CN117835901A - Lead impedance measurement for physiological and device management - Google Patents
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Abstract
An example system includes a memory configured to store a plurality of lead impedances (leadzs) and a processing circuit communicatively coupled to the memory. The processing circuit is configured to determine a first sensed lead z and determine a second sensed lead z. The processing circuit is configured to determine a first difference between the first sensed lead z and the second sensed lead z, and determine the parameter based at least in part on the first difference. The first sensed lead z and the second sensed lead z are sensed during the same first cardiac cycle or adjacent cardiac cycles of the heart that is receiving the pacing.
Description
Technical Field
The present disclosure relates generally to implantable medical devices, and more particularly to implantable medical devices having one or more leads.
Background
Implantable Medical Devices (IMDs) may be surgically implanted in a patient to monitor one or more physiological parameters of the patient and/or to administer therapy to inhibit one or more symptoms of the patient. For example, an IMD may include a cardiac monitor configured to deliver cardiac pacing or another stimulation therapy to a patient, and/or configured to terminate a tachyarrhythmia by delivering a high energy shock. Such IMDs may include or be coupled to one or more leads that may include electrodes for delivering therapy and/or sensing one or more physiological parameters of a patient. The clinician or patient may use an external computing device to retrieve information collected by the IMD and/or to configure or adjust one or more parameters of the therapy provided by the IMD.
Disclosure of Invention
In general, the present disclosure describes techniques for sensing a physiological parameter of a patient using lead impedance (LeadZ) of an Implantable Medical Device (IMD). The lead z may be used for lead management purposes in an IMD, where periodic measurements of impedance during pacing provide an indication of whether a lead problem has occurred. Lead offset, lead integrity issues, or lead loosening from the IMD may be determined by the change in lead z over time. The lead z may also be used to determine a physiological parameter of the patient. For example, lead z may be used to sense patient respiration to derive contractility physiological indicators, may be used for capture management, effective capture management, rate responsive pacing, rate adaptive AV interval management, selective or regional Left Bundle Branch Block (LBBB) and capture of the his bundle, dragging capture Against Tachycardia Pacing (ATP), perfusion to determine tachycardia, impulse-free electrical activation detection, and the like.
In one example, the present disclosure describes a method comprising: determining a first sensed lead impedance (LeadZ); determining a second sensed LeadZ; determining a first difference between the first sensed lead z and the second sensed lead z; and determining a parameter based at least in part on the first difference, wherein the first sensed lead z and the second sensed lead z are sensed during a same first cardiac cycle of the heart that is receiving the beat.
In another example, the present disclosure describes a system comprising: a memory configured to store a plurality of lead impedances (LeadZ) sensed by the medical device; and processing circuitry communicatively coupled to the memory, the processing circuitry configured to: determining a first sensed lead impedance (LeadZ); determining a second sensed LeadZ; determining a first difference between the first sensed lead z and the second sensed lead z; and determining a parameter based at least in part on the first difference, wherein the first sensed lead z and the second sensed lead z are sensed during a same first cardiac cycle of the heart that is receiving the beat.
In another example, the disclosure describes a non-transitory computer-readable medium storing instructions that, when executed by processing circuitry, cause the processing circuitry to: determining a first sensed lead impedance (LeadZ); determining a second sensed LeadZ;
determining a first difference between the first sensed lead z and the second sensed lead z; and determining a parameter based at least in part on the first difference, wherein the first sensed lead z and the second sensed lead z are sensed during a same first cardiac cycle of the heart that is receiving the beat.
This summary is intended to provide an overview of the subject matter described in this disclosure. It is not intended to provide an exclusive or exhaustive explanation of the apparatus and methods described in detail in the following figures and description. Further details of one or more examples are set forth in the accompanying drawings and the description below.
Drawings
Fig. 1 is a conceptual diagram illustrating a system that may be used to monitor a physiological parameter of a patient in accordance with the techniques of the present invention.
Fig. 2 is a conceptual diagram illustrating an IMD and leads of the system of fig. 1 in more detail.
Fig. 3 is a block diagram illustrating an exemplary external computing device in accordance with the techniques of this disclosure.
Fig. 4 is a schematic diagram illustrating respiratory sensing using lead z in accordance with the techniques of the present disclosure.
Fig. 5 is a schematic diagram showing LeadZ sensing for physiological parameters other than respiration.
Fig. 6 is a schematic diagram showing the pressure and volume changes during the cardiac cycle.
Fig. 7 is a schematic diagram illustrating an exemplary determination of capture of selective or regional LBBB or his bundle.
Fig. 8 is a schematic diagram showing an exemplary determination of the draw of ATP.
Fig. 9 is a flowchart illustrating another example of a configuration technique according to the present disclosure.
Like reference numerals refer to like elements throughout the drawings and description.
Detailed Description
Various medical devices, including Implantable Medical Devices (IMDs) such as pacemakers, may include or be coupled to leads that may include electrodes to provide pacing to a patient's heart and/or to sense a physiological parameter of the patient. The IMD may be powered by a rechargeable battery or a non-rechargeable battery.
Bioimpedance (BioZ) may be used in IMDs for high fidelity acute sensing from different programmable vectors, and may be used to sense certain physiological parameters of a patient, such as respiratory rate. The BioZ may be sensed from a can electrode on the IMD to a coil electrode on the lead and filtered to determine the respiration rate of the patient. However, bioZ can have a relatively high sampling rate and can cause significant current drain on the battery of the IMD, which can prevent continued use of the BioZ. However, in some cases, continuous sensing of physiological parameters may be highly desirable, such as sensing respiratory rate in cardiac patients with sleep apnea, chronic Obstructive Pulmonary Disease (COPD), or other respiratory problems. Thus, different, less power intensive techniques for sensing chronic respiratory rate and other physiological and device parameters may be needed. The loadz may be used to address this need. The lead z is a measure of the impedance between the lead and the tissue. For example, changes in multiple measurements made of the lead z during the cardiac cycle in cardiac capture management, effective capture management, rate responsive pacing, rate adaptive AV interval management, selective or regional Left Bundle Branch Block (LBBB) and capture of the his bundle, dragging capture of anti-tachycardia pacing (ATP), perfusion to determine tachycardia, impulse-free electrical activation detection, and the like are used to derive a physiological indicator of contractility.
In some examples, the lead z may be sensed from the right ventricular ring electrode to the right ventricular coil electrode, however other electrode configurations are also contemplated. The lead z may be sensed during one or more portions of the respective cardiac cycle during pacing of the pacing beats or during the absolute refractory period in the case of sensed beats. The sensed lead z may be acquired at a particular point in the cardiac cycle (e.g., a T-wave peak), at a preset time interval during the cycle (e.g., every 400 ms), or a combination thereof. For long-term measurements of respiration rate, lead z may be used whereby impedance measurements are made on the lead during each pace, or during stimulation on the lead during the absolute non-responsive period of the chamber in which the lead is located after pacing. As described further below, short-term (e.g., intra-beat measurements) and long-term (e.g., during respiration) trends of the lead z may be used to determine one or more physiological parameters of the patient, and pacing may be adjusted accordingly.
Fig. 1 is a block diagram illustrating a system 10 that may be used to monitor a physiological parameter of a patient in accordance with the techniques of the present disclosure. As shown in the exemplary system 10 of fig. 1, in some examples, IMD 16 may be, for example, an implantable cardiac pacemaker, an implantable cardioverter/defibrillator (ICD), or a pacemaker/cardioverter/defibrillator. Although described herein primarily with respect to an implantable cardiac pacemaker, the techniques of the present disclosure may be used with any implantable medical device having leads or leads coupled to a sensor configured to sense lead z.
IMD 16 is connected to leads 18, 20 and 22, and is communicatively coupled to an external computing device 24.IMD 16 senses electrical signals attendant to the depolarization and repolarization of heart 12, such as cardiac Electrograms (EGMs), via electrodes on one or more leads 18, 20, and 22 or the housing of IMD 16. In some examples, IMD 16 may sense a LeadZ between the right ventricular ring electrode and the right ventricular coil electrode. IMD 16 may also deliver therapy to heart 12 in the form of electrical signals via electrodes located on one or more leads 18, 20 and 22 or a housing of IMD 16. The therapy may be pacing pulses, cardioversion pulses, and/or defibrillation pulses. IMD 16 may monitor EGM signals collected by electrodes on leads 18, 20 or 22 and diagnose and treat heart attacks based on the EGM signals. IMD 16 may include a LeadZ circuit 19 configured to determine a LeadZ value based on the sensed signal.
In some examples, IMD 16 includes communication circuitry 17 including any suitable circuitry, firmware, software, or any combination thereof for communicating with another device, such as external computing device 24 of fig. 1. For example, the communication circuitry 17 may include one or more processors, memories, radios, antennas, transmitters, receivers, modulation and demodulation circuitry, filters, amplifiers, and the like for radio frequency communications with other devices, such as the computing device 24.IMD 16 may use such communication circuitry to, for example, transmit one or more advertisements indicating the availability of the IMD for the wireless connection during the time period in which IMD 16 is discoverable. After establishing a wireless connection to external computing device 24, IMD 16 may use communication circuitry 17 to receive data from external computing device 24 to control one or more operations of IMD 16 and/or to send upstream data, such as sensed physiological parameters, to external computing device 24.
In some examples, IMD 16 includes processing circuitry 15. Processing circuitry 15 may be configured to implement functionality attributed to IMD 16 and/or process instructions for execution within IMD 16. For example, processing circuitry 15 may be capable of processing instructions stored in a memory of IMD 16 (not shown). In some examples, the processing circuitry includes a loadz circuit 19. In some examples, processing circuitry 15 may be configured to evaluate EGM signals or other physiological parameters sensed by IMD 16. For example, processing circuitry 15 may determine contractility, analyze capture management of pacing beats, evaluate effective capture of pacing beats, analyze rate-responsive pacing, analyze rate-adaptive atrioventricular intervals, analyze capture of selective or regional LBBB or his bundles, analyze dragging capture of ATP, determine perfusion of tachyarrhythmias, detect pulseless electrical activation (where QRS complexes are not accompanied by meaningful beats), and so forth.
Examples of processing circuitry 15 may include any one or more of the following: a microprocessor, a controller, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA), or an equivalent discrete or integrated logic circuit.
Leads 18, 20, 22 extend into heart 12 of patient 14 to sense electrical activity of heart 12 and/or deliver electrical stimulation to heart 12. In the example shown in fig. 1, right Ventricular (RV) lead 18 extends through one or more veins (not shown), the superior vena cava (not shown) and right atrium 26, and into right ventricle 28. Left Ventricular (LV) lead 20 extends through one or more veins, the vena cava, right atrium 26, and into coronary sinus 30 to a region adjacent the free wall of left ventricle 32 of heart 12. Right Atrial (RA) lead 22 extends through one or more veins and the vena cava and into right atrium 26 of heart 12.
In some examples, the external computing device 24 takes the form of a handheld computing device, a computer workstation, a networked computing device, a smart phone, a tablet, a laptop, an external programmer, or an external monitor that includes a user interface for presenting information to and receiving input from a user. A user, such as a physician, technician, surgeon, electrophysiologist, other clinician, or patient, may interact with external computing device 24 to retrieve physiological or diagnostic information from IMD 16. The user may also interact with external computing device 24 to program IMD 16, such as to select operating parameter values for the IMD. External computing device 24 may contain a processor configured to evaluate EGM signals or other physiological parameters transmitted from IMD 16 to external computing device 24. For example, external computing device 24 may determine contractility, analyze capture management of pacing beats, evaluate effective capture of pacing beats, analyze rate-responsive pacing, analyze rate-adaptive atrioventricular intervals, analyze capture of selective or regional LBBB or his bundles, analyze dragging capture of ATP, determine perfusion of tachyarrhythmia, detect pulseless electrical activation (where QRS complex is not accompanied by meaningful beats), and the like. Although the evaluation of EGM signals or other physiological parameters has been described as being performed by processing circuitry 15 of IMD 16 and by processing circuitry of external computing device 24, in some examples, the techniques of this disclosure may be performed by a combination of processing circuitry 15 and processing circuitry of external computing device 24.
IMD 16 and external computing device 24 may communicate via wireless communication using any techniques known in the art. Examples of communication technologies may include, for example, communications according to personal area network technology, such asOr BLE protocol. Other communication techniques are also contemplated. The external computing device 24 may also communicate with one or more other external computing devices using a variety of known communication techniques, both wired and wireless.
In accordance with the techniques of this disclosure, apparatuses, systems, and techniques for determining parameters using a lead z are described. For example, processing circuitry 15 and/or processing circuitry of external computing device 24 may determine a first sensed lead impedance (lead z), determine a second sensed lead z, determine a first difference between the first sensed lead z and the second sensed lead z, and determine the parameter based at least in part on the first difference. The first sensed lead z and the second sensed lead z may be sensed during the same first cardiac cycle of the heart that is receiving the pacing.
Fig. 2 is a conceptual diagram illustrating IMD 16 and leads 18, 20, and 22 of system 10 in greater detail. In the illustrated example, bipolar electrodes 40 and 42 are positioned adjacent the distal end of lead 18, and bipolar electrodes 48 and 50 are positioned adjacent the distal end of lead 22. In addition, four electrodes 44, 45, 46 and 47 are positioned adjacent the distal end of lead 20. Lead 20 may be referred to as a quadrupolar LV lead. In other examples, lead 20 may include more or fewer electrodes. In some examples, LV lead 20 includes segmented electrodes, e.g., each of a plurality of longitudinal electrode locations of the lead in the segmented electrodes, such as the locations of electrodes 44, 45, 46, and 47, including a plurality of discrete electrodes arranged at respective circumferential locations around the circumference of the lead.
In the illustrated example, electrodes 40 and 44-48 take the form of ring electrodes, and electrodes 42 and 50 may take the form of extendable helix tip electrodes retractably mounted within insulated electrode heads 52 and 56, respectively. Leads 18 and 22 also contain elongated electrodes 62 and 64, respectively, which may take the form of coils. In some examples, each of electrodes 40, 42, 44-48, 50, 62, and 64 is electrically coupled to a respective conductor within the lead body of its associated lead 18, 20, 22, and thereby to circuitry within IMD 16.
In some examples, IMD 16 includes one or more housing electrodes, such as housing electrode 4 (which may also be referred to as a can electrode) shown in fig. 2, which may be integrally formed with an outer surface of hermetic housing 8 of IMD 16 or otherwise coupled to housing 8. In some examples, housing electrode 4 is defined by an uninsulated portion of an outward facing portion of housing 8 of IMD 16. Other separations between insulated and uninsulated portions of housing 8 may be used to define two or more housing electrodes. In some examples, the housing electrode includes substantially all of the housing 8.
The housing 8 encloses a signal generator containing circuitry configured to generate therapeutic stimulation (such as cardiac pacing pulses, cardioversion pulses, and defibrillation pulses) and a sensing module containing circuitry configured to sense electrical signals that accompany depolarization and repolarization of the heart 12. The housing 8 may also enclose a memory for storing the sensed electrical signals. Housing 8 may also enclose communication circuitry 17 for communication between IMD 16 and external computing device 24. For example, the communication circuitry 17 may be configured to communicate via personal area networking technology (such asOr BLE wireless protocol) communicates with the external computing device 24. Additionally, or alternatively, the communication circuitry 17 may be configured to communicate with the external computing device 24 via another wireless technology, such as cellular or local area network wireless technology. IMD 16 may use communication circuitry 17 to communicate with patient devices and/or clinician devices.
IMD 16 senses electrical signals attendant to the depolarization and repolarization of heart 12 via electrodes 4, 40, 42, 44-48, 50, 62 and 64. IMD 16 may sense such electrical signals via any bipolar combination of electrodes 40, 42, 44-48, 50, 62 and 64. Further, any of the electrodes 40, 42, 44 to 48, 50, 62 and 64 may be used in combination with the housing electrode 4 for monopolar sensing. For example, IMD 16 may sense a LeadZ between the right ventricular ring electrode and the right ventricular coil electrode.
The illustrated number and configuration of leads 18, 20, and 22 and electrodes are merely examples. Other configurations, i.e., the number and location of leads and electrodes, are also possible. In some examples, the system 10 may include additional leads or lead segments having one or more electrodes positioned at different locations in the cardiovascular system for sensing the patient 14 and/or delivering therapy to the patient. For example, system 10 may include one or more epicardial or extravascular (e.g., subcutaneous or substernal) leads that are not positioned within heart 12 in lieu of or in addition to intracardiac leads 18, 20 and 22.
Fig. 3 is a block diagram illustrating an exemplary computing device 24 operating in accordance with one or more techniques of this disclosure. In one example, the external computing device 24 includes processing circuitry 102 for executing the application 124 described herein. Although shown in fig. 3 as a separate external computing device 24 for purposes of example, the external computing device 24 may be any component or system that contains processing circuitry or other suitable computing environment for executing software instructions, and for example does not necessarily contain one or more of the elements shown in fig. 3 (e.g., communication circuitry 106; and in some examples, components such as one or more storage devices 108 may not be co-located or in the same rack as other components). In some examples, the external computing device 24 may be a cloud computing system distributed across multiple devices.
As shown in the example of fig. 3, the external computing device 24 includes processing circuitry 102, one or more input devices 104, communication circuitry 106, one or more output devices 112, one or more storage devices 108, and a User Interface (UI) device 110. In one example, the external computing device 24 also includes one or more application programs 124 and an operating system 116 that are executable by the external computing device 24. Each of the components 102, 104, 106, 108, 110, and 112 are coupled (physically, communicatively, and/or operatively) for inter-component communication. In some examples, communication channel 114 may include a system bus, a network connection, an inter-process communication data structure, or any other method for communicating data. For example, components 102, 104, 106, 108, 110, and 112 may be coupled by one or more communication channels 114.
In one example, processing circuitry 102 is configured to implement functions and/or processing instructions for execution within external computing device 24. For example, the processing circuitry 102 may be capable of processing instructions stored in the storage 108. For example, processing circuitry 102 may determine contractility, analyze capture management of pacing beats, evaluate effective capture of pacing beats, analyze rate-responsive pacing, analyze rate-adaptive atrioventricular intervals, analyze capture of selective or regional LBBB or his bundles, analyze dragging capture of ATP, determine perfusion of tachyarrhythmias, detect pulseless electrical activation (where QRS complexes are not accompanied by meaningful beats), and the like. Examples of processing circuitry 102 may include any one or more of a microprocessor, a controller, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA), or equivalent discrete or integrated logic circuitry.
The one or more storage devices 108 may be configured to store information within the external computing device 24 during operation. In some examples, one or more storage devices 108 are described as computer-readable storage media. In some examples, the one or more storage devices 108 are temporary storage, meaning that the primary purpose of the one or more storage devices 108 is not long-term storage. In some examples, one or more of the storage devices 108 are described as volatile memory, meaning that the storage devices 108 do not maintain stored content when the computer is turned off. Examples of volatile memory include Random Access Memory (RAM), dynamic Random Access Memory (DRAM), static Random Access Memory (SRAM), and other forms of volatile memory known in the art. In some examples, one or more storage devices 108 are used to store program instructions for execution by processing circuitry 102. In one example, one or more storage devices 108 are used by software or applications 124 running on external computing device 24 to temporarily store information during program execution.
In some examples, the one or more storage devices 108 further include one or more computer-readable storage media. The one or more storage devices 108 may be configured to store a greater amount of information than the volatile memory. The storage 108 may be further configured for long-term storage of information. In some examples, the one or more storage devices 108 include non-volatile storage elements. Examples of such non-volatile storage elements include magnetic hard disks, optical disks, floppy disks, flash memory, or various forms of electrically programmable memory (EPROM) or Electrically Erasable and Programmable (EEPROM) memory.
In some examples, the external computing device24 further comprise a communication circuit 106. In one example, external computing device 24 utilizes communication circuitry 106 to communicate with IMD 16 or other external computing devices (not shown). Communication circuitry 106 may include a network interface card, such as an ethernet card, an optical transceiver, a radio frequency transceiver, or any other type of device that may send and receive information. Other examples of such network interfaces may include3G, 4G, 5G and WiFi radios.
In one example, the external computing device 24 also includes one or more user interface devices 110. In some examples, the one or more user interface devices 110 are configured to receive input from a user through tactile, audio, or video feedback. Examples of one or more user interface devices 110 include a presence-sensitive display, a mouse, a keyboard, a voice response system, a camera, a microphone, or any other type of device for detecting commands from a user. In some examples, the presence-sensitive display includes a touch-sensitive screen.
One or more output devices 112 may also be included in the external computing device 24. In some examples, the one or more output devices 112 are configured to provide output to a user using tactile, audio, or video stimuli. In one example, the one or more output devices 112 include a presence-sensitive display, a sound card, a video graphics adapter card, or any other type of device for converting signals into a suitable form understandable to humans or machines. Additional examples of one or more output devices 112 include a speaker, a Cathode Ray Tube (CRT) monitor, a Liquid Crystal Display (LCD), or any other type of device that can produce an understandable output to a user.
The external computing device 24 may include an operating system 116. In some examples, the operating system 116 controls the operation of components of the external computing device 24. For example, in one example, the operating system 116 facilitates communication of one or more application programs 124 with the processing circuitry 102, the communication circuitry 106, the one or more storage devices 108, the one or more input devices 104, the one or more user interface devices 110, and the one or more output devices 112.
The application 124 may also include program instructions and/or data executable by the external computing device 24. Exemplary applications 124 executable by the external computing device 24 may include applications configured to perform the techniques of this disclosure. Other additional applications not shown may be included alternatively or additionally to provide other functions described herein, and are not depicted for simplicity.
In accordance with the techniques of this disclosure, processing circuitry 15 and/or processing circuitry 102 may determine a first sensed lead impedance (lead z), determine a second sensed lead z, determine a first difference between the first sensed lead z and the second sensed lead z, and determine a parameter based at least in part on the first difference. The first sensed lead z and the second sensed lead z may be sensed during the same first cardiac cycle of the heart that is receiving the pacing, which may be used to determine the ejection fraction, contractility, or other useful information of that cycle. Additionally, or alternatively, the first sensed lead z and the second sensed lead z may be sensed during different cardiac cycles (e.g., adjacent cycles) of the heart to determine a respiratory condition of the patient.
Fig. 4 is a schematic diagram illustrating respiratory sensing using lead z in accordance with the techniques of the present disclosure. Techniques for respiratory condition measurement using a lead z include sensing the lead z one or more times during each cardiac beat and analyzing the trend of the lead z over a series of cardiac cycles. In some examples, an indication of a phase of the cardiac cycle (e.g., peak of the T wave or peak QRS amplitude), pacing rate (e.g., set time interval), a combination thereof, or the like may be used to determine when to sense the LeadZ. The heart rate will likely be faster than the respiration rate, so there may be multiple beats per respiration cycle, such as about three to five beats per respiration cycle.
From the sensed LeadZ discrete points, the processing circuit 102 (fig. 3) may create a continuous waveform by interpolation between the discrete points. The processing circuit 15 and/or the processing circuit 102 may also process the continuous waveform to determine the respiration or respiration state of the patient 14 (fig. 1). For example, in graph 130, each circle (such as circle 132) represents a lead z sense once per cardiac cycle. The observed periodic oscillations (e.g., peak-to-peak) of the lead z represent changes associated with the respiratory cycle. In graph 140 (post-processing of graph 130), each circle (such as circle 142) located at 0 on the Y-axis represents respiration. Further, a trend change (e.g., decrease or increase) in the lead z over a corresponding respiratory cycle may indicate a respiratory state (e.g., inspiration or expiration). The processing circuit 102 may interpolate between the sensed leadzs, may filter the interpolated signal, and use peak detection, valley detection, or zero crossings to determine the respiration rate, respiration status, etc. of the patient 14.
In some examples, a determination of the patient's respiration rate or state using the lead z may be used to adjust the pacing rate of IMD 16. For example, in normal breathing, the heart rate is uneven. There is a normal up-down variation, which gives a measure of heart rate variability. Including Respiratory Sinus Arrhythmia (RSA). In RSA, the heart rate generally increases during inspiration and decreases during expiration. The mechanism behind this involves a reduced intrathoracic pressure during inspiration, which increases venous return to the heart. This increase in venous return increases contractility due to the Frank-Starling mechanism and heart rate increase. In addition, there may be a slight delay between the precise phase of inspiration and expiration and the increase in heart rate. When the heart is paced at a set heart rate, RSA is lost, which may lead to suboptimal results. By determining the respiration rate or respiration state of the patient based on the lead z, IMD 16 may be configured to slightly increase the pacing rate during inspiration and slightly decrease the pacing rate during expiration to restore RSA. In some examples, this change in pacing rate corresponds to recovered RSA, which may be about plus or minus 2 beats per minute.
As described further below, during a normal cardiac cycle, the change in LeadZ will correspond to the volume within the heart. In addition, periodic oscillations of the LeadZ measurements corresponding to inspiration and expiration may also be imposed on short-term variations of the LeadZ measurements of the normal cardiac cycle during the respiratory cycle. For example, during inspiration there is more venous return and the ventricular volume will generally be greater at the beginning of systole, so the lead z will be lower. Likewise, during exhalation, venous return is less, and ventricular volume will be relatively low at the beginning of systole, so the lead z is relatively high. In addition to the short-term, periodic oscillations associated with ventricular emptying and contractility observed in a single cardiac cycle, this longer-term, breath-based lead z oscillation can also be measured. Utilizing respiratory-based changes and cardiac cycle-based lead z changes may be used to determine the state of inspiration/expiration and the contractility or ejection fraction of the heart and may be used to determine one or more other physiological parameters, the health of the patient, etc. Additionally, or alternatively, such measurements may be used to modify pacing parameters of IMD 16.
In some examples, the respiration rate or respiration state may be observed by measuring the lead z over a plurality of cardiac cycles (at least once per cardiac cycle) and determining a periodic variation of the lead z associated with respiration. For example, IMD 16 may be configured to sense the LeadZ in a common increment at each beat or at multiple times per beat. In some examples, the sensed LeadZ may be sensed during a sensing phase (such as the onset of a T wave, the peak of a QRS complex, etc.); at set intervals (e.g., associated with pacing rates), or a combination thereof. In some such examples, pacing may be overdriven to ensure the likelihood that all beats are paced. The processing circuit 15 and/or the processing circuit 102 may be configured to interpolate between the sensed LeadZ signals to provide an interpolated LeadZ sampling rate, such as 16Hz over a plurality of cardiac cycles. In some examples, processing circuitry 15 and/or processing circuitry 102 may filter the interpolated signal to attenuate any signal outside of the typical respiratory rate. For example, processing circuitry 15 and/or processing circuitry 102 may apply a particular low-pass filter and/or high-pass filter to the interpolated signal. Processing circuitry 15 and/or processing circuitry 102 may then calculate the respiration rate of patient 14 using peak detection, valley detection, or zero crossing detection techniques. By making a lead z measurement at least once per cardiac cycle, such as after ventricular pacing or ventricular sensing, in combination with providing an alternative combination of interpolated lead z measurements, processing circuitry may determine a waveform, such as the waveform of graph 140, that shows peaks that may correspond to respiration, allowing for the determination of respiration rate and respiration cycle. In some examples, IMD 16 may be configured to change the pacing rate to coincide with the respiratory cycle and restore RSA.
Fig. 5 is a schematic diagram showing LeadZ sensing for physiological parameters other than respiration. The LeadZ may be measured multiple times during the corresponding cardiac cycle. For example, a fixed period of time between measurements may be employed to sense the lead z multiple times during a single cardiac cycle. In another example, a second measurement (or more) of the LeadZ may be triggered by a sensed parameter (such as a T wave, peak QRS amplitude, etc.). Graph 150 depicts cardiac activity sensed using a dynamic electrocardiogram monitor. Graph 160 depicts a sensed LeadZ. Graph 170 depicts, for example, an electrocardiogram QRS amplitude sensed by IMD 16.
The data in graph 160 shows two overlapping waveforms, one offset from the other, such as waveform 162 and waveform 164, over the cardiac cycle. Such changes within the beat may be used to determine a physiological parameter or a device-related parameter. For example, processing circuitry 15 and/or processing circuitry of external computing device 24 may determine a first sensed lead z, determine a second sensed lead z, determine a first difference between the first sensed lead z and the second sensed lead z, and determine a parameter based at least in part on the first difference. The first sensed lead z and the second sensed lead z may be sensed during the same first cardiac cycle of the heart. In some examples, the heart is receiving pacing.
In some examples, this shift may represent the instantaneous right ventricular volume at the time of sensing. In this way, the lead z sensed during a time in the cardiac cycle that is inconsistent with pacing or during an absolute non-responsive period may represent the volume of the right ventricle at that point in time. For example, in a typical cardiac cycle, the lead z will start lower at the beginning of systole, then increase to a peak, then decrease during diastole. This periodic intra-beat oscillation of the lead z corresponds to a change in the volume of the heart during the cardiac cycle. Intervention to change the time course of the volume change in the right ventricle (or other chamber) may be measured by making one or more additional lead z measurements during the cardiac cycle. By IMD 16 sensing the LeadZ multiple times during a single cardiac cycle, processing circuitry 15 and/or processing circuitry 102 may in turn determine contractility, ejection fraction, analyze capture management of pacing beats, evaluate effective capture of pacing beats, analyze rate responsive pacing, analyze rate adaptive atrioventricular intervals, analyze selective or regional LBBB or shizandra capture, analyze dragline capture of ATP, determine perfusion of tachyarrhythmias, detect pulseless electrical activation (where QRS complexes are not accompanied by meaningful beats), and the like. Long-term tracking of such physiological parameters (e.g., ejection fraction or contractility) may in turn be used to provide an indication of worsening heart failure.
A description of the functions of each technology and the actual use of each parameter is summarized below. A shrink substitute will now be discussed. There may be a relationship between the real-time high capture frequency impedance signal from multiple vectors across the heart chamber and the contractive surrogate, such as peak or maximum dp/dt (rate of pressure change over time) or volume change. In fact, sensing multiple leadzs during the cardiac cycle may act as a sub-sample to acquire the high capture frequency signal. Processing circuitry 15 and/or processing circuitry 102 may use the subsamples to infer a change in contractility. For example, IMD 16 may sense the LeadZ with the pacing or sensing at another point in time in the same cardiac cycle. The change in lead z between two time points in the beat can be used to infer the change in volume (or contractility value) during the cycle. The range of these changes can be used to establish different values of shrinkage or volume change. For example, IMD 16 may change pacing configurations and sense the LeadZ of each pacing configuration at multiple points in the cardiac cycle. Processing circuitry 15 and/or processing circuitry 102 may select a particular pacing configuration based on the pacing configuration that demonstrates the greatest improvement in contractility.
For example, processing circuitry 15 and/or processing circuitry 102 may change the pacing configuration from a first pacing configuration to a second pacing configuration, wherein the changed pacing configuration is used to pace the heart. The pacing configuration may include a pacing rate and/or electrodes for pacing the heart. The processing circuit 15 and/or the processing circuit 102 may determine the third sensed lead z and determine the fourth sensed lead. The processing circuit 15 and/or the processing circuit 102 may determine a second difference between the third sensed lead z and the fourth sensed lead z and compare the first difference to the second difference. Processing circuitry 15 and/or processing circuitry 102 may select a pacing configuration of either of the first pacing configuration and the second pacing configuration based on the comparison. The third sensed lead z and the fourth sensed lead z may be sensed during the same second cardiac cycle.
Capture management is now discussed. Whether or not a pacing pulse is captured will likely result in a different contractility or time course of chamber volume changes. Processing circuitry 15 and/or processing circuitry 102 may use the change to determine whether a beat was captured. For example, during capture management testing, during or after regular pacing, processing circuitry 15 and/or processing circuitry 102 may compare the difference in changes within the LeadZ beat from beat to beat. If there is a significant difference in this intra-beat change from one beat to the next, processing circuitry 15 and/or processing circuitry 102 may determine that a beat outside of the predetermined range is an unobscured beat. For example, processing circuitry 15 and/or processing circuitry 102 may determine an intra-beat change during a period of known capture (such as during a high pacing output) and compare the intra-beat change to an intra-beat change during a period of unknown capture (such as when the pacing output is low). If the characteristics of the intra-beat change between the two determined intra-beat changes are relatively unchanged for the two time periods, processing circuit 15 and/or processing circuit 102 may determine that capture has been maintained at the power pacing output. If the characteristics of the intra-beat change are relatively different for the two time periods, processing circuitry 15 and/or processing circuitry 102 may determine that capture is likely to have been lost at the power pacing output.
In some examples, processing circuitry 15 and/or processing circuitry 102 may store the value of the intra-beat change in the non-captured beat and compare the intra-beat change established for each new intra-beat change value of the non-captured beat to determine whether the beat was captured. In some examples, processing circuit 15 and/or processing circuit 102 may update the predetermined range based on intra-beat changes in the non-captured beats.
For example, the processing circuit 15 and/or the processing circuit 102 may determine a third sensed LeadZ and determine a fourth sensed LeadZ. The third sensed lead z and the fourth sensed lead z may be sensed during the same second cardiac cycle. The processing circuit 15 and/or the processing circuit 102 may determine a second difference between the third sensed lead z and the fourth sensed lead z and compare the first difference to the second difference. Processing circuitry 15 and/or processing circuitry 102 may determine whether the second difference differs from the first difference by more than a first predetermined amount. Processing circuitry 15 and/or processing circuitry 102 may classify the same second cardiac cycle as a non-captured beat based on the second difference differing from the first difference by more than a first predetermined amount.
For example, processing circuitry 15 and/or processing circuitry 102 may determine whether the first difference is greater than or equal to a predetermined threshold and classify the beat as a non-captured beat based on the first difference being greater than or equal to the predetermined threshold. The processing circuit 15 and/or the processing circuit 102 may update the first predetermined threshold based on the first difference.
Effective capture is now discussed. Similar to the discussion above regarding capture management, processing circuitry 15 and/or processing circuitry 102 may use multiple sensed leadzs during a cardiac cycle to determine whether a pacing beat is not captured, is fully captured, or is pseudo-fused. False fusion capture is an ineffective pacemaker spike on the spontaneous P or QRS complex. For example, processing circuitry 15 and/or processing circuitry 102 may use intra-beat LeadZ variation to classify beats into one of three categories based on the value of the variation value.
For example, the processing circuit 15 and/or the processing circuit 102 may determine a fifth sensed lead z and determine a sixth sensed lead z. The fifth sensed lead z and the sixth sensed lead z may be sensed during the same third cardiac cycle. The processing circuit 15 and/or the processing circuit 102 may determine a third difference between the fifth sensed lead z and the sixth sensed lead z and compare the first difference to the third difference. The processing circuit 15 and/or the processing circuit 102 may determine whether the third difference differs from the first difference by more than a second predetermined amount and less than the first predetermined amount. The processing circuit 15 and/or the processing circuit 102 may classify the same third cardiac cycle as a pseudo-fusion beat based on the third difference differing from the first difference by more than the second predetermined amount and less than the first predetermined amount.
In some examples, processing circuitry 15 and/or processing circuitry 102 may determine a "degree" of pseudo-fusion based on the degree of variation of the intra-beat LeadZ measurement. For example, pacing may be ineffective because the ventricles may have spontaneously depolarized, so pacing does not result in ventricular contractions.
The rate response will now be discussed. If IMD 16 senses the second lead z at a fixed point in time during the cardiac cycle, this may result in a change in lead z during exercise or in different beats when a change in heart rate is desired. The processing circuit 15 and/or processing circuit 102 may monitor the value of the change in the LeadZ within the beat for a relatively long period of time. If the value of the change in the lead z within the beat drifts outside of a predetermined expected range (e.g., if the value differs by a predetermined fixed amount), the processing circuitry 15 and/or processing circuitry 102 may determine that the heart rate of the heart 12 of the patient 14 is insufficient to keep up with the demand. IMD 16 may then vary the pacing rate to correct for intra-beat LeadZ changes and bring the intra-beat LeadZ changes back within the intended predetermined or programmed range.
For example, the processing circuitry 15 and/or the processing circuitry 102 may determine a plurality of sensed leadzs during each cardiac cycle over a period of time. The processing circuitry 15 and/or processing circuitry 102 may determine respective differences between the plurality of sensed leadzs during each cardiac cycle over a period of time. The processing circuit 15 and/or the processing circuit 102 may compare the first respective difference to the second respective difference and determine that the first respective difference differs from the second respective difference by more than a predetermined amount. Processing circuitry 15 and/or processing circuitry 102 may change the pacing rate based on the first respective difference differing from the second respective difference by more than a predetermined amount.
The rate adaptive AV interval will now be discussed. Similar to the techniques for rate response and contractility assessment, the intra-beat changes in the sensed lead z can be used to establish the appropriate AV interval to maximize contractility. For example, the processing circuit 15 and/or the processing circuit 102 may determine a third sensed LeadZ and determine a fourth sensed LeadZ. The third sensed lead z and the fourth sensed lead z may be sensed during the same second cardiac cycle, and a time difference between sensing the first sensed lead z and the second sensed lead z may be equal to a time difference between sensing the third sensed lead z and the fourth sensed lead z. The processing circuit 15 and/or the processing circuit 102 may determine a second difference between the third sensed lead z and the fourth sensed lead z. The processing circuit 15 and/or the processing circuit 102 may compare the first difference to the second difference and determine whether the second difference differs from the first difference by more than a first predetermined amount. Processing circuitry 15 and/or processing circuitry 102 may change the pacing configuration based on the second difference differing from the first difference by more than a first predetermined amount.
Fig. 6 is a schematic diagram 180 showing the pressure and volume changes during the cardiac cycle. For example, if two measurements are taken over a fixed time interval, the processing circuitry 15 and/or processing circuitry 102 may use the difference in intra-beat values of the lead Z to determine a change in volume or contractility between the two time points. Processing circuitry 15 and/or processing circuitry 102 may use the difference in intra-beat values of the lead z to determine whether a beat was captured. In addition, processing circuitry 15 and/or processing circuitry 102 may use the difference in intra-beat values of the lead z to determine other measurements of mechanical effects (e.g., effective capture). Processing circuitry 15 and/or processing circuitry 102 may use the difference in intra-beat values of the lead z to optimize pacing therapy, or perform other techniques of the present disclosure.
In some examples, processing circuit 15 and/or processing circuit 102 may use the difference in intra-beat values to determine whether a stimulation pulse of the ATP series is being carried, to determine whether a cardiac rhythm is accompanied by a beating ventricle, to detect non-pulsed electrical activity, to determine whether a fast rhythm is being perfused, or to determine the necessity of a shock.
Fig. 7 is a schematic diagram illustrating an exemplary determination of capture of selective or regional LBBB or his bundle. For example, processing circuitry 15 and/or processing circuitry 102 may use the difference between the sensed lead z (VP) and the second sensed lead z (IS) at the time of pacing to determine capture. Selective capture is expected to produce a more "normal" electrical activation pattern and thus a stronger contraction. This will result in a higher second impedance measurement and a larger difference from the VP measurement. Nonselective pacing beats would be expected to have less contraction. Thus, the first four beats represent selective capture 190 and the last two beats represent non-selective capture 192. For example, processing circuitry 15 and/or processing circuitry 102 may use the difference in the intra-beat LeadZ to determine the selective capture of the LBBB or his bundle.
For example, the processing circuit 15 and/or the processing circuit 102 may determine a third sensed LeadZ and determine a fourth sensed LeadZ. The third sensed lead z and the fourth sensed lead z may be sensed during the same second cardiac cycle. The processing circuit 15 and/or the processing circuit 102 may determine a second difference between the third sensed lead z and the fourth sensed lead z and compare the first difference to the second difference. Processing circuitry 15 and/or processing circuitry 102 may determine whether the second difference differs from the first difference by more than a predetermined amount. Processing circuitry 15 and/or processing circuitry 102 may determine that the same second cardiac cycle is a non-selective pacing beat based on the second difference differing from the first difference by more than a first predetermined amount.
Fig. 8 is a schematic diagram showing an exemplary determination of the draw of ATP. For example, processing circuit 15 or processing circuit 102 may determine a stall in ATP capture by determining the mode of both VP and IS loadz sense signals. In non-dragging of ATP, ventricular pacing may not be captured, and thus the sensed LeadZ will not be sensed at the same point in time for each cardiac cycle. As a result, there may be a random pattern as shown in graph 200. However, in graph 210, a series of paces of the tow are shown in a more uniform shape.
For example, the processing circuit 15 and/or the processing circuit 102 may determine a third sensed LeadZ and determine a fourth sensed LeadZ. The third sensed lead z and the fourth sensed lead z may be sensed during the same second cardiac cycle. The processing circuit 15 and/or the processing circuit 102 may determine a second difference between the third sensed lead z and the fourth sensed lead z and compare the first difference to the second difference. Processing circuitry 15 and/or processing circuitry 102 may determine whether the second difference differs from the first difference by more than a predetermined amount. Processing circuitry 15 and/or processing circuitry 102 may determine that the same second cardiac cycle is non-dragging antithyroid pulse capture beats based on the second difference differing from the first difference by more than a first predetermined amount.
In a similar manner, processing circuitry 15 may determine whether the tachyarrhythmia is shockable or non-shockable, as to whether the rhythm is perfusing or non-perfusing. The perfusion rhythm will be expected to show ventricular contractions with each beat, and thus should show an up-down pattern between the two sensed leadzs (such as in graph 210), or an up-down amplitude above some predetermined threshold (which may be absolute or relative to the baseline LeadZ amplitude of the patient 14). For example, the processing circuit 15 may determine whether the first difference is greater than or equal to a first threshold and determine the first cardiac cycle as a perfusion beat based on the first difference being greater than the first threshold.
Pulse-free electrical activity is the absence of perfusion pulses in the presence of a cardiac rhythm. However, the heart rhythm may not be a normal rhythm, but may be regular or fast enough to potentially allow normal perfusion. There are many reasons for pulse-free electrical activity, such as mechano-electrolytic dissociation. In this case, IMD 16 may sense loss of regular up-down pattern of multi-lead z sensing during the cardiac cycle (such as in graph 200).
For example, the processing circuit 15 and/or the processing circuit 102 may determine a third sensed LeadZ and determine a fourth sensed LeadZ. The third sensed lead z and the fourth sensed lead z may be sensed during the same second cardiac cycle. The processing circuit 15 and/or the processing circuit 102 may determine a second difference between the third sensed lead z and the fourth sensed lead z and compare the first difference to the second difference. Processing circuitry 15 and/or processing circuitry 102 may determine whether the second difference differs from the first difference by more than a first predetermined amount. The processing circuit 15 and/or the processing circuit 102 may classify the same second cardiac cycle as pulse-free electrical activity based on the second difference differing from the first difference by more than a first predetermined amount.
The timing of multiple lead z sensing during the cardiac cycle of a lead z change within a beat that processing circuit 15 and/or processing circuit 102 may use to determine will now be discussed. In some examples, IMD 16 may overdrive pacing to produce a constant rate and chamber capture. This may be desirable to ensure that the first lead z sensing during pacing is performed consistently during the pacing beat. In the case of intermittent pacing and sensing, the paced beat, leadZ, will be sensed during pacing and during the sensed beat, leadZ sensing will be taken after sensing and during the absolute non-responsive period. The baseline value may vary from beat to beat, so a consistent baseline may be desired.
In another example, IMD 16 may sense the LeadZ at a fixed time after the first event. For example, IMD 16 may sense the first LeadZ during a cardiac cycle during a pacing or sensing event. IMD 16 may then sense the second lead z at a fixed point in time thereafter (e.g., after 400 ms). This technique may be beneficial when determining changes in intra-beat lead z that occur due to patient activity or changing needs (e.g., rate response or rate-adaptive atrioventricular interval).
In another example, IMD 16 may use the rate adaptation time after the first event. For example, IMD 16 may sense the first LeadZ during a cardiac cycle during a pacing or sensing event. IMD 16 may then sense the second lead z at a time that may be 40% or 50% of the length of the entire cardiac cycle, such as the previous R-R interval.
In another example, IMD 16 may use event driven timing of second lead z sensing. For example, IMD 16 may sense the first LeadZ during a cardiac cycle during a pacing or sensing event. IMD 16 may then sense the second LeadZ at a subsequent event, such as a T wave.
In addition to using changes in the intra-beat LeadZ to determine the parameters discussed herein, processing circuitry 15 and/or processing circuitry 102 may use timing from pacing or sensing of T-wave sensing. For example, the change in timing may be related to a change in capture or effective capture, as the timing of the T wave may be expected to change.
Fig. 9 is a flowchart illustrating an example of the use of a LeadZ according to the techniques of this disclosure. The processing circuit 15 and/or the processing circuit 102 may determine a first sensed lead z (300). For example, IMD 16 may sense LeadZ using a right ventricular ring electrode and a right ventricular coil electrode. The processing circuit 15 may determine the first sensed LeadZ based on the sensing. In some examples, IMD 16 may communicate with external computing device 24 and forward the first sensed LeadZ to external computing device 24. The processing circuit 102 may determine the first sensed lead z by reading the first sensed lead z from the storage 108 or from the communication circuit 106.
The processing circuit 15 and/or the processing circuit 102 may determine a second sensed lead z (302). For example, IMD 16 may sense LeadZ using a right ventricular ring electrode and a right ventricular coil electrode. The second sensed lead z may be taken during the same cardiac cycle or during an adjacent cardiac cycle (e.g., during the same phase). The processing circuit 15 may determine a second sensed lead z based on the sensing. In some examples, IMD 16 may communicate with external computing device 24 and forward the second sensed LeadZ to external computing device 24. The processing circuit 102 may determine the second sensed lead z by reading the second sensed lead z from the storage device 108 or from the communication circuit 106.
The processing circuit 15 and/or the processing circuit 102 may determine a first difference between the first sensed lead z and the second sensed lead z (304). For example, the processing circuitry 15 and/or the processing circuitry 102 may subtract the first LeadZ from the second LeadZ, or may subtract the second LeadZ from the first LeadZ. Processing circuitry 15 and/or processing circuitry 102 may determine a parameter based at least in part on the first difference (306). For example, processing circuitry 15 and/or processing circuitry 102 may determine a physiological indicator of contractility, whether the beat is an unobscured beat, whether the beat is a pseudofusion beat, whether pacing parameters should be changed, whether the atrioventricular interval should be changed, whether Left Bundle Branch Block (LBBB) and the capture of the his bundle are selective, whether capture of anti-tachycardia pacing (ATP) is entrained, whether tachycardia perfusion is present, whether no pulse electrical activation is detected, the volume or ejection fraction of the heart, respiration rate, current respiration state (e.g., inspiration or expiration), and the like. In some examples, the first sensed lead z and the second sensed lead z are sensed during the same first cardiac cycle of the heart that is receiving the pacing. Such measurements may determine a physiological index (e.g., ejection fraction) associated with the cardiac cycle. Additionally, or alternatively, the first sensed lead z and the second sensed lead z are sensed during different cardiac cycles (e.g., adjacent cycles) of the heart that is receiving the pacing. Such measurements may determine a physiological index associated with the respiratory cycle.
In some examples, processing circuitry 15 and/or processing circuitry 102 may change the pacing configuration from the first pacing configuration to the second pacing configuration, wherein the changed pacing configuration is used to pace the heart. The pacing configuration may include a pacing rate and/or electrode combination for pacing the heart. The processing circuit 15 and/or the processing circuit 102 may determine the third sensed LeadZ. The processing circuit 15 and/or the processing circuit 102 may determine the fourth sensed LeadZ. The processing circuit 15 and/or the processing circuit 102 may determine a second difference between the third sensed lead z and the fourth sensed lead z. Processing circuitry 15 and/or processing circuitry 102 may compare the first difference to the second difference. Processing circuitry 15 and/or processing circuitry 102 may select a pacing configuration of the first pacing configuration or the second pacing configuration based on the comparison. The third sensed lead z and the fourth sensed lead z are sensed during the same second cardiac cycle or adjacent cycles.
In some examples, processing circuitry 15 and/or processing circuitry 102 may determine whether the first difference is greater than or equal to a predetermined threshold. Based on a determination of whether the first difference is greater than or equal to a predetermined threshold, processing circuitry 15 and/or processing circuitry 102 may classify the beat as an unobscured beat. In some examples, if the first difference is greater than or equal to a predetermined threshold, the beat may be classified as a non-captured beat. In other examples, if the first difference is not greater than or equal to the predetermined threshold, the beat may be classified as a non-captured beat.
In some examples, processing circuitry 15 and/or processing circuitry 102 may update the first predetermined threshold based on the first difference.
In some examples, processing circuitry 15 and/or processing circuitry 102 may determine a third sensed LeadZ. The processing circuit 15 and/or the processing circuit 102 may determine a fourth sensed lead z, wherein the third sensed lead z and the fourth sensed lead z are sensed during the same second cardiac cycle. The processing circuit 15 and/or the processing circuit 102 may determine a second difference between the third sensed lead z and the fourth sensed lead z. Processing circuitry 15 and/or processing circuitry 102 may compare the first difference to the second difference. Processing circuitry 15 and/or processing circuitry 102 may determine whether the second difference differs from the first difference by more than a first predetermined amount. Processing circuitry 15 and/or processing circuitry 102 may classify the same second cardiac cycle as non-capture pulsatile or non-pulse electrical activity based on the second difference differing from the first difference by more than a first predetermined amount.
In some examples, processing circuitry 15 and/or processing circuitry 102 may determine a fifth sensed LeadZ. The processing circuit 15 and/or the processing circuit 102 may determine a sixth sensed lead z, wherein the fifth sensed lead z and the sixth sensed lead z are during the same third cardiac cycle. The processing circuit 15 and/or the processing circuit 102 may determine a third difference between the fifth sensed lead z and the sixth sensed lead z. The processing circuit 15 and/or the processing circuit 102 may compare the first difference with the third difference. The processing circuit 15 and/or the processing circuit 102 may determine whether the third difference differs from the first difference by more than a second predetermined amount and less than the first predetermined amount. The processing circuit 15 and/or the processing circuit 102 may classify the same third cardiac cycle as a pseudo-fusion beat based on the third difference differing from the first difference by more than the second predetermined amount and less than the first predetermined amount.
In some examples, processing circuit 15 and/or processing circuit 102 determine a plurality of sensed leadzs during each cardiac cycle over a period of time. The processing circuitry 15 and/or processing circuitry 102 may determine respective differences between the plurality of sensed leadzs during each cardiac cycle over a period of time. The processing circuit 15 and/or the processing circuit 102 may compare the first respective difference value with the second respective difference value. The processing circuit 15 and/or the processing circuit 102 may determine that the first respective difference differs from the second respective difference by more than a predetermined amount. Based on the difference between the first corresponding difference and the second corresponding difference being greater than a predetermined amount, processing circuitry 15 and/or processing circuitry 102 may change the pacing rate.
In some examples, processing circuitry 15 and/or processing circuitry 102 may determine a third sensed LeadZ. The processing circuit 15 and/or the processing circuit 102 may determine a fourth sensed lead z, wherein the third sensed lead z and the fourth sensed lead z are sensed during the same second cardiac cycle, and wherein a time difference between sensing the first sensed lead z and the second sensed lead z is equal to a time difference between sensing the third sensed lead z and the fourth sensed lead z. The processing circuit 15 and/or the processing circuit 102 may determine a second difference between the third sensed lead z and the fourth sensed lead z. Processing circuitry 15 and/or processing circuitry 102 may compare the first difference to the second difference. Processing circuitry 15 and/or processing circuitry 102 may determine whether the second difference differs from the first difference by more than a first predetermined amount. Processing circuitry 15 and/or processing circuitry 102 may change the pacing configuration based on the second difference differing from the first difference by more than a first predetermined amount.
In some examples, processing circuitry 15 and/or processing circuitry 102 may determine a third sensed LeadZ. The processing circuit 15 and/or the processing circuit 102 may determine a fourth sensed lead z, wherein the third sensed lead z and the fourth sensed lead z are sensed during the same second cardiac cycle. The processing circuit 15 and/or the processing circuit 102 may determine a second difference between the third sensed lead z and the fourth sensed lead z. Processing circuitry 15 and/or processing circuitry 102 may compare the first difference to the second difference. Processing circuitry 15 and/or processing circuitry 102 may determine whether the second difference differs from the first difference by more than a first predetermined amount. Processing circuitry 15 and/or processing circuitry 102 may determine that the same second cardiac cycle is a non-selective pacing pulse or a non-dragging anti-tachycardia pulse capture pulse based on the second difference differing from the first difference by more than a first predetermined amount.
In some examples, processing circuitry 15 and/or processing circuitry 102 may determine whether the first difference is greater than or equal to a first threshold. The processing circuit 15 and/or the processing circuit 102 may determine that the first cardiac cycle is a perfusion beat based on the first difference being greater than a first threshold.
In some examples, IMD 16 may overdrive pacing. In some examples, the first sensed lead z is during pacing or during a sensed beat, and the second sensed lead z is during an absolute non-responsive period following the pacing or sensed beat. In some examples, the first sensed lead z is during pacing or during a sensed beat, and the second sensed lead z is a predetermined time after the first lead z is sensed. In some examples, the first sensed lead z is during pacing or during a sensed beat, and the second sensed lead z is at a predetermined portion of a previous R-R interval. In some examples, the first sensed lead z is during pacing or during a sensed beat, and processing circuitry 15 may determine a sensed cardiac event, wherein the timing of sensing the second sensed lead z is based on determining the sensed cardiac event.
The techniques described in this disclosure may be implemented, at least in part, in hardware, software, firmware, or any combination thereof. For example, aspects of the described techniques may be implemented within one or more processors, including one or more microprocessors, digital Signal Processors (DSPs), application Specific Integrated Circuits (ASICs), field Programmable Gate Arrays (FPGAs), or any other equivalent integrated or discrete logic circuitry, as well as any combinations of such components. The term "processor" or "processing circuit" may generally refer to any of the foregoing logic circuits, alone or in combination with other logic circuits, or any other equivalent circuit. The control unit including hardware may also perform one or more of the techniques of this disclosure.
Such hardware, software, and firmware may be implemented within the same device or within separate devices to support the various operations and functions described in this disclosure. Moreover, any of the described units, modules, or components may be implemented together or separately as discrete but interoperable logic devices. Depiction of different features as modules or units is intended to highlight different functional aspects and does not necessarily imply that such modules or units must be realized by separate hardware or software components. Rather, functionality associated with one or more modules or units may be performed by separate hardware or software components, or integrated in common or separate hardware or software components.
The techniques described in this disclosure may also be embodied or encoded in a non-transitory computer-readable medium, such as a computer-readable storage medium containing instructions. Instructions embedded or encoded in a non-transitory computer-readable storage medium may cause a programmable processor or other processor to perform the method, for example, when executing the instructions. The non-transitory computer-readable storage medium may include Random Access Memory (RAM), read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), flash memory, a hard disk, a CD-ROM, a floppy disk, a cassette, magnetic media, optical media, or other computer-readable media.
The present disclosure includes the following non-limiting examples.
Various examples have been described. These and other examples are within the scope of the following claims.
Claims (15)
1. A method for determining parameters of a patient with an implantable pacing medical device, the method comprising with a pacing device:
determining a first sensed lead impedance (LeadZ);
determining a second sensed lead z, wherein the first and second sensed lead z are sensed during the same first cardiac cycle or during adjacent cardiac cycles of a heart receiving pacing from the implantable pacing medical device;
Determining a first difference between the first sensed lead z and the second sensed lead z; and
a parameter is determined based at least in part on the first difference.
2. The method of claim 1, the method further comprising:
determining a third sensed LeadZ;
determining a fourth sensed lead z, wherein the second sensed lead z and the third sensed lead z are sensed during the same first cardiac cycle, and wherein the second sensed lead z and the third sensed lead z are sensed during the same second cardiac cycle of the heart;
determining a second difference between the third sensed lead z and the fourth sensed lead z;
comparing the first difference with the second difference; and performing at least one of:
changing the pacing configuration from the first pacing configuration to a second pacing configuration based on the comparison; or (b)
A change in contractility is determined based on the comparison.
3. The method of claim 2, wherein changing the pacing configuration further comprises:
determining a respiration state based on comparing the first difference to the second difference; and
performing at least one of: the pacing rate is increased during the inspiratory breathing state or decreased during the expiratory breathing state.
4. The method of claim 1, the method further comprising:
determining a third sensed LeadZ;
determining a fourth sensed lead z, wherein the second sensed lead z and the third sensed lead z are sensed during the same first cardiac cycle, and wherein the second sensed lead z and the third sensed lead z are sensed during the same second cardiac cycle of the heart;
determining a second difference between the third sensed lead z and the fourth sensed lead z;
comparing the first difference with the second difference;
determining whether the second difference differs from the first difference by more than a first predetermined amount; and
the same second cardiac cycle is classified as non-capture beats, non-pulse electrical activity, non-selective pacing beats, non-dragging anti-tachycardia pulse capture beats based on the second difference differing from the first difference by more than the first predetermined amount.
5. The method of claim 4, the method further comprising:
determining a fifth sensed LeadZ;
determining a sixth sensed lead z, wherein the fifth sensed lead z and the sixth sensed lead z are sensed during a same third cardiac cycle;
Determining a third difference between the fifth sensed lead z and the sixth sensed lead z;
comparing the first difference with the third difference;
determining whether the third difference differs from the first difference by more than a second predetermined amount and less than the first predetermined amount; and
classifying the same third cardiac cycle as a pseudo-fusion beat based on the third difference differing from the first difference by more than the second predetermined amount and less than the first predetermined amount.
6. The method of any one of claims 1 to 5, further comprising:
determining whether the first difference is greater than or equal to a predetermined threshold;
classifying beats as non-captured beats based on the determination of whether the first difference is greater than or equal to a predetermined threshold; and
a first predetermined threshold is updated based on the first difference.
7. The method of any of claims 1-6, wherein the first sensed lead z is sensed during pacing of the first cardiac cycle or during a sensed beat, and the second sensed lead z is sensed during an absolute non-responsive period, during a sensed cardiac event, or during a predetermined time after sensing first lead z.
8. A system, the system comprising:
a memory configured to store a plurality of lead impedances (LeadZ) sensed by a medical device; and
processing circuitry communicatively coupled to the memory, the processing circuitry configured to:
determining a first sensed lead impedance (LeadZ);
determining a second sensed lead z, wherein the first sensed lead z and the second sensed lead z are sensed during a same first cardiac cycle or during adjacent cardiac cycles of the heart receiving pacing;
determining a first difference between the first sensed lead z and the second sensed lead z; and
a parameter is determined based at least in part on the first difference.
9. The system of claim 8, wherein the processing circuit is further configured to:
determining a third sensed LeadZ;
determining a fourth sensed lead z, wherein the second sensed lead z and the third sensed lead z are sensed during the same first cardiac cycle, wherein the second sensed lead z and the third sensed lead z are sensed during the same second cardiac cycle of the heart;
determining a second difference between the third sensed lead z and the fourth sensed lead z;
Comparing the first difference with the second difference; and performing at least one of:
changing the pacing configuration from the first pacing configuration to a second pacing configuration based on the comparison; or (b)
A change in contractility is determined based on the comparison.
10. The system of claim 9, wherein the processing circuit is configured to:
determining a respiration state based on respective differences between the plurality of sensed leadzs; and
performing at least one of: the pacing rate is increased during an inspiratory breathing state or decreased during an expiratory breathing state.
11. The system of claim 8, wherein the processing circuit is further configured to:
determining a third sensed LeadZ;
determining a fourth sensed lead z, wherein the second sensed lead z and the third sensed lead z are sensed during the same first cardiac cycle, wherein the third sensed lead z and the fourth sensed lead z are sensed during the same second cardiac cycle;
determining a second difference between the third sensed lead z and the fourth sensed lead z;
comparing the first difference with the second difference;
Determining whether the second difference differs from the first difference by more than a first predetermined amount; and
classifying the same second cardiac cycle as non-capture beats, non-pulse electrical activity, non-selective pacing beats, non-dragging anti-tachycardia pulse capture beats based on the second difference differing from the first difference by more than the first predetermined amount.
12. The system of claim 11, wherein the processing circuit is further configured to:
determining a fifth sensed LeadZ;
determining a sixth sensed lead z, wherein the fifth sensed lead z and the sixth sensed lead z are sensed during a same third cardiac cycle;
determining a third difference between the fifth sensed lead z and the sixth sensed lead z;
comparing the first difference with the third difference;
determining whether the third difference differs from the first difference by more than a second predetermined amount and less than a first predetermined amount; and
classifying the same third cardiac cycle as a pseudo-fusion beat based on the third difference differing from the first difference by more than the second predetermined amount and less than the first predetermined amount.
13. The system of any of claims 8 to 12, wherein the processing circuit is further configured to:
Determining whether the first difference is greater than or equal to a predetermined threshold;
classifying beats as non-captured beats based on the determination of whether the first difference is greater than or equal to the predetermined threshold; and
updating the first predetermined threshold based on the first difference.
14. The system of any of claims 8 to 13, wherein the first sensed lead z is sensed during pacing of the first cardiac cycle or during a sensed beat, and the second sensed lead z is sensed during an absolute non-responsive period, during a sensed cardiac event, or during a predetermined time after sensing the first lead z.
15. A non-transitory computer-readable medium storing instructions that, when executed by processing circuitry of an implantable medical device, cause the processing circuitry to:
determining a first sensed lead impedance (LeadZ);
determining a second sensed LeadZ;
determining a first difference between the first sensed lead z and the second sensed lead z; and
determining a parameter based at least in part on the first difference,
wherein the first sensed lead z and the second sensed lead z are sensed during the same cardiac cycle or during adjacent cardiac cycles of the heart that is receiving the pacing.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US63/236,947 | 2021-08-25 | ||
| US17/878,557 | 2022-08-01 | ||
| US17/878,557 US20230068078A1 (en) | 2021-08-25 | 2022-08-01 | Lead impedance measurement for physiological and device management |
| PCT/IB2022/057709 WO2023026142A1 (en) | 2021-08-25 | 2022-08-17 | Lead impedance measurement for physiological and device management |
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| CN117835901A true CN117835901A (en) | 2024-04-05 |
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