EP4735103A1 - Implantable medical device circuitry integrity detection - Google Patents

Abstract

An example device includes a hold capacitor configured to store electrical energy for delivery to a patient as a stimulation pulse; one or more charge pump capacitors; a charge circuit coupled to the one or more charge pump capacitors, the charge circuit configured to charge the hold capacitor with electrical energy; a switch positioned between the charge circuit and the hold capacitor; and a charge pump monitor circuit coupled to the charge circuit and configured to monitor charging of the hold capacitor with electrical energy.

Description

IMPLANTABLE MEDICAL DEVICE CIRCUITRY INTEGRITY DETECTION

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63/510,505, filed June 27, 2023, the entire content of which is incorporated herein by reference.

TECHNICAL FIELD

[0002] This disclosure relates generally to medical devices and, more particularly, to techniques for evaluating the integrity of implantable medical device circuitry.

BACKGROUND

[0003] Some types of implantable medical devices (IMDs), such as cardiac pacemakers or implantable cardioverter defibrillators systems, may be used to provide cardiac sensing and therapy for a patient via one or more electrodes. Monitoring performance and integrity of an IMD while using IMD to perform stimulation therapy is important for delivering safe and appropriate therapy. For example, changes to the integrity of circuitry used to deliver electrical stimulation therapy, such as cardiac pacing, may be reflected in changed impedance, and may result in variance of the amplitude or other amount of stimulation delivered to the patient from what was prescribed/intended.

SUMMARY

[0004] In general, this disclosure is directed to devices, systems, and techniques for determining integrity of one or more of a charge circuit, hold capacitor, and/or stimulation delivery path of an IMD such as a pacemaker or cardioverter defibrillator. In some examples of devices, systems, and techniques described herein, circuitry of an IMD may initiate a counter to determine a duration of a charge cycle to recharge a capacitor, such as a hold capacitor, and generate data, such as an alert, communication, flag, etc., to indicate an integrity issue in one or more of a charge circuit, hold capacitor, and/or stimulation delivery path of an IMD based on whether the duration of the charge cycle satisfies an integrity issue threshold (or other criterion).

[0005] In some examples of devices, systems, and techniques described herein, the detection of integrity issues based on determining a duration of charge cycle to recharge a hold capacitor is pace-delivery independent. Determining a duration of a charge cycle of a hold capacitor, while being pace-delivery independent, may help determine satisfaction of an integrity issue criterion without potentially out of specification therapy being applied to a patient. In addition, some examples of devices, systems, and techniques described herein may be able to identify integrity issues while reducing or avoiding use (and consequently a presence in the IMD) of sample capacitors, which may reduce charge lost due to sample capacitors and reduce a risk of short-circuit of a sample capacitor that may lead to inappropriate stimulation therapy delivery.

[0006] Some examples of devices, systems, and techniques described herein may help identify isolate and identify a particular charge pump capacitor that has the integrity issue. In some examples, if there is a partial integrity issue within a charge circuit that causes the recharge state to take twice as long to complete, the particular configuration of circuitry described herein may capture this integrity issue without any reprogramming despite the impedance remaining constant. In addition, the particular configuration of circuitry described herein may be sensitive to leakage of a hold capacitor. For example, if a hold capacitor has leakage, impedance would remain constant even if the first sample voltage is lower than expected. The particular configuration of circuitry described herein may determine a duration of a charge cycle of a hold capacitor to determine an increase in recharge time and detect a hold capacitor leakage without any additional hardware.

Accordingly, the particular configuration of circuitry described herein is able to determine additional types of integrity issues and/or additional locations of integrity issues.

[0007] In one example, the disclosure describes a device comprising a hold capacitor configured to store electrical energy for delivery to a patient as a stimulation pulse; one or more charge pump capacitors; a charge circuit coupled to the one or more charge pump capacitors, the charge circuit configured to charge the hold capacitor with electrical energy; a switch positioned between the charge circuit and the hold capacitor; and a charge pump monitor circuit coupled to the charge circuit and configured to monitor charging of the hold capacitor with electrical energy.

[0008] In another example, this disclosure describes a device comprising a memory; and circuitry coupled to the memory, the circuitry configured to: determine a duration of a charge cycle of a hold capacitor configured to store electrical energy for delivery to a patient as a stimulation pulse; determine whether the duration of the charge cycle satisfies an integrity issue criterion; and in response to a determination that the duration of the charge cycle satisfies the integrity issue criterion, generate data indicating an integrity issue.

[0009] In another example, this disclosure describes a method for performing a charge cycle to charge a hold capacitor configured to store electrical energy for delivery to a patient as a stimulation pulse; determining a duration to perform the charge cycle; determining whether the duration satisfies a failure threshold criterion; and in response to a determination that the duration satisfies the failure threshold criterion, generating data indicating a failure.

[0010] In another example, the disclosure describes a non-transitory computer- readable storage medium storing instructions that, when executed, cause one or more processors of a device configured to process patient data to perform performing a charge cycle to charge a hold capacitor configured to store electrical energy for delivery to a patient as a stimulation pulse; determining a duration to perform the charge cycle; determining whether the duration satisfies a failure threshold criterion; and in response to a determination that the duration satisfies the failure threshold criterion, generating data indicating a failure.

[0011] 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 within the accompanying drawings and description below. Further details of one or more examples are set forth in the accompanying drawings and the description below.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The details of one or more examples of this disclosure are set forth in the accompanying drawings and the descriptions below. Other features, objects, and advantages of this disclosure will be apparent from the description and drawings, and from the claims.

[0013] FIG. 1 is a conceptual diagram illustrating an example medical device implanted in the heart of a patient, in accordance with one or more aspects of this disclosure. [0014] FIG. 2 is a conceptual illustration of an example configuration of the example implantable medical device of FIG. 1, in accordance with one or more aspects of this disclosure.

[0015] FIG. 3 is a functional block diagram illustrating an example configuration of the IMD of FIGS. 1-2, in accordance with one or more aspects of this disclosure.

[0016] FIG. 4 is a circuit diagram illustrating an example of circuitry on an example IMD, in accordance with one or more aspects of this disclosure.

[0017] FIG. 5 is a timing diagram illustrating an example of hold capacitor voltage, a counter, and an implantable medical device state with respect to a time axis, in accordance with one or more aspects of this disclosure.

[0018] FIG. 6 is a circuit diagram illustrating an example of a charge pump monitor circuit, in accordance with one or more aspects of this disclosure.

[0019] FIG. 7 is a flowchart illustrating an example process of an IMD with circuitry of FIG. 4, in accordance with one or more aspects of this disclosure.

DETAILED DESCRIPTION

[0020] In general, this disclosure describes example IMDs, such as cardiac pacemakers or implantable cardioverter defibrillators (ICDs), circuitry on such IMDs, and methods for generating data indicating integrity issues based, at least in part, on a determined duration of a charge cycle to recharge a hold capacitor.

[0021] IMDs that measure pre -pace and post-pace voltage on a respective capacitor to determine a delivery voltage, discharge a pre-pace voltage at a known rate until it matches a post-pace voltage. Those IMDs then analyze counts, once parity is reached, to determine if shorts or open circuits are present.. In other words, such IMDs require delivery of a pacing pulse to determine if shorts or open circuits are present. In addition, the counter in such IMDs is used as a proxy for determining impedance within the IMD circuitry, also referred to as IMD impedance. These IMDs may not be able to determine integrity issues in a charge circuit, such as charge pump capacitors, or integrity issues in a hold capacitor. For example, since the counter is used as a proxy for determining IMD impedance, such IMDs may not be able to detect integrity issues, such as a partial integrity issue in charging circuitry that causes the recharge state to take longer to complete, as the impedance remains constant in such cases. In addition, such IMDs may also not be able to detect leakages in a hold capacitor because impedance would be constant even if a first sample voltage in the hold capacitor is lower than expected.

[0022] Unlike IMDs that are pace-delivery dependent and/or use a counter as a proxy for determining IMD impedance, the IMD, circuitry, and techniques described herein may determine charge circuit, charge pump capacitor, and/or hold capacitor integrity issues. For example, if there is a partial integrity issue within a charge circuit that causes the recharge state to take twice as long to complete, the particular configuration of circuitry described herein may capture this integrity issue without any reprogramming despite the impedance of the circuitry remaining constant. In addition, the particular configuration of circuitry described herein may be sensitive to leakage of a hold capacitor. For example, if a hold capacitor has leakage, impedance would remain constant even if the first sample voltage is lower than expected. The particular configuration of circuitry described herein may determine a duration of a charge cycle of a hold capacitor to determine an increase in charge time and detect a hold capacitor leakage without any additional hardware.

Accordingly, the particular configuration of circuitry described herein is able to determine additional types of integrity issues and/or additional locations of integrity issues, and is able to identify integrity issues with reduced use of sample capacitors or without sample capacitors, as the particular configuration of the circuitry described herein is able to determine an integrity issue based on a charge cycle of a hold capacitor configured to store electrical energy for delivery to a patient as a stimulation pulse. Reducing or removing sample capacitors may reduce or remove short-circuits of sample capacitors that may lead to failed stimulation therapy delivery.

[0023] FIG. 1 is a conceptual diagram illustrating an example device 104A implanted in the heart 102 of a patient, in accordance with one or more aspects of this disclosure. Device 104 A is shown implanted in the right atrium (RA) of the patient’s heart 102 in a target implant region 106, such as the triangle of Koch, in heart 102 of the patient with a distal end of device 104A directed toward the left ventricle (LV) of the patient’s heart 102. Target implant region 106 may lie between the bundle of His and the coronary sinus and may be adjacent the tricuspid valve. Although in the example of FIG. 1 the distal end of device 104 A is directed toward the LV, the distal end may be directed to other targets, such as interventricular septum, ventricular apex, atrial appendage, or other targets of heart 102. [0024] Device 104 A includes a distal end 110 and a proximal end 116. Distal end 110 includes a first electrode 112, and a second electrode 114. First electrode 112 may define a helical shape, e.g., as illustrated in FIG. 1. First electrode 112 extends from distal end 110 and may penetrate through the wall tissue of a first chamber (e.g., the RA in the illustrated example) into wall tissue of a second chamber (e.g., ventricular myocardium 108 of the LV in the illustrated example). Second electrode 114 may extend distally from distal end 110 and be configured to be placed in contact with the wall tissue of the first chamber without penetration of the wall tissue of the first chamber by second electrode 114. Second electrode 114 may contact the wall tissue of the first chamber as first electrode 112 penetrates the wall tissue of the first chamber.

[0025] The configuration of electrodes 112 and 114 illustrated in FIG. 1 allows device 104A to sense cardiac signals and/or deliver cardiac pacing to multiple chambers of heart 102, e.g., the RA and ventricle(s) in the illustrated example. In this manner, the configuration of electrodes 112 and 114 may facilitate the delivery of A-V synchronous pacing by single device 104A implanted within the single chamber, e.g., the RA. While device 104 A is implanted at target implant region 106 to sense in and/or pace the RA and ventricle(s) in the example shown in FIG. 1, a device having such an electrode configuration or another electrode configuration, e.g., including one or more than two distal electrodes, may be implanted at any of a variety of locations to sense in and/or pace any one, two or more chambers of heart 102. For example, device 104A may be implanted at region 106 or another region, and first electrode 112 may extend into tissue, e.g., myocardial tissue, of the LV or interventricular septum to, for example, facilitate the delivery of A-V synchronous pacing. Furthermore, a device implementing techniques in accordance with the examples of this disclosure may be implanted at any of a variety of locations within a patient for sensing and/or delivery of therapy to other patient tissue. In some examples, first electrode 112 extends into the tissue of heart 102 at region 106 and affixes device 104A to the tissue of heart 102.

[0026] Device 104 A is an example of a device configured to determine a duration of a charge cycle to recharge a capacitor, such as a hold capacitor, and generate data to indicate an integrity issue in one or more of a charge circuit, hold capacitor, and/or stimulation delivery path of device 104 based on whether the duration of the charge cycle satisfies an integrity issue threshold (or other criterion/criteria). FIG. 1 illustrates one example of device 104A as an intracardiac pacemaker. Other examples of medical devices that may implement the techniques of this disclosure may include transvenous pacemakers and/or defibrillators, ICDs, neurostimulators, gastric stimulators, or other implantable medical devices that deliver electrical stimulation therapy.

[0027] FIG. 2 is a conceptual illustration of another example configuration of a device 104. Device 104B is configured to be implanted within a chamber of a heart of a patient, e.g., to monitor electrical activity of the heart and/or provide electrical therapy to the heart. In the example shown in FIG. 2, device 104B includes outer housing 150, a plurality of fixation tines 110 and electrodes 100 and 160. Device 104B is an example of a device configured to determine a duration of a charge cycle to recharge a capacitor, such as a hold capacitor, and generate data to indicate an integrity issue in one or more of a charge circuit, hold capacitor, and/or stimulation delivery path of device 104 based on whether the duration of the charge cycle satisfies an integrity issue threshold (or other criterion). [0028] Outer housing 150 has a size and form factor that allows device 104B to be entirely implanted within a chamber of a heart of a patient. In some examples, outer housing 150 may have a cylindrical (e.g., pill-shaped) form factor. Device 104B may include a fixation mechanism configured to fix device 104B to cardiac tissue. For example, in the example shown in FIG. 2, device 104B includes fixation tines 110 extending from housing 150 and configured to engage with cardiac tissue to substantially fix a position of housing 150 within a chamber of the heart. Fixation tines 110 are configured to anchor housing 150 to the cardiac tissue such that device 104B moves along with the cardiac tissue during cardiac contractions. Fixation tines 110 may be fabricated from any suitable material, such as a shape memory material (e.g., Nitinol). Although device 104B includes a plurality of fixation tines 110 that are configured to anchor device 104B to cardiac tissue in a chamber of a heart, in other examples, device 104B may be fixed to cardiac tissue using other types of fixation mechanisms, such as, but not limited to, barbs, coils (e.g., a helical electrode or non-electrode fixation element as illustrated in FIG. 1), and the like.

[0029] Housing 150, also referred to as an elongated housing, houses electronic components of device 104B, e.g., sensing circuitry for sensing cardiac electrical activity via electrodes 100 and 160 and therapy generation circuitry for delivering electrical stimulation therapy via electrodes 100 and 160. Electronic components may include any discrete and/or integrated electronic circuit components that implement analog and/or digital circuits capable of producing the functions attributed to device 104B described herein. In some examples, housing 150 may also house components for sensing other physiological parameters, such as acceleration, pressure, sound, and/or impedance. Although shown with both electrodes 100 and 160, in some examples, housing 150 may only include one or the other of electrodes 100 and 160.

[0030] Additionally, housing 150 may also house a memory that includes instructions that, when executed by processing circuitry housed within housing 150, cause device 104B to perform various functions attributed to pacing device 104B herein. In some examples, housing 150 may house communication circuitry that enables pacing device 104B to communicate with other electronic devices, such as a medical device programmer. In some examples, housing 150 may house an antenna for wireless communication. Housing 150 may also house a power source, such as a battery. Housing 150 can be hermetically or near-hermetically sealed in order to help prevent fluid ingress into housing 150.

[0031] Device 104B is configured to sense electrical activity of the heart and deliver electrical stimulation to the heart via electrodes 100 and 160. Electrode 100 and/or electrode 160 may be mechanically connected to housing 150. As another example, electrode 100 and/or electrode 160 may be defined by an outer portion of housing 150 that is electrically conductive. For example, electrode 160 may be defined by a conductive portion of housing 150. Although not illustrated in FIG. 1, device 104A may similarly include one or more proximal electrodes, which may be defined by one or more uninsulated portions of a housing of device 104A.

[0032] In the example of FIG. 2, housing 150 includes a first portion 152A and a second portion 152B. Portion 152B may, in some examples, define at least part of a power source case that houses a power source (e.g., a battery) of device 104B. The power source case may house a power source (e.g., a battery) of device 104B. In some examples, the portion 152B may include the conductive portion of housing that forms electrode 160.

[0033] Electrodes 100 and 160 are electrically isolated from each other. Electrode 100 may be referred to as a tip electrode, and fixation tines 110 may be configured to anchor device 104B to cardiac tissue such that electrode 100 maintains contact with the cardiac tissue. In some examples, a portion of housing 150 may be covered by, or formed from, an insulative material to isolate electrodes 100 and 160 from each other and/or to provide a desired size and shape for one or both of electrodes 100 and 160. Electrode 160 may be a portion of housing 150, e.g., housing portion 152B, that does not include such insulative material. Electrode 160 can be most or all of housing 150, but most of housing 150 (other than electrode 160, may be covered with an insulative coating. Additionally or alternatively, electrode 160 may be coated with materials to promote conduction. In some examples, electrode 160 may be part of a separate ring portion of housing 150 that is conductive. Electrodes 100 and 160, which may include conductive portion(s) of housing 150, may be electrically connected to at least some electronics of device 104B (e.g., sensing circuitry, electrical stimulation circuitry, or both). In some examples, housing 150 may include an end cap 172, which may include a feedthrough assembly to electrically couple electrode 100 to the electronics within housing 150, while electrically isolating electrode 100 from housing 150, e.g., including electrode 160 or other conductive portions of housing 150.

[0034] In the example of FIG. 2, the proximal end of device 104B includes a flange 158 that defines an opening. Flange 158 may enable medical instruments to attach to device 104B, e.g., for delivery and/or extraction of device 104B. For example, a tether that extends through a catheter inserted into heart 102 (FIG. 1) may be attached to flange 158 and/or threaded through the opening to implant or extract pacing device 104B.

[0035] FIG. 3 is a functional block diagram illustrating an example configuration of a device 104, which may correspond to any of device 104A and device 104B described with respect to FIGS. 1 and 2. As illustrated in FIG. 3, device 104 include electrodes 212, 214, which may correspond to any of the electrodes described with respect to FIGS. 1 and 2, e.g., electrodes 112, 114, 100, and 160. Although illustrated as including two electrodes, device 104 may include more than two electrodes.

[0036] In the example shown in FIG. 3, device 104 includes switch circuitry 302, sensing circuitry 304, signal generation circuitry 306, sensor(s) 308, processing circuitry 310, communication circuitry 312, memory 314, and power source 316. The various circuitry may be, or include, programmable or fixed function circuitry configured to perform the functions attributed to respective circuitry. Memory 314 may store computer- readable instructions that, when executed by processing circuitry 310, cause device 104 to perform various functions. Memory 314 may be a storage device or other non-transitory medium. The components of device 104 illustrated in FIG. 3 may be housed within housing 200.

[0037] Signal generation circuitry 306 generates electrical stimulation signals, e.g., cardiac pacing pulses. Switch circuitry 302 is coupled to electrodes 112, 114, may include one or more switch arrays, one or more multiplexers, one or more switches (e.g., a switch matrix or other collection of switches), one or more transistors, or other electrical circuitry. Switch circuitry 302 is configured to direct stimulation signals from signal generation circuitry 306 to a selected combination of electrodes 112, 114, having selected polarities, e.g., to selectively deliver pacing pulses to the RA, the RV, the LV, and/or interventricular septum of heart 102.

[0038] Switch circuitry 302 may also selectively couple sensing circuitry 304 to selected combinations of electrodes 212, 214, e.g., to selectively sense the electrical activity of the RA or ventricles of heart 102. Sensing circuitry 304 may include filters, amplifiers, analog-to-digital converters, or other circuitry configured to sense cardiac electrical signals via electrodes 112 and/or 114. For example, switch circuitry 302 may couple one or more sensing vectors to respective sensing channels provided by sensing circuitry 304 to sense ventricular or atrial cardiac electrical signals. Switch circuitry 302 may then direct signals from one or more of electrodes 112 and 114 composing a sensing vector to the corresponding sensing channel.

[0039] In some examples, sensing circuitry 304 may select sensing vectors for the sensing of the electrical activity. Each sensing vector may be a combination of signal components from one or more of electrodes 112 and 114. Sensing circuitry 304 may represent any vector within the 3D coordinate system based on one or more sensing vectors.

[0040] In some examples, sensing circuitry 304 is configured to detect events, (e.g., depolarizations) and/or cardiac conditions (e.g., presence of arrhythmias, tachycardia, or the like) within the cardiac electrical signals, and provide indications thereof to processing circuitry 310. In this manner, processing circuitry 310 may determine the timing of atrial and ventricular depolarizations, and control the delivery of cardiac pacing, e.g., AV synchronized cardiac pacing, based thereon. Processing circuitry 310 may select pacing vectors within the 3D coordinate system defined by electrodes 112, 114. Processing circuitry 310 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), discrete logic circuitry, or any other processing circuitry configured to provide the functions attributed to processing circuitry 310 herein may be embodied as firmware, hardware, software or any combination thereof.

[0041] Sensor(s) 308 may include one or more sensing elements that transduce patient physiological activity to an electrical signal to sense values of a respective patient parameter. Sensor(s) 308 may include one or more accelerometers, optical sensors, chemical sensors, temperature sensors, pressure sensors, or any other types of sensors. Sensor(s) 308 may output patient parameter values that may be used as feedback to control sensing and delivery of therapy by device 104.

[0042] Communication circuitry 312 supports wireless communication between device 104 and an external programmer (not shown in FIG. 3) or another computing device under the control of processing circuitry 310. Processing circuitry 310 of device 104 may receive, as updates to operational parameters from the computing device, and provide collected data, e.g., sensed heart activity or other patient parameters, via communication circuitry 312. Communication circuitry 312 may accomplish communication by radiofrequency (RF) communication techniques, e.g., via an antenna (not shown).

[0043] Power source 316 delivers operating power to various components of device 104. Power source 316 may include a rechargeable or non-rechargeable battery and a power generation circuit to produce the operating power. Recharging may be accomplished through proximal inductive interaction between an external charger and an inductive charging coil within device 104.

[0044] Device 104 is an example of a device configured to determine a duration of a charge cycle to recharge a capacitor, such as a hold capacitor, and generate data to indicate an integrity issue in one or more of a charge circuit, hold capacitor, and/or stimulation delivery path of device 104 based on whether the duration of the charge cycle satisfies an integrity issue threshold (or other criterion/criteria). For example, circuitry of device 104, e.g., signal generation circuitry 306, may be configured to deliver stimulation pulses along a stimulation delivery path using energy stored in the hold capacitor. Upon the delivery of stimulation pulses using energy stored in the hold capacitor, circuitry of device 104, e.g., processing circuitry 310, may initiate a recharge of the hold capacitor. Further, circuitry of device 104, e.g., processing circuitry 310, may be configured to determine a count or duration based on a charge cycle to recharge the hold capacitor and compare the count or duration to one or more integrity thresholds or criteria. If the count or duration satisfies an integrity threshold or other criterion/criteria, processing circuitry 310 may generate data, e.g., a flag stored in memory 314, or an alert or other communication via communication circuitry 312, indicating an integrity issue in one or more of a charge circuit, hold capacitor, and/or stimulation delivery path of device 104.

[0045] FIG. 4 is a diagram of an example of circuitry 402 of IMD 104. While FIGS. 1- 3 show examples of IMD 104, circuitry 402 may be positioned or implemented in other examples of IMDs with different configurations than shown in FIGS. 1-3. Such IMDs include, but are not limited to, implantable stimulators coupled to implantable leads, leadless implantable stimulators, etc. configured to be fixed at any location or tissue of the body. In some examples, circuitry 402 may include or be a part of one or more of switch circuitry 302, sensing circuitry 304, signal generation circuitry 306, processing circuitry 310, communication circuitry 312, and/or power source 316 illustrated in FIG. 3.

[0046] IMD 104 includes circuitry 402 having a power source 412, charge circuit 404, a charge pump monitor circuit 406, switches SI and S2, a hold capacitor 408 (Chold 408), charge pump capacitor (Cpump) 405 A, charge pump capacitor 405B, and a tip capacitor (Ctip) 418. While FIG. 4 shows circuitry 402 having two charge pump capacitors 405 A, 405B, in some examples circuitry 402 may include one charge pump capacitor. In other examples, circuitry 402 may include more than two charge pump capacitors.

[0047] As shown in FIG. 4, charge circuit 404 is electrically coupled to power source 412. In some examples, charge circuit 404 may be directly coupled to power source 412. As shown in FIG. 4, charge pump monitor circuit 406 is coupled to charge circuit 404. In some examples, charge pump monitor circuit 406 is directly coupled to charge circuit 404, as shown in FIG. 4. In some examples, switch SI is positioned between Chold 408 and both charge circuit 404 and charge pump monitor circuit 406. In some examples, charge pump monitor circuit 406 being directly coupled to charge circuit 404, and/or switch S 1 being positioned between Chold 408 and both charge circuit 404 and charge pump monitor circuit 406, may avoid directly impacting the stimulation delivery path when determining integrity of circuitry 402. This in turn may reduce potential damage inflicted by a short circuit on the circuitry 402 (e.g., a short circuit on circuitry 402 may not cause failed therapy delivery). In some examples, Cpumps 405A, 405B are coupled to charge circuit 404. In some examples, one or more of Cpumps 405A, 405B are directly coupled to charge circuit 404. In some examples, switch S2 is positioned between Ctip 418 and switch SI and is also positioned between Ctip 418 and Chold 408. In some examples, switch S2 is closed for a specified period of time (corresponding to a desired stimulation pulse width) to cause a stimulation pulse to be delivered to the patient body 420 by IMD 104, such as via one or more of electrodes 212 and/or 214.

[0048] The charge circuit 404 and switch S 1 may be used to store energy, such as from power source 412, on Chold 408. In some examples, Cpumps 405A, 405B may provide charge pumps to charge or recharge Chold 408 to a particular state, such as a programmed amplitude state. The period of time Chold 408 is being charged and/or recharged, such as from beginning of charging/recharging to when Chold 408 is charged to a particular voltage amplitude, such as a desired amplitude or programmed amplitude, may be referred to as a charge cycle. In some examples, a desired and/or programmed voltage amplitude state of Chold 408 corresponds to a full or complete amplitude state of Chold 408. In some examples, once the Chold 408 is recovered to a particular state, such as a programmed amplitude state, Cpumps 405A, 405B may be shut down for a period of time as the charge of Chold 408 is complete. In some examples, Chold 408 may provide electrical energy to generate a stimulation pulse to be delivered to the patient body 420 by IMD 104. After providing electrical energy to generate a stimulation pulse, Chold 408 may need to be recharged, such as by the charge circuit 404 and/or Cpumps 405 A, 405B, to a particular state, such as a programmed amplitude state.

[0049] In some examples, power source 412 may be any type of battery suitable to power an IMD, such as a pacemaker. In some examples, Ctip 418 may be a direct current (DC) blocking capacitor. In some examples, Ctip 418 may also be referred to more generally as a stimulation return capacitor.

[0050] In some examples, a Chold 408 recharge may be activated, e.g., by charge circuit 404 as controlled by processing circuitry 310 (FIG. 3). For example, a Chold 408 recharge may be activated by a regular refresh, such as after delivery of a pacing pulse. In some examples, a Chold 408 recharge may be activated by receiving instructions, such as to conduct a test, such as a manual test, or other instructions to perform a recharge of Chold 408. [0051] In some examples, in response to Chold 408 recharge being activated, charge pump monitor circuit 406 may determine a duration needed to perform a charge cycle of Chold 408. In some examples, the duration to perform a charge cycle of Chold 408 may be an amount of time to perform a charge cycle of Chold 408. In some examples, the duration to perform a charge cycle of Chold 408 may be an amount of charge pumps, such as by one or more of Cpumps 405 A, 405B, to perform a charge cycle of Chold 408. In some examples, the duration to perform a charge cycle of Chold 408 may be indicative of an amount of charge to perform a charge cycle of Chold 408. In some examples, duration to perform a charge cycle of Chold 408 and/or an amount of charge to perform a charge cycle of Chold 408 may indicate impedance and/or impedance changes of a stimulation delivery path. In some examples, charge pump monitor circuit 406 may determine a duration to perform a charge cycle of Chold 408 by counting an amount of time charge pumps are applied by charge circuit 404, such as by Cpumps 405 A, 405B, to Chold 408 during a charge cycle. In some examples, charge pump monitor circuit 406 may determine a duration to perform a charge cycle of Chold 408 by counting an amount of charge pumps that are applied by charge circuit 404, such as by Cpumps 405 A, 405B, to Chold 408 during a charge cycle. In some examples, charge pump monitor circuit 406 may determine an amount of time charge pumps are applied by charge circuit 404 based on counting an amount of charge pumps that are applied by charge circuit 404 to Chold 408 during a charge cycle. By monitoring capacitors, such as Cpumps 405A, 405B, which are positioned, with respect to switch SI, on a same side as power source 412, charge circuit 404, and charge pump monitor circuit 406, impact on a stimulation delivery path may be minimized and/or avoided to reduce or avoid a short-circuit that may lead to a failed delivery of stimulation.

[0052] FIG. 5 shows an example of the waveforms of Chold 408 and counting of time during a charge cycle of Chold 408. Waveform 602 shows Chold 408 voltage. In some examples, a particular state of amplitude of Chold 408, such as a desired amplitude and/or a programmed amplitude state, is shown at 604 in waveform 602. Waveform 612 shows examples of different states of IMD 104. As shown in waveform 612 of FIG. 5, when IMD 104 is idle 614, Chold 408 voltage remains mostly constant and at a desired particular amount and/or a programmed amplitude amount 604. When IMD 104 enters a delivery state of stimulation pulses 615, voltage of Chold 408 decreases 605. When IMD enters a hold period 616, Chold 408 voltage remains relatively constant 606, but at an amount less than a desired particular amount and/or a programmed amplitude amount 604. When IMD 104 enters a charging state 617, voltage of Chold 408 increases 607. In some examples, when Chold 408 voltage reaches a desired particular amount and/or a programmed amplitude amount 604, IMD 104 enters an idle state 618.

[0053] In addition, waveform 622 shows a state of a counter 603 of Chold. In some examples, a Chold counter 603 may be implemented by or in charge pump monitor circuit 406. In some examples, Chold counter 603 may be charge count circuit 504 in charge pump monitor circuitry 406. As shown in FIG. 5, Chold counter 603 remains idle until IMD 104 enters a charging state 617 of Chold 408. In some examples, when IMD 104 enters a charging state 617 of Chold 408, Chold counter 603 enters a counting state 627 and determines a duration, such as an amount of time (t), IMD 104 is in the charging state 617, which may correspond to a charge cycle. In some examples, when Chold 408 voltage reaches a desired particular amount and/or a programmed amplitude amount 604, Chold counter 603 enters an idle state 628. In addition, in response to Chold counter 603 entering idle state 628, charge count circuit 504 may determine whether the determined duration of the charging cycle satisfies an integrity threshold 629.

[0054] Referring again to FIG. 4, an example of a charge cycle of Chold 408 is shown in 440, as it takes clocks 1, 2, 3....N to recharge Chold 408 to a particular amplitude amount that is considered full or complete. In some examples, an amount of clocks it takes to recharge Chold 408 may be referred to as a clock cycle. In some examples, charge pump monitor circuit 406 counts a number of clocks during a charge cycle of Chold 408. In some examples, a respective clock corresponds to a respective charge pump provided by Cpumps 405A, 405B to Chold 408 to charge Chold 408.

[0055] FIG. 6 is a diagram of an example of charge pump monitor circuit 406. In some examples, charge pump monitor circuit 406 may comprise a charge state machine 502 and a charge count circuit 504. In some examples, charge state machine 502 may send a signal to charge circuit 404 to enable charge circuit 404 to charge Chold 408. Charge state machine 502 may send a clock signal to charge circuit 404 and/or charge count circuit 504 and may send a count start signal to charge count circuit 504. In some examples, charge state machine 502 and/or charge count circuit 504 may receive a signal, via charge circuit 504, that recharge is complete. In some examples, charge state machine 502 may send count threshold criterion/criteria to charge count circuit 504, such as a minimum count threshold and/or a maximum count threshold. In some examples, charge count circuit 504 may output a final count value to other circuitry in IMD 104. In some examples, circuitry in IMD 104 may output a final count value to another computing device.

[0056] In some examples, such as charge count circuit 504 determining whether a determined duration of a charge cycle satisfies an integrity threshold 629 (FIG. 5), charge count circuit 504 may compare a final count value to a respective count threshold criterion. In some examples, if charge count circuit 504 determines the final count value satisfies a respective integrity criterion, charge count circuit 504 may generate data indicating an integrity issue. In some examples, the generated data indicating an integrity issue may indicate one or more of charge circuit 404 integrity issue, Chold 408 integrity issue, and/or stimulation delivery path integrity issue. For example, if charge count circuit 504 determines the final count value is below a respective minimum integrity criterion, charge count circuit 504 may generate data indicating an integrity issue. For example, if charge count circuit 504 determines the final count value is above a respective maximum integrity criterion, charge count circuit 504 may generate data indicating an integrity issue. [0057] In some examples, IMD 104 may determine, such as by processing circuitry 310 and/or other circuitry in IMD 104, one or more of charge circuit 404 integrity, Chold 408 integrity, and stimulation delivery path integrity based on the duration counted by Chold counter 603 of a charge cycle. For example, IMD 104 may respectively compare the counted time of a charge cycle to respective integrity threshold criteria of charge circuit 404, integrity threshold criteria of Chold 408, and/or integrity threshold criteria of stimulation delivery path. In response to the counted time of a charge cycle satisfying a particular integrity threshold criterion, IMD 104 may generate data indicating the determined integrity issue. In some examples, the integrity issue may be one or more of charge circuit 404 integrity issue, Chold 408 integrity issue, and/or stimulation delivery path integrity issue. In some examples, a charge circuit 404 integrity issue may include an integrity issue of one or more Cpumps 405A, 405B. In some examples, in cases in which one or more Cpumps 405 A, 405B, include an integrity issue, IMD 104 may determine which particular Cpump 405A, 405B includes an integrity issue based on the duration counted by Chold counter 603. [0058] In some examples, the particular configuration of circuitry 402, as described above, may be used on any charge cycle of Chold 408, such as due to a manual recharge trigger, which makes the detection of an integrity issue by circuitry 402 pace-delivery independent. Determining a duration of a charge cycle of Chold 408, while being pacedelivery independent, the configuration of circuitry 402 may help determine a count violation without potentially malformed therapy being applied to a patient. In addition, the configuration of circuitry 402 may help isolate and identify which Cpump 405A, 405B has failed. In addition, in some examples, the particular configuration of circuitry 402, as described above, may reduce or avoid a presence of sample capacitors, which may reduce charge lost due to sample capacitors and reduce a risk of short-circuit of a sample capacitor that may lead to failed stimulation therapy delivery.

[0059] In some examples, while circuitry 402 includes the ability to determine impedance within the circuitry of IMD 104, such as within circuitry 402, and monitor impedance changes within the circuitry of IMD 104, such as within circuitry 402, the particular configuration of circuitry 402, as described above, is also able to determine charge circuit 404, Cpump 405A, 405B, and/or Chold 408 integrity issues. For example, if there is a partial integrity issue within charge circuit 404 that causes the recharge state to take twice as long to complete, the particular configuration of circuitry 402 may identify this integrity issue without any reprogramming despite the impedance remaining constant. In addition, the particular configuration of circuitry 402 may be sensitive to leakage of Chold 408. For example, if Chold 408 has leakage, impedance would remain constant even if the first sample voltage is lower than expected. The particular configuration of circuitry 402 may determine a duration of a charge cycle of Chold 408, determine an increase in recharge time and detect a Chold 408 leakage without any additional hardware. Accordingly, the particular configuration of circuitry 402 is able to determine additional types of integrity issues and/or is able to reduce or remove an amount of sample capacitors present to detect integrity issues, which may reduce or remove short-circuits of sample capacitors that may lead to failed stimulation therapy delivery.

[0060] FIG. 7 is a flowchart illustrating an example process of IMD 104 with circuitry 402 of FIG. 4. While the example process of FIG. 7 is described primarily with reference to circuitry 402 as illustrated in FIG. 4, the example techniques of FIG. 7 may be applied with any other example systems described herein or which are otherwise suitable. [0061] A charge circuit 404 may perform a charge cycle to charge Chold 408 (702). In some examples, Cpumps 405A, 405B may perform a charge cycle to provide charge pumps to charge or recharge Chold 408 to a particular state, such as a programmed amplitude state. In some examples, a desired and/or programmed amplitude state of Chold 408 corresponds to a full or complete amplitude state of Chold 408. In some examples, Chold 408 may provide electrical energy to generate a stimulation pulse to be delivered to the patient body 420 by IMD 104. After providing electrical energy to generate a stimulation pulse, Chold 408 may need to be recharged, such as by the charge circuit 404 and/or Cpumps 405 A, 405B, to a particular state, such as a programmed amplitude state. [0062] A charge pump monitor circuit may determine a duration to perform the charge cycle of Chold 408 (704). In some examples, the duration to perform a charge cycle of Chold 408 may be an amount of time to perform a charge cycle of Chold 408. In some examples, the duration to perform a charge cycle of Chold 408 may be an amount of charge pumps, such as by one or more of Cpumps 405 A, 405B, to perform a charge cycle of Chold 408. In some examples, the duration to perform a charge cycle of Chold 408 may be indicative of an amount of charge to perform a charge cycle of Chold 408. In some examples, duration to perform a charge cycle of Chold 408 and/or an amount of charge to perform a charge cycle Chold 408 may indicate impedance and/or impedance changes of a stimulation delivery path. In some examples, charge pump monitor circuit 406 may determine a duration to perform a charge cycle of Chold 408 by counting an amount of time charge pumps are applied by charge circuit 404, such as by Cpumps 405 A, 405B, to Chold 408 during a charge cycle.

[0063] In some examples, charge pump monitor circuit 406, such as a charge count circuit 504 of charge pump monitor circuit 406, may determine whether the duration satisfies an integrity issue threshold criterion (706). In some examples, the integrity issue threshold criterion may correspond to one or more of charge circuit 404 integrity issue, Chold 408 integrity issue, and/or stimulation delivery path integrity issue. In some examples, a charge circuit 404 integrity issue may include an integrity issue of one or more Cpumps 405A, 405B. In some examples, in cases in which one or more Cpumps 405 A, 405B, fail, charge pump monitor circuit 406 may determine which particular Cpump 405 A, 405B had failed based on the duration counted by Chold counter 603. [0064] In response to a determination that the duration satisfies an integrity issue threshold criterion, charge pump monitor circuit 406, such as charge count circuit 504 in charge pump monitor circuit 406, may generate data indicating an integrity issue (708). In some examples, the generated data indicating an integrity issue may indicate one or more of charge circuit 404 integrity issue, Chold 408 integrity issue, and/or stimulation delivery path integrity issue. For example, if charge count circuit 504 determines the final count value is below a respective minimum integrity issue criterion, charge count circuit 504 may generate data indicating an integrity issue. For example, if charge count circuit 504 determines the final count value is above a respective maximum integrity issue criterion, charge count circuit 504 may generate data indicating an integrity issue.

[0065] In some examples, the techniques of the disclosure include a system that comprises means to perform any method described herein. In some examples, the techniques of the disclosure include a computer-readable medium comprising instructions that cause processing circuitry to perform any method described herein.

[0066] It should be understood that various aspects disclosed herein may be combined in different combinations than the combinations specifically presented in the description and accompanying drawings. It should also be understood that, depending on the example, certain acts or events of any of the processes or methods described herein may be performed in a different sequence, may be added, merged, or left out altogether (e.g., all described acts or events may not be necessary to carry out the techniques). In addition, while certain aspects of this disclosure are described as being performed by a single module, unit, or circuit for purposes of clarity, it should be understood that the techniques of this disclosure may be performed by a combination of units, modules, or circuitry associated with, for example, a medical device.

[0067] The techniques described in this disclosure may be implemented, at least in part, in hardware, software, firmware, or any combination thereof. For example, various aspects of the techniques may be implemented within one or more microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable logic arrays (FPGAs), or any other equivalent integrated or discrete logic QRS circuitry, as well as any combinations of such components, embodied in external devices, such as physician or patient programmers, stimulators, or other devices. The terms “processor” and “processing circuitry” may generally refer to any of the foregoing logic circuitry, alone or in combination with other logic circuitry, or any other equivalent circuitry, and alone or in combination with other digital or analog circuitry.

[0068] For aspects implemented in software, at least some of the functionality ascribed to the systems and devices described in this disclosure may be embodied as instructions on a computer-readable storage medium such as RAM, DRAM, SRAM, magnetic discs, optical discs, flash memories, or forms of EPROM or EEPROM. The instructions may be executed to support one or more aspects of the functionality described in this disclosure. [0069] In addition, in some aspects, the functionality described herein may be provided within dedicated hardware and/or software modules. 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 within common or separate hardware or software components. Also, the techniques could be fully implemented in one or more circuits or logic elements. The techniques of this disclosure may be implemented in a wide variety of devices or apparatuses, including an IMD, an external programmer, a combination of an IMD and external programmer, an integrated circuit (IC) or a set of ICs, and/or discrete electrical circuitry, residing in an IMD and/or external programmer.

[0070] The following examples are illustrative of the techniques described herein. [0071] Example 1 : A device includes a hold capacitor configured to store electrical energy for delivery to a patient as a stimulation pulse; one or more charge pump capacitors; a charge circuit coupled to the one or more charge pump capacitors, the charge circuit configured to charge the hold capacitor with electrical energy; a switch positioned between the charge circuit and the hold capacitor; and a charge pump monitor circuit coupled to the charge circuit and configured to monitor charging of the hold capacitor with electrical energy.

[0072] Example 2: The device recited in example 1, wherein the charge pump monitor circuit is directly coupled to the charge circuit.

[0073] Example 3: The device recited in any of examples 1-2, wherein the charge circuit is configured to perform a charge cycle to charge the hold capacitor. [0074] Example 4 : The device recited in example 3, wherein the charge cycle is from initiating charging of the hold capacitor to when an amplitude of the hold capacitor reaches a particular voltage amplitude threshold.

[0075] Example 5: The device recited in any of examples 3-4, wherein the charge pump monitor circuit is configured to determine a duration to perform the charge cycle. [0076] Example 6: The device recited in example 5, wherein the charge pump monitor circuit is configured to determine the duration to perform the charge cycle based on determining a number of pumps provided by the one or more charge pump capacitors during the charge cycle.

[0077] Example 7: The device recited in example 5, wherein the charge pump monitor circuit is configured to determine the duration to perform the charge cycle based on determining an amount of time of the charge cycle.

[0078] Example 8: The device recited in any of examples 5-7, wherein the charge pump monitor circuit is configured to determine whether the duration of the charge cycle satisfies an integrity issue criterion.

[0079] Example 9: The device recited in example 8, wherein, in response to a determination that the duration of the charge cycle satisfies the integrity issue criterion, the charge pump monitor circuit is configured to generate data indicating an integrity issue. [0080] Example 10: The device recited in example 9, wherein the indicated integrity issue is one or more of an integrity issue of the charge circuit, an integrity issue of the hold capacitor, or an integrity issue of a stimulation pulse delivery path.

[0081] Example 11: The device recited in any of examples 1-10, wherein the charge pump monitor circuit is directly coupled to the charge circuit.

[0082] Example 12: A device includes a memory; and circuitry coupled to the memory, the circuitry configured to: determine a duration of a charge cycle of a hold capacitor configured to store electrical energy for delivery to a patient as a stimulation pulse; determine whether the duration of the charge cycle satisfies an integrity issue criterion; and in response to a determination that the duration of the charge cycle satisfies the integrity issue criterion, generate data indicating an integrity issue.

[0083] Example 13: The device recited in example 12, wherein the indicated integrity issue is one or more of an integrity issue of a charge circuit of the circuitry, an integrity issue of the hold capacitor, or an integrity issue of a stimulation pulse delivery path. [0084] Example 14: The device recited in any of examples 12-13, wherein the processing circuitry is further configured to initiate the charge cycle of the hold capacitor. [0085] Example 15: The device recited in any of examples 12-14, wherein the charge cycle is from initiating charging of the hold capacitor to when an amplitude of the hold capacitor reaches a particular voltage amplitude threshold.

[0086] Example 16: A method includes performing a charge cycle to charge a hold capacitor configured to store electrical energy for delivery to a patient as a stimulation pulse; determining a duration to perform the charge cycle; determining whether the duration satisfies a failure threshold criterion; and in response to a determination that the duration satisfies the failure threshold criterion, generating data indicating a failure.

[0087] Example 17: The method of example 16, wherein the indicated failure is one or more of a failure of a charge circuit, a failure of the hold capacitor, or a failure of a stimulation pulse delivery path.

[0088] Example 18: The method of any of examples 16-17, the method further includes sending a signal to initiate the charge cycle of the hold capacitor.

[0089] Example 19: The method of any of examples 16-18, wherein the charge cycle extends from initiating charging of the hold capacitor to when an amplitude of the hold capacitor reaches a particular voltage amplitude threshold.

[0090] Example 20: A non-transitory computer-readable storage medium storing instructions that, when executed, cause one or more processors of a device configured to process patient data to perform any combination of methods of examples 16-19.

[0091] Various aspects of the disclosure have been described. These and other aspects are within the scope of the following claims.

Claims

WHAT IS CLAIMED IS:

1. A device comprising: a hold capacitor configured to store electrical energy for delivery to a patient as a stimulation pulse; one or more charge pump capacitors; a charge circuit coupled to the one or more charge pump capacitors, the charge circuit configured to charge the hold capacitor with electrical energy; a switch positioned between the charge circuit and the hold capacitor; and a charge pump monitor circuit coupled to the charge circuit and configured to monitor charging of the hold capacitor with electrical energy.

2. The device recited in claim 1, wherein the charge pump monitor circuit is directly coupled to the charge circuit.

3. The device recited in any of claims 1-2, wherein the charge circuit is configured to perform a charge cycle to charge the hold capacitor.

4. The device recited in claim 3, wherein the charge cycle is from initiating charging of the hold capacitor to when an amplitude of the hold capacitor reaches a particular voltage amplitude threshold.

5. The device recited in any of claims 3-4, wherein the charge pump monitor circuit is configured to determine a duration to perform the charge cycle.

6. The device recited in claim 5, wherein the charge pump monitor circuit is configured to determine the duration to perform the charge cycle based on determining a number of pumps provided by the one or more charge pump capacitors during the charge cycle.

7. The device recited in claim 5, wherein the charge pump monitor circuit is configured to determine the duration to perform the charge cycle based on determining an amount of time of the charge cycle.

8. The device recited in any of claims 5-7, wherein the charge pump monitor circuit is configured to determine whether the duration of the charge cycle satisfies an integrity issue criterion.

9. The device recited in claim 8, wherein, in response to a determination that the duration of the charge cycle satisfies the integrity issue criterion, the charge pump monitor circuit is configured to generate data indicating an integrity issue.

10. The device recited in claim 9, wherein the indicated integrity issue is one or more of an integrity issue of the charge circuit, an integrity issue of the hold capacitor, or an integrity issue of a stimulation pulse delivery path.

11. The device recited in any of claims 1-10, wherein the charge pump monitor circuit is directly coupled to the charge circuit.

12. A device comprising: a memory; and circuitry coupled to the memory, the circuitry configured to: determine a duration of a charge cycle of a hold capacitor configured to store electrical energy for delivery to a patient as a stimulation pulse; determine whether the duration of the charge cycle satisfies an integrity issue criterion; and in response to a determination that the duration of the charge cycle satisfies the integrity issue criterion, generate data indicating an integrity issue.

13. The device recited in claim 12, wherein the indicated integrity issue is one or more of an integrity issue of a charge circuit of the circuitry, an integrity issue of the hold capacitor, or an integrity issue of a stimulation pulse delivery path.

14. The device recited in any of claims 12-13, wherein the processing circuitry is further configured to initiate the charge cycle of the hold capacitor.

15. The device recited in any of claims 12-14, wherein the charge cycle is from initiating charging of the hold capacitor to when an amplitude of the hold capacitor reaches a particular voltage amplitude threshold.