacing impulse energy (as listed, e.g., in Tables 4a-c (unipolar/bipolar case) and 6a-c (unipolar only case)).
If a threshold is not identified, a check is performed to determine if the lowest pacing impulse energy has been reached (operation 820). If not, the pacing impulse energy is decreased and the process of applying a pacing impulse, measuring the corresponding response, and comparing the response to the previously collected response for purposes of identifying a threshold is repeated.
If, on the other hand, a threshold is identified, minimum pacing impulse energy is reached, or (as noted above) loss of capture occurs, the test process is ended (operation 824). When loss of capture or reaching a minimum pacing impulse energy results in termination of the pacing test, various remedial steps may be initiated including, among other things, generating and transmission of alerts or alarms, restarting of the pacing test, initiation of a backup pacing routine, and the like.
In cases where the test process is terminated in response to identifying a threshold (e.g., a HIS bundle capture threshold or correction threshold), completing the test process at operation 824 includes configuring the pacing settings of the stimulation device based on the threshold. In particular, the pacing settings of the stimulation device are configured such that the pacing impulse energy of the stimulation device is the lowest at which the threshold is not crossed. In applications in which the threshold is for HIS bundle capture or BBB correction, for example, the pacing settings of the stimulation device would be modified to have the lowest pacing energy at which HIS bundle capture or BBB correction are achieved. As a result, the stimulation device is automatically configured to achieve HIS bundle capture or correction efficiently by using the minimum pacing impulse energy possible.
In certain applications of the present disclosure, accuracy of the capture threshold test may be improved by capturing multiple sets of response data for each pacing impulse energy and relying on a statistical combination of such responses in identifying thresholds and capture types. For example, FIG. 9 is a flow chart illustrating a method 9000 for collecting multiple sets of response data for each of a range of pacing impulse voltages and FIG. 10 is a flow chart illustrating a method 1000 in which the results obtained from the method 900 of FIG. 9, are analyzed and classified to determine pacing settings for the stimulation device.
Referring first to FIG. 9, the method 9 generally begins with initializing the pacing impulse energy setting of the stimulation device (operation 902). Although the initial pacing impulse energy settings may vary, in at least certain implementations of the present disclosure, the initial pacing impulse energy is the maximum output energy of the stimulation device or a similar upper bound value.
At operation 904 a first pacing impulse at the current pacing impulse energy setting is applied to the HIS bundle and a first corresponding response is recorded (operation 906). In at least certain implementations the first response includes one or both of a unipolar response and a bipolar, which may be recorded as an EGM or similar data. During recordation of the response, the stimulation device may generally monitor for a response to the applied pacing impulse (operation 908) and, if no such response is detected prior to a timeout (operation 910), a backup impulse may be applied (operation 920) and the current pacing impulse energy setting may be classified as resulting in loss of capture (operation 922). In certain implementations, the test may then be terminated (with each subsequent pacing impulse energy similarly being designated as resulting in loss of capture) and the stimulation device may proceed to analyzing of the test results (operation 918).
When a response is detected, on the other hand, the recorded responses are stored in memory of the stimulation device (operation 912). The stimulation device then determines whether a required quantity of responses (e.g., three) for the current pacing impulse energy have been collected (operation 913). If not, another pacing impulse is applied at the current energy and another response is recorded and stored. If, on the other hand, the quantity of recorded responses for the current pacing impulse energy is met, another check is conducted to see if the current pacing impulse energy is a minimum pacing impulse energy (operation 914). If so, then response collection is complete, and analysis begins (operation 918). If not, the pacing impulse energy is decreased (operation 916) and response data is collected for the reduced energy.
The method 900 results in the collection of multiple sets of response data for each of a range of pacing impulse energies. Following such collection, the collected response data may subsequently be analyzed to identify capture thresholds, to identify preferred pacing impulse energy settings for the stimulation device, or perform similar operations.
In one example implementation, analysis of the multiple sets of response data may include averaging or otherwise mathematically combining the response data for each pacing impulse energy. For example, the response data for each pacing impulse energy may be averaged to generate a mean response for each pacing impulse energy. The combined responses may then be analyzed (such as by using the method 700 of FIG. 7) to identify capture thresholds, capture type transitions, and the like for purposes of determining optimal pacing impulse settings.
In other implementations, analyzing the multiple sets of response data may include identifying pacing impulse energies that resulted in highly variable or otherwise inconsistent responses. To the extent such pacing impulse energies are identified, they may be rejected as potential settings for the pacing impulse energy. In certain implementations, additional analysis may also be conducted to determine whether the inconsistency of the response data for a given pacing impulse energy is a result of poor detection or a result of the pacing impulse energy being at or near a transition energy between two capture types. In the former case, the pacing impulse energy may still be considered a candidate for the optimal pacing impulse energy setting. In the latter case, however, the pacing impulse energy would result in inconsistent and unpredictable capture and would therefore remain rejected as a potential candidate for the optimal pacing impulse energy setting. By way of this process, potentially problematic pacing impulse energy settings (e.g., those that may result in multiple capture types) are avoided and the likelihood that the ultimately selected pacing impulse energy setting will consistently result in the best available capture scenario is increased.
FIGS. 9 and 10 are flow charts of example methods 900, 1000 for collecting and analyzing response data and identifying an optimal pacing impulse setting for a given patient based on the response data. More specifically, the method 900 illustrates a method for collecting response data for a patient that includes multiple response data samples for a range of pacing impulse energies. The method 1000, in contrast, illustrates analysis of such response data for purposes of identifying an optimal pacing impulse energy setting for the patient. The methods 900 and 1000 may be executed by an implanted stimulation device or a programming unit in communication with such an implanted stimulation device.
The method 1000 generally assumes that patient response data is available for analysis. The patient response data generally includes a range of pacing impulse energies and, for each pacing impulse energy, measured responses/samples for each of multiple pacing impulses delivered to the patient at the pacing impulse energy. In certain implementations, each measured response may be stored as one or both of a unipolar or bipolar EGM or as values corresponding to one or both of a unipolar or bipolar EGM.
The method 1000 begins by obtaining response data (operation 1002), such as by executing the response collection method 900 of FIG. 9. Next, any pacing impulse energies resulting in inconsistent responses are excluded (operation 1004). Although the approach to identifying inconsistent responses may vary, in at least one example implementation, a variance metric is calculated for each pacing impulse energy that indicates the variance between the measured responses for the particular pacing impulse energy. If the variance metric exceeds a threshold (or similar value), the pacing impulse energy is excluded from further consideration as a potential pacing impulse energy setting.
The variance metric may be any suitable measure of variability. However, in certain implementations, the variance metric may correspond to the variance for one or more response characteristics and, in particular, response characteristics that may later be used to identify transitions between capture types. For example, as previously discussed, in certain implementations of the present disclosure, transitions between capture types may be identified based on unipolar width and bipolar stim-to-peak. In such implementations, when evaluating a given pacing impulse energy, the variance metric used to determine whether to exclude the pacing impulse energy, may be based on the variance in unipolar width and/or bipolar stim-to-peak time for the pacing impulse energy. For example, if unipolar width and/or bipolar stim-to-peak time vary by 10% or more for the pacing impulse energy, the pacing impulse energy may be excluded.
In certain implementations, the process of excluding inconsistent pacing impulse energies may include generating updated patient response data that omits the pacing impulse energies having inconsistent responses. In other implementations, each of the inconsistent pacing impulse energies may be marked, flagged, or otherwise noted for exclusion from further consideration and analysis.
After identifying and excluding pacing impulse energies exhibiting high variance, a subsequent analysis of the remaining pacing impulse energy candidates may be conducted to determine an optimal pacing impulse energy setting. Such analysis may vary in implementations of the present disclosure; however, the process of analyzing the updated patient response data generally includes comparing characteristics of the response data for consecutive pacing impulse energies to identify transitions between capture types.
In the specific example of the method 1000, analysis begins by initializing an index for purposes of traversing the updated patient response data (operation 1006). The index of the example method 1000 is assumed to be initialized to the second pacing impulse energy of the updated patient response data, i.e., to the pacing impulse energy that is one step below the maximum pacing impulse energy included in the updated patient response data.
The index of the method 1000 is just one approach to traversing the updated patient response data. More generally, any suitable method for comparing responses for consecutive pacing impulse energies of the updated patient response data may be used in implementations of the present disclosure.
At operation 1008, the response data for the current pacing impulse energy is compared to that of the next highest pacing impulse energy to determine whether a capture type transition has occurred. As previously noted, each pacing impulse energy includes a set of measured responses. Accordingly, comparing the responses of any two pacing impulse energies may first include averaging or otherwise combining the set of measured responses for each of the two pacing impulses. Combining a set of measured responses may include generating an average response from which one or more response characteristics may be determined. So, for example, in implementations in which multiple responses are obtained for each pacing impulse energy and each response includes a bipolar and unipolar EGM, combining the set of measured responses may include generating each of an average bipolar EGM and an average unipolar EGM representative of the set. In other implementations, combining a set of measured responses for a particular pacing impulse energy may include calculating average values for one or more response characteristics for each response in the set and, in particular, for response characteristics that may be used subsequently to identify transitions between capture types. For example, in implementations in which transitions are identified using bipolar stim-to-peak and unipolar width, combining a set of measured responses for a particular pacing impulse energy may include calculating each of an average bipolar stim-to-peak value and an average unipolar width representative of the set.
Regardless of how response data for each pacing impulse energy is combined, operation 1008 generally includes comparing the combined response data for the current pacing impulse energy to that of the next highest pacing impulse energy to determine whether a change in response occurred between the two pacing impulse energies (operation 1010). As previously discussed in the context of FIG. 7, the threshold for determining whether a change in response has occurred may vary between applications and particular patients; however, in at least one implementation, a change may be considered to have occurred if a given response characteristics varies between the combined response data of the current pacing impulse energy and the combined response data of the next highest pacing impulse energy by at least about 10%. If a change is identified in operation 1010, the current pacing impulse energy may be marked, flagged, or otherwise noted as corresponding to a transition (operation 1012).
The foregoing operations may be repeated for each pacing impulse energy included in the updated patient response data. For example, in one implementation, if the current index is not the maximum index (i.e., the index corresponding to the last available voltage) (operation 1014), the index is incremented (operation 1016) and the process of comparing response data to identify a change/transition is repeated for the next consecutive pair of pacing impulse energies included in the updated patient response data.
If, on the other hand, the maximum index is reached, the stimulation device determines the capture type for each pacing impulse voltage (operation 1018) and the stimulation device sets its pacing settings based on the available capture types (operation 1020) using processes substantially similar to those discussed above in the context of FIG. 7. As discussed in the context of FIG. 7, such a process may generally include identifying capture types based on the number of observed transitions, the nature of the changes observed between transitions, and/or an initial capture type for the patient. Based on the identified capture types, the stimulation device may then identify the lowest pacing impulse energy that results in the best available capture type for the particular patient (e.g., the lowest pacing impulse energy that maintains capture of the HIS bundle or that corrects a branch bundle block). In contrast to the method of FIG. 7, however, such analysis in the context of the method 1000 excludes from consideration any pacing impulse energies identified as potentially resulting in inconsistent pacing responses. By doing so, the stimulation device improves the likelihood that the selected pacing impulse energy setting will result in consistent pacing and capture/correction.
Certain implementations of the current disclosure may also include additional analysis of pacing impulse energies excluded in operation 1004 to determine whether the inconsistent response data for the excluded pacing impulse energy was a result of poor detection during collection of the response data or a result of the pacing impulse energy corresponding to a transition between capture types. In the former case, the pacing impulse energy may be reconsidered as a potential pacing impulse setting while in the latter case, the pacing impulse energy would remain excluded.
One example approach to the foregoing analysis for a pacing impulse energy may include examining the response data and/or capture type for each of the next highest and next lowest pacing impulse energies. If the next highest and next lowest pacing impulse energies resulted in substantially similar response characteristics or otherwise resulted in the same capture type, the inconsistent response data for the pacing impulse energy in question is likely the result of poor detection. In such cases, the pacing impulse energy may be assigned the same capture type as the neighboring pacing impulse energies and may be reconsidered as a candidate for the pacing impulse energy setting of the stimulation device. Alternatively, new response data for the pacing impulse energy may be collected with the goal of obtaining consistent response data. Such new response data may be subsequently analyzed as discussed above. Conversely, if the next highest and next lowest pacing impulse resulted in substantially different response characteristics or otherwise resulted in different capture types, then the inconsistent response data for the pacing impulse energy in question is likely the result of the pacing impulse energy being at or near a transition energy between capture types. Accordingly, to avoid unpredictable pacing results, the pacing impulse energy in question would remain excluded from consideration as a pacing impulse energy setting.
As discussed above, the method 900 of FIG. 9 and the method 1000 of FIG. 10 provide methods for collecting and then analyzing response data, respectively. According to the methods, a full set of response data is collected and then subsequently analyzed. In other implementations, aspects, and operations of the method 900 of FIG. 9 and the method 1000 of FIG. 10 may be combined such that the process of collecting and analyzing the response data is combined. For example and similar to the method 800 of FIG. 8, the response data for each pacing impulse energy may be analyzed as it is collected. Such analysis may include, among other things, determining whether the samples of response data for the pacing impulse energy are consistent and whether the response data indicates a transition from a previously applied pacing impulse energy, each of which are discussed above.

Non-Sequential Capture Threshold Testing

The HIS capture threshold test is generally performed while the IMD is operating in a DDD mode, utilizing a short AV delay, or the IMD is operating in a WI mode, while utilizing overdrive pacing, both of which introduce added pacing beyond what a patient may normally experience, thereby introducing patient discomfort. Embodiments herein seek to minimize the HIS capture threshold test duration to reduce any patient discomfort. In addition, during HIS capture threshold testing, embodiments herein seek to avoid or limit the Wedensky effect, in which capture thresholds measured, in response to successive HBP at decrementing amplitudes, are usually slightly lower as compared to capture thresholds that are measured, in response to successive HBP at incrementing amplitudes.
As previously noted, threshold searching refers to the process of identifying particular impulse characteristics at which different types of capture occur. In general, such processes include applying a pacing impulse at a starting voltage, measuring the corresponding response (e.g., by IEGM), determining what type of capture (if any) has occurred, and based on the type of capture, modifying the voltage. The process of applying an impulse, measuring, and classifying the response, and adjusting the voltage for a subsequent impulse is repeated to eventually converge on an optimal voltage setting. As described below and in the applications and patents referenced and incorporated herein, approaches to setting the starting voltage, modifying the voltage, and conducting other aspects of the threshold test may be varied.
FIG. 11 illustrates a process for implementing a nonsequential capture threshold test in accordance with embodiments herein. As explained herein, the non-sequential threshold search first performs “rough” decremental HB pacing followed by processing of the evoked response to identify candidate NS, S, and/or Myo capture thresholds. Afterward, the nonsequential threshold search performs “fine” incremental HB pacing starting from below the identified candidate NS, S and/or Myo thresholds to determine the NS, S and/or Myo thresholds more precisely. The capture threshold test is considered a “nonsequential, in that one or both of i) steps between successive HBP pacing pulses are decremented over a portion of the test and then incremented over a portion of the test, and/or ii) steps between a first subset of the HBP pacing pulses have one amplitude, while steps between a second subset of the HBP pacing pulses have a second different amplitude.
Further, the nonsequential capture threshold test manages the upper and lower limits and range for the second subset of HBP pacing pulses based on one or more transitions identified from the first subset of HBP pacing pulses.
For example, the fine incremental HB pacing may terminate at 0.25V above the candidate capture thresholds identified from the rough decremental HB pacing to account for the Wedensky effect. Depending on the underlying capture type, the non-sequential threshold search may be 40% to 50% shorter in duration than a sequential threshold search while achieving the same or better precision.
In general, the method illustrated in FIG. 11 may be viewed as a “rough step down/fine step up” approach to threshold searching. In particular, the method applies a first impulse that achieves non-selective capture and reduces the voltage until capture of the HIS bundle is lost. The step size is decreased, and the step is inverted such that the voltage is increased until capture is regained. This process repeats with progressively smaller step sizes until a final impulse voltage is reached.
At 1102, the one or more processors initialize the HB pacing for a rough capture test.
At 1104, the one or more processors apply one or more HB pacing pulses at an impulse energy (as defined by an amplitude and duration) set for the rough capture test. At operation 1104, the impulse voltage is set to a relatively high initial value (e.g., 7.5V) and a relatively large negative step size (e.g., −1.0V).
At 1106, the one or more processors measures response data for a corresponding response characteristic, also referred to as an evoked response (ER) characteristic of interest. More generally, the one or more processors, in response to applying the first pacing impulse, collect first response data using at least one sensing electrode configured to sense electrical activity of the heart.
In addition, at 1106, the one or more processors determine one or more response characteristics based on the measured response. One response characteristic may represent an ER interval from the time when the HB pacing pulse is delivered to a time when onset of the evoked response is detected (also referred to as onset ER interval). Optionally, the ER interval may be from the time when the HB pacing pulse is delivered to a peak of the evoked response (also referred to as stim-to-peak time). Optionally, the ER interval may be from the time when the HB pacing pulses delivered to an ending point of the evoked response (also referred to as termination ER interval).
Additionally or alternatively, the response characteristic may represent a maximum slope of the evoked response. For example, the maximum slope may be identified as the point at which the derivative of the evoked response is at a maximum level. Additionally or alternatively, the response characteristic may correspond to a morphology of the evoked response, an area under the curve in the evoked response, a duration of the evoked response, a maximum amplitude of the evoked response and the like.
At 1106, the one or processors maintain a list associating each HBP impulse level with the response characteristics. Optionally, at 1106, the one or more processors may classify the response to determine a type of capture that was achieved (e.g., in S, Selective, Myo, LOC). Optionally, the one or more processors may not necessarily classify the response into one of the various types of capture, but instead may simply determine whether the HIS bundle has been captured.
At 1108, the one or more processors determine whether the process has reached the limit for the rough HBP test. For example, upper and lower limits may be defined for the rough HBP test (e.g., 7.5 V and a 0.5 V). At 1108, the one or more processors determine whether the impulse voltage for the current HBP has reached the lower limit. When the limit of the rough test has not been reached, flow returns to 1110. Alternatively, when the limit of the rough test is reached, flow continues to 1112.
At 1110, the one or more processors change the impulse level of the HBP by a rough step. For example, the one or more processors may decrease the impulse level by a negative rough step size (e.g., 1.0 V). Thereafter, a new HBP is applied at the new impulse level at 1104. The operations at 1104-1110 are repeated until the decision at 1108 moves the flow to 1112. The operations at 1104-1110 build a list of HBP impulse levels with corresponding response characteristics, where each of the response characteristic is indicative of a corresponding type of capture achieved by the HBP. Changes in the level of the response characteristic are indicative of changes in a type of capture achieved by the HBP. For example, when the voltage delivered at the HBP is relatively low, the HBP may not achieve capture. When loss of capture is present, the ER interval from the HBP to ER onset may be 140 ms or greater. As another nonlimiting example, when the HBP achieves selective capture, the ER interval from the HBP to ER onset may be between 80 ms and 140 ms. When the HBP achieves nonselective capture, the ER interval may be between 110 ms and 80 ms. Embodiments herein record the ER interval in connection with each level of the HBP as an indication of a type of capture and/or whether a change in the type of capture has occurred.
Additionally or alternatively, the response characteristic may correspond to a maximum slope in the evoked response. Each type of capture may exhibit a corresponding maximum ER slope, with at least some types of capture exhibiting different maximum ER slopes relative to one another. For example, the nonselective capture type may exhibit a substantially greater maximum ER slope, as compared to the maximum ER slope exhibited during myocardial only capture. In addition, the maximum ER slope during selective capture may substantially differ from the maximum ER slope during nonselective capture or during myocardial only capture. When the maximum ER slope is relatively constant between successive HBP, the process may interpret the relatively constant condition as an indication that the capture type is not changing. Alternatively, when the maximum ER slope significantly changes between successive HBP, the process interprets the relative change as an indication that the capture type is changed. As a further example, when the maximum ER slope exhibits a significant decrease (e.g., 20% or more reduction) between successive HBP, the process may interpret the change as an indication that the capture type has changed from nonselective to myocardial only.
By way of example, embodiments herein may distinguish between NS, MYO and LOC capture types by utilizing the ER interval to identify the transition between MYO and LOC capture types and then utilized the ER slope to identify transitions between NS and MYO capture types.
At 1112, the one or more processors analyzes the results of the rough HBP test to identify changes in the response characteristics indicative of transitions between capture types. For example, Table 5 illustrates examples of a collection of rough HBP voltages and fine HBP voltages along with corresponding measurements for ER intervals and ER slopes. Changes in the ER interval, that exceed a limit or step between ranges, are indicative of transitions between capture types. For example, a capture type transition may be indicated when an ER interval switches between first and second ER interval ranges associated with different capture types (e.g., transitioning from a first ER interval range of 60-80 milliseconds to a second ER interval range of 80-140 ms). In the example of table 5, a change in the ER interval is noted, during the rough HBP test, from 4 V to 3V, thereby indicating a transition from nonselective capture to selective capture, with 4V being the nonselective capture threshold Also, during the rough HBP test, from 1 V to 0.5V, a second transition occurs indicating a change from selective capture to loss of capture, with 1V being the selective capture threshold Additionally or alternatively, a transition between capture types may be indicated by changes in the ER interval that exceed certain percentage limits, such as a change of 25% or more between successive HBP test may indicate a transition between capture types.
Additionally or alternatively, the transitions in capture type may be denoted by the changes in the ER slope. For example, certain limits may be defined for ER slopes, where each ER slope range is associated with the corresponding capture type. As another example, a capture type transitions may be indicated by a predetermined percentage change in an ER slope (e.g., a change of 20% or more reduction) (Table 2).
By way of example, in connection with TABLE 5, embodiments herein may distinguish between NS, S and LOC capture types based on the ER interval along, such that ER slope may not be utilized to distinguish between NS, S and LOC capture types.

TABLE 5

HBP			HBP
Voltage	ER	ER	Voltage	ER	ER
(Rough Test)	Interval	Slope	(Fine Test)	Interval	Slope

7.0 V	65	ms	1	mV/ms	0.75	V	140	ms	1.1	mV/ms
6.0 V	65	ms	1	mV/ms	1.0	V	100	ms	1.1	mV/ms
5.0 V	65	ms	1	mV/ms	1.25	V	100	ms	1.1	mV/ms
4.0 V	65	ms	1	mV/ms	3.25	V	100	ms	1.1	mV/ms
3.0 V	100	ms	1.1	mV/ms	3.5	V	65	ms	1	mV/ms
2.0 V	100	ms	1.1	mV/ms	3.75	V	65	ms	1	mV/ms
1.0 V	100	ms	1.1	mV/ms	4.0	V	65	ms	1	mV/ms
0.5 V	140	ms	1.1	mV/ms	4.25	V	65	ms	1	mV/ms

By way of example, in connection with TABLE 6, embodiments herein may distinguish between NS, MYO and LOC capture types by utilizing the ER interval to identify the transition between MYO and LOC capture types and then utilized the ER slope to identify transitions between NS and MYO capture types.

TABLE 6

HBP			HBP
Voltage	ER	ER	Voltage	ER	ER
(Rough Test)	Interval	Slope	(Fine Test)	Interval	Slope

7.0 V	65	ms	1	mV/ms	0.75	V	140	ms	1.1	mV/ms
6.0 V	65	ms	1	mV/ms	1.0	V	65	ms	0.5	mV/ms
5.0 V	65	ms	1	mV/ms	1.25	V	65	ms	0.5	mV/ms
4.0 V	65	ms	1	mV/ms	3.25	V	65	ms	0.5	mV/ms
3.0 V	65	ms	0.5	mV/ms	3.5	V	65	ms	1	mV/ms
2.0 V	65	ms	0.5	mV/ms	3.75	V	65	ms	1	mV/ms
1.0 V	65	ms	0.5	mV/ms	4	V	65	ms	1	mV/ms
0.5 V	140	ms	1.1	mV/ms	4.25	V	65	ms	1	mV/ms

At 1112, the one or more processors identify one or more transition points indicated by the response characteristics. In the example of table 5, transition points are indicated at 4 V and 1 V. Accordingly, the one or more processors define a first HBP fine test generally centered about the lower transition point at 1.0 V and a second HBP fine test generally centered about the upper transition point at 4.0 V. At 1112, the one or more processors define upper and lower limits for each fine test. For example, the upper and lower limits may be set to be a predetermined voltage amount above and below the voltage identified in the rough HBP test as a transition point. In the above example, the upper and lower limits for a first fine test are defined at 0.75 V and 1.2 V, namely 0.25 V above and below the transition point of 1.0 V identified in the rough HBP test.
As another example above, upper and lower limits are defined for a second fine HBP test at 3.25 V and 4.25 V, namely 0.25 V above the transition point of 4.0 V minus the rough decremental step size (4V-1V+0.25V=3.25V) and 0.25 V above the transition point of 4.0 V. The upper and lower limits for the second fine HBP test are not necessarily evenly distributed about the transition point identified during the rough HBP test.
At 1114, the one or more processors apply one or more HB pacing pulses at an impulse level set for the first fine capture test. Continuing the example of table 5, the first HBP voltage is set at 0.75 V.
At 1116, the one or more processors measure a corresponding evoked response to the HBP. In addition, at 1116, the one or more processors determine one or more response characteristic based on the measured response (e.g., ER interval, ER slope). Additionally or alternatively, the response characteristic may correspond to a morphology of the evoked response, an area under the curve in the evoked response, a duration of the evoked response, a maximum amplitude of the evoked response and the like.
At 1116, the one or processors updates the list associating each HBP impulse level, from the fine HBP test, with the corresponding response characteristics. At 1118, the one or more processors determine whether the process has reached the limit for the fine HBP test. For example, upper and lower limits may be defined for the first fine HBP test (e.g., 0.75 V and 1.25 V) with a 0.25 V step between successive HBPs. At 1118, the one or more processors determine whether the impulse voltage for the current HBP has reached the lower limit. When the limit of the fine test has not been reached, flow returns to 1120. In addition, when the limit of the first fine test has been reached, the one or more processors determine whether additional fine test should be performed. In the above example, first and second fine test are to be applied. Accordingly, once the first fine test has been completed, flow returns to 1114 and the operations at 1114-1120 are repeated for the second fine test with upper and lower limits set at 3.25 V and 4.25 V, and with a 0.25 V step between successive HBPs. When all of the fine test have been completed, flow moves to 1122.
At 1122, the one or more processors analyze the results recorded in the table and set the HBP based on the measured responses. For example, in the above table 5, the one or more processors may determine that, at least 1.0 V is needed to achieve selective capture, with voltage levels below 1.0 V resulting in loss of capture. In addition, from the results recorded in table 5, the one or more processors may determine that a stimulus level of 3.5 V is necessary to achieve nonselective capture, with voltage levels above 3.5 V resulting in nonselective capture. The final pacing pulse amplitude is programmed based on the capture threshold of either selective or nonselective capture, whichever is lower, plus a safety margin programmed by the user in clinic. For example, in the above table 5, given a safety margin of 1V, the final pacing pulse amplitude would be programmed to 2.0V (1.0V for selective capture+1V safety margin). In another example, in the above Table 6, given a safety margin of 1V, the final pacing amplitude would be programmed to 4.5V since only nonselective capture is available and the nonselective capture threshold is 3.5V.
In the process of FIG. 11, the rough HBP test is implemented in a decreasing manner, in which a maximum/upper voltage is initially used and stepped down at each successive HBP pulse applied during the rough test. The fine HBP test is implemented in an increasing manner, in which a minimum/lowest voltage is initially used and stepped up at each successive HBP pulse applied during the fine test. In the foregoing example, a large transition steps from 1.25 V up to 3.25 V when switching from the fine test surrounding the lower transition point in the rough HBP up to the upper transition point in the rough HBP.
The foregoing search approach can be applied to identify thresholds for any or all types of capture associated with a patient. For example, it may be desirable to first identify a nonselective capture threshold and/or upper and lower limits for non-selective capture. Next, the process may be repeated to identify a selective capture threshold and/or upper and lower limits for selective capture. Next, the process may be repeated to identify a myocardial only capture threshold and/or upper and lower limits for myocardial only capture.
It should be appreciated that the foregoing threshold search method is provided merely as an example search method that may be used in implementations of the present disclosure. Moreover, to the extent any specific values are included in the foregoing description (e.g., for the initial voltage, initial step size, and the like), such values are included only as examples and should not be viewed as limiting.
As explained herein, in accordance with another aspect herein, a method is provided for identifying pacing thresholds and programming a stimulation device for His bundle pacing (HBP), the stimulation device including a pulse generator, a stimulating electrode in proximity to a His bundle of a patient heart, and at least one sensing electrode adapted to sense electrical activity of the patient heart. The method comprises: applying, using the pulse generator and stimulating electrode, a HBP pulse having an impulse energy to the His bundle; in response to the applying a first pacing impulse, measuring response data for a corresponding evoked response using the at least one sensing electrode; determining a response characteristic based on the response data; adjusting the impulse energy and repeating the applying, measuring and determining, wherein the impulse energy is adjusted in a non-sequential manner between HBP pulses; identifying a change in the response characteristic indicative of a change from a first capture type and a second capture type; and setting one or more parameters of a HBP therapy based on the change in the response characteristic.
In accordance with other aspects herein, the repeating the applying, measuring, determining, and adjusting obtains a collection of response characteristics for a collection of HBP pulses at corresponding different impulse energies. Additionally or alternatively, the adjusting in the non-sequential manner includes at least one rough energy adjustment between first and second HBP pulses and at least one fine energy adjustment between third and fourth HBP pulses. Additionally or alternatively, the at least one rough energy adjustment includes a voltage step-up of at least 1.0V between the first and second HBP pulses and the at least one fine energy adjustment includes a voltage step-down of no more than 0.25V between the third and fourth HBP pulses. Additionally or alternatively, the adjusting applies the at least one rough energy adjustment during a rough HBP test between upper and lower rough limits and applies the at least one fine energy adjustment during a fine HBP test between upper and lower fine limits, the upper and lower fine limits defined based on a transition point identified during the rough HBP test. Additionally or alternatively, the identifying further comprises identifying a rough transition point based on the response characteristic associated with the first and second HBP pulses separated by the at least one rough energy adjustment and refining the rough transition point to a fine transition point based on the response characteristic associated with the third and fourth HBP pulses separated by the at least one fine energy adjustment.
In accordance with new and unique aspects herein, a system is provided. The system comprises: a HIS electrode configured to be located proximate to the HIS bundle and to at least partially define a HIS sensing channel; memory to store cardiac activity (CA) signals obtained over the HIS sensing channel, the memory to store program instructions; and one or more processors that, when executing the program instructions, are configured for: applying, using a pulse generator and a stimulating electrode, a HBP pulse having an impulse energy to the His bundle; in response to applying a first pacing impulse, measuring response data for a corresponding evoked response using at least one sensing electrode; determining a response characteristic based on the response data; adjusting the impulse energy and repeating the applying, measuring and determining, wherein the impulse energy is adjusted in a non-sequential manner between HBP pulses; identifying a change in the response characteristic indicative of a change from a first capture type and a second capture type; and setting one or more parameters of a HBP therapy based on the change in the response characteristic.
Additionally or alternatively, the one or more processors repeat the applying, measuring, determining, and adjusting to obtain a collection of response characteristics for a collection of HBP pulses at corresponding different impulse energies. Additionally or alternatively, the adjusting in the non-sequential manner includes at least one rough energy adjustment between first and second HBP pulses and at least one fine energy adjustment between third and fourth HBP pulses. Additionally or alternatively, the at least one rough energy adjustment includes a voltage step-up of at least 1.0V between the first and second HBP pulses and the at least one fine energy adjustment includes a voltage step-down of no more than 0.25V between the third and fourth HBP pulses. Additionally or alternatively, the adjusting applies the at least one rough energy adjustment during a rough HBP test between upper and lower rough limits and applies the at least one fine energy adjustment during a fine HBP test between upper and lower fine limits, the upper and lower fine limits defined based on a transition point identified during the rough HBP test. Additionally or alternatively, the identifying further comprises identifying a rough transition point based on the response characteristic associated with the first and second HBP pulses separated by the at least one rough energy adjustment and refining the rough transition point to a fine transition point based on the response characteristic associated with the third and fourth HBP pulses separated by the at least one fine energy adjustment.

CLOSING STATEMENTS

It should be clearly understood that the various arrangements and processes broadly described and illustrated with respect to the Figures, and/or one or more individual components or elements of such arrangements and/or one or more process operations associated of such processes, can be employed independently from or together with one or more other components, elements and/or process operations described and illustrated herein. Accordingly, while various arrangements and processes are broadly contemplated, described and illustrated herein, it should be understood that they are provided merely in illustrative and non-restrictive fashion, and furthermore can be regarded as but mere examples of possible working environments in which one or more arrangements or processes may function or operate.
As will be appreciated by one skilled in the art, various aspects may be embodied as a system, method, or computer (device) program product. Accordingly, aspects may take the form of an entirely hardware embodiment or an embodiment including hardware and software that may all generally be referred to herein as a “circuit,” “module” or “system.” Furthermore, aspects may take the form of a computer (device) program product embodied in one or more computer (device) readable storage medium(s) having computer (device) readable program code embodied thereon.
Any combination of one or more non-signal computer (device) readable medium(s) may be utilized. The non-signal medium may be a storage medium. A storage medium may be, for example, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of a storage medium would include the following: a portable computer diskette, a hard disk, a random access memory (RAM), a dynamic random access memory (DRAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.
Program code for carrying out operations may be written in any combination of one or more programming languages. The program code may execute entirely on a single device, partly on a single device, as a stand-alone software package, partly on single device and partly on another device, or entirely on the other device. In some cases, the devices may be connected through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made through other devices (for example, through the Internet using an Internet Service Provider) or through a hard wire connection, such as over a USB connection. For example, a server having a first processor, a network interface, and a storage device for storing code may store the program code for carrying out the operations and provide this code through its network interface via a network to a second device having a second processor for execution of the code on the second device.
Aspects are described herein with reference to the figures, which illustrate example methods, devices, and program products according to various example embodiments. These program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing device or information handling device to produce a machine, such that the instructions, which execute via a processor of the device implement the functions/acts specified. The program instructions may also be stored in a device readable medium that can direct a device to function in a particular manner, such that the instructions stored in the device readable medium produce an article of manufacture including instructions which implement the function/act specified. The program instructions may also be loaded onto a device to cause a series of operational steps to be performed on the device to produce a device implemented process such that the instructions which execute on the device provide processes for implementing the functions/acts specified.
The units/modules/applications herein may include any processor-based or microprocessor-based system including systems using microcontrollers, reduced instruction set computers (RISC), application specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), logic circuits, and any other circuit or processor capable of executing the functions described herein. Additionally or alternatively, the modules/controllers herein may represent circuit modules that may be implemented as hardware with associated instructions (for example, software stored on a tangible and non-transitory computer readable storage medium, such as a computer hard drive, ROM, RAM, or the like) that perform the operations described herein. The above examples are exemplary only, and are thus not intended to limit in any way the definition and/or meaning of the term “controller.” The units/modules/applications herein may execute a set of instructions that are stored in one or more storage elements, in order to process data. The storage elements may also store data or other information as desired or needed. The storage element may be in the form of an information source or a physical memory element within the modules/controllers herein. The set of instructions may include various commands that instruct the modules/applications herein to perform specific operations such as the methods and processes of the various embodiments of the subject matter described herein. The set of instructions may be in the form of a software program. The software may be in various forms such as system software or application software. Further, the software may be in the form of a collection of separate programs or modules, a program module within a larger program or a portion of a program module. The software also may include modular programming in the form of object-oriented programming. The processing of input data by the processing machine may be in response to user commands, or in response to results of previous processing, or in response to a request made by another processing machine.
It is to be understood that the subject matter described herein is not limited in its application to the details of construction and the arrangement of components set forth in the description herein or illustrated in the drawings hereof. The subject matter described herein is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items.
It is to be understood that the above description is intended to be illustrative, and not restrictive. For example, the above-described embodiments (and/or aspects thereof) may be used in combination with each other. In addition, many modifications may be made to adapt a particular situation or material to the teachings herein without departing from its scope. While the dimensions, types of materials and coatings described herein are intended to define various parameters, they are by no means limiting and are illustrative in nature. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the embodiments should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Moreover, in the following claims, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements on their objects or order of execution on their acts.
All references, including publications, patent applications and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.

Claims

What is claimed is:

1. A system, comprising:

a HIS electrode configured to be located proximate to a HIS bundle and to at least partially define a HIS sensing channel;

memory to store cardiac activity (CA) signals obtained over the HIS sensing channel, the memory to store program instructions; and

one or more processors that, when executing the program instructions, are configured for:

utilizing an atrial oversensing (AO) process to analyze the CA signals, obtained over the HIS sensing channel during an AO avoidance (AOA) window, for an atrial activity (AA) component to identify AA beats;

applying a consistency criteria to the AA beats to determine a number of the AA beats that are indicative of consistent AO;

based on the consistency criteria and the number of AA beats indicative of consistent AO, performing at least one of adjusting an AO parameter utilized by the AO process or disabling the AO process; and

managing HIS bundle pacing based on a ventricular event.

2. The system of claim 1, wherein the one or more processors are further configured to determine, for at least a portion of the AA beats, an interval between a paced or sensed atrial (A) event and a characteristic of interest (COI) within the AA component (A/AA interval) of the corresponding AA beat, the applying the consistency criteria including identifying a subset of the AA beats, for which the A/AA interval is within a first connection criteria.

3. The system of claim 1, wherein the one or more processors are further configured to determine, for at least a portion of the AA beats, a peak of the AA component (AA peak) of the corresponding AA beat, the applying the consistency criteria including identifying a subset of the AA beats, for which the AA peak is within a second connection criteria.

4. The system of claim 1, wherein the one or more processors are further configured to identify first and second subsets of the AA beats, for which first and second characteristics of interest (COI) of the AA components fall within the corresponding first and second limits; and determining whether a number of beats in the first and second subsets of the AA beats is indicative of consistent AO.

5. The system of claim 4, wherein the consistency criteria correspond to limits about first and second median values for corresponding first and second COI, the one or more processors further configured to utilize the consistency criteria to distinguish between candidate AA beats and outlier AA beats.

6. The system of claim 1, wherein the one or more processors are further configured to adjust an AO parameter utilized by the AO process when the number of AA beats indicative of AO exceed a threshold, the AO parameter representing at least one of i) a start time for the AOA window, a duration for the AOA window, or an AO sensitivity profile utilized to analyze the CA signals over the HIS sensing channel during the AOA window.

7. The system of claim 1, wherein the one or more processors are further configured to disable the AO process when the number of AA beats indicative of AO fall below a threshold.

8. The system of claim 1, wherein the one or more processors are further configured to manage the HIS pacing by lowering a sensitivity level of a ventricular event (VE) sensitivity profile for the HIS sensing channel.

9. The system of claim 1, wherein the one or more processors are further configured to maintain a count of a number of AA components over a series of beats and, based on the count, determine whether to maintain or change current settings for the length of the AOA window and/or sensitivity profile.

10. The system of claim 1, wherein the AOA window represents a time window enclosing atrial component activity components.

11. A method for pacing a HIS bundle of a patient heart using an implantable medical device (IMD), the method comprising:

obtaining cardiac activity (CA) signals over a HIS sensing channel, the HIS sensing channel utilizing a HIS electrode;

managing HIS bundle pacing based on a ventricular event.

12. The method of claim 11, further comprising determining, for at least a portion of the AA beats, an interval between a paced or sensed atrial (A) event and a characteristic of interest (COI) within the AA component (A/AA interval) of the corresponding AA beat, the applying the consistency criteria including identifying a subset of the AA beats, for which the A/AA interval is within a first connection criteria.

13. The method of claim 12, further comprising determining, for at least a portion of the AA beats, a peak of the AA component (AA peak) of the corresponding AA beat, the applying the consistency criteria including identifying a subset of the AA beats, for which the AA peak is within a second connection criteria.

14. The method of claim 11, wherein the applying the consistency criteria further comprises identifying first and second subsets of the AA beats, for which first and second characteristics of interest (COI) of the AA components fall within the corresponding first and second limits; and determining whether a number of beats in the first and second subsets of the AA beats is indicative of consistent AO.

15. The method of claim 14, wherein the consistency criteria correspond to limits about first and second median values for corresponding first and second COI, the method further comprising utilizing the consistency criteria to distinguish between candidate AA beats and outlier AA beats.

16. The method of claim 11, wherein the performing includes adjusting an AO parameter utilized by the AO process when the number of AA beats indicative of AO exceed a threshold, the AO parameter representing at least one of i) a start time for the AOA window, a duration for the AOA window, or an AO sensitivity profile utilized to analyze the CA signals over the HIS sensing channel during the AOA window.

17. The method of claim 11, wherein the performing includes disabling the AO process when the number of AA beats indicative of AO fall below a threshold.

18. The method of claim 11, wherein the managing the HIS pacing includes lowering a sensitivity level of a ventricular event (VE) sensitivity profile for the HIS sensing channel.

19. The method of claim 11, further comprising maintaining a count of a number of AA components over a series of beats and, based on the count, determining whether to maintain or change current settings for the length of the AOA window and/or sensitivity profile.

20. The method of claim 11, wherein the AOA window represents a time window enclosing atrial component activity components.