T-wave morphology monitoring for assessing cardiac pacing

Abstract

A medical device system delivers ventricular pacing pulses as conduction system pacing (CSP) pulses in at least one example. The medical device system senses at least one cardiac electrical signal and obtains at least one post-pace T-wave from the at least one cardiac electrical signal sensed following a delivered CSP pulse. The medical device system may determine at least one T-wave match metric between the at least one post-pace T-wave and at least one T-wave template and determine that effective CSP criteria corresponding to capture of at least a portion of a cardiac conduction system are not met based on the at least one T-wave match metric.

Description

Ref. No. A0012277W001T-WAVE MORPHOLOGY MONITORING FOR ASSESSING CARDIAC PACINGCROSS-RELATED APPLICATION

[0001] This application claims the benefit of U.S Provisional Patent Application Serial No. 63 / 692,526 filed September 9, 2024, the entire content of which is incorporated herein by reference.TECHNICAL FIELD

[0002] The disclosure relates generally to a cardiac medical device and method for analyzing T-wave signals for assessing cardiac pacing, such as conduction system pacingBACKGROUND

[0003] During normal sinus rhythm (NSR), the heartbeat is regulated by electrical signals produced by the sino-atrial (SA) node located in the right atrial wall. Each depolarization signal produced by the SA node spreads across the atria, causing the depolarization and contraction of the atria, and arrives at the atrioventricular (AV) node. The AV node responds by propagating a depolarization signal through the bundle of His of the atrioventricular septum and thereafter to the left and right bundle branches and the Purkinje fibers of the right and left ventricles, sometimes referred to as the “His-Purkinje system” and referred to herein as the “conduction system.”

[0004] Patients with poor SA node function, poor AV node conduction (referred to as AV block), or conduction system abnormalities of the His bundle or left and / or right bundle branches (e.g., bundle branch block) or other conduction system abnormalities may receive a pacemaker to restore a more normal heart rhythm and heart chamber synchrony. Atrial pacing may be performed to provide a regular atrial rate in a patient having SA node dysfunction. Ventricular pacing may be performed to promote a regular ventricular rate in a patient having AV conduction abnormalities or bundle branch block, for example. A single chamber ventricular pacemaker may be coupled to a transvenous ventricular lead carrying electrodes, which may be placed in the right ventricle (RV) for instance. The pacemaker itself is generally implanted in a subcutaneous pocket with the transvenous lead tunneled to the subcutaneous pocket. The pacemaker may sense cardiac electricalRef. No. A0012277W001 signals via electrodes carried by the transvenous lead and deliver ventricular pacing as needed. Intracardiac pacemakers have been introduced or proposed for implantation entirely within a patient’s heart, eliminating the need for transvenous leads. An intracardiac pacemaker may provide sensing and pacing from within a chamber of the patient’s heart, e.g., from within the right ventricle in a patient having AV conduction block.

[0005] Dual chamber pacemaker systems are available which may include a transvenous atrial lead carrying electrodes which are placed in the right atrium and a transvenous ventricular lead carrying electrodes that are placed in the right ventricle via the right atrium. Some leadless dual chamber pacemaker systems have been proposed for implantation within a patient’s heart, without requiring transvenous leads. A dual chamber pacemaker system senses atrial electrical signals and ventricular electrical signals and can provide both atrial pacing and ventricular pacing as needed to promote a normal atrial and ventricular rhythm and promote AV synchrony when SA node, AV node, bundle branch block or other conduction abnormalities are present.SUMMARY

[0006] In general, this disclosure is directed to a medical device system capable of sensing cardiac electrical signals and providing cardiac pacing and provides techniques for analyzing T-wave signals for assessing cardiac pacing, such as conduction system pacing (CSP) delivered to promote physiologically normal electrical and mechanical synchrony of the heart chambers. For example, T-waves, attendant to the repolarization of the ventricles, may be sensed by an implantable medical device and analyzed to assess CSP for use in detecting CSP capture, guiding CSP electrode placement, selecting or adjusting CSP control parameters, and / or monitoring for T-wave morphology changes over time that may occur with disease progression, cardiac remodeling or CSP electrode shifting or dislodgment.

[0007] For example, an implantable medical device operating according to the techniques disclosed herein may deliver ventricular pacing pulses, sense post-pace T-waves acquired following delivered ventricular pacing pulses, and determine one or more T-wave match metrics between the post-pace T-waves and one or more T-wave templates. Based on theRef. No. A0012277W001T-wave match metrics, the medical device may generate a notification and / or adjust a pacing control parameter.

[0008] In one example, the disclosure provides a medical device system including a therapy delivery circuit configured to deliver ventricular pacing pulses including CSP pulses and a sensing circuit configured to sense at least one cardiac electrical signal. The medical device system includes a memory configured to store at least one T-wave template. The medical device system includes control circuitry configured to obtain at least one post-pace T-wave from the at least one cardiac electrical signal sensed by the sensing circuit following a CSP pulse delivered by the therapy delivery circuit and determine at least one T-wave match metric between the at least one post-pace T-wave and at least one T-wave template stored in the memory. The control circuitry may be further configured to determine that effective CSP criteria corresponding to capture of at least a portion of a cardiac conduction system are not met based on the at least one T-wave match metric, generate an output in response to the effective CSP criteria not being met and store the output in the memory for controlling a response to determining that the effective CSP criteria are not met.

[0009] In another example, the disclosure provides a method including delivering ventricular pacing pulses comprising CSP pulses, sensing at least one cardiac electrical signal and storing at least one T-wave template in a memory of a medical device system. The method may further include obtaining at least one post-pace T-wave from the at least one cardiac electrical signal sensed following a delivered CSP pulse, determining at least one T-wave match metric between the at least one post-pace T-wave and at least one T- wave template stored in the memory and determining that effective CSP criteria corresponding to capture of at least a portion of a cardiac conduction system are not met based on the at least one T-wave match metric. The method may include generating an output in response to the effective CSP criteria not being met, and storing the output in the memory for controlling a response to determining that the effective CSP criteria are not met.

[0010] In yet another example, the disclosure provides a non-transitory, computer readable medium storing a set of instructions that, when executed by control circuitry of a medical device system, cause the medical device system to deliver ventricular pacing pulses including CSP pulses, sense at least one cardiac electrical signal and obtain at leastRef. No. A0012277W001 one post-pace T-wave from the at least one cardiac electrical signal sensed following a delivered CSP pulse. The instructions may further cause the medical device system to determine at least one T-wave match metric between the at least one post-pace T-wave and at least one T-wave template, determine that effective CSP criteria corresponding to capture of at least a portion of a cardiac conduction system are not met based on the at least one T-wave match metric and generate an output in response to the effective CSP criteria not being met. The instructions may further cause the medical device system to control a response to determining that the effective CSP criteria are not met based on the output.

[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 DRAWINGS

[0012] FIG. l is a diagram of a medical device system for sensing and analyzing cardiac electrical signals and delivering cardiac pacing according to some examples.

[0013] FIG. 2 is a diagram of a leadless pacemaker that may be configured to operate according to the methods disclosed herein in some examples.

[0014] FIG. 3 is a diagram of a medical device system including a leadless pacemaker implanted at a different CSP site than the position shown in FIG. 2.

[0015] FIG. 4 is a diagram of circuitry that may be enclosed within an implantable pacemaker configured to deliver cardiac electrical stimulation therapies and sense cardiac electrical signals according to the techniques disclosed herein.

[0016] FIG. 5 is a flow chart of a method for performing T-wave analysis by a medical device system, e.g., ofFIGs. 1 — 3, according to some examples.

[0017] FIG. 6 is a diagram of post-pace T-waves and that may be analyzed by processing circuitry of a medical device system for determining one or more T-wave match metrics according to some examples.

[0018] FIG. 7 is a flow chart of a method for establishing an intrinsic T-wave template and a CSP T-wave template according to some examples.Ref. No. A0012277W001

[0019] FIG. 8 is a flow chart of a method for providing user feedback during CSP electrode positioning according to some examples.

[0020] FIG. 9 is a flow chart of a method that may be performed by a medical device for selecting a pacing control parameter based on T-wave morphology analysis according to some examples.

[0021] FIG. 10 is a flow chart of a method that may be performed by a medical device for selecting a pacing pulse output used for delivering CSP based on analysis of T-wave morphology according to some examples.

[0022] FIG. 11 is a diagram of T-wave templates, each shown as a representative waveform morphology, that may be established by a medical device system and stored in memory for comparing to post-pace T-waves during a CSP capture test.

[0023] FIG. 12 is a flow chart of a method that may be performed by a medical device system for monitoring changes in the post-pace T-wave morphology over time according to some examples.

[0024] FIG. 13 is a diagram of T-wave match metrics that may be determined by a medical device system and logged in memory for long-term monitoring of T-wave morphology.DETAILED DESCRIPTION

[0025] A medical device system is disclosed herein that is capable of delivering cardiac pacing, sensing cardiac electrical signals, and monitoring post-pace T-waves of a sensed cardiac electrical signal for detecting changes in the T-wave morphology. In some examples, the medical device system performing techniques disclosed herein may be configured to deliver ventricular pacing via the conduction system, referred to herein as “conduction system pacing” (CSP). In this case, at least one electrode of a ventricular pacing electrode vector may be implanted in operative proximity to the conduction system, e.g., in the area of the His bundle, the left bundle branch (LBB), right bundle branch (RBB) and / or Purkinje fibers, for pacing and capturing at least a portion of the conduction system. Myocardial ventricular pacing, via electrodes at or near the right ventricular apex for instance, has been found to be associated with increased risk of atrial fibrillation and heart failure. Delivery of ventricular pacing at sites along or in the area of the His-Purkinje conduction system for capturing at least a portion of the conduction system may promote aRef. No. A0012277W001 more physiological electrical activation pattern of the heart because the pacing-evoked depolarizations can be propagated along the native conduction system. Pacing the ventricles via the His bundle, the RBB and / or the LBB for example, allows recruitment along the heart’s natural conduction system, including the Purkinje fibers.

[0026] When CSP is being delivered, a ventricular pacing pulse that captures the cardiac tissue to cause a pacing evoked response may capture a portion of the conduction system, myocardial tissue or both. The term “capture” refers to the pacing-evoked depolarization of cardiac tissue propagating through the ventricles and resulting in a QRS complex in the cardiac electrical signal that is caused by a delivered pacing pulse as opposed to an intrinsic depolarization of the cardiac tissue (e.g., arising from the SA node, conducted via the AV node, or arising from an ectopic site) and the associated intrinsic QRS complex that occurs in the cardiac signal when a pacing pulse is not delivered.

[0027] A cardiac pacing evoked response signal, e.g., the QRS waveform following a ventricular pacing pulse, is followed by the T-wave during myocardial repolarization. The T-wave can have a morphology that changes if the type of capture achieved by the CSP pulse changes, e.g., conduction system capture without myocardial capture (referred to herein as “selective CSP capture”), myocardial only capture without conduction system capture (e.g., loss of conduction system capture), or a combination of both conduction system capture and myocardial capture (referred to herein as “non-selective CSP capture”). Accordingly, a change in the CSP pulse output (e.g., pacing pulse amplitude and / or pacing pulse width defining the delivered energy of the pacing pulse) can result in a change in the post-pace T-wave morphology. A change in the position of the pacing electrodes, e.g., relative to a portion of the conduction system, can alter the type of capture being achieved (or loss of capture) resulting in a change in the post-pace T-wave. Changes in other pacing control parameters, e.g., the AV pacing interval used to control the timing of CSP pulses after an atrial P-wave or atrial pacing pulse, can result in a change in the T- wave morphology as the repolarization of the ventricles may become relatively more synchronous (e.g., relatively lower temporal or spatial heterogeneity in repolarization of the ventricular myocardium) or more dyssynchronous (e.g., relatively greater temporal or spatial heterogeneity in repolarization). According to the techniques disclosed herein, an implantable medical device, e.g., a pacemaker or implantable cardioverter defibrillator (ICD), may assess post-pace T-wave morphology following CSP pulses for use inRef. No. A0012277W001 monitoring for capture, adjusting CSP control parameters, guiding electrode placement, and / or generating a notification when a change in T-wave morphology is detected that may be due to a shift or change in electrode location.

[0028] In addition to or alternatively to detecting short term, acute changes in T-wave morphology that may occur as a pacing control parameter is changed or a pacing electrode position is adjusted, aspects of the techniques disclosed herein may be performed for detecting T-wave morphology changes that may occur more gradually over time. Intrinsic and / or post-pace T-wave morphology can change over time due to cardiac remodeling, disease progression (or regression), or dislodgement or shifting in pacing electrode location, as examples. A medical device system performing the techniques disclosed herein may detect a change in T-wave morphology over time and generate a notification or T-wave morphology report as further described according to the examples presented herein.

[0029] FIG. 1 is a diagram of a medical device system 10 for sensing and analyzing cardiac electrical signals and delivering cardiac pacing according to some examples. Medical device system 10 includes a pacemaker 14 connected to an atrial lead 16 and a ventricular lead 18 in this example. In some examples, the medical device system 10 may include a coronary sinus lead 40 for delivering left ventricular pacing pulses, e.g., during cardiac resynchronization therapy (CRT). Pacemaker 14 includes a housing 15, which may be hermetically sealed, to enclose internal circuitry corresponding to the various circuits and components for sensing cardiac signals from heart 8 and controlling cardiac pacing delivered to heart 8 by pacemaker 14. The housing 15 may be formed of a conductive material, such as titanium or titanium alloy. The housing 15 may function as an electrode (sometimes referred to as a “can” electrode). In some examples, housing 15 may be available as a return anode electrode for delivering unipolar pacing pulses and / or in a sensing electrode vector for sensing cardiac electrical signals in combination with electrodes carried by lead 16 and lead 18.

[0030] Pacemaker 14 includes a connector assembly 13 (sometimes referred to as a “connector block” or “header”), coupled to housing 15, having connector bores configured to receive the proximal lead connectors (not shown) of atrial lead 16 and ventricular lead 18. Connector block 13 may have one or more connector bores for receiving one or more leads. For example, connector block 13 may include a third connector bore for receiving aRef. No. A0012277W001 coronary sinus lead for providing pacing and sensing in the left ventricle (LV) of heart 8 from a location in a cardiac vein along the left lateral free wall in some examples.

[0031] Atrial lead 16 is shown advanced transvenously into the right atrium (RA) of a patient’s heart 8 for sensing atrial signals, e.g., P-waves attendant to atrial depolarizations, and for delivering atrial pacing pulses. Atrial lead 16 includes pacing and sensing electrodes 20 and 22. Electrode 20 is shown as a screw-in, helical tip electrode at the distal end of atrial lead 16. Electrode 22 is shown as a ring electrode (e.g., circumscribing the atrial lead body 17) spaced proximally from tip electrode 20. Electrodes 20 and 22 can form a bipolar pair for sensing atrial signals and delivering atrial pacing pulses via tip electrode 20 as a cathode electrode and ring electrode 22 as the return anode electrode, for example. Atrial lead 16 includes an elongated lead body 17 through which insulated electrical conductors extend from the respective electrodes 20 and 22 to the proximal lead connector (not shown) connected to the pacemaker 14 via connector assembly 13. The electrodes 20 and 22 are thereby connected to internal electronics of pacemaker 14 via respective electrical feedthroughs in connector assembly 13 that cross pacemaker housing 15.

[0032] Ventricular lead 18 is shown advanced transvenously into the right atrial chamber of a patient’s heart 8 and further into the right ventricle (RV) for positioning tip electrode 32 within the interventricular septum 12. Tip electrode 32 may be operatively positioned in the vicinity of the heart’s conduction system, e.g., at a His bundle pacing site, a left bundle branch area pacing (LBBAP) site or at a right bundle branch area pacing (RBBAP) site. Delivery of ventricular pacing via the conduction system, e.g., His bundle pacing, LBBAP or RBBAP, may promote a relatively more normal electrical activation pattern of the ventricles than pacing the ventricular myocardium. Myocardial ventricular pacing via electrodes at or near the right ventricular apex, for example, has been found to be associated with increased risk of atrial fibrillation and heart failure. Delivery of ventricular pacing at sites along the His-Purkinje conduction system of the heart, for capturing at least a portion of the conduction system, may promote a more physiological electrical activation pattern of the heart because the pacing-evoked depolarizations can be propagated along the native conduction system, e.g., along the bundle branches and Purkinje fibers. Pacing the ventricles via the His bundle, the RBB and / or the LBB for example, allows recruitment along the heart’s natural conduction system, including the Purkinje fibers, and subsequentRef. No. A0012277W001 propagation of the depolarization wavefronts through the ventricular myocardium followed by repolarization. CSP can promote improvement in electrical synchrony, which can be accompanied by improved hemodynamics, and may be reflected in changes in the post-pace T-wave morphology during effective CSP compared to a baseline or intrinsic T- wave morphology.

[0033] Ventricular lead 18 is positioned for sensing ventricular event signals and for delivering ventricular pacing pulses as CSP pulses. Ventricular lead 18 includes pacing and sensing electrodes 32 and 34 for delivering CSP pulses and sensing ventricular event signals, e.g., R-waves attendant to intrinsic depolarization of the ventricular myocardium, post-pace R-waves attendant to pacing-evoked ventricular depolarizations, intrinsic T- waves attendant to repolarization of the ventricular myocardium following an intrinsic R- wave, and post-pace T-waves attendant to ventricular repolarization following pacing- evoked R-waves.

[0034] Electrode 32 is shown as a screw-in, helical tip electrode at the distal end of ventricular lead 18. Electrode 34 is shown as a ring electrode spaced proximally from tip electrode 32 and circumscribing ventricular lead body 19. Electrodes 32 and 34 can form a bipolar pair for sensing ventricular signals and delivering pacing pulses via tip electrode 32 as a cathode electrode and ring electrode 34 as the return anode electrode, for example. While the electrodes 20, 22, 32 and 34 are represented as either helical screw-in electrodes or ring electrodes in FIG. 1, it is to be understood that other electrode types may be used such as button electrodes, hook electrodes, segmented electrodes, short coil electrodes, or the like. Tip electrode 32 of ventricular lead 18 may be a tissue-piercing electrode, which may or may not have a helical shape, to facilitate advancement of tip electrode 32 into the interventricular septum 12 to a CSP site in the area of the His bundle, LBB or RBB in some examples.

[0035] In some instances, pacemaker 14 may be capable of delivering cardioversion / defibrillation (CV / DF) shocks for treating ventricular tachyarrhythmias. In this case, ventricular lead 18 (and / or another lead coupled to pacemaker 14) may carry one or more coil electrodes 36 and 38 for use in delivering high voltage CV / DF shocks. As such, while pacemaker 14 is referred to as a “pacemaker” herein, it could be referred to as “implantable cardioverter defibrillator” or “ICD” when capable of delivering high voltage CV / DF shocks in addition to the pacing functionality as disclosed herein.Ref. No. A0012277W001

[0036] Ventricular lead 18 includes an elongated lead body 19 through which insulated electrical conductors extend from the respective electrodes 32 and 34 (and coil electrodes 36 and 38 if present) to a proximal lead connector (not shown) connected to the pacemaker 14 via connector assembly 13. The electrodes 32 and 34 (and coil electrodes 36 and 38 if present) are thereby connected to internal electronics of pacemaker 14 via respective electrical feedthroughs in connector assembly 13 that cross pacemaker housing 15.

[0037] Electrodes 20, 22, 32, and 34 (and 36 and 38 if present) may be formed from titanium, platinum, iridium or alloys thereof, as examples with no limitation intended, and may include a low polarizing coating, such as titanium nitride, iridium oxide, ruthenium oxide, platinum black, among others. Lead bodies 17 and 19 may each be formed from a non-conductive material, including silicone, polyurethane, fluoropolymers, mixtures thereof, and / or other appropriate materials. Each lead body may be shaped to form one or more lumens within which one or more insulated electrical conductors extend between the proximal lead connectors and the distal electrodes 20, 22, 32, 34, 36 and 38 carried by the respective lead 16 or 18.

[0038] While ventricular lead 18 is shown advanced into the RV for positioning tip electrode 32 in the interventricular septum 12 for delivering ventricular pacing pulses in the septum 12, e.g., in the area of the LBB or the RBB for delivering CSP, it is to be understood that the distal end of ventricular lead 18 may be positioned at other locations for delivering ventricular pacing to heart 8 for causing depolarizations of the tissue of the conduction system and / or ventricular myocardium thereby pacing the ventricles. For instance, ventricular lead tip electrode 32 may be positioned along or in the area of the His bundle and / or the RBB or LBB in a basal portion of the interventricular septum 12. In other examples, ventricular lead 18 may be advanced into the right atrium with tip electrode 32 advanced into the interatrial septum toward the His bundle, e.g., at the inferior end of the interatrial septum. The tip electrode 32 of ventricular lead 18 may be advanced toward the His bundle from a location beneath the AV node and near the tricuspid valve annulus, generally in the Triangle of Koch, to position tip electrode 32 near the His bundle from a right atrial approach. The techniques disclosed herein are not limited to particular ventricular pacing and sensing locations and may be practiced in a variety of medical device systems including at least one electrode that can be positioned atRef. No. A0012277W001 a ventricular pacing site, e.g., a CSP site, including leadless pacemakers and / or pacemakers or ICDs coupled to one or more leads.

[0039] Ventricular lead 18 is shown as an example “true bipolar lead,” including tip electrode 32 and ring electrode 34 for sensing ventricular electrical signals from the bipolar sensing electrode vector between tip electrode 32 and ring electrode 34. Pacemaker 14 may additionally or alternatively sense ventricular signals using the tip electrode 32 and the coil electrode 36 in an integrated bipolar sensing electrode pair. The ventricular sensing electrode vector can be “true bipolar” between the tip electrode 32 and a ring electrode 34 or “integrated-bipolar” between tip electrode 32 and coil electrode 36. In some examples, ventricular lead 18 may be an “integrated bipolar lead,” e.g., having tip electrode 32 and at least one high voltage coil electrode 36, without ring electrode 34 such that ventricular signal sensing is performed using an integrated bipolar sensing electrode vector. The techniques disclosed herein for monitoring T-wave morphology can be implemented in conjunction with true bipolar sensing, integrated bipolar sensing or unipolar sensing of a cardiac electrical signal from which T-waves are acquired and analyzed.

[0040] Pacemaker 14 includes therapy delivery circuitry for generating pacing pulses delivered via the atrial lead 16 and ventricular lead 18. As described below, cardiac electrical signal sensing circuitry included in pacemaker 14 may receive an atrial electrical signal sensed from electrodes carried by atrial lead 16 and a ventricular electrical signal sensed from electrodes carried by ventricular lead 18 for use in sensing cardiac event signals and controlling the timing and delivery of atrial pacing pulses and ventricular pacing pulses.

[0041] While pacemaker 14 may be configured as a dual chamber pacemaker receiving both atrial lead 16 and ventricular lead 18, it is to be understood that in other examples, pacemaker 14 may be a single chamber device, e.g., configured to receive one lead for sensing cardiac electrical signals and delivering ventricular pacing without necessarily having atrial pacing capabilities. A lead and electrode configuration for delivering ventricular pacing may be configured to enable dual chamber (atrial and ventricular) sensing by the pacemaker, e.g., when ventricular lead 18 is advanced to a His bundle pacing site from the right atrium such that atrial signals and ventricular signals can be sensed by electrodes carried by ventricular lead 18. In still other examples, pacemaker 14Ref. No. A0012277W001 may be a multi-chamber pacemaker configured to sense cardiac signals and deliver atrial pacing via atrial lead 16, ventricular pacing via ventricular lead 18, and left ventricular pacing via coronary sinus lead 40 that may be advanced via the coronary sinus (CS) ostium of the right atrium into the coronary sinus and further into a cardiac vein to a left ventricular pacing site, e.g., for delivering left ventricular pacing pulses during cardiac resynchronization therapy (CRT).

[0042] Coronary sinus lead 40 may be included in medical device system 10 in some examples to provide pacing and sensing in the left ventricle (LV) of heart 8 from a location in a cardiac vein along the left lateral free wall, for instance. Coronary sinus lead 40, or an LV epicardial lead in other examples, may be provided for delivering CRT to promote electrical and mechanical synchrony of the left and right ventricles. In CRT, an LV pacing pulse may be delivered at an AV pacing interval from a sensed P-wave or atrial pacing pulse to promote synchrony (e.g., fusion) with an intrinsically conducted ventricular depolarization. In other instance, an LV pacing pulse may be delivered at an interventricular (VV) pacing interval relative to an R-wave sensed in the RV or relative to an RV pacing pulse or a CSP pulse. For instance, the LV pacing pulse delivered by coronary sinus lead 40 may be delivered at an AV pacing interval following an atrial P- wave or atrial pacing pulse and the CSP pulse delivered by lead 18 may be delivered at a VV interval from the LV pacing pulse. In other instances, the CSP pacing pulse delivered by lead 18 may be delivered at an AV pacing interval following an atrial P-wave or atrial pacing pulse and the LV pacing pulse delivered by coronary sinus lead 40 may be delivered at a VV interval from the CSP pulse to deliver coordinated multi-chamber or biventricular pacing.

[0043] Coronary sinus lead 40 is shown carrying four electrodes 44, 45, 46 and 47 along the distal portion of lead body 41, which may be advanced through the RA, into the coronary sinus (CS) ostium, and further into a cardiac vein in or along the LV free wall. Insulated electrical conductors (not shown) extending through lead body 41 from a proximal lead connector (not shown) to each of the respective electrodes 44, 45, 46 and 47 allow for signals to be carried from / to electrodes 44, 45, 46 and 47 to / from internal electronics of pacemaker 14 via respective electrical feedthroughs in connector assembly 13 that cross pacemaker housing 15. Electrodes 44, 45, 46 and 47 are shown as ring electrodes (e.g., circumscribing the coronary sinus lead body 41) spaced apart along aRef. No. A0012277W001 distal portion of lead body 41. An LV sensing and / or pacing electrode vector may be selected from electrodes 44, 45, 46 and 47 for coupling to sensing circuitry and / or pacing circuitry included in pacemaker 14 (e.g., as shown in FIG. 4 and described below). For example, any pair of electrodes 44, 45, 46 and 48 can form a bipolar pair for sensing LV signals and / or delivering LV pacing pulses. Any one of electrodes 44, 45, 46 or 48 may be paired with housing 15 for unipolar sensing or pacing.

[0044] Medical device system 10 is shown including an external medical device 50 for receiving data from pacemaker 14 and for transmitting programming commands to pacemaker 14, which may include various sensing and pacing control parameters used by pacemaker 14. External device 50 may receive data from pacemaker 14 which may include atrial and / or ventricular electrical signal episodes, sensed cardiac event signal data, and therapy delivery data logged by pacemaker 14.

[0045] External device 50 may be embodied as a programmer used in a hospital, clinic or physician’s office to program pacemaker 14 and to acquire data from pacemaker 14. External device 50 may alternatively be embodied as a handheld device, such as a tablet or cell phone. In some examples, external device 50 is a home monitor configured to interrogate pacemaker 14 to receive signals or data from pacemaker 14 and transmit data to pacemaker 14 via a wireless communication link 48. An example programmer that may be configured to program pacemaker 14 and included in medical device system 10 configured to perform the techniques disclosed herein is the CARELINK® Programmer, commercially available from Medtronic, Inc., Dublin, Ireland.

[0046] External device 50 may include a processor 52, memory 53, display unit 54, user interface unit 56, and telemetry unit 58. Processor 52 is coupled to the other components and units of external device 50, e.g., via a data bus, for controlling the functions attributed to external device 50 herein. Processor 52 may execute instructions stored in memory 53. Processor 52 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 analog logic circuitry. In some examples, processor 52 may include multiple components, such as any combination of one or more microprocessors, one or more controllers, one or more DSPs, one or more ASICs, or one or more FPGAs, as well as other discrete or integrated logic circuitry. The functions attributed to processor 52 herein may be embodied as software, firmware, hardware or anyRef. No. A0012277W001 combination thereof. Memory 53 may include any volatile, non-volatile, magnetic, optical, or electrical media, such as a random access memory (RAM), read-only memory (ROM), non-volatile RAM (NVRAM), electrically-erasable programmable ROM (EEPROM), flash memory, or any other digital or analog media. Memory 53 may include non- transitory computer-readable media that may store instructions that, when executed by processor 52, cause medical device system 10 to perform various methods and functions attributed to medical device system 10 as disclosed herein.

[0047] User interface unit 56 may include a mouse, touch screen, keypad or the like to enable a user to interact with external device 50, e.g., to initiate and terminate an interrogation session for retrieving data from pacemaker 14, adjust settings of display unit 54, enter programming commands or selections or make other user requests. Display unit 54, which may include a liquid crystal display, light emitting diodes (LEDs) and / or other visual display components, may generate a display of cardiac electrical signals received from pacemaker 14 and / or data derived therefrom. Display unit 54 may be configured to generate a graphical user interface (GUI) including various windows, icons, user selectable menus, etc. to facilitate interaction by a user with the external device 50. Display unit 54 may display various windows to a user, e.g., in a GUI, for enabling a clinician or other user to review cardiac event signal sensing and therapy delivery related data retrieved from pacemaker 14.

[0048] Display unit 54 may function as an input and / or output device using technologies including liquid crystal displays (LCD), quantum dot display, dot matrix displays, light emitting diode (LED) displays, organic light-emitting diode (OLED) displays, cathode ray tube displays, e-ink, or monochrome, color, or any other type of display capable of generating tactile, audio, and / or visual output. In some examples, display unit 54 is a presence-sensitive display. Display unit 54 may serve as a user interface device that operates both as one or more input devices and one or more output devices.

[0049] External device 50 may receive data, via telemetry unit 58, from pacemaker 14 via the wireless communication link 48. Data received from pacemaker 14 may include cardiac signals, e.g., intracardiac electrogram (EGM) signals sensed by pacemaker 14, marker channel data indicating the timing of pacing pulses delivered by pacemaker 14 and sensed cardiac event signals (e.g., P-waves, R-waves and T-waves), and data relating to the pacing history.Ref. No. A0012277W001

[0050] Telemetry unit 58 includes a transceiver and antenna configured for bidirectional communication with a communication circuit included in an implantable pacemaker 14, e.g., in response to user requests. Telemetry unit 58 includes communication circuitry configured to operate in conjunction with processor 52 for sending and receiving data relating to pacemaker functions via a wireless communication link 48 with the implantable pacemaker 14. Communication link 48 may be established using a radio frequency (RF) link such as BLUETOOTH®, Wi-Fi, Medical Implant Communication Service (MICS) or other communication bandwidth. In some examples, external device 50 may include a programming head that is placed proximate pacemaker 14 to establish and maintain communication link 48, and in other examples external device 50 and pacemaker 14 may be configured to communicate using a distance telemetry algorithm and circuitry that does not require the use of a programming head and does not require user intervention to maintain a communication link 48.

[0051] It is contemplated that external device 50 may be in wired or wireless connection to a communications network via telemetry unit 58 that includes a transceiver and antenna or via a hardwired communication line for transferring data to a centralized database or computer to allow remote management of the patient. External device telemetry unit 58 may be coupled to a communication network / cloud (not shown in FIG. 1) for receiving and transmitting data to a remote computing device (not shown in FIG. 1), which may be a personal computer, personal mobile device or other computing device at a remote location from the patient to enable remote monitoring of data obtained from pacemaker 14 by a clinician or other user. The CARELINK™ network available from Medtronic, Inc., Dublin, Ireland, is an example of a remote patient monitoring system and database that may collect and display data retrieved from a patient’s pacemaker for review by a clinician or other user.

[0052] FIG. 2 is a diagram of a leadless pacemaker 114 that may be configured to operate according to the methods disclosed herein in some examples. The pacemaker 114 may be positioned within the right atrium for providing ventricular pacing via the conduction system in the area of the His bundle. Pacemaker 114 may include a distal tip electrode 132 extending away from a distal end 112 of the pacemaker housing 115. Leadless pacemaker 114 is shown implanted in the right atrial chamber of the patient’s heart for advancing distal tip electrode 132 to a His bundle pacing site from a right atrial approach. ForRef. No. A0012277W001 example, the distal tip electrode 132 may be inserted into the inferior end of the interatrial septum, beneath the AV node and near the tricuspid valve annulus, generally in the Triangle of Koch, to advance tip electrode 132 to a His bundle pacing site. As described above in conjunction with FIG. 1, in other examples, a tip electrode 32 of ventricular lead 18 (shown in FIG. 1) may be advanced to a His bundle pacing site from a right atrial approach to deliver CSP via a pacing lead, e.g., ventricular lead 18, and pacemaker 14 instead of the leadless pacemaker 114 as shown here.

[0053] In other examples, intracardiac leadless pacemaker 114 may be implanted within the right ventricle, e.g., high along the interventricular septum, for positioning distal tip electrode 132 in the basal portion of the interventricular septum in the vicinity of the His bundle or in another interventricular septal location along the His-Purkinje system for delivering CSP, e.g., in the area of the RBB or LBB. However, leadless pacemaker 114 is not necessarily limited to being implantable at CSP sites and may be implanted at another cardiac site within or on the heart for sensing cardiac signals, delivering pacing pulses and analyzing T-wave morphology according to methods disclosed herein.

[0054] Distal tip electrode 132 may be a helical electrode providing fixation to anchor the pacemaker 114 at the implant position. In other examples, pacemaker 114 may include a fixation member that includes one or more tines, hooks, barbs, helices or other fixation member(s) that anchor the distal end of the pacemaker 114 at the implant site. A proximal portion of the distal tip electrode 132 may be electrically insulated such that only the most distal end of tip electrode 132, furthest from housing distal end 112, is exposed to provide targeted pacing at a tissue site, which may include a portion of the conduction system in some examples.

[0055] One or more housing-based electrodes 120 and 134 may be carried on the surface of the housing 115 of pacemaker 114. Electrodes 120 and 134 are shown as ring electrodes circumscribing the longitudinal sidewall of pacemaker housing 115 that extends from the housing distal end 112 to housing proximal end 110. In other examples, a return anode electrode used in sensing and pacing may be positioned on housing proximal end 110. Ventricular pacing may be achieved using the distal tip electrode 132 as the cathode electrode and either of the housing-based electrodes 120 or 134 as the return anode. In some examples, pacing of atrial tissue may be achieved by delivering atrial pacing pulses via the distal ring electrode 120 using proximal ring electrode 134 as the return anodeRef. No. A0012277W001 electrode. In other examples, distal ring electrode 120 shown circumscribing the lateral sidewall of housing 115 for the sake of clarity in FIG. 2 may be located on the pacemaker distal end 112 for providing atrial pacing and atrial sensing, e.g., in combination with proximal ring electrode 134. Ventricular pacing pulses may be delivered in the area of the His bundle via tip electrode 132 with proximal ring electrode 134 as the return anode. In this way, dual chamber pacing of the atria and the ventricles may be delivered by leadless pacemaker 114. In other examples more than two ring electrodes (or other types of electrodes) may be provided on housing 115, e.g., to provide two distinct atrial and ventricular pacing and sensing electrode vectors.

[0056] Cardiac electrical signals may be sensed by pacemaker 114 using one or more sensing electrode pairs selected from electrodes 120, 132 and 134. For example, a ventricular electrical signal may be sensed using distal tip electrode 132 and distal ring electrode 120 or proximal ring electrode 134. Intrinsic R-waves may be sensed by sensing circuitry of pacemaker 114 via the ventricular electrical signal sensing electrode pair for use in inhibiting a scheduled ventricular pacing pulse and scheduling the next ventricular pulse. Pacemaker 114 may sense intrinsic and / or post-pace T-waves from the ventricular electrical signal for assessing T-wave morphology according to the techniques disclosed herein.

[0057] An atrial electrical signal may be sensed using electrodes 120 and 134, for example. Intrinsic P-waves may be sensed by the atrial electrical signal sensing electrode pair for use in inhibiting and scheduling atrial pacing pulses and / or for scheduling atrial synchronous ventricular pacing pulses. The cardiac electrical signals sensed by pacemaker 114 may be used for determining the atrial rate, ventricular rate, and / or for detecting atrial and / or ventricular tachyarrhythmias.

[0058] While external device 50 is not shown in FIG. 2, it is to be understood that pacemaker 114 can be included in a medical device system including external device 50 configured to communicate with pacemaker 114 and in some cases, as described above, with a network / cloud based patient database and / or a remote computing device. Pacemaker 114 may be configured to communicate via a communication circuit with external device 50 for receiving programming commands and transmitting data to external device 50 as generally described above in conjunction with FIG. 1. Leadless pacemaker 114 may be configured to transmit data to external device 50, which may be furtherRef. No. A0012277W001 analyzed by external device processor 52 and / or used in generating a graphical user interface of data acquired by pacemaker 114 for review by a clinician.

[0059] FIG. 3 is a diagram of a medical device system 200 including leadless pacemaker 114 implanted at a different CSP site than the position shown in FIG. 2. In this example, tip electrode 132 may be advanced into the interventricular septum 12 from a right ventricular approach for delivering CSP pulses in the area of the LBB or the area of the RBB, for example, for capturing at least a portion of the conduction system, with or without capturing local myocardial tissue. In other examples, ventricular pacing may be delivered that captures septal myocardial tissue without necessarily capturing a portion of the His-Purkinje conduction system. Pacemaker 114 may sense a ventricular electrical signal using tip electrode 132 and ring electrode 134 for sensing R-waves based on R- wave sensing threshold crossings by the ventricular electrical signal. Pacemaker 114 may apply a post-pace T-wave window for sensing T-waves following CSP pulses that can be assessed for use in adjusting pacing control parameters and / or determining the effectiveness of CSP, CSP capture thresholds, and / or T-wave morphology changes over time according to any of the examples described herein.

[0060] In some cases, the medical device system 200 may include a second leadless pacemaker 214 implanted in the right atrium for delivering atrial pacing pulses and sensing atrial electrical signals. In this example, pacemaker 214 includes a tip electrode 232 that may be paired with a proximal ring electrode 234 circumscribing the lateral sidewall of cylindrical housing 215 of pacemaker 214. Tip electrode 232 is shown as a non-tissue piercing button electrode in this example but may be provided as a tissue piercing or non-tissue piercing electrode and may be any of the types of example electrodes listed herein. Pacemaker 214 may include a fixation member 213, e.g., provided as one or more fixation tines, extending from distal end 212 of pacemaker housing 215 to provide fixation of pacemaker 214 at an atrial pacing site.

[0061] In some examples, atrial pacemaker 214 can provide atrial pacing and sensing and ventricular pacemaker 114 can provide ventricular pacing (via the conduction system and / or ventricular myocardium) and sensing in a dual chamber leadless pacemaker system 200. Atrial pacemaker 214 and ventricular pacemaker 114 may communicate wirelessly, as shown by arrow 218, to coordinate dual chamber pacing delivery. For example, atrial pacemaker 214 may transmit a signal to ventricular pacemaker 114 when an atrial pacingRef. No. A0012277W001 pulse is delivered or an atrial P-wave is sensed so that ventricular pacemaker 114 can deliver an atrial synchronous ventricular pacing pulse at a desired atrioventricular (AV) pacing interval. In other examples, ventricular pacemaker 114 may sense atrial systolic event signals, e.g., from an electrical signal sensed by pacemaker 114 or from an acceleration signal sensed by an accelerometer included in pacemaker 114, for use in synchronizing ventricular pacing pulses to the atrial event signals. While not shown in FIG. 3, it is to be understood that external device 50 as shown in FIG. 1, which may be in communication with a network / cloud and / or remote computing device, may be included in the medical device system 200 and may be configured to send data to and receive data from pacemaker 114 and pacemaker 214, if present.

[0062] While several examples of medical device systems are shown and described in conjunction with FIGs. 1 — 3, it is to be understood that the methods for analyzing postpace T-wave morphology during CSP, as described further in the examples below, are not limited to a particular cardiac device system. The methods disclosed herein may be practiced in any medical device system that includes a medical device that is capable of sensing cardiac electrical signals including T-waves and delivering pacing pulses. In some examples, the medical device that is sensing and analyzing T-waves is not necessarily the same device that is delivering pacing pulses. For example, a subcutaneous cardiac monitor, such as the LINQ® implantable loop recorder available from Medtronic, Inc., Dublin, Ireland, may record T-waves and analyze the T-wave morphology or transmit T- wave signals to external device 50 for analysis by external device processor 52. The T- waves may be sensed by the cardiac monitor following delivery of CSP pulses by pacemaker 14 or 114, for instance. In other examples, an ICD coupled to an extra-cardiac lead or a non-transvenous lead may be co-implanted with a pacemaker, e.g., pacemaker 114, delivering CSP pulses. The ICD may sense ECG signals using electrodes positioned outside the heart and may perform the post-pace T-wave analysis techniques disclosed herein. In still other examples, an implantable medical device such as pacemaker 14 or pacemaker 114 may deliver CSP, and an external cardiac monitor, which may be a wearable device, can be configured to sense cardiac electrical signals and assess post-pace T-wave morphology. As such, the techniques disclosed herein may be performed cooperatively between two or more medical devices included in a medical device system, and processing of T-wave signals for assessing the T-wave morphology and detecting andRef. No. A0012277W001 responding to changes in T-wave morphology may be performed by a different medical device than the device delivering ventricular pacing or in a distributed manner by processing circuitry of the medical device system.

[0063] FIG. 4 is a diagram of circuitry that may be enclosed within implantable pacemaker 14 of FIG. 1 configured to deliver cardiac electrical stimulation therapies and sense cardiac electrical signals according to the techniques disclosed herein. The diagram of FIG. 4 is described with reference to pacemaker 14 connected to atrial lead 16 carrying electrodes 20 and 22 and ventricular lead 18 carrying electrodes 32, 34, 36 and 38. When pacemaker 14 is coupled to a coronary sinus lead in a biventricular or multi-chamber pacing system, e.g., lead 40 shown in FIG. 1, additional electrodes may be selectively coupled to therapy delivery circuit 84 and sensing circuit 86 for delivery of LV pacing pulses, e.g., during CRT. Furthermore, it is to be understood that the functionality attributed to the various circuits and components shown in FIG. 4 may correspond to circuitry enclosed in a pacemaker configured to perform techniques disclosed herein when connected to other pacing lead and electrode configurations or in a leadless pacemaker. For instance, when pacemaker 14 is configured as an implantable cardioverter defibrillator (ICD) with an integrated bipolar lead, one or both of coil electrodes 36 and / or 38 may be present and coupled to therapy delivery circuit 84 for delivering CV / DF shocks and may be coupled to sensing circuit 86 for use in sensing cardiac electrical signals, e.g., in an integrated bipolar sensing electrode vector including tip electrode 32 and ring electrode 34 may be omitted. Pacemaker 14 may be configured to receive one or more leads for electrical connection to circuitry enclosed by housing 15 to enable selection of a variety of pacing and / or sensing electrode configurations for sensing cardiac electrical signals and delivering cardiac pacing therapies. Housing 15 is depicted in FIG. 4 as an electrode coupled to pacemaker circuitry, e.g., for use in a unipolar pacing and / or sensing electrode vector.

[0064] Furthermore, a pacemaker configured to perform the techniques disclosed herein may be a leadless pacemaker, e.g., pacemaker 114 shown in FIG. 2, including housingbased electrodes for sensing atrial signals, delivering atrial pacing pulses, sensing ventricular signals and delivering ventricular pacing pulses. In this case, the multiple housing based electrodes, e.g., electrodes 120, 132 and 134 shown in FIG. 2, can be coupled to sensing circuit 86 and therapy delivery circuit 84. In still other examples,Ref. No. A0012277W001 circuitry generally described in conjunction with FIG. 4 may be included in pacemaker 114 implanted in the right ventricle as shown in FIG. 3 for sensing cardiac signals and delivering ventricular pacing pulses to a pacing site, e.g., in the interventricular septum. The circuitry and functionality of pacemaker 14 described in conjunction with FIG. 4 may be adapted for implementation in a leadless pacemaker or in pacemakers configured to receive one or more pacing leads for performing cardiac signal sensing, cardiac pacing, and T-wave signal analysis as described herein.

[0065] The electronic circuitry enclosed within housing 15 (shown conceptually as an electrode in FIG. 4) includes software, firmware and hardware that cooperatively monitor cardiac electrical signals, determine when a pacing pulse is necessary, and deliver electrical pacing pulses to the patient’s heart as needed according to a programmed pacing mode and other pacing control parameters. The electronic circuitry may include a control circuit 80, memory 82, therapy delivery circuit 84, cardiac electrical signal sensing circuit 86 (also referred to herein as “sensing circuit” 86), communication circuit 88 and power source 98. In some examples, pacemaker 14 may include one or more other sensors 90 for sensing physiological signals. For instance, pacemaker 14 may include a motion sensor such as an accelerometer for sensing patient physical activity, monitoring patient posture, and / or sensing cardiac motion (e.g., when the pacemaker is implanted within the heart such as in the examples of FIGs. 2 or 3). Other examples of physiological sensors that may be included in pacemaker 14 include heart sound sensors, pressure sensors, temperature sensors, oxygen sensors, impedance measurement circuitry or the like.

[0066] Power source 98 provides power to the circuitry of pacemaker 14 including each of the components 80, 82, 84, 86, 88 and 90 as needed. Power source 98 may include one or more energy storage devices, such as one or more rechargeable or non-rechargeable batteries. The connections between power source 98 and each of the other components 80, 82, 84, 86, 88 and 90 are to be understood from the general block diagram of FIG. 4 but are not shown for the sake of clarity. For example, power source 98 may be coupled to one or more charging circuits included in therapy delivery circuit 84 for providing the power needed to charge holding capacitors included in therapy delivery circuit 84 that are discharged at appropriate times under the control of control circuit 80 for delivering pacing pulses. Power source 98 is also coupled to components of sensing circuit 86 (such as sense amplifiers, analog-to-digital converters, switching circuitry, etc.), communicationRef. No. A0012277W001 circuit 88, sensors 90 and memory 82 to provide power to the various components and circuits as needed.

[0067] The components shown in FIG. 4 represent functionality included in pacemaker 14 (or pacemaker 114) and may include any discrete and / or integrated electronic circuit components that implement analog and / or digital circuits capable of producing the functions attributed to pacemaker 14 (and pacemaker 114) herein. The various components may include an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that execute one or more software or firmware programs, a combinational logic circuit, state machine, or other suitable components or combinations of components that provide the described functionality. Providing software, hardware, and / or firmware to accomplish the described functionality in the context of any modem medical device, given the disclosure herein, is within the abilities of one of skill in the art.

[0068] Control circuit 80 communicates, e.g., via a data bus, with therapy delivery circuit 84 and sensing circuit 86 for cooperatively sensing cardiac electrical signals and controlling delivery of cardiac electrical stimulation pulses in response to sensed cardiac event signals (or absence thereof), e.g., R-waves attendant to ventricular depolarization and / or P-waves attendant to atrial depolarization, in accordance with a pacing mode. Electrodes 20, 22, 32, 34, 36 and 38 and housing 15 may be electrically coupled to therapy delivery circuit 84 for delivering electrical stimulation pulses generated by therapy delivery circuit 84. Electrodes 20, 22, 32, 34, 36 and 38 and housing 15 may be electrically coupled to sensing circuit 86 for sensing cardiac electrical signals produced by the heart. Sensing circuit 86 may sense intrinsic signals (such as intrinsic P-waves, intrinsic R-waves and intrinsic T-waves) produced by the heart in the absence of a pacing pulse that captures the respective heart chambers, atrial or ventricular. Sensing circuit 86 may sense evoked response signals, e.g., pacing-evoked P-waves and pacing evoked R- waves, following a delivered pacing pulse of sufficient energy to cause cardiac capture. As further described below, a post-pace T-wave may be sensed following a CSP pulse and the pacing-evoked R-wave for analyzing T-wave morphology during CSP.

[0069] Sensing circuit 86 may include an input pre-filter and amplifier 140 for receiving a cardiac electrical signal from a pair of sensing electrodes, e.g., atrial lead electrodes 20 and 22 and ventricular lead electrodes 32 and 34 or ventricular lead electrodes 32 and 36,Ref. No. A0012277W001 as non-limiting examples of sensing electrode pairs. The filtered and amplified signal may be passed to an analog-to-digital converter and wide bandpass filter (ADC) 141 for producing a multi-bit digital cardiac electrical signal that may be passed to control circuit 80 and is referred to herein as a cardiac electrogram or “EGM” signal when the raw signal is sensed from electrodes on or within a heart chamber.

[0070] In some examples, a wideband filtered EGM signal may be passed to control circuit 80, e.g., from the ADC 141 of a ventricular sensing channel prior to narrowband filtering of the EGM signal that is passed to cardiac event detector circuit 143. The wideband filtered EGM signal may be used for performing morphology analysis of cardiac event signals, e.g., P-waves, R-waves and / or T-waves. For instance, in some examples, an analysis of the T-wave in the wide-band filtered EGM signal may be performed for use in detecting T-wave morphology changes due to changes in pacing electrode position, changes in pacing control parameters, changes in pacing capture threshold, and / or longterm changes in T-wave morphology due to cardiac remodeling, disease progression or other changes. T-wave morphology analysis that may be performed by control circuit 80 of a wide-band or narrow-band EGM signal sensed by a true bipolar, integrated bipolar or unipolar sensing electrode vector is further described below in conjunction with the accompanying flow charts and diagrams.

[0071] Sensing circuit 86 may include a rectifier and narrowband filter / amplifier 142 for receiving the ADC signal and passing a rectified, filtered signal to cardiac event detector circuit 143. Cardiac event detector circuit 143 may produce a cardiac sensed event signal, e.g., a sensed ventricular event (Vsense) signal or a sensed atrial event (Asense) signal, in response to the respective rectified ventricular EGM signal or atrial EGM signal crossing a sensing threshold amplitude, e.g., an R-wave sensing threshold or a P-wave sensing threshold, respectively.

[0072] Sensing circuit 86 may include multiple sensing channels, e.g., a ventricular sensing channel and an atrial sensing channel, and in some examples a far field morphology sensing channel. For example, sensing circuit 86 may include an atrial sensing channel configured to receive an atrial signal from atrial electrodes 20 and 22, which may be filtered, amplified, rectified and passed to an atrial event detector circuit included in cardiac event detector circuit 143. Cardiac event detector circuit 143 may generate an Asense signal in response to the atrial signal crossing a P-wave sensingRef. No. A0012277W001 threshold. A ventricular sensing channel of sensing circuit 86 may receive a ventricular signal from ventricular electrodes 32 and 34 for bipolar sensing, from electrode 32 and either of coil electrodes 36 or 38 (e.g., in an integrated bipolar sensing electrode pair), electrode 34 and either of coil electrodes 36 or 38, or any of ventricular lead electrodes 32, 34, 36 or 38 paired with housing 15, as examples. The ventricular sensing channel may include the same or a different narrowband filter than the atrial sensing channel. A ventricular event detector circuit of cardiac event detector circuit 143 can be configured to generate a Vsense signal in response to the narrowband filtered ventricular signal crossing an R-wave sensing threshold. Each atrial sensing channel and ventricular sensing channel may include separate pre-filter / amplifiers 140, ADC 141, rectifier and narrowband filter / amplifier 142 and cardiac event detector circuit 143 or some components may be shared between the different sensing channels. Cardiac event detector circuit 143 may include one or more sense amplifiers, comparators and / or other components configured to receive the filtered, amplified and (at least in some cases) rectified atrial and ventricular signals, compare the signals to respective P-wave and R-wave sensing thresholds, and generate respective Asense and Vsense signals passed to control circuit 80.

[0073] The sensed event signal can be passed to control circuit 80 for use in controlling pacing pulses. For example, in response to receiving an Asense signal from sensing circuit 86, pace timing and control circuit 147 included in control circuit 80 may set a pacing escape interval timer for scheduling a ventricular pacing pulse at an AV pacing interval (when pacemaker 14 is operating in an atrial synchronous ventricular pacing mode). Control circuit 80 may inhibit an atrial pacing pulse in response to the Asense signal and schedule a subsequent atrial pacing pulse by starting an atrial lower rate interval (LRI) to provide bradycardia pacing of the atria when the LRI expires without an Asense signal being received from sensing circuit 86. The LRI may correspond to a programmed base pacing rate and is used by control circuit 80 to control the minimum heart rate of the patient to be at least the base pacing rate. At other times, the LRI may be a temporary rate response pacing interval based on a patient activity metric determined by control circuit 80 from a patient activity signal received from sensors 90.

[0074] In response to receiving a Vsense signal, a scheduled ventricular pacing pulse may be inhibited, and a ventricular pacing interval, e.g., a ventricular LRI, may be started for scheduling a ventricular pacing pulse. If the ventricular LRI expires before a Vsense signalRef. No. A0012277W001 is received and before an Asense signal is received or an atrial pacing pulse is delivered for triggering an atrial synchronous ventricular pacing pulse at the AV pacing interval, therapy delivery circuit 84 may deliver the scheduled ventricular pacing pulse to pace the ventricles.

[0075] Pace timing and control circuit 147 may include various timers or counters for performing timing related functions of control circuit 80 including, but not limited to, counting down various pacing escape intervals set according to a permanent or temporary pacing mode. The pacing modes of pacemaker 14 may include various bradycardia pacing modes such as single chamber atrial pacing, dual chamber atrial synchronous ventricular pacing, dual chamber atrial asynchronous ventricular pacing, and single chamber ventricular pacing, as non-limiting examples, and may include bradycardia pacing with rate response pacing in some examples. A sensed event signal received from sensing circuit 86 by control circuit 80 may cause pace timing and control circuit 147 to trigger or inhibit a pacing pulse depending on the particular pacing mode in effect.

[0076] The time expired of a pacing escape interval started by pace timing and control circuit 147 when a sensed event signal is received from sensing circuit 86 may be passed to processor 148 as a cardiac event interval for use in determining the heart rhythm, e.g., for detecting tachycardia and / or fibrillation. For example, the time expired of a ventricular pacing escape interval (started in response to a Vsense signal or a delivered ventricular pacing pulse) when the next Vsense signal is received may be determined as an RR interval (RRI). Processor 148 may compare RRIs to a ventricular tachycardia (VT) detection interval and / or a ventricular fibrillation (VF) detection interval for detecting VT and / or VF intervals (VT / VF intervals). Control circuit 80 may include one or more counters used for counting VT / VF intervals, e.g., a VT interval counter, a VF interval counter and / or a combined VT / VF interval counter. When a counter, which may be an X of Y counter, reaches a required number of intervals to detect (NID) VT or VF, control circuit 80 may detect a VT / VF episode and control therapy delivery circuit 84 to deliver a cardiac electrical stimulation therapy, e.g., anti-tachycardia pacing (ATP) or a cardioversion or defibrillation (CV / DF) shock.

[0077] Control circuit 80 may be configured to control therapy delivery circuit 84 to deliver atrial and ventricular pacing pulses according to a programmed or automatically selected pacing mode and programmed or automatically adjusted pacing controlRef. No. A0012277W001 parameters. Therapy delivery circuit 84 is configured to generate pacing pulses and includes a charging circuit 144 including one or more charge storage devices such as one or more holding capacitors, an output circuit 146, and switching circuitry 145. Switching circuitry 145 can be controlled by control signals from control circuit 80 to control when the holding capacitor(s) of charging circuit 144 are charged and when the charged holding capacitor(s) are discharged through the output circuit 146 to deliver pacing pulses via a selected pacing electrode vector for pacing the atria and / or the ventricles (which may be paced via the His-Purkinje conduction system) according to the programmed pacing mode.

[0078] Output circuit 146 may include switching circuitry for selecting the pacing electrode vector(s) and associated pacing electrode polarities coupled to a holding capacitor of charging circuit 144 via switching circuitry 145. For instance, output circuit 146 may include switching circuitry for selecting the ventricular lead tip electrode 32 as a pacing cathode electrode with return anode ring electrode 34 for bipolar CSP in the area of the His bundle, LBB or RBB or at a myocardial pacing site. Alternatively, ring electrode 34 may be selected as a cathode electrode with tip electrode 32 selected as the return anode in a bipolar pacing electrode vector for delivering ventricular pacing via the conduction system and / or ventricular myocardium. The atrial lead electrodes 20 and 22 may be selected by switching circuitry included in output circuit 146 in an atrial pacing electrode vector for delivering atrial pacing pulses.

[0079] Charging of a holding capacitor to a programmed pacing voltage amplitude and discharging of the capacitor for a programmed pacing pulse width may be performed by therapy delivery circuit 84 according to control signals received from control circuit 80. For example, pace timing and control circuit 147 included in control circuit 80 may include programmable digital counters set by processor 148 for controlling the basic pacing time intervals, which can also be referred to as “escape intervals,” associated with various single chamber and dual chamber pacing modes, and in some examples multichamber or bi-ventricular pacing modes. Control circuit 80 may also set the amplitude, pulse width, polarity, or other characteristics of the cardiac pacing pulses, which may be based on programmed values stored in memory 82.

[0080] Therapy delivery circuit 84 may include multiple pacing channels for delivering pacing pulses, e.g., an atrial pacing channel and a ventricular pacing channel. Each pacing channel may be coupled to selected electrodes via switching circuitry included in outputRef. No. A0012277W001 circuit 146 for selecting various unipolar or bipolar pacing electrode combinations for delivering pacing pulses. In some examples, multiple pacing channels may include an additional left ventricular pacing channel, e.g., when pacemaker 14 is coupled to a coronary sinus lead to facilitate delivery of CRT.

[0081] When pacemaker 14 is configured to deliver high voltage CV / DF shocks, therapy delivery circuit 84 may include a high voltage therapy circuit for generating high voltage CV / DF shock pulses in addition to a low voltage therapy circuit that generates cardiac pacing pulses. Therapy delivery circuit 84 may operate under the control of control circuit 80 to deliver a variety of cardiac electrical stimulation pulses, which may include bradycardia pacing pulses, ATP pulses, induction pulses for defibrillation testing, CV / DF shock pulses, post-shock pacing pulses, and impedance measurement drive signals, as examples.

[0082] Sensor(s) 90 may include a patient activity sensor provided for sensing a signal correlated to patient physical activity for use by control circuit 80 in controlling rate response pacing. In one example, the activity sensor is an accelerometer, e.g., a single or multi-axis piezoelectric sensor or MEMS device, for sensing an acceleration signal. The accelerometer may produce an electrical signal correlated to motion or vibration of the accelerometer, e.g., when subjected to patient body motion. The activity sensor may include one or more filter, amplifier, rectifier, anal og-to-digi tai converter (ADC) and / or other components for producing an acceleration signal that may be passed to control circuit 80 for use in determining a patient physical activity metric for controlling rate response pacing.

[0083] In various examples, an acceleration signal received from sensor(s) 90 by control circuit 80 may be filtered by a band pass or low pass filter, e.g., a 1-10 Hz bandpass filter or a 10 Hz low pass filter, digitized by an ADC and rectified for use by processor 148 of control circuit 80 for determining a patient physical activity metric. Various activity metrics may be derived from the acceleration signal by control circuit 80 that are correlated to patient physical activity. For instance, the activity metric derived from the acceleration signal may be obtained by integrating the absolute value of an acceleration signal received from activity sensor 90 over a predetermined time duration (such as 2 seconds). The amplitude of the sampled data points over a two-second interval may be summed to obtain the activity metric. This activity metric may be referred to as anRef. No. A0012277W001“activity count” and is correlated to the acceleration due to patient body motion imparted on the pacemaker 14 during the predetermined time interval. The 2-second (or other time interval) activity counts may be used by control circuit 80 for determining a sensor indicated pacing rate (SIR) for use in controlling rate response pacing. A patient activity metric or SIR may be used to control the rate of atrial or ventricular pacing pulses according to a temporary rate response pacing interval, based on the SIR, that is shortened by control circuit 80 from the programmed LRI.

[0084] When pacemaker 114 is placed in the ventricles for delivering ventricular pacing, control circuit 80 may be configured to sense atrial event signals corresponding to atrial systole or “atrial kick” from a sensor signal, e.g., from an accelerometer signal, received from sensors 90. Therapy delivery circuit 84 may deliver CSP pulses at an AV pacing interval from a sensed atrial event signal for providing atrial synchronous ventricular pacing. As such, CSP pulses may be delivered by pacemaker 114 of FIGs. 2 or 3 in coordination with P-wave sensing from an atrial electrical signal, in coordination with atrial mechanical event signals sensed from an accelerometer signal or other sensor signal, or in coordination with communication signals received from an atrial pacemaker 214 included in the medical device system to provide atrial synchronous ventricular pacing pulses delivered at an AV interval.

[0085] Communication circuit 88 may include a transceiver and antenna for communicating with external device 50 (shown in FIG. 1) using radio frequency communication as described above. Control parameters utilized by control circuit 80 for sensing cardiac event signals, analyzing EGM signals, and controlling cardiac pacing may be programmed into memory 82 via communication circuit 88 for retrieval and execution by processor 148 of control circuit 80. Under the control of control circuit 80, communication circuit 88 may receive downlink telemetry from and send uplink telemetry to the external device 50. As described above in conjunction with pacemaker 114 in FIG. 3, in some examples, communication circuit 88 may be configured to communicate with another implanted device, e.g., the atrial pacemaker 214 shown in FIG. 3, for coordinating dual chamber pacing in a two device system. In some examples, inter-device communication performed by communication circuit 88 may include tissue conductance communication.Ref. No. A0012277W001

[0086] FIG. 5 is a flow chart 300 of a method for performing T-wave analysis by pacemaker 14 according to some examples. For the sake of illustration, FIG. 5 and other flow charts presented herein are described with reference to pacemaker 14 of FIG. 1 and FIG. 4. It is to be understood, however, that the disclosed techniques attributed to pacemaker 14 and components of FIG. 4 may be implemented in other medical devices, including the leadless pacemaker 114 shown in FIGs. 2 and 3 or in a cardiac monitoring device that may be co-implanted with a cardiac pacemaker configured to deliver CSP. In still other examples, aspects of the methods described in conjunction with the flow charts presented herein may be performed by another implantable, external or wearable device configured to sense cardiac electrical signals to acquire T-waves, which may be intrinsic and / or post-pace T-waves following ventricular pacing pulses delivered by an implanted pacemaker, e.g., pacemaker 14 or 114.

[0087] At block 302, at least one T-wave template is stored in memory 82. Control circuit 80 may establish at least one CSP T-wave template during CSP that is delivered according to a given set of pacing control parameters, e.g., AV interval, CSP electrode vector, and pacing pulse output (pulse amplitude and pulse width). The pacing control parameter may be deemed optimal or acceptable for the patient, e.g., as evidenced by an improvement in electrical synchrony compared to the intrinsic, non-paced ventricular rhythm during a permanent or intermittent conduction disorder episode (e.g., AV block, bundle branch block, etc.) or other electrical or mechanical dyssynchrony. In addition to or alternatively to establishing the CSP T-wave template during CSP, control circuit 80 may establish an intrinsic T-wave template that is stored in memory 82 during a non-paced ventricular rhythm.

[0088] The T-wave template(s) can be established by control circuit 80 in response to a programming command received by communication circuit 88 from external device 50, e.g., at the time of pacemaker implant or during a patient follow-up. For instance, a clinician may confirm optimal or acceptable CSP for the given patient by viewing ECG signals recorded from surface ECG electrodes, viewing one or more EGM signals transmitted by pacemaker 14, and / or reviewing T-wave signal features determined by pacemaker 14 from one or more EGM signal sensed by sensing circuit 86 that are transmitted to external device 50 for display by display unit 50. The clinician may enter a command via user interface 56 to trigger pacemaker 14 to determine T-wave template(s)Ref. No. A0012277W001 during an intrinsic ventricular rhythm and / or during one or more paced ventricular rhythms.

[0089] In other examples, control circuit 80 may identify optimal or acceptable CSP control parameters based on an analysis of QRS waveforms and / or T-waves. For instance, control circuit 80 may determine one or more features of the pacing evoked QRS waveforms during CSP to determine when acceptable or optimal CSP is being delivered. For example, control circuit 80 may determine when one or more QRS waveform features exhibit relative improvement in the post-pace QRS waveform (following CSP pulses) compared to the intrinsic QRS waveform and / or compared to post-pace QRS waveforms delivered according to different pacing control parameters. Control circuit 80 may determine that the QRS waveform features exhibit an improvement in electrical synchrony by determining a decrease in the left ventricular activation time (LVAT) determined as the time interval from a delivered CSP pulse to a fiducial time point identified from the QRS waveform, a narrowed QRS width, an increased QRS peak amplitude, an increased QRS peak slope, or other relative change in the post-pace QRS waveform that is evidence of improved ventricular electrical synchrony or any combination thereof. When the acceptable or optimal pacing control parameters are identified by control circuit 80 based on QRS waveform features, control circuit 80 may establish and store a CSP T-wave template at block 302 during CSP delivered according to the identified pacing control parameters.

[0090] In still other examples, in addition to or alternatively to determining an improvement in electrical synchrony based on analysis of the QRS waveform, control circuit 80 may identify acceptable or optimal pacing control parameters used for delivering CSP based on an analysis of the post-pace T-waves that follow CSP pulses. As described below in conjunction with FIG. 7, control circuit 80 may compare post-pace T- waves to each other and / or to an intrinsic T-wave template stored in memory 82 to identify optimal or acceptable pacing control parameters. Control circuit 80 may identify pacing control parameters that result in T-wave morphology changes relative to the intrinsic T- wave and / or other post-pace T-waves that indicate an improvement in repolarization synchrony, such as short QT interval, higher T-wave amplitude, narrower T-wave width, higher T-wave slope, and / or higher T-wave frequency content as non-limiting examples. Control circuit 80 may establish a CSP T-wave template at block 302 from post-pace T-Ref. No. A0012277W001 waves sensed following CSP pulses delivered according to the identified pacing control parameters.

[0091] As further described below, control circuit 80 may obtain one or more post-pace T- waves, e.g., spanning one or more T-wave windows applied to a received EGM signal following delivery of one or more respective CSP pulses, for establishing a CSP T-wave template. Additionally or alternatively, control circuit 80 may obtain one or more intrinsic T-waves, e.g., spanning one or more T-wave windows applied to a received EGM signal following a Vsense signal received from sensing circuit 86, for establishing an intrinsic T- wave template.

[0092] The intrinsic T-wave template may be representative of ventricular repolarization dyssynchrony or heterogeneity during the intrinsic ventricular rhythm (which may be during a paced or intrinsic atrial rhythm that is conducted to the ventricles). As further described below, control circuit 80 may analyze post-pace T-waves obtained during CSP for assessing the effectiveness of the CSP in improving ventricular electrical synchrony as evidenced by T-wave morphology changes compared to an intrinsic ventricular rhythm during a permanent or intermittent conduction disorder or other electrical or mechanical dyssynchrony. Control circuit 80 may determine that the CSP is effective when the postpace T-waves do not match the intrinsic T-wave template, which may be evidence of the intrinsic repolarization dyssynchrony being improved or alleviated by the CSP.Additionally or alternatively, control circuit 80 may determine that CSP is effective when the post-pace T-waves closely match a CSP T-wave template, which may correspond to an optimized or acceptable improvement in electrical synchrony of the ventricles.

[0093] In some patients, the intrinsic T-wave template may be representative of ventricular repolarization synchrony, e.g., during an intrinsic ventricular rhythm when an intermittent conduction abnormality is not present (e.g., during times of normal AV conduction in a patient with intermittent AV block, during times of normal bundle branch conduction in a patient with intermittent bundle branch block, etc.). As further described below, control circuit 80 may analyze post-pace T-waves obtained during CSP for assessing the effectiveness of the CSP in improving ventricular electrical synchrony as evidenced by a post-pace T-wave morphology that matches the intrinsic ventricular rhythm during a period of normal conduction in a patient that experiences intermittent conduction block. Control circuit 80 may determine that the CSP is effective when theRef. No. A0012277W001 post-pace T-waves match the intrinsic T-wave template, representative of intrinsic repolarization synchrony in this case. Additionally or alternatively, control circuit 80 may determine that CSP is effective when the post-pace T-waves closely matches a CSP T- wave template, which may correspond to an optimized or acceptable electrical synchrony of the ventricles. In patients having an intermittent conduction abnormality, more than one intrinsic T-wave template may be established and stored in memory 82. One intrinsic T- wave template may correspond to the patient’s normal intrinsic rhythm and a second intrinsic T-wave template may correspond to the patient’s intrinsic rhythm during an episode of impaired or abnormal conduction or electrical dyssynchrony. A clinician or other user may identify each intrinsic T-wave template so that they may be stored in memory with a corresponding label and used in determining when effective CSP criteria are met based on T-wave match metrics as further described below.

[0094] Control circuit 80 may establish the T-wave template(s) stored in memory 82 at block 302 by storing the digitized sample points of the T-wave window, storing wavelet transform coefficients, and / or storing one or more T-wave features determined from the T- waves. Examples of T-wave features that may be determined by control circuit 80 and stored in memory 82 as a T-wave template include wavelet coefficients, a maximum absolute peak amplitude, peak positive slope, peak negative slope, T-wave width, T-wave area, time from the maximum absolute peak amplitude to an ending time of the T-wave, time to the maximum absolute peak amplitude from the CSP pulse, time to the maximum absolute peak amplitude from a fiducial point of the preceding QRS waveform (e.g., an Il- wave threshold crossing or maximum peak amplitude of the T-wave), time to a maximum T-wave slope (positive or negative) from the CSP pulse or a fiducial point of the QRS waveform, QT interval, ST interval, and / or any of the foregoing time intervals normalized by the ventricular rate.

[0095] Other examples of T-wave features that may be determined by control circuit 80 and stored in memory 82 as a T-wave template include T-wave frequency content (e.g., as determined by performing a Fourier Transform). Control circuit 80 may perform a frequency domain analysis, in addition to or alternatively to a time domain analysis for determining T-wave template features. For instance, control circuit 80 may determine a power spectrum of the T-waves for identifying the T-wave principle frequency component. Frequency content may be estimated by control circuit 80 by determining theRef. No. A0012277W001 amplitude of the T-wave after applying one or more narrow bandpass filters, determining the maximum slew rate of the T-wave, or determining a maximum peak of a derivative or nth order (e.g., first order, second order or other higher order) difference signal determined from the T-wave. Any combination of the foregoing examples may be determined by control circuit 80 (or external device processor 52) and stored in memory 82 as the T-wave template for a given set of pacing control parameters and / or the intrinsic ventricular rhythm. It is to be understood that storing the T-wave template in memory 82 may include storing the digitized sample points of the T-wave.

[0096] At block 304, control circuit 80 controls therapy delivery circuit 84 to deliver CSP pulses. The CSP pulses may be delivered at a given set of pacing control parameters that corresponds to the set of pacing control parameters used to establish a CSP T-wave template stored in memory 82. At other times, the CSP pulses may be delivered according to one or more test settings of a pacing control parameter. In still other examples, the CSP pulses may be delivered according to a given set of pacing control parameters as the CSP electrode (e.g., tip electrode 32 shown in FIG. 1) is being advance toward a CSP site.

[0097] At block 306, control circuit 80 determines one or more T-wave match metrics between at least one post-pace T-wave sensed following a CSP pulse and one or more T- wave templates stored in memory 82. Control circuit 80 may determine a T-wave match metric as a morphology matching score by performing a wavelet transform and summing the distances between the wavelet coefficients of a post-pace T-wave and a T-wave template. The wavelet coefficients may be weighted to increase contributions of certain time-scales of the wavelet transform coefficients. Example methods of performing a Haar wavelet transform for determining a morphology match score that may be adapted for use in determining a T-wave morphology match score are generally disclosed in U.S. Patent No. 6,393,316 (Gillberg, et al., filed May 8, 2000) and in U.S. Patent No. 8,521,268 (Zhang, et al., filed May 10, 2011), the entire content of both incorporated herein by reference.

[0098] Control circuit 80 may determine a T-wave match metric by determining a difference between a post-pace T-wave feature and the analogous feature of the T-wave template. T-wave feature differences may be determined for any one or more of the example T-wave features listed above. In some examples, a T-wave match metric may be determined as a combination of two or more T-wave feature differences. When two orRef. No. A0012277W001 more T-wave feature differences are combined to determine a T-wave match metric, the individual T-wave feature differences may have different weightings. To illustrate, a combination of the maximum peak amplitude difference (between the post-pace T-wave and the intrinsic T-wave template or CSP T-wave template) and the maximum slope difference (between the post-pace T-wave and the intrinsic T-wave template or CSP T- wave template) may be determined and summed. In some examples, one T-wave match metric, e.g., the maximum slope difference, may have a higher weighting factor than the other T-wave feature difference, e.g., the maximum absolute peak amplitude difference (or vice versa). The combination of the maximum slope difference and the maximum absolute peak amplitude difference is provided here for the sake of illustration with no limitation intended. A variety of combinations of T-wave feature differences, which may be determined between the post-pace T-wave and multiple different T-wave templates, can be determined as a T-wave match metric that can be correlated to a change in the repolarization synchrony (or heterogeneity) or more generally a change in ventricular electrical synchrony.

[0099] Control circuit 80 may determine one or more T-wave match metrics using a CSP T-wave template and / or an intrinsic T-wave template. The T-wave match metrics may include morphology matching scores, T-wave feature differences, and / or combinations of T-wave feature differences and / or morphology matching scores, which may be weighted linear or non-linear combinations of the T-wave feature differences and / or morphology matching scores.

[0100] At block 310 control circuit 80 compares the T-wave match metric(s) to effective CSP criteria. The effective CSP criteria may include one or more thresholds or ranges that, when met by a respective T-wave match metric, indicate that the post-pace T-wave morphology represents an acceptable or optimal repolarization synchrony (or more generally ventricular electrical synchrony). Control circuit 80 may determine that the effective CSP criteria are met when the T-wave match metric(s) determined using a CSP T-wave template meet the threshold(s) / range(s) of the effective CSP criteria, indicating that the post-pace T-wave(s) match the CSP T-wave template, which may be established from T-waves sensed during CSP determined to result in improved ventricular electrical synchrony (e.g., compared to the intrinsic ventricular rhythm and / or non-optimized pacing control parameters). Additionally or alternatively, control circuit 80 may determine thatRef. No. A0012277W001 the effective CSP criteria are met when the T-wave match metric(s) determined using an intrinsic T-wave template do not meet the threshold(s) / range(s), indicating that the postpace T-wave(s) do not match the intrinsic T-wave template. In this case, the intrinsic T- wave template may be representative of an intrinsic ventricular rhythm during a conduction abnormality. In other examples, control circuit 80 may determine that the effective CSP criteria are met when the T-wave match metric(s) determined between a post-pace T-wave and the intrinsic T-wave template do indicate a morphology match. In this case, the intrinsic T-wave template may be representative of intrinsic ventricular rhythm during normal conduction and ventricular electrical synchrony, for example during an episode of normal conduction in a patient having an intermittent conduction block.

[0101] Depending on the T-wave match metric being evaluated, the T-wave match metric may need to be greater than or less than a corresponding threshold for indicating whether the post-pace T-wave matches or does not match a T-wave template. For example, a morphology matching score may be required to be greater than a match threshold and a T- wave feature difference may be required to be less than a difference threshold in order to determine a match between the post-pace T-wave and a T-wave template. Depending on the type of T-wave template, a match may indicate effective CSP criteria are met, e.g., when comparing to a CSP T-wave template established for acceptable or optimized pacing control parameters. When comparing the post-pace T-wave to an intrinsic T-wave template, however, a match may indicate that effective CSP criteria are or are not met, depending on whether the intrinsic T-wave template is established during normal conduction or during impaired conduction or electrical dyssynchrony, e.g., during an episode of conduction block.

[0102] In some examples, multiple post-pace T-waves sensed following CSP pulses delivered under the same conditions (e.g., same electrode location and same pacing control parameters) may be compared to one or more T-wave templates for determining multiple T-wave match metrics. Control circuit 80 may determine that the effective CSP criteria are met when at least a threshold number (e.g., 2 out of 3, 3 out of 5, or other threshold number of X out of Y) of post-pace T-waves meet the effective CSP criteria. In still other examples, multiple post-pace T-waves may be acquired and ensemble averaged for comparison to one or more T-wave templates for determining at least one T-wave metric at block 306 that is compared to the effective CSP criteria at block 310. Furthermore,Ref. No. A0012277W001 control circuit 80 may be configured to determine that effective CSP criteria are met based on T-wave match metrics in combination with other cardiac electrical signal features or analysis, e.g., based on the pacing-evoked QRS waveform morphology features. Control circuit 80 may determine a post-pace QRS waveform feature (e.g., any of the example QRS waveform features listed above) from at least one cardiac electrical signal sensed by the sensing circuit 86 following a CSP pulse and determine that effective CSP criteria are met based on the post-pace QRS waveform feature and one or more T-wave match metrics.

[0103] If the effective CSP criteria are met, as determined at block 310, control circuit 80 may return to block 304 to continue delivering CSP according to the current pacing control parameters. Control circuit 80 may redetermine the T-wave match metrics at scheduled time intervals (e.g., once per minute, once per hour, daily, weekly, monthly etc.) or according to another T-wave morphology monitoring protocol or in response to a programming command.

[0104] If the effective CSP criteria are determined not to be met (“no” branch of block 310), control circuit 80 may advance to block 314 to generate an output to control a response performed when the effective CSP criteria are not met. The output may be stored in memory 82. The output may include a notification transmitted to external device 50. The output may include determined post-pace T-wave features, the T-wave match metrics, an EGM signal episode, a representative T-wave signal, and / or other data related to determining that the effective CSP criteria are unmet. The stored output data may be transmitted to external device 50 for review by a clinician.

[0105] Additionally or alternatively, the output generated by control circuit 314 may include a pacing control parameter adjustment. Control circuit 80 may adjust an AV pacing interval, the pacing pulse output (e.g., pulse amplitude and / or pulse width), or the CSP electrode vector, as examples. The adjusted pacing control parameter may be stored in memory 82.

[0106] If a pacing control parameter adjustment is performed at block 314 in response to the generated output, control circuit 80 may return to block 304 to control therapy delivery circuit 84 to deliver CSP according to the adjusted pacing control parameter. Control circuit 80 may redetermine the T-wave match metric(s) at block 306 (without necessarily waiting for a next scheduled T-wave morphology monitoring time) during CSP deliveredRef. No. A0012277W001 according to the adjusted pacing control parameter. In this way, one or more pacing control parameters may be adjusted by control circuit 80 until the effective CSP criteria are met at block 310. If the CSP criteria remain unmet after a maximum number of attempts at adjusting a pacing control parameter or after all available pacing control parameter settings are tested (e.g., a range of AV pacing intervals, up to a maximum CSP pulse output, and / or all available CSP electrode vectors are tested), control circuit 80 may generate an output at block 314 indicating that effective CSP criteria are unmet, which may be transmitted to external device 50.

[0107] In some examples, the process of flow chart 300 may be performed during an implant procedure as a CSP electrode, e.g., tip electrode 32 of FIG. 1, is being advanced to a CSP site. In this case, the output generated at block 314 may be a notification transmitted to external device 50 for display by display unit 54. The notification may be a prompt to adjust (e.g., advance, retract or relocate) the CSP electrode position when the effective CSP criteria are not met. When the CSP criteria are met, control circuit 80 may generate a notification that the electrode position is acceptable as further described below in conjunction with FIG. 8.

[0108] FIG. 6 is a diagram 350 of post-pace T-waves 354 and 374 that may be analyzed by processing circuitry of a medical device system for determining one or more T-wave match metrics. In the example of FIG. 6, a ventricular pacing pulse (VP) 352 is delivered by therapy delivery circuit 84 and is followed by a pacing evoked QRS waveform 351 and post-pace T-wave 354. VP 352 may be delivered as a CSP pulse, e.g., in the area of the LBB, RBB, or His bundle, according to a given set of pacing control parameters, e.g., pacing pulse amplitude, pacing pulse width, pacing electrode vector, and pacing interval (ventricular LRI or AV interval). VP 352 captures at least a portion of the conduction system resulting in the pacing evoked QRS waveform 351 followed by the post-pace T- wave 354.

[0109] In the lower part of diagram 350, VP 372 may represent a CSP pulse delivered according to a different pacing control parameter than VP 352. For example, VP 372 may be delivered having a relatively lower pacing pulse amplitude that fails to capture the conduction system, resulting in a different morphology of the pacing evoked QRS waveform 371 and post-pace T-wave 374. Post-pace T-wave 374 may represent a T-waveRef. No. A0012277W001 that occurs following myocardial only capture, for instance, without conduction system capture.

[0110] Control circuit 80 may acquire T-waves 354 and 374 during a T-wave window 362 that is applied to an EGM signal received from sensing circuit 86. T-wave window 362 may have a starting time at a specified time interval 360 after the respective VP 352 or VP 372, e.g., 100 to 350 ms or about 200 to 250 ms after VP 352 or VP 372, to acquire the T- wave signal 354 or 374 after the pacing evoked QRS waveform 351 or 371 and after any pacing artifact (not shown in FIG. 6) has substantially dissipated. Pacing artifact due to post-pace polarization, for example, may introduce challenges in sensing and analyzing the pacing evoked QRS waveforms 351 and 371 during CSP. The T-wave window starting time 360 can be scheduled after VP 352 and VP 372 at a time after the QRS waveform 351 or 371, when the pacing artifact is expected to be substantially diminished.[oni] The T-wave window 362 may extend from the starting time 360 to the ending time 361 that may be 300 to 600 ms or 400 to 500 ms after the respective VP 352 or VP 372. In an illustrative example, with no limitation intended, T-wave window 362 begins 175 to 225 ms after the respective VP 352 or VP 372 and ends 500 to 600 ms after the VP 352 or 372 for a total duration of 275 to 425 ms.

[0112] The T-wave window 362 may be adjusted to have an earlier or later starting time 360 and / or earlier or later ending time 362 depending on the ventricular pacing rate in some examples. Generally, if the ventricular pacing rate increases the starting time 360 may be earlier after the VP, and if the ventricular pacing rate decreases the starting time360 may be later after the VP. The T-wave window starting time 360 and / or ending time361 may be set or adjusted based on the timing of the pacing evoked QRS signal 351 or 371 instead of or in addition to the pacing rate in some examples. For example, control circuit 80 may set the T-wave window starting time 360 to be a specified time interval after an R-wave sensing threshold crossing or the maximum peak amplitude of pacing evoked QRS waveform 351 or 371. In still other examples, the T-wave window 362 may have a dynamically adjusted starting time 360 that begins when the cardiac electrical signal deviation from baseline reaches a threshold value, e.g., for a specified number of sample points, following a CSP pulse (which may also be after a QRS waveform delay interval). When a T-wave is being acquired post-sense (after an R-wave sensing threshold crossing), the T-wave window starting time may begin at a specified time interval from anRef. No. A0012277W001R-wave sensing threshold crossing, for example, and the T-wave window starting time 360 may be adjusted earlier or later relative to the timing of an R-wave sensing threshold crossing based on the sensed ventricular rate.

[0113] As described above, control circuit 80 may determine a T-wave match metric by determining a morphology match score between a stored T-wave template, e.g., a CSP T- wave template and / or an intrinsic T-wave template, and the T-wave 354 or T-wave 374 acquired during the T-wave window 362. Additionally or alternatively, one or more time domain and / or frequency domain features of the T-wave 354 or T-wave 374 may be determined by control circuit 80 for comparison to an analogous feature of a T-wave template, intrinsic and / or CSP T-wave template. A T-wave match metric may be determined as a T-wave feature difference or a combination of different T-wave feature differences as described above.

[0114] For example, the post-pace T-wave maximum absolute peak amplitude 358, 378 may be determined by control circuit 80 as a T-wave feature. The maximum slope 355, 375 prior to the respective maximum absolute peak amplitude 358, 378 may be determined by control circuit 80 as a T-wave feature. The maximum slope 357, 377 after the respective maximum absolute peak amplitude 358, 378 may be determined by control circuit 80 as a T-wave feature. The time interval 390, 392 from the respective VP 352, 372 (or a feature of the QRS waveform 351 or 371) to the T-wave maximum slope 355, 375 may be determined. The time interval 394, 396 to the maximum absolute peak 358, 378 from the respective VP 352, 372 may be determined. The time interval 391, 393 from the maximum peak of the QRS waveform 351 or 371 to the maximum absolute peak 358, 378 may be determined. The time interval 380, 382 from the maximum peak 358, 378 to the end of the respective T-wave 354, 374 (e.g., to a return to baseline) may be determined. Any of the time intervals represented in FIG. 6 may be normalized by ventricular rate. Other examples of T-wave features that may be determined by control circuit 80 include T-wave width 384, 386, T-wave area 385, 387, the number of peaks, the polarity (positive or negative) of the maximum absolute peak, the T-wave area 385, 387 normalized by the maximum peak amplitude 358, 378, or the T-wave width 384, 386 normalized by the maximum peak amplitude 358, 378, and / or frequency content, e.g., a primary frequency component or a maximum peak of a difference or derivative signal.Ref. No. A0012277W001

[0115] One or more T-wave match metrics may be determined by control circuit 80 as the difference between a T-wave feature determined from the acquired post-pace T-wave 354 or 374 and a T-wave template stored in memory 82. In some examples, control circuit 80 may determine a T-wave match metric as a combination of multiple individual T-wave feature differences, e.g., a weighted combination of multiple different T-wave feature differences determined between a post-pace T-wave and one or more T-wave templates, which can include a morphology match score determined by performing a wavelet transform. Control circuit 80 may compare one or more T-wave match metrics to respective thresholds, ranges or values to determine if the acquired T-wave 354 or 374 matches a stored T-wave template, indicating a similar repolarization pattern of the ventricles during the acquired T-wave and the T-wave template, or does not match, indicating a different repolarization pattern during the acquired T-wave and the T-wave template.

[0116] The T-waves 354 and 374 may be acquired from a sensing electrode vector selected from any of the available electrodes coupled to pacemaker 14. In some examples, post-pace T-waves may be acquired from multiple sensing electrode vectors. For example, a bipolar sensing electrode vector may be used to sense a relatively near field T-wave, e.g., using electrodes 32 and 34, electrodes 32 and 36 or electrodes 34 and 36 (all shown in FIG. 1). A unipolar sensing electrode vector or relatively far field sensing electrode vector may be used to sense a relatively far field T-wave, e.g., using any of electrodes 32, 34, 36 or 38 with housing 15, as non-limiting examples. Control circuit 80 may receive the sensing electrode vector signals from sensing circuit 86, obtain the T-waves during the T- wave windows applied to two or more sensing electrode vector signals, determine one or more T-wave features from each acquired T-wave and compare the T-wave features to an intrinsic T-wave template and / or a CSP T-wave template for determining T-wave match metrics. For instance, in some examples, T-wave features determined from one sensing electrode vector signal may be compared to an intrinsic T-wave template and T-wave features determined from a second sensing electrode vector may be compared to a CSP T- wave template for detecting when effective CSP criteria are met. Control circuit 80 may determine that the effective CSP criteria are met when the T-wave feature(s) from the first sensing electrode vector do not match the intrinsic T-wave template and the T-wave feature(s) from the second sensing electrode vector do match the CSP T-wave template,Ref. No. A0012277W001 for instance. In other examples, T-waves acquired from two or more different sensing electrode vectors may be compared to intrinsic and / or CSP T-wave templates established for the respective sensing electrode vector for determining T-wave match metrics for comparison to effective CSP criteria for use in selecting pacing control parameters, guiding electrode placement, detecting CSP capture, and / or detecting long-term changes in the T-wave morphology.

[0117] FIG. 7 is a flow chart 400 of a method for establishing an intrinsic T-wave template and a CSP T-wave template according to some examples. At block 401, control circuit 80 may acquire one or more post-sense T-waves from a cardiac electrical signal sensed by a selected sensing electrode vector by sensing circuit 86 during respective T- wave windows following sensed intrinsic R-waves. At block 402 control circuit 80 may establish an intrinsic T-wave template from the post-sense T-waves.

[0118] The T-wave windows may have a start time at a specified time interval following an R-wave sensing threshold crossing. In other examples, the T-wave window may have a start time at a specified time interval following a maximum peak amplitude of the sensed R-wave or another fiducial point of the sensed, intrinsic QRS waveform. In some examples, multiple post-sense T-waves may be acquired during respective T-wave windows and aligned for ensemble averaging for obtaining a representative post-sense T- wave from which T-wave features, such as wavelet transform coefficients and / or any of the example T-wave features listed herein, may be determined and stored in memory 82 as the intrinsic T-wave template. The stored T-wave template may include the sample point amplitudes of the digitized post-sense T-wave.

[0119] Post-sense T-wave signals acquired from multiple T-wave windows may be aligned with respect to time for ensemble averaging. The post-sense T-waves may be aligned from the start of the T-wave window or by time-aligning fiducial points of the T- waves, such as by shifting the acquired T-waves (horizontally left or right) to align the maximum peak amplitude times, maximum peak slope times, or other fiducial time points of the T-waves. T-wave signals may be aligned with respect to amplitude by shifting the acquired T-waves (vertically up or down) to align the amplitude of the maximum peak, the amplitude at the time of the maximum slope, or other fiducial amplitude point. The intrinsic T-wave template may be established at block 402 from the ensemble average ofRef. No. A0012277W001 multiple time- and / or amplitude-aligned post-sense T-waves acquired during respective T- wave windows applied following sensed intrinsic R-waves.

[0120] At block 404, control circuit 80 may control therapy delivery circuit 84 to deliver CSP pulses. The CSP pulses may be delivered according to programmed pacing control parameters, e.g., a selected CSP electrode vector, pulse amplitude, pulse width, and AV pacing interval or ventricular pacing rate. In some examples, the CSP is delivered according to pacing control parameters selected by a clinician or other user as acceptable or optimized pacing control parameters. In other examples, the pacing control parameters may be test parameters set to starting values for delivering CSP to enable acquisition of post-pace T-waves for analysis for identifying a selected set of pacing control parameters for subsequently establishing the CSP T-wave template. At block 405, control circuit 80 may obtain one or more post-pace T-waves sensed during respective post-pace T-wave windows during the CSP. These post-pace T-waves obtained for establishing a CSP T- wave template may be referred to as “baseline” post-pace T-waves. Multiple baseline T- waves acquired during respective post-pace T-wave windows may be aligned with respect to time and / or amplitude, as generally described above with regard to post-sense T-waves, to obtain an ensemble averaged post-pace T-wave for the given CSP control parameters in some examples.

[0121] At block 406, control circuit 80 may determine T-wave features, including wavelet transform coefficients and / or any of the other example T-wave features listed herein. Control circuit 80 may store the T-wave features in memory 82, and optionally the sample point amplitudes of the baseline post-pace T-wave, as a temporary CSP T-wave template at block 406. Control circuit 80 may determine T-wave match metrics between the temporary CSP T-wave template and the established intrinsic T-wave template at block 407. As further described below, control circuit 80 may evaluate the difference between the temporary CSP T-wave template and the intrinsic T-wave template and / or compare the temporary CSP T-wave template to other temporary CSP T-wave templates to determine if the pacing control parameters used to deliver CSP at block 404 result in effective CSP.

[0122] In some examples, control circuit 80 may determine at block 408 if another pacing control parameter setting is to be tested for delivering CSP during the process of establishing a CSP T-wave template. In some cases, the first temporary CSP T-wave template is established as the CSP T-wave template without adjusting pacing controlRef. No. A0012277W001 parameters for evaluating additional post-pace T-waves. For instance, when a user selects the pacing control parameters used to deliver CSP at block 404 as acceptable or optimized pacing control parameters, the temporary CSP T-wave template determined at block 406 may be identified as the CSP T-wave template at block 412 and stored in memory 82 at block 414.

[0123] In other examples, if the first temporary CSP T-wave template meets acceptable T- wave template criteria (as further described below), control circuit 80 may store the first temporary CSP T-wave template as the established CSP T-wave template without testing different pacing control parameters. In other examples, control circuit 80 may adjust a pacing control parameter at block 410 when multiple pacing control parameter settings are to be tested. Control circuit 80 may return to block 404 to control therapy delivery circuit 84 to deliver the CSP according to the adjusted pacing control parameters. Control circuit 80 may select a different pacing electrode vector (or polarity), a different pacing pulse output (pulse amplitude and / or pulse width) and / or a different AV pacing interval or ventricular pacing rate at block 410. The process of obtaining post-pace T-waves and determining T-wave features for establishing another temporary CSP T-wave template may be repeated until control circuit 80 determines that no additional pacing control parameters are to be tested or until an acceptable CSP T-wave template is identified. In some instances, an acceptable CSP T-wave template may not be identifiable in which case control circuit 80 may generate a user notification for transmission by telemetry circuit 88.

[0124] At block 412, control circuit 80 may compare the T-wave features of one or more temporary CSP T-wave templates to criteria for accepting a CSP T-wave template as being representative of effective CSP. For example, one or more T-wave features that represent an amplitude, slope, width, area, time interval or frequency aspect of the temporary CSP T-wave template may be compared to a respective threshold or range that is indicative of effective CSP. Additionally or alternatively, control circuit 80 may determine T-wave match metrics between each of the temporary CSP T-wave match metrics and the intrinsic T-wave template for identifying one of the temporary CSP T-wave templates that is the most different, or at least a threshold difference, from the intrinsic T-wave template (when the intrinsic T-wave template is established during an intrinsic rhythm representative of electrical dys synchrony). In other examples, control circuit 80 may determine T-wave match metrics between each of the temporary CSP T-wave match metrics and the intrinsicRef. No. A0012277W001T-wave template for identifying one of the temporary CSP T-wave templates that is the best match to the intrinsic T-wave template (when the intrinsic T-wave template is established during an intrinsic rhythm representative of electrical synchrony). Additionally or alternatively, control circuit 80 may determine T-wave match metrics between each of the temporary CSP T-wave templates determined at block 406 for different pacing control parameters to identify a temporary CSP T-wave template having T-wave features that are representative of or correlated to the greatest improvement in repolarization synchrony.

[0125] At block 414, control circuit 80 may store the identified temporary CSP T-wave template that meets acceptable CSP T-wave template criteria as the CSP T-wave template that is stored in memory 82 for subsequent monitoring of T-wave morphology. The CSP T-wave template stored at block 414 may represent a greatest improvement in repolarization synchrony (or more generally ventricular electrical synchrony) based on identifying the most optimal or most improved T-wave features (e.g., greatest change in T- wave width, T-wave amplitude, slope, time interval to a T-wave feature, or other T-wave feature change indicative of decreased repolarization heterogeneity) compared to other temporary CSP T-wave templates. Additionally or alternatively, the CSP T-wave template stored at block 414 may represent poorest match or greatest change from the intrinsic T- wave template established during impaired conduction and / or best match or least change from an intrinsic T-wave template established during normal conduction. In other examples, the CSP T-wave template stored at block 414 may be a temporary T-wave template that is determined to meet acceptable CSP T-wave template criteria, which may not necessarily represent a maximum improvement in electrical synchrony or maximally optimized post-pace T-wave features.

[0126] When the acceptable CSP T-wave template is identified for a given set of pacing control parameters, control circuit 80 may establish multiple CSP T-wave templates from T-waves sensed from multiple different sensing electrode vectors for the given set of pacing control parameters. Furthermore, while one or more CSP T-wave templates may be stored for a respective number of sensing electrode vectors for a given set of pacing control parameters, control circuit 80 may store CSP T-wave templates for one or more sensing electrode vectors for multiple sets of pacing control parameters in some examples. For instance, control circuit 80 may store CSP T-wave templates for different pacing pulse outputs, different pacing electrode vectors and / or multiple different AV pacing intervalsRef. No. A0012277W001 for each of one or more sensing electrode vectors. The multiple CSP T-wave templates that are stored in memory at block 414 can be subsequently used for assessing post-pace T-waves during CSP. The multiple CSP T-wave templates may be identified at block 412 from among the temporary CSP T-wave templates based on T-wave match metrics determined between the temporary CSP T-wave templates and the intrinsic T-wave template and / or T-wave match metrics determined between different temporary CSP T- wave templates.

[0127] FIG. 8 is a flow chart 500 of a method for providing user feedback during CSP electrode positioning according to some examples. At block 502, a T-wave template may be stored in memory 82. In some examples, a standardized CSP T-wave template may be programmed into pacemaker memory 82. The standardized CSP T-wave template may be based on empirical data acquired from a population of patients during CSP. The standardized CSP T-wave template may be representative of a desired or acceptable T- wave morphology during CSP that is generally indicative of improved or physiologically normal ventricular electrical synchrony (and associated mechanical synchrony of the ventricles and improved or normal hemodynamics) that can be achieved by CSP in patients.

[0128] Additionally or alternatively, an intrinsic T-wave template may be established by control circuit 80 and stored in memory 82 at block 502, e.g., according to the methods described above in conjunction with FIG. 7. The intrinsic T-wave template may be established from post-sense T-waves sensed using a sensing electrode vector that is the same as the CSP electrode vector in some examples. In this case, the intrinsic T-wave template may be established when the cathode electrode is in contact with ventricular tissue, e.g., endocardial or interventricular septal tissue, but may not yet be in position for capturing the conduction system. In other examples, the intrinsic T-wave template may be established from T-waves sensed using a sensing electrode vector that is different than the CSP electrode vector, e.g., a relatively far-field or unipolar sensing electrode vector when the CSP electrode vector is a bipolar electrode vector.

[0129] At block 504, control circuit 80 may transmit a notification signal, via communication circuit 88, to external device 50. External device 50 may display a user prompt on display unit 54 in response to receiving the notification signal to prompt a user to advance the CSP electrode, e.g., tip electrode 32 (shown in FIG. 1), to a CSP site.Ref. No. A0012277W001Control circuit 80 may control therapy delivery circuit 84 to deliver CSP at block 506 during the advancement of the CSP electrode and acquire post-pace T-waves as the CSP electrode is being advanced. In other examples, control circuit 80 may wait to receive a command from external device 50, via communication circuit 88, to perform a T-wave morphology analysis for determining if the CSP electrode is at a location that results in effective CSP. Upon receipt of the command, control circuit 80 may obtain post-pace T- waves from sensing circuit 86 as therapy delivery circuit 84 delivers CSP pulses.

[0130] At block 508, control circuit 80 may analyze the post-pace T-waves to determine if effective CSP criteria are met. For example, control circuit 80 may compare one or more post-pace T-waves (which may be ensemble averaged) to the stored T-wave template(s). Control circuit 80 may determine that effective CSP criteria are met when a T-wave match metric, determined according to any of the examples given above, between the post-pace T-wave(s) and a stored intrinsic T-wave template indicates that the post-pace T-wave and intrinsic T-wave do not match (e.g., when the intrinsic T-wave template represents poor or impaired electrical synchrony) or do match (e.g., when the intrinsic T-wave template represents normal electrical synchrony. In some examples, when the morphology match score is determined as a T-wave match metric, the match threshold may be 30, 40, 50, 60, or 70 as non-limiting examples, when the morphology match score can be in the range of 0 to 100. If the morphology match score is less than the match threshold, the post-pace T- wave does not match the intrinsic T-wave template. Control circuit 80 may determine effective CSP criteria are met or not depending on the status of the intrinsic rhythm (electrical synchrony or electrical desynchrony) at the time the intrinsic T-wave template was established.

[0131] Additionally or alternatively, control circuit 80 may determine that effective CSP criteria are met when a T-wave match metric determined as a T-wave feature difference between a post-pace T-wave feature and the intrinsic T-wave template is greater than a threshold difference (e.g., when the intrinsic T-wave template represents poor or impaired ventricular electrical synchrony). Control circuit 80 may determine that effective CSP criteria are met when a combination of weighted differences between multiple post-pace T-wave features and respective features of the intrinsic T-wave template is greater than a specified threshold. Generally, when a poor match between the post-pace T-wave and the intrinsic T-wave template corresponding to electrical dyssynchrony is determined, controlRef. No. A0012277W001 circuit 80 may determine that effective CSP criteria are met at block 508. When a good match between the post-pace T-wave and the intrinsic T-wave template corresponding to electrical synchrony is determined, control circuit 80 may determine that effective CSP criteria are met at block 508

[0132] Additionally or alternatively, control circuit 80 may determine that the effective CSP criteria are met when the post-pace T-wave feature(s) are determined to match a standardized CSP T-wave template stored in memory 82. In this case, control circuit 80 may determine that the effective CSP criteria are met by determining that a morphology match score determined between a post-pace T-wave and the standardized CSP T-wave template is greater than a specified match threshold. The match threshold may be 30, 40 50, 60, 70 or 80, as non-limiting examples, when the morphology match score can have a minimum value of 0 and a maximum value of 100.

[0133] Additionally or alternatively, control circuit 80 may determine that effective CSP criteria are met when a T-wave match metric determined as the difference between a postpace T-wave feature and the standardized T-wave template is less than a threshold difference. In some instances, control circuit 80 may determine a T-wave match metric as a weighted combination of T-wave feature differences. Control circuit 80 may determine that effective CSP criteria are met when a weighted combination of T-wave feature differences between multiple post-pace T-wave features and respective features of the standardized CSP T-wave template is less than a specified difference threshold. Generally, when a good match between the standardized CSP T-wave template and the post-pace T- wave is determined, control circuit 80 may determine that effective CSP criteria are met at block 508.

[0134] When the effective CSP criteria are not met at block 508 (“no” branch), control circuit 80 may transmit a notification (via communication circuit 88) to external device 50 to prompt the user (via display unit 54) to adjust the CSP electrode position at block 510. A user may retract, advance or otherwise reposition the CSP electrode, e.g., tip electrode 32 shown in FIG. 1, or select a different pacing site.

[0135] Therapy delivery circuit 84 may deliver CSP at block 506, either continuously according to a programmed AV pacing interval or ventricular pacing rate or in response to a command from external device 50 to restart the CSP after the user has confirmed the new CSP electrode position or site. Control circuit 80 may acquire one or more new post-Ref. No. A0012277W001 pace T-waves for comparative analysis to the stored intrinsic T-wave template and / or standardized CSP T-wave template at block 508. When control circuit 80 determines that the effective CSP criteria are met at block 508, control circuit 80 may generate a notification signal at block 512 as an output for transmission by telemetry circuit 88 to external device 50 to indicate to the user (e.g., via a displayed icon or message on display unit 54) that the pacing site is acceptable for achieving effective CSP.

[0136] During the process of flow chart 500, CSP pulses may be delivered by therapy delivery circuit 84 at a relatively high pacing pulse output to increase the likelihood that capture of the conduction system occurs when the CSP electrode is in an acceptable pacing site. The CSP pulses may be delivered at an overdrive pacing rate, e.g., faster than the intrinsic ventricular rate (e.g., at 60% to 90% or about 80% of the ventricular rate) or at relatively short AV intervals (e.g., 20% to 80% of an intrinsic AV conduction time or about 30% to 60% of the intrinsic AV conduction time), to avoid fusion with an intrinsically conducted ventricular depolarization and promote the likelihood of post-pace T-waves falling in the T-wave window after a pacing evoked QRS waveform. In this way, any change detected in the post-pace T-waves as the pacing electrode location is adjusted is likely due to the change in pacing site and not other confounding factors.

[0137] FIG. 9 is a flow chart 600 of a method that may be performed by control circuit 80 for selecting a pacing control parameter based on T-wave morphology analysis according to some examples. At block 602, one or more T-wave templates may be stored in memory 82, including an intrinsic T-wave template and / or a CSP T-wave template, which may be a standardized template based on empirical data from a population of patients or established from post-pace T-waves acquired from the patient during CSP as described above in conjunction with FIG. 7.

[0138] At block 604, control circuit 80 may control therapy delivery circuit 84 to deliver CSP according to a starting value of a pacing control parameter. The pacing control parameter may be the AV interval. In other examples, the pacing control parameter may be the CSP pulse amplitude or the CSP pulse width. In still other examples, the pacing control parameter may be the pacing electrode polarity, e.g., selecting the tip electrode 32 as the pacing cathode or the pacing anode (paired with a second electrode serving as an anode or cathode, respectively). At block 606, control circuit 80 may acquire one or moreRef. No. A0012277W001 post-pace T-waves during delivery of CSP according to the starting pacing control parameter.

[0139] At block 608, control circuit 80 may determine if effective CSP criteria are met. Control circuit 80 may determine one or more T-wave match metrics at block 608, e.g., any of the example T-wave metrics described herein. Control circuit 80 may compare the T-wave match metrics to thresholds or ranges that indicate when the post-pace T-wave matches or does not match a stored T-wave template. Control circuit 80 may determine that effective CSP criteria are met by the T-wave metrics according to any of the examples given above. Examples of T-wave features and T-wave match metrics that may be determined for comparison to effective CSP criteria are described above.

[0140] When the effective CSP criteria are not met (“no” branch of block 608), control circuit 80 may adjust the pacing control parameter (block 610) that was set to a starting value at block 604 and / or adjust a different pacing control parameter. For example, control circuit 80 may adjust the AV interval to a different AV interval that is longer or shorter than the starting AV interval. Control circuit 80 may switch the pacing electrode polarity from the electrode polarity initially selected at block 604. Control circuit 80 may increase the pacing pulse amplitude and / or pulse width.

[0141] Therapy delivery circuit 84 may deliver CSP according to the adjusted pacing control parameter at block 606, and control circuit 80 may acquire one or more post-pace T-waves during the CSP. Control circuit 80 may repeat the comparative analysis of the post-pace T-waves and the stored T-wave template(s) at block 608 for determining if effective CSP criteria are met. Control circuit 80 may adjust a pacing control parameter and repeat the process of determining if the effective CSP criteria are met multiple times. When control circuit 80 determines that the effective CSP criteria are met at block 608, control circuit 80 may store in memory 82 the current value of the pacing control param eter(s) used to deliver CSP that resulted in post-pace T-waves that meet the effective CSP criteria. Control circuit 80 may control therapy delivery circuit 84 to deliver CSP according to the stored value(s) of the pacing control parameter(s) at block 612.

[0142] FIG. 10 is a flow chart 650 of a method that may be performed by a medical device system for selecting a pacing pulse output used for delivering CSP based on analysis of T- wave morphology according to some examples. At block 652, multiple CSP T-wave templates may be stored in memory 82 for multiple capture types, which may be inRef. No. A0012277W001 addition to an intrinsic T-wave template. Control circuit 80 may determine the intrinsic T- wave template and store it in memory 82 according to the example methods described above in conjunction with FIG. 7. The intrinsic T-wave template may correspond to the T- wave morphology that is expected when loss of capture occurs following a CSP pulse. For the sake of example, the intrinsic T-wave template in this case may represent ventricular electrical dyssynchrony, e.g., during conduction block or other delayed conduction of the ventricular depolarization.

[0143] When a CSP pulse is delivered, different types of capture may result. In some instances, the pacing pulse output is less than the capture threshold of the conduction system tissue but may be greater than the myocardial tissue capture threshold. As such, the CSP pulse may capture myocardial tissue only without capturing at least a portion of the conduction system. This type of capture is referred to as “myocardial only capture.” In other instances, the pacing pulse output may result in capture of only (at least a portion of) the conduction system without capturing myocardial tissue. This type of capture is referred to herein as “selective CSP capture.” In still other instances, the pacing pulse output may result in capture of at least a portion of the conduction system and capture of myocardial tissue. This type of capture is referred herein to as “non-selective CSP capture.” When the pacing pulse output is less than the capture threshold of both myocardial tissue and conduction system tissue in the area of the pacing electrode, a CSP pulse may result in loss of capture, with no pacing evoked response or post-pace T-wave occurring during the T- wave window (unless an intrinsic T-wave coincidentally occurs during the T-wave window following an intrinsic R-wave).

[0144] In some examples, control circuit 80 may establish a CSP T-wave template for different capture types. Control circuit 80 may control therapy delivery circuit 84 to deliver CSP pulses at multiple different pacing pulse outputs (different pulse amplitudes and / or different pulse widths). As described below in conjunction with FIG. 11, control circuit 80 may be configured to detect changes in the T-wave wave morphology as the pacing pulse output is adjusted (e.g., progressively increased or progressively decreased) and establish a CSP T-wave template each time a T-wave morphology change is detected to represent the T-wave morphology associated with different capture types.

[0145] In other examples, a clinician may observe the patient’s ECG during CSP delivered by pacemaker 14 and / or an EGM signal transmitted from pacemaker 14 to external deviceRef. No. A0012277W00150 during CSP so that the clinician can enter a user confirmation command when a change in capture type is observed based on changes in the ECG and / or EGM signals are observed, which may include changes observed in the QRS waveform. In still other examples, external device processor 52 may be configured to receive ECG signals and / or a transmitted EGM signal for processing and analysis for detecting when a change in capture type occurs. A change in capture type may be detected by control circuit 80 or by external device processor based on R-wave morphology and / or T-wave morphology changes that are detected as the pacing pulse output is adjusted. External device 50 may transmit a confirmation signal to pacemaker 14 when a change in capture type is identified by the external device processor 52.

[0146] When a change in capture type is detected by control circuit 80 (based on analysis of the R-wave morphology and / or T-wave morphology by control circuit 80 or based on a confirmation signal received from external device 50), control circuit 80 may establish a CSP T-wave template. In some cases, the T-wave morphology and corresponding CSP T- wave template may be labeled a specified capture type when the capture type can be identified as selective CSP capture, non-selective CSP capture or myocardial only capture, for example. However, the particular capture type may not necessarily be identified by control circuit 80. Rather, the CSP T-wave template may be identified as having a different morphology and therefore identified as a different capture type than another CSP T-wave template established at block 652 for a different (e.g., higher or lower) pacing pulse output and / or than the intrinsic T-wave template.

[0147] Control circuit 80 may establish at least two different CSP T-wave templates at block 652, e.g., a myocardial only CSP T-wave template and a conduction system (CS) capture T-wave template, which may correspond to selective CSP capture or non-selective CSP capture. In other examples, control circuit 80 may store at least three CSP T-wave templates at block 652, e.g., a myocardial only CSP T-wave template, a selective CSP capture T-wave template and a non-selective CSP capture T-wave template. However, the CSP T-wave templates may or may not be labeled according to a specific capture type in memory 82 because control circuit 80 may not discern between specific capture types beyond detecting a change in capture type based on a change in R-wave and / or T-wave morphology as the CSP pulse output is varied. As such, each CSP T-wave template that is established at block 652 may be stored with a corresponding pacing pulse output toRef. No. A0012277W001 indicate which CSP T-wave template was obtained at a relatively higher pacing pulse output and which at the lowest pacing pulse output. The corresponding pacing pulse output may correspond to the lowest pacing pulse output at which the T-wave morphology change (and / or R-wave morphology change) was detected and may therefore be the capture threshold for the corresponding CSP T-wave template. As described below in conjunction with FIG. 11, the CSP T-wave templates may be established at a pacing pulse output that corresponds to a capture threshold associated with a change in T-wave morphology and likely change in capture type or at another pacing pulse output that is a safety margin above the capture threshold associated with a change in capture type.

[0148] FIG. 11 is a diagram 680 of T-wave templates 682, 684 and 686, each shown as the representative waveform morphology, that may be established by a medical device system and stored in memory for comparing to post-pace T-waves during a capture test. For example, an intrinsic T-wave template 682 may be established from post-sense T-waves acquired when ventricular pacing is not being delivered (or delivered using sub-threshold pacing pulse output as indicated by the label 0 volts). During a capture test, when T-wave match metrics determined between a post-pace T-wave and the intrinsic T-wave template 682 indicate a matching morphology, control circuit 80 may determine a pacing loss of capture or at least determine that effective CSP criteria are not met.

[0149] Processing circuitry of the medical device system, e.g., control circuit 80 or external device processor 52, may establish one or more CSP T-wave templates 684 and 686 for different post-pace T-wave morphologies. For instance, under the control of control circuit 80, therapy delivery circuit 84 may progressively increase the pacing pulse output starting from 0 volts (or other subthreshold pulse output) until a post-pace R-wave (evoked response) is detected and / or a post-pace T-wave is detected in the post-pace T- wave window (indicating that the pacing pulse resulted in a pacing evoked depolarization following by the repolarization waveform at an expected time interval after the pacing pulse). The post-pace T-wave may be detected during the T-wave window based on an amplitude threshold, slope threshold or other signal detection methodology. In other examples, the evoked response may be detected based on a post-pace R-wave sensed within an expected time interval from the pacing pulse, indicating that the delivered pacing pulse captured cardiac tissue and that the subsequent T-wave may be acquired during the T-wave window as a post-pace T-wave.Ref. No. A0012277W001

[0150] Processing circuitry of the medical device system, e.g., control circuit 80, may establish a CSP T-wave template from one or more post-pace T-waves acquired during the T-wave window following respective pacing pulses delivered at (or a safety margin greater) than the lowest pacing pulse output that results in a detected evoked response and / or a detected post-pace T-wave during the T-wave window. In the example shown, a CSP T-wave template 684 corresponding to a first capture type is established during CSP at a pacing pulse output of 1.5 V. The pacing pulse output of 1.5 V may be lowest pacing voltage amplitude (for a given pulse width) that captures cardiac tissue in this illustrative example. The capture type may not necessarily be discriminated as a specific capture type by control circuit 80 in that the capture type may be myocardial only capture, selective CSP capture or non-selective CSP capture. However, the T-wave morphology is different than the intrinsic T-wave template 682 such that control circuit 80 may establish a CSP T- wave template for the capture type that occurs when the pacing pulse amplitude is at least 1.5 V in this example.

[0151] Control circuit 80 may continue to increase the pacing pulse output and compare post-pace T-wave(s) to the CSP T-wave template 684 established for the pacing pulse output at the lowest capture threshold. As the pacing pulse output is increased further, the capture type may change resulting in a T-wave morphology that does not match the first CSP T-wave template 684 (or the intrinsic T-wave template 682).

[0152] In the example shown, at a pacing pulse amplitude of 2.5 V, the post-pace T-wave morphology changes. Control circuit 80 may detect this T-wave morphology change that occurs with a change in capture type (based on post-pace T-wave comparisons to the first CSP T-wave template 684) and establish a second CSP T-wave template 686. Control circuit 80 may establish the second CSP T-wave template 686 by acquiring one or more post-pace T-waves following a respective pacing pulse delivered at the capture threshold (lowest pacing pulse output) at which the T-wave morphology change is detected. In other examples, control circuit 80 may establish the CSP T-wave template 686 from one or more post-pace T-waves acquired following pacing pulses delivered at a safety margin greater than the capture threshold at which the T-wave morphology change was detected. Control circuit 80 may first verify that the T-wave morphology at the higher pacing pulse output matches the T-wave morphology that occurs at the capture threshold associated with a change in T-wave morphology.Ref. No. A0012277W001

[0153] Control circuit 80 may continue to increase the pacing pulse output to determine if another T-wave morphology change occurs by comparing post-pace T-waves to the second CSP T-wave template 686. If no further change in T-wave morphology is detected, the first and second CSP T-wave templates 684 and 686 may be stored in memory 82, optionally along with the intrinsic T-wave template 682, for use in determining T-wave match metrics with post-pace T-waves acquired during capture tests and for determining when effective CSP criteria are met.

[0154] For the sake of illustration, the first CSP T-wave template 684 may correspond to a first capture type that could be non-selective conduction system capture in which myocardial tissue of the interventricular septum is captured with a portion of the conduction system. In other examples, the first CSP T-wave template 684 may correspond to partial LBB capture, myocardial only capture or another capture type. Control circuit 80 may store the first CSP T-wave template 684 with a corresponding capture threshold (e.g., 1.5 volts) indicating the lowest pacing pulse output at which the corresponding T-wave morphology was detected. The first CSP T-wave template 684 may or may not represent capture of at least a portion of the conduction system but may be determined by control circuit 80 as not being effective CSP capture based on T-wave morphology features, T- wave feature differences compared to the intrinsic T-wave template not meeting a threshold difference, and / or QRS waveform features, such as a left ventricular activation time, QRS width, or other features that indicate when the conduction system is being captured. Example methods for detecting conduction system capture based on QRS waveforms that may be incorporated in conjunction with the methods disclosed herein for establishing CSP T-wave templates for different capture types are generally disclosed in U.S. Patent No. 10,773,086 (Sheldon, et al., filed Nov. 8, 2018) and in U.S. Patent Application Publication No. 2022 / 0080210 (Cao et al., filed November 22, 2021).

[0155] The second CSP T-wave template 684 may be identified as being effective CSP based on one or more features of the second CSP T-wave template 686, such as a higher peak amplitude, narrower pulse width, higher maximum slope, higher frequency content, or other features compared to the first CSP T-wave template 684, greater T-wave feature differences relative to the intrinsic T-wave template 682 than the first CSP T-wave template 684, and / or based on QRS waveform features of the pacing evoked response following the CSP pulses delivered at 2.5 volts. As such, control circuit 80 may select aRef. No. A0012277W001 pacing voltage amplitude for delivering CSP that is equal to or greater than (e.g., a safety margin greater than) 2.5 V to promote effective CSP associated with an improvement in electrical synchrony of the ventricles.

[0156] The second CSP T-wave template 686 may correspond to selective conduction system capture, non-selective conduction system capture, or complete LBB capture in various examples. The specific capture type may not necessarily be identified by control circuit 80 but is identified as a different capture type than the capture type associated with the first CSP T-wave template 684. Control circuit 80 need not necessarily determine the capture type in terms of what tissue is being captured (e.g., selective, non-selective or myocardial only) but only that different capture types are being detected and, at least in some examples, that the features of at least one CSP T-wave template are evidence of effective CSP associated with improved electrical synchrony. Control circuit 80 may identify one of the CSP T-wave templates and corresponding capture threshold as a preferred capture type associated with improved electrical synchrony and establish that CSP T-wave template, e.g., template 686, as the preferred matching template for determining when effective CSP criteria are met. In other examples, a user may select which CSP T-wave template corresponds to a desired capture type and improved ventricular electrical synchrony for use in performing subsequent T-wave morphology assessments.

[0157] Referring again to FIG. 10, after establishing and storing one or more intrinsic and CSP T-wave templates at block 652, control circuit 80 may wait at block 654 for the time for a capture test to be performed according to a capture management protocol. For example, capture tests may be performed on a beat by beat basis (to verify capture), after a specified number of ventricular cycles or delivered ventricular pacing pulses, at scheduled time intervals or at scheduled times of day. In various examples, capture tests may be performed once per minute, hourly, daily or weekly. In some examples, control circuit 80 may determine that it is time to perform a capture test at block 654 when an evoked response QRS waveform is not sensed after a CSP pulse or when a post-pace T-wave is not sensed in the T-wave window, indicating a possible loss of capture. When it is time to perform a capture test, therapy delivery circuit 84 may deliver a CSP pulse at block 655 having a test pacing pulse output.Ref. No. A0012277W001

[0158] In some instances, control circuit 80 performs the capture test to verify capture by determining that a post-pace T-wave has an expected morphology corresponding to a stored CSP T-wave template without performing a capture threshold search. In this case, control circuit 80 may control therapy delivery circuit 84 to deliver the CSP pacing pulse at block 655 having a test pacing pulse output equal to the pacing pulse amplitude and pulse width currently in effect for delivering CSP. Control circuit 80, however, may adjust (e.g., shorten) the AV interval or the ventricular lower rate interval to promote delivery of the capture test pacing pulse earlier than an intrinsic QRS waveform to avoid fusion of the pacing evoked response with an intrinsic depolarization or delivering the capture test pacing pulse during physiological refractory.

[0159] At block 656, control circuit 80 may acquire one or more post-pace T-waves, e.g., each sensed during the T-wave window applied following a CSP pulse delivered at the test pacing pulse output. At block 657, control circuit 80 may compare post-pace T-wave(s) to one or more of the stored T-wave templates to determine T-wave match metric(s) according to any of the examples described above. In some examples, control circuit 80 may compare the post-pace T-wave to a CSP T-wave template corresponding to an expected T-wave morphology for the delivered pacing pulse output. For example, with reference to FIG. 11, if the second stored CSP T-wave template is identified as effective CSP and a desired capture type, control circuit 80 may compare the post-pace T-wave(s) acquired at block 656 to the second CSP T-wave template 686 at block 657 to determine if an expected CSP T-wave template match is detected at block 658. However, in other examples, if the test pacing pulse output applied at block 655 is less than the capture threshold corresponding to the second CSP T-wave template 686 but equal to or greater than the capture threshold associated with the first CSP T-wave template 684, control circuit 80 may compare the post-pace T-wave(s) acquired at block 656 to the first CSP T- wave template 684.

[0160] When control circuit 80 determines that the post-pace T-wave matches the expected CSP T-wave template at block 658, control circuit 80 may determine that CSP capture is confirmed at block 666. Control circuit 80 may keep the current pacing pulse output settings at block 668 (no adjustment required) and advance to block 670 to continue delivering CSP using the current CSP pulse output (used as the test pacing pulse output at block 655). No further testing of different pacing pulse outputs may be performed byRef. No. A0012277W001 control circuit 80 if capture is confirmed based on the post-pace T-wave matching the expected CSP T-wave template.

[0161] If the expected CSP T-wave template does not match the post-pace T-wave acquired for the test pacing pulse output, control circuit 80 may start a pacing capture threshold search or compare the post-pace T-wave to a different stored template at block 660 in some examples. For instance, control circuit 80 may compare the post-pace T-wave to the intrinsic T-wave template and detect loss of capture at block 660 when the post-pace T-wave matches the intrinsic T-wave template. In this case, an acceptable CSP T-wave template match is not detected (“no” branch of block 660). Control circuit 80 may advance to block 662 to begin a capture threshold search by adjusting the pacing pulse output to a different (e.g., higher) setting at block 664. In some examples, however, control circuit 80 may compare the post-pace T-wave to a different CSP T-wave template, e.g., the first T- wave template 684 of FIG. 11. Control circuit 80 may still detect capture if the post-pace T-wave matches a different CSP T-wave template, e.g., the first T-wave template 684 of FIG. 11, but not the expected CSP T-wave template, e.g. the second T-wave template 686 of FIG. 11. The post-pace T-wave morphology matching the first T-wave template 684 may not be considered effective CSP capture or may not be the expected or desired capture type but may still be evidence of capture. In some instances, detection of capture based on a match with a different CSP T-wave template that is not an expected capture type may still be determined as an acceptable capture type (block 660), e.g., if the capture threshold has increased such that pacing at a higher pulse output than the current test pulse output would unacceptably shorten the expected life of the pacemaker power source. In this case, control circuit 80 may advance to block 668 to set the CSP pulse output to the current test pacing pulse output or a safety margin greater. CSP may be delivered at block 670 using the selected pacing pulse output.

[0162] Referring again to block 660, if the acquired post-pace T-wave matches a different CSP T-wave template, e.g., the first CSP T-wave template 684, but not the expected CSP T-wave template, or matches the intrinsic T-wave template, control circuit 80 may determine if another test pacing pulse output setting is available at block 662. Control circuit 80 may adjust the pacing pulse output at block 664 if an additional test pulse output settings are available that have not been tested or if a maximum pulse output has not been reached (as determined at block 662).Ref. No. A0012277W001

[0163] If the expected CSP T-wave template match is not detected at block 658 (with or without determining other T-wave template matches at block 660), control circuit 80 may perform a capture threshold search by adjusting the pacing pulse output, e.g., increasing the pacing pulse output, to determine if a subsequently acquired post-pace T-wave (block 656) following pacing pulses delivered at the adjusted pacing pulse output does match the expected CSP T-wave match template (blocks 657 and 658). The capture threshold associated with the expected CSP T-wave match template may change over time. Control circuit 80 may perform a capture threshold search by repeating the process of adjusting the pacing pulse output (block 664), acquiring post-pace T-waves (block 656) and redetermining the T-wave match metrics (block 657) one or more times. In this way, control circuit 80 may determine the capture threshold for the expected CSP T-wave template as the lowest pacing pulse output at which the post-pace T-wave morphology matches the expected CSP T-wave template (block 658).

[0164] When the expected CSP T-wave template match is detected at block 658, the desired capture type can be confirmed at block 666. Control circuit 80 may set the CSP pulse output based on the capture threshold determined for the expected CSP T-wave template at block 668. For example, control circuit 80 may set the CSP pulse output equal to or a safety margin greater than the capture threshold for the expected CSP T-wave template. CSP may be delivered at block 670 by therapy delivery circuit 84 using the selected CSP pulse output.

[0165] Referring again to block 662, if a capture threshold search is being performed and another test pacing pulse output setting is not available (“no” branch of block 662), control circuit 80 may set the CSP pulse output at block 668 based on a determined T-wave template match. For instance, as described above, if a post-pace T-wave matches the first CSP T-wave template 684 of FIG. 11 but no post-pace T-waves at any test pacing pulse output match the second CSP T-wave template 686, control circuit 80 may select the CSP pulse output to be equal to or greater than the capture threshold for the first CSP T-wave template. In other examples, control circuit 80 may set the CSP pulse output to a maximum allowable pacing pulse output to promote capture of at least a portion of the conduction system. In still other examples, control circuit 80 may select a CSP pacing pulse output to be equal to or greater than the lowest pacing pulse output that resulted in a post-pace T-wave that does not match the intrinsic T-wave template (e.g., a minimumRef. No. A0012277W001 capture threshold for capturing cardiac tissue, which may or may not include capture of the conduction system).

[0166] Therapy delivery circuit 84 may deliver ventricular pacing at the selected CSP pulse output at block 670. It is to be understood that in some instances ventricular pacing may be delivered at a selected CSP pulse output that captures at least a portion of the conduction system but in other instances the ventricular pacing may be delivered at a CSP pulse output that results in myocardial capture without conduction system capture.

[0167] In some examples, when the expected CSP T-wave template does not match the post-pace T-wave delivered at any tested pacing pulse output, a gradual change in the T- wave morphology may have occurred due to disease progression, cardiac remodeling or other factors. As such, in some examples, control circuit 80 may restart the process of flow chart 650 at block 652 to re-establish and update T-wave templates for intrinsic T-waves and / or one or more CSP T-wave templates for different capture types.

[0168] FIG. 12 is a flow chart 700 of a method that may be performed by a medical device system for monitoring changes in the post-pace T-wave morphology over time according to some examples. At block 702, control circuit 80 may establish one or more T-wave templates according to any of the examples described above. At block 706, control circuit 80 may wait for a specified monitoring interval for assessing a trend in T-wave match metrics. T-wave match metrics between post-pace T-waves acquired during CSP may be determined daily, weekly, or monthly, for example, for monitoring a trend in the T-wave match metrics.

[0169] At block 708, control circuit 80 may determine one or more T-wave match metrics between at least one post-pace T-wave acquired during CSP and one or more stored T- wave templates. Any of the example T-wave metrics described herein may be determined at block 708. The T-wave match metrics may be determined between the post-pace T- wave and the intrinsic T-wave template and / or one or more CSP T-wave templates. For the purposes of monitoring long term trends in T-wave match metrics (as opposed to acute changes in the T-wave morphology due to changing pacing control parameters or changing pacing electrode location), the CSP pulse output delivered for acquiring postpace T-waves and determining T-wave match metrics at block 708 may be a standardized pulse output, e.g., a high pulse amplitude such as 5.0 volts.Ref. No. A0012277W001

[0170] At block 710, control circuit 80 may determine if there is a change in the trend of a T-wave match metric. T-wave match metrics may be logged in memory 82 as they are determined so that a trend in the T-wave match metric may be tracked. For example, a short-term moving average of recently determined T-wave match metrics may be compared to a historical or long-term average T-wave match metric. A short term variability measurement of the T-wave match metric may be compared to a long term or historical variability measurement. For instance, the difference between a current T-wave match metric and a long-term or historical average T-wave match metric may be determined. The difference may be compared to a difference threshold or multiple successively determined differences may be compared to detect an increasing or decreasing trend in the T-wave match metric relative to a historical or long-term average.

[0171] When a change in the trend of the T-wave match metric is not detected (“no” branch of block 710), the T-wave match metric(s) determined for the current monitoring time point may be logged in memory 82 at block 712. Control circuit 80 may return to block 706 to wait for the next monitoring interval to expire. The logged T-wave match metric(s) may be used to update a short term average and / or short term variability measurement used for detecting a change in the T-wave match metric trend at the next monitoring time point.

[0172] When a change in the trend of T-wave match metrics is detected at block 710 (“yes” branch), control circuit 80 may transmit a T-wave morphology report at block 714. The T-wave morphology report may include a notification that a change in T-wave match metric trend is detected. The T-wave morphology report may additionally include logged T-wave match metrics and / or any historical or long term averages or variability measurements, short term averages or variability measurements or other statistical data used by control circuit 80 in detecting the change in the trend of the T-wave match metrics. The transmitted report may include T-wave match metric data that can be used by external device processor 52 to generate a graph, table or other data presentation of the T- wave match metric data (such as the graph shown in FIG. 13) for display in a graphical user interface by display unit 54 (shown in FIG. 1).

[0173] In some examples, after detecting a change in the trend of the T-wave match metric(s), control circuit 80 may determine if the T-wave match metric(s) meet effective CSP criteria. The same or different T-wave match metrics may be used for detecting theRef. No. A0012277W001 change in the trend of T-wave match metrics than the T-wave match metrics used for determining if effective CSP criteria are met. In some instances, a change in the trend of T-wave match metrics may occur but T-wave match metrics may still meet thresholds, ranges or other criteria that indicate effective CSP. If effective CSP criteria are not met at block 716, control circuit 80 may adjust one or more CSP control parameters at block 718 until the effective CSP criteria are met at block 716 (or a maximum number of attempts has been reached).

[0174] If the effective CSP criteria are met at block 716, control circuit 80 may return to block 706 to wait for the next monitoring interval. In other examples, as shown in FIG. 12, after transmitting the report at block 714 and optionally making any adjustments to CSP control parameters to meet effective CSP criteria, control circuit 80 may return to block 702 to update the T-wave template(s) stored in memory 82. A new T-wave template may be established to replace an existing intrinsic and / or CSP T-wave template when the T- wave morphology has changed from a historical baseline or long-term average as evidenced by the detected change in the T-wave match metric trend. The stored T-wave template(s) may become outdated or irrelevant has myocardial remodeling, disease progression or other long-term changes occur.

[0175] FIG. 13 is a diagram 750 of T-wave match metrics that may be determined by control circuit 80 and logged in memory 82 for long-term monitoring of T-wave morphology. A T-wave match metric, e.g., a morphology match score, a weighted combination of T-wave feature differences or other match metric, is plotted along the y- axis over time on the x-axis. For the sake of illustration, a first T-wave match metric 752 (solid circles) may be a morphology match score determined between a post-pace T-wave acquired at the monitoring time point and a CSP T-wave template. The morphology match score may be determined from the distances between wavelet transform coefficients of the post-pace T-wave and the CSP T-wave template. A second T-wave match metric 762 (open squares) may be determined between the post-pace T-wave acquired at each of the same monitoring time points and an intrinsic T-wave template. In this illustrative example, the intrinsic T-wave template may represent ventricular electrical dyssynchrony such that a post-pace T-wave that does not match the intrinsic T-wave template may correspond to an improvement in ventricular electrical synchrony. In the example shown, daily T-wave match metrics are determined for monitoring the trend in T-wave match metrics, howeverRef. No. A0012277W001T-wave match metrics may be determined at different time intervals according to an implemented monitoring protocol.

[0176] Control circuit 80 may determine a historical or baseline average T-wave match metric from a specified number of monitoring time points, e.g., starting from day 0. For example, the average morphology match score 754 for the first T-wave match metric 752 and the average morphology match score 764 of the second T-wave metric 762 may be determined from the first 3, 5, 7, 10, 15, 30 or other specified number of daily T-wave match metrics. In the example shown the baseline average T-wave morphology match scores 754 and 764 (corresponding to the CSP T-wave template and the intrinsic T-wave template, respectively) are determined from the first 7 days of T-wave morphology monitoring.

[0177] After establishing a historical or baseline average T-wave match metric, in this case average morphology matching scores, control circuit 80 may determine short-term moving averages that can be compared to the baseline average T-wave match metric. For the sake of illustration, 5-day moving averages may be determined at each monitoring time point after establishing the baseline averages 754 and 764. The short-term moving averages may be compared to the baseline averages 754 and 764 for each respective T- wave match metric 752 and 762. The differences between the short-term moving averages and the respective baseline averages may be determined and compared to a threshold change. For example, the difference 758 between the baseline average 754 and the 5-day average 756 of T-wave match metric 752 may be compared to a first difference threshold. The difference 768 between the baseline average 764 and the 5-day average 766 of the second T-wave match metric 762 may be compared to a second difference threshold. When one or both of difference 758 and / or difference 768 is greater than the respective first difference threshold or second difference threshold, control circuit 80 may detect a change in the T-wave metric trend.

[0178] In some examples, the morphology match scores determined between post-pace T- waves and the CSP T-wave template as the first T-wave metric 752 can be compared to a first match threshold 755 for determining when effective CSP criteria are met. Additionally or alternatively, morphology match scores determined between post-pace T- waves and the intrinsic T-wave template as the second T-wave metric 762 can be compared to a second match threshold 765 for determining when effective CSP criteria areRef. No. A0012277W001 met. Control circuit 80 may determine that effective CSP criteria are met when the first T- wave match metric 752 is greater than the first threshold 755 and / or when the second T- wave match metric 762 is less than the second threshold 765. As such, in the example shown, control circuit 80 may detect a change in the trend of the T-wave match metrics 752 and 762 as described above but still determine that effective CSP criteria are met based on the match thresholds 755 and 765. In this case, control circuit 80 may transmit a report to indicate a change in T-wave match metric trend without necessarily adjusting CSP control parameters. In some examples, control circuit 80 may update the stored T- wave templates, however, so that subsequent comparisons to the stored templates can be performed for detecting a future change in the T-wave match metric trend and currently relevant T-wave templates can be stored in memory 82 for determining when effective CSP criteria are met.

[0179] In other examples, rather than comparing short-term averages to a historical average, as described above, control circuit 80 may determine a running average 757 of the T-wave match metric 752 that is updated with each T-wave match metric. Each T- wave metric may be compared to the average 757 or a threshold based thereon (e.g., a percentage of average 757). When a specified number of successive T-wave match metrics 752 fall below the average 757 (or a threshold difference less than the average 757), control circuit 80 may detect a change in the trend of the T-wave match metric 752. In still other examples, a variability measure may be determined (e.g., using differences between T-wave match metrics and the running average 757) and compared to a threshold for detecting when a change in T-wave morphology is detected.

[0180] In various examples, a change in the trend of T-wave match metrics may be detected using a reference average that is determined over different time scales. For example, a historical average determined over a specified time interval from the time of pacemaker implant may remain fixed for comparison to later T-wave match metrics. A running average that is updated as the average of T-wave match metrics determined at all time points may be determined. Additionally or alternatively, one or more moving averages, e.g., a monthly moving average, a weekly moving average and / or a daily moving average, as examples, may each be determined for comparisons to the most recently determined T-wave metrics for determining a change in the trend of the T-wave metrics over different time scales. Changes in the T-wave metrics that occur over differentRef. No. A0012277W001 time scales may indicate different causes of the change that may occur relatively more or less gradually, such as a relatively short term change (e.g., in one day or in less than one week) caused by a shift, migration or dislodgement of the pacing electrode, a mid-term change (e.g., over one week or a few weeks) due to a change in medication, illness or edema, or a relatively long term change (e.g., over several weeks or months) caused by cardiac remodeling. Comparisons of T-wave match metrics to reference averages of different time scales enable control circuit 80 to generate notifications that may indicate the relative time scale of the T-wave morphology change.

[0181] Further disclosed herein is the subject matter of the following examples:

[0182] Example 1. A medical device system including a therapy delivery circuit configured to deliver ventricular pacing pulses comprising conduction system pacing (CSP) pulses and a sensing circuit configured to sense at least one cardiac electrical signal. The medical device system includes a memory configured to store at least one T-wave template and a control circuitry configured to obtain at least one post-pace T-wave from the at least one cardiac electrical signal sensed by the sensing circuit following a CSP pulse delivered by the therapy delivery circuit. The control circuitry may be further configured to determine at least one T-wave match metric between the at least one postpace T-wave and at least one T-wave template stored in the memory, determine that effective CSP criteria corresponding to capture of at least a portion of a cardiac conduction system are not met based on the at least one T-wave match metric, generate an output in response to the effective CSP criteria not being met and store the output in the memory.

[0183] Example 2. The medical device system of example 1 wherein the control circuitry is further configured to receive one or more intrinsic T-waves from the cardiac electrical signal, determine an intrinsic T-wave template from the one or more intrinsic T-waves and store the intrinsic T-wave template in the memory as one of the at least one T-wave templates. The control circuitry may determine the at least one T-wave match metric by determining a first T-wave match metric between the intrinsic T-wave template and the at least one post-pace T-wave and determine that the effective CSP criteria are not met based on at least the first T-wave metric.

[0184] Example 3. The medical device system of any one of examples 1 — 2 wherein the control circuitry is further configured to receive one or more first baseline CSP T-waves sensed from the cardiac electrical signal during CSP delivered by the therapy deliveryRef. No. A0012277W001 circuit according to a first set of pacing control parameters and determine a first CSP T- wave template from the one or more first baseline CSP T-waves. The control circuitry may store the first CSP T-wave template in the memory as one of the at least one T-wave templates, determine the at least one T-wave match metric by determining a second T- wave match metric between the first CSP T-wave template and the at least one post-pace T-wave and determine that the effective CSP criteria are not met based on at least the second T-wave metric.

[0185] Example 4. The medical device system of example 3 wherein the control circuitry can be further configured to receive one or more second baseline CSP T-waves sensed from the cardiac electrical signal during CSP delivered by the therapy delivery circuit according to a second set of pacing control parameters different than the first set of pacing control parameters, wherein the first set of pacing control parameters result in a first pacing capture type and the second set of pacing control parameters result in a second pacing capture type different than the first pacing capture type. The control circuitry may be configured to determine a second CSP T-wave template from the one or more second baseline CSP T-waves and store the second CSP T-wave template in the memory as one of the at least one T-wave templates. The control circuitry may determine the at least one T- wave match metric by determining a third T-wave match metric between the second CSP T-wave template and the at least one post-pace T-wave and determine that the effective CSP criteria are not met based on at least the third T-wave metric.

[0186] Example 5. The medical device system of any one of examples 1 — 4 wherein the control circuitry is further configured to generate the output comprising an adjusted pacing control parameter setting in response to determining that the effective CSP criteria are not met. The therapy delivery circuit may be further configured to deliver CSP pulses according to the adjusted pacing control parameter setting.

[0187] Example 6. The medical device system of any one of examples 1 — 5 wherein the control circuitry is further configured to determine the at least one T-wave match metric by determining a post-pace T-wave feature from the at least one post-pace T-wave and determining a difference between the post-pace T-wave feature and an analogous feature of the one of the stored T-wave templates.

[0188] Example 7. The medical device system of any one of examples 1 — 6 wherein the control circuitry is further configured to determine the at least one T-wave match metricRef. No. A0012277W001 by determining a plurality of post-pace T-wave features from the at least one post-pace T- wave and, for each of the plurality of post-pace T-wave features, determining a difference between the post-pace T-wave feature and an analogous feature of one of the stored T- wave templates. The control circuitry may be configured to determine the T-wave match metric as a weighted combination of the plurality of differences.

[0189] Example 8. The medical device system of any one of examples 1 — 7 wherein the control circuitry is further configured to determine the at least one T-wave match metric by determining at least one of: a morphology match score; a T-wave width; a T-wave peak amplitude; a T-wave peak amplitude time; a maximum slope; a maximum slope time; and / or a T-wave frequency metric.

[0190] Example 9. The medical device system of any one of examples 1 — 8 further comprising a telemetry circuit configured to transmit a notification. The control circuit may be further configured to generate the output comprising a notification to adjust an electrode position for transmission by the telemetry circuit.

[0191] Example 10. The medical device system of any one of examples 1 — 9 wherein the sensing circuit is further configured to sense at least one cardiac electrical signal by receiving a first cardiac electrical signal via a first sensing electrode vector and receiving a second cardiac electrical signal via a second sensing electrode vector that is different than the first sensing electrode vector. The control circuitry may be further configured to obtain the at least one post-pace T-wave from the at least cardiac electrical signal by receiving a first post-pace T-wave of the first cardiac electrical signal and receiving a second post-pace T-wave of the second cardiac electrical signal. The control circuitry may determine at least one T-wave match metric by determining a first T-wave difference between at least one T-wave template stored in the memory and the first post-pace T-wave and a second T-wave difference between at least one T-wave template stored in the memory and the second post-pace T-wave.

[0192] Example 11. The medical device system of any one of examples 1 — 10 wherein the therapy delivery circuit is further configured to deliver a plurality of test CSP pulses according to a plurality of sets of pacing control parameters. The control circuitry is further configured to, for each set of the plurality of sets of pacing control parameters, receive at least one post-pace T-wave and determine the at least one T-wave match metric. Based on the T-wave match metrics determined for the plurality of sets of pacing controlRef. No. A0012277W001 parameters, the control circuitry may select a set of pacing control parameters from among the plurality of sets of pacing control parameters. The therapy delivery circuit may deliver CSP pulses according to the selected set of pacing control parameters.

[0193] Example 12. The medical device system of example 11 wherein the memory is configured to store the at least one T-wave template comprising an intrinsic T-wave template. The control circuit may be further configured to determine the at least one T- wave match metric by determining a first T-wave match metric between the intrinsic T- wave template and the at least one post-pace T-wave for each set of the plurality of sets of pacing control parameters and select the set of pacing control parameters based on the T- wave match metrics including the first T-wave match metrics determined for each set of the plurality of sets of pacing control parameters.

[0194] Example 13. The medical device system of any one of examples 1 — 12 further comprising a telemetry circuit configured to transmit a T-wave morphology report. The control circuitry may be further configured to determine the at least one T-wave match metric at each of a plurality of monitoring time points and detect a change in a T-wave match metric trend based on the at least one T-wave match metric determined at each of a plurality of monitoring time points. The control circuitry may generate the T-wave morphology report comprising at least a notification signal indicating the change in the T- wave match metric trend in response to detecting the change in the T-wave match metric trend.

[0195] Example 14. The medical device system of any one of examples 1 — 13 further comprising a telemetry circuit for transmitting a notification signal. The control circuitry may be further configured generate the output by generating at least one of: an adjusted pacing control parameter setting used by the therapy delivery circuit to deliver the CSP pulses and / or the notification signal for transmission by the telemetry circuit.

[0196] Example 15. The medical device system of any one of examples 1 — 14 wherein the control circuitry is further configured to generate the output comprising an adjustment of a pacing control parameter setting of at least one of: a CSP electrode vector; a CSP electrode polarity; a pacing interval; a pacing pulse amplitude and / or a pacing pulse width.

[0197] Example 16. The medical device system of any one of examples 1 — 15 wherein the control circuitry is further configured to determine CSP capture based on a QRSRef. No. A0012277W001 waveform of the at least one sensed cardiac electrical signal and establish the at least one T-wave template as a CSP T-wave template in response to determining the CSP capture.

[0198] Example 17. The medical device system of any one of examples 1 — 16 wherein the control circuitry is further configured to determine a post-pace QRS waveform feature from the at least one cardiac electrical signal sensed by the sensing circuit following the CSP pulse delivered by the therapy delivery circuit and determine that effective CSP criteria are not met based on the post-pace QRS waveform feature and the at least one T- wave match metric.

[0199] Example 18. A method including delivering ventricular pacing pulses comprising conduction system pacing (CSP) pulses, sensing at least one cardiac electrical signal and storing at least one T-wave template in a memory of a medical device system. The method may further include obtaining at least one post-pace T-wave from the at least one cardiac electrical signal sensed following a delivered CSP pulse and determining at least one T- wave match metric between the at least one post-pace T-wave and at least one T-wave template stored in the memory. The method may include determining that effective CSP criteria corresponding to capture of at least a portion of a cardiac conduction system are not met based on the at least one T-wave match metric, generating an output in response to the effective CSP criteria not being met and storing the output in the memory.

[0200] Example 19. The method of example 18 further including receiving one or more intrinsic T-waves from the cardiac electrical signal, determining an intrinsic T-wave template from the one or more intrinsic T-waves and storing the intrinsic T-wave template in the memory as one of the at least one T-wave templates. The method may include determining the at least one T-wave match metric by determining a first T-wave match metric between the intrinsic T-wave template and the at least one post-pace T-wave and determining that the effective CSP criteria are not met based on at least the first T-wave metric.

[0201] Example 20. The method of any one of examples 18 — 19 further including receiving one or more first baseline CSP T-waves sensed from the cardiac electrical signal during CSP delivered according to a first set of pacing control parameters, determining a first CSP T-wave template from the one or more first baseline CSP T-waves and storing the first CSP T-wave template in the memory as one of the at least one T-wave templates. The method may include determining the at least one T-wave match metric by determiningRef. No. A0012277W001 a second T-wave match metric between the first CSP T-wave template and the at least one post-pace T-wave and determining that the effective CSP criteria are not met based on at least the second T-wave metric.

[0202] Example 21. The method of example 20 further comprising receiving one or more second baseline CSP T-waves sensed from the cardiac electrical signal during CSP delivered according to a second set of pacing control parameters different than the first set of pacing control parameters, wherein the first set of pacing control parameters result in a first pacing capture type and the second set of pacing control parameters result in a second pacing capture type different than the first pacing capture type. The method may include determining a second CSP T-wave template from the one or more second baseline CSP T- waves, storing the second CSP T-wave template in the memory as one of the at least one T-wave templates and determining the at least one T-wave match metric by determining a third T-wave match metric between the second CSP T-wave template and the at least one post-pace T-wave. The method may include determining that the effective CSP criteria are not met based on at least the third T-wave metric.

[0203] Example 22. The method of any one of examples 18 — 21 further including generating the output comprising an adjusted a pacing control parameter setting in response to determining that the effective CSP criteria are not met and delivering CSP pulses according to the adjusted pacing control parameter setting.

[0204] Example 23. The method of any one of examples 18 — 22 wherein determining the at least one T-wave match metric may include determining a post-pace T-wave feature from the at least one post-pace T-wave and determining a difference between the postpace T-wave feature and an analogous feature of the one of the stored T-wave templates.

[0205] Example 24. The method of any one of examples 18 — 23 wherein determining the at least one T-wave match metric may include determining a plurality of post-pace T-wave features from the at least one post-pace T-wave and, for each of the plurality of post-pace T-wave features, determining a difference between the post-pace T-wave feature and an analogous feature of one of the stored T-wave templates. The method may further include determining the T-wave match metric as a weighted combination of the plurality of differences.

[0206] Example 25. The method of any one of examples 18 — 24 wherein determining the at least one T-wave match metric may include determining at least one of a morphologyRef. No. A0012277W001 match score; a T-wave width; a T-wave peak amplitude; a T-wave peak amplitude time; a maximum slope; a maximum slope time and / or a T-wave frequency metric.

[0207] Example 26. The method of any one of examples 18 — 25 further including generating the output comprising a notification to adjust an electrode position and transmitting the notification.

[0208] Example 27. The method of any one of examples 18 — 26 further including sensing the at least one cardiac electrical signal by receiving a first cardiac electrical signal via a first sensing electrode vector and receiving a second cardiac electrical signal via a second sensing electrode vector that is different than the first sensing electrode vector. The method may further include obtaining the at least one post-pace T-wave from the at least cardiac electrical signal by receiving a first post-pace T-wave of the first cardiac electrical signal and receiving a second post-pace T-wave of the second cardiac electrical signal. The method may include determining at least one T-wave match metric by determining a first T-wave difference between at least one T-wave template stored in the memory and the first post-pace T-wave and a second T-wave difference between at least one T-wave template stored in the memory and the second post-pace T-wave.

[0209] Example 28. The method of any one of examples 18 — 27 further including delivering a plurality of test CSP pulses according to a plurality of sets of pacing control parameters. The method may include, for each set of the plurality of sets of pacing control parameters, receiving at least one post-pace T-wave and determining the at least one T- wave match metric. The method may further include based on the T-wave match metrics determined for the plurality of sets of pacing control parameters, selecting a set of pacing control parameters from among the plurality of sets of pacing control parameters and delivering CSP pulses according to the selected set of pacing control parameters.

[0210] Example 29. The method of example 28 further including storing the at least one T-wave template comprising an intrinsic T-wave template and determining the at least one T-wave match metric by determining a first T-wave match metric between the intrinsic T- wave template and the at least one post-pace T-wave for each set of the plurality of sets of pacing control parameters. The method may further include selecting the set of pacing control parameters based on the T-wave match metrics including the first T-wave match metrics determined for each set of the plurality of sets of pacing control parameters.Ref. No. A0012277W001

[0211] Example 30. The method of any one of examples 18 — 29 further including determining the at least one T-wave match metric at each of a plurality of monitoring time points and detecting a change in a T-wave match metric trend based on the at least one T- wave match metric determined at each of a plurality of monitoring time points. The method may include generating a T-wave morphology report comprising at least a notification signal indicating the change in the T-wave match metric trend in response to detecting the change in the T-wave match metric trend and transmitting the T-wave morphology report.

[0212] Example 31. The method of any one of examples 18 — 30 further including generating the output by generating at least one of an adjusted pacing control parameter setting used to deliver CSP pulses and / or a notification signal for transmission to another device.

[0213] Example 32. The method of any one of examples 18 — 31 wherein generating the output comprises generating an adjustment of a pacing control parameter setting of at least one of: a CSP electrode vector; CSP electrode polarity; a pacing interval; a pacing pulse amplitude and / or a pacing pulse width.

[0214] Example 33. The method of any one of examples 18 — 32 further including determining CSP capture based on a QRS waveform of the at least one sensed cardiac electrical signal and establishing the at least one T-wave template as a CSP T-wave template in response to determining the CSP capture.

[0215] Example 34. The method of any one of examples 18 — 33 further including determining a post-pace QRS waveform feature from the at least one cardiac electrical signal sensed following the delivered CSP pulse and determining that effective CSP criteria are not met based on the post-pace QRS waveform feature and the at least one T- wave match metric.

[0216] Example 35. A non-transitory computer readable medium storing instructions that, when executed by control circuitry of the medical device system, cause the medical device system to deliver ventricular pacing pulses comprising CSP pulses, sense at least one cardiac electrical signal, obtain at least one post-pace T-wave from the at least one cardiac electrical signal sensed following a delivered CSP pulse and determine at least one T-wave match metric between the at least one post-pace T-wave and at least one T-wave template. The instructions may further cause the medical device system to determine that effectiveRef. No. A0012277W001CSP criteria corresponding to capture of at least a portion of a cardiac conduction system are not met based on the at least one T-wave match metric. The instructions may cause the medical device system to generate an output in response to the effective CSP criteria not being met.

[0217] It should be understood that, depending on the example, certain acts or events of any of the methods described herein can be performed in a different sequence, in parallel, may be added, merged, or left out altogether (e.g., not all described acts or events are necessary for the practice of the method). Moreover, in certain examples, acts or events may be performed concurrently, e.g., through multi -threaded processing, interrupt processing, or multiple processors, rather than sequentially. In addition, while certain aspects of this disclosure are described as being performed by a single processor, circuit or unit for purposes of clarity, it should be understood that the techniques of this disclosure may be performed by a combination of processors, units or circuits associated with, for example, a medical device system.

[0218] In one or more examples, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored as one or more instructions or code on a computer-readable medium and executed by one or more hardware-based processing units. Computer- readable media may include computer-readable storage media, which corresponds to a tangible medium such as data storage media (e.g., RAM, ROM, EEPROM, flash memory, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer).

[0219] Instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general purpose microprocessors, application specific integrated circuits (ASICs), field programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuitry. Accordingly, the term “processor,” as used herein may refer to any of the foregoing structure or any other structure suitable for implementation of the techniques described herein. Also, the techniques could be fully implemented in one or more circuits or logic elements.Ref. No. A0012277W001

[0220] Thus, a medical device system has been presented in the foregoing description with reference to specific examples. It is to be understood that various aspects disclosed herein may be combined in different combinations than the specific combinations presented in the accompanying drawings. It is appreciated that various modifications to the referenced examples may be made without departing from the scope of the disclosure and the following claims.

Claims

1. Ref. No. A0012277W001WHAT IS CLAIMED IS:

1. A medical device system comprising: a therapy delivery circuit configured to deliver ventricular pacing pulses comprising conduction system pacing (CSP) pulses; a sensing circuit configured to sense at least one cardiac electrical signal; a memory configured to store at least one T-wave template; and control circuitry configured to: obtain at least one post-pace T-wave from the at least one cardiac electrical signal sensed by the sensing circuit following a CSP pulse delivered by the therapy delivery circuit; determine at least one T-wave match metric between the at least one post-pace T-wave and at least one T-wave template stored in the memory; determine that effective CSP criteria corresponding to capture of at least a portion of a cardiac conduction system are not met based on the at least one T-wave match metric; generate an output for controlling a response to the effective CSP criteria not being met.

2. The medical device system of claim 1 wherein: the control circuitry is further configured to: receive one or more intrinsic T-waves from the cardiac electrical signal; determine an intrinsic T-wave template from the one or more intrinsic T- waves; store the intrinsic T-wave template in the memory as one of the at least one T-wave templates; determine the at least one T-wave match metric by determining a first T- wave match metric between the intrinsic T-wave template and the at least one postpace T-wave; and determine that the effective CSP criteria are not met based on at least the first T-wave metric.

3. The medical device system of any one of claims 1 — 2 wherein:Ref. No. A0012277W001 the control circuitry is further configured to: receive one or more first baseline CSP T-waves sensed from the cardiac electrical signal during CSP delivered by the therapy delivery circuit according to a first set of pacing control parameters; determine a first CSP T-wave template from the one or more first baseline CSP T-waves; store the first CSP T-wave template in the memory as one of the at least one T-wave templates; determine the at least one T-wave match metric by determining a second T- wave match metric between the first CSP T-wave template and the at least one post-pace T-wave; and determine that the effective CSP criteria are not met based on at least the second T-wave metric.

4. The medical device system of claim 3 wherein: the control circuitry is further configured to: receive one or more second baseline CSP T-waves sensed from the cardiac electrical signal during CSP delivered by the therapy delivery circuit according to a second set of pacing control parameters different than the first set of pacing control parameters, wherein the first set of pacing control parameters result in a first pacing capture type and the second set of pacing control parameters result in a second pacing capture type different than the first pacing capture type; determine a second CSP T-wave template from the one or more second baseline CSP T-waves; store the second CSP T-wave template in the memory as one of the at least one T-wave templates; determine the at least one T-wave match metric by determining a third T- wave match metric between the second CSP T-wave template and the at least one post-pace T-wave; and determine that the effective CSP criteria are not met based on at least the third T-wave metric.Ref. No. A0012277W0015. The medical device system of any one of claims 1 — 4 wherein: the control circuitry is further configured to generate the control parameter output comprising an adjusted pacing control parameter setting in response to determining that the effective CSP criteria are not met; and the therapy delivery circuit is further configured to deliver CSP pulses according to the adjusted pacing control parameter setting.

6. The medical device system of any one of claims 1 — 5 wherein the control circuitry is further configured to determine the at least one T-wave match metric by: determining a post-pace T-wave feature from the at least one post-pace T-wave; and determining a difference between the post-pace T-wave feature and an analogous feature of the one of the stored T-wave templates.

7. The medical device system of any one of claims 1 — 6 wherein the control circuitry is further configured to determine the at least one T-wave match metric by: determining a plurality of post-pace T-wave features from the at least one postpace T-wave; for each of the plurality of post-pace T-wave features, determining a difference between the post-pace T-wave feature and an analogous feature of one of the stored T- wave templates; and determining the T-wave match metric as a weighted combination of the plurality of differences.

8. The medical device system of any one of claims 1 — 7 wherein the control circuitry is further configured to determine the at least one T-wave match metric by determining at least one of: a morphology match score; a T-wave width; a T-wave peak amplitude; a T-wave peak amplitude time; a maximum slope;Ref. No. A0012277W001 a maximum slope time; or a T-wave frequency metric.

9. The medical device system of any one of claims 1 — 8 further comprising a telemetry circuit configured to transmit a notification; and wherein the control circuit is further configured to generate the control parameter output comprising a notification to adjust an electrode position for transmission by the telemetry circuit.

10. The medical device system of any one of claims 1 — 9 wherein: the sensing circuit is further configured to sense at least one cardiac electrical signal by: receiving a first cardiac electrical signal via a first sensing electrode vector; and receiving a second cardiac electrical signal via a second sensing electrode vector that is different than the first sensing electrode vector; and the control circuitry is further configured to: obtain the at least one post-pace T-wave from the at least cardiac electrical signal by: receiving a first post-pace T-wave of the first cardiac electrical signal; and receiving a second post-pace T-wave of the second cardiac electrical signal; and determine at least one T-wave match metric by determining a first T-wave difference between at least one T-wave template stored in the memory and the first post-pace T-wave and a second T-wave difference between at least one T-wave template stored in the memory and the second post-pace T-wave.

11. The medical device system of any one of claims 1 — 10 wherein: the therapy delivery circuit is further configured to deliver a plurality of test CSP pulses according to a plurality of sets of pacing control parameters; the control circuitry is further configured to: for each set of the plurality of sets of pacing control parameters:Ref. No. A0012277W001 receive at least one post-pace T-wave; and determine the at least one T-wave match metric; and based on the T-wave match metrics determined for the plurality of sets of pacing control parameters, determine a selected set of the plurality of sets of pacing control parameters for which the effective CSP criteria corresponding to capture of at least a portion of a cardiac conduction system are met; generate the control parameter output comprising the selected set of the plurality of sets of pacing control parameters; and the therapy delivery circuit being further configured to deliver CSP pulses according to the selected set of pacing control parameters.

12. The medical device system of claim 11 wherein: the memory is configured to store the at least one T-wave template comprising an intrinsic T-wave template; and the control circuit is further configured to: determine the at least one T-wave match metric by determining a first T- wave match metric between the intrinsic T-wave template and the at least one postpace T-wave for each set of the plurality of sets of pacing control parameters; and select the set of pacing control parameters based on the T-wave match metrics including the first T-wave match metrics determined for each set of the plurality of sets of pacing control parameters.

13. The medical device system of any one of claims 1 — 12 further comprising a telemetry circuit configured to transmit a T-wave morphology report; and wherein the control circuitry is further configured to: determine the at least one T-wave match metric at each of a plurality of monitoring time points; detect a change in a T-wave match metric trend based on the at least one T- wave match metric determined at each of a plurality of monitoring time points; and generate the T-wave morphology report comprising at least a notification signal indicating the change in the T-wave match metric trend in response to detecting the change in the T-wave match metric trend.Ref. No. A0012277W00114. The medical device system of any one of claims 1 — 13 wherein the control circuitry is further configured to: determine a post-pace QRS waveform feature from the at least one cardiac electrical signal sensed by the sensing circuit following the CSP pulse delivered by the therapy delivery circuit; determine that effective CSP criteria are not met based on the post-pace QRS waveform feature and the at least one T-wave match metric.

15. A method comprising: delivering ventricular pacing pulses comprising conduction system pacing (CSP) pulses; sensing at least one cardiac electrical signal; storing at least one T-wave template in a memory of a medical device system; obtaining at least one post-pace T-wave from the at least one cardiac electrical signal sensed following a delivered CSP pulse; determining at least one T-wave match metric between the at least one post-pace T-wave and at least one T-wave template stored in the memory; determining that effective CSP criteria corresponding to capture of at least a portion of a cardiac conduction system are not met based on the at least one T-wave match metric; generating a control parameter output for controlling a response to the effective CSP criteria not being met.

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