Antitachycardia pacing therapy for cardiac conduction system pacing

Abstract

Antitachycardia pacing (ATP) therapy may be delivered to the cardiac conduction system using cardiac conduction system pacing therapy. An initial cardiac conduction system ATP pulse set including three or less cardiac conduction system ATP pulses may be delivered to the patient's cardiac conduction system. A first cardiac conduction system ATP pulse of the initial cardiac conduction system ATP pulse set may be delivered at an interval configured to provide maximal capture of the cardiac conduction system.

Description

ANTITACHYCARDIA PACING THERAPY FOR CARDIAC CONDUCTION SYSTEM PACING

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 711,914, filed October 25, 2024, the entire content of which is incorporated herein by reference.

[0002] The present disclosure relates generally to antitachycardia pacing therapy for cardiac conduction system pacing.

[0003] Implantable medical devices (IMDs), such as cardiac pacemakers or implantable cardioverter defibrillators, deliver therapeutic stimulation to patients’ hearts thereby improving the lives of millions of patients living with heart conditions.Conventional pacing techniques involve pacing one or more of the four chambers of a patient’s heart 12 as illustrated in FIG. 1, including the left atrium 33, the right atrium 26, the left ventricle 32 and the right ventricle 28. One common conventional therapeutic pacing technique that treats a slow heart rate, referred to as bradycardia, involves delivering an electrical pulse to a patient’s right ventricular tissue. In response to the electrical pulse, both the right and left ventricles contract. However, the heart beat process may be significantly delayed because the pulse travels from the right ventricle through the left ventricle. The electrical pulse passes through the muscle cells that are referred to as myocytes. Myocyte-to-myocyte conduction may be very slow. Delayed electrical pulses can cause the left ventricle to be unable to maintain synchrony with the right ventricle.

[0004] Over time, the left ventricle can become significantly inefficient at pumping blood to the body. In some patients, heart failure can develop such that the heart is too weak to pump blood to the body. Heart failure may be a devastating diagnosis since, for example, fifty percent of the heart failure patients have a life expectancy of five years or less. Another possible cause of heart failure is due to atrial fibrillation, which is an irregular and often very rapid heart rhythm or arrhythmia. During atrial fibrillation, the atria of the heart can beat out of sync with the ventricles of the heart because of the arrythmia of the atria, which can lead to blood clots in the heart and increase the risk of stroke or heart failure, for example.

[0005] To avoid potential development of heart failure, some physicians have considered alternative pacing methods that involve the cardiac conduction system. Pacing the cardiac conduction system may quickly conduct electrical pulses (for example, akin toa car driving on a highway), whereas pacing cardiac muscle, or myocardial, tissue may more slowly conduct electrical pulses (for example, akin to a car driving on a dirt road).

[0006] The cardiac conduction system includes the sinoatrial node 1, atrial intemodal tracts 2, 4, 5 (i.e., anterior intemodal 2, middle internodal 4, and posterior internodal 5), atrioventricular node 3, His bundle 13 (also known as the atrioventricular bundle or bundle of His), left bundle branch 8a, and right bundle branch 8b as shown in FIG. 1. The arch of aorta 6 and the Bachman’s bundle 7 are also shown in FIG. 1. The sinoatrial node 1, located at the junction of the superior vena cava and right atrium, is considered to be the natural pacemaker of the heart as sinoatrial node 1 continuously and repeatedly emits electrical impulses. The electrical impulses spread through the muscles of right atrium 26 to left atrium 33 to cause synchronous contraction of the atria. The electrical impulses are also carried through atrial internodal tracts to the atrioventricular node 3 — the sole connection between the atria and the ventricles. The conduction through the atrioventricular node or atrioventricular nodal tissue takes longer than through the atrial tissue, which results in a delay between the atrial contractions and the start of the ventricular contractions. The atrioventricular delay, which is the delay between atrial contractions and ventricular contractions, allows the atria to empty blood into the ventricles. Then, the valves between the atria and ventricles close in conjunction with ventricular contraction via branches of the bundle of His. The bundle of His, or His bundle, 13 is located in the membranous atrioventricular septum near the annulus of the tricuspid valve. The His bundle 13 splits into the left and right bundle branches 8a, 8b and are formed of specialized fibers called “Purkinje fibers” 9. The Purkinje fibers 9 may be described as being capable of rapidly conducting an action potential down the ventricular septum (VS), spreading the depolarization wavefront quickly through the remaining ventricular myocardium, and producing a coordinated contraction of the ventricular muscle mass.

[0007] Anti tachycardia pacing (ATP) therapy is often an effective treatment to cease, or terminate, ventricular tachycardia. When the ATP site (that is, where the electrode delivering the ATP is located) is distant from the re-entrant circuit causing the ventricular tachycardia, a delay in paced wavefronts may result in less effective antitachycardia pacing therapy, especially if cell-to-cell conduction defects exist (e.g., due to myocardial infarction, heart disease, etc.).SUMMARY

[0008] Capture of the specialized His-Purkinje system through cardiac conduction system pacing therapy (e.g., His-bundle or left bundle branch area pacing) can create multiple points of ATP-initiated wavefronts across the ventricles resulting in more effective antitachycardia pacing therapy than traditional ATP delivered to the myocardium or myocardial tissue. The illustrative devices and methods provide antitachycardia pacing therapy using the cardiac conduction system of the patient, and more specifically, the illustrative devices and methods may be described as including delivery of antitachycardia pacing therapy using an electrode configured to deliver cardiac conduction system pacing therapy to the cardiac conduction system.

[0009] The illustrative devices and methods may be described as leveraging the unique properties of the cardiac conduction system to delivery antitachycardia pacing therapy. In one or more embodiments, the illustrative devices and methods described herein have demonstrated in computational models the ability to terminate ventricular tachycardia in two to three paces as opposed to eight or more paces as often used in traditional antitachycardia pacing therapy delivered to myocardial tissue. Due to the nature of the cardiac conduction system, the processes, methods, and timings of the antitachycardia pacing therapy delivered to the cardiac conduction system are different than that of traditional antitachycardia pacing therapy delivered to myocardial tissue. For example, an initial cardiac conduction system ATP pulse set may be delivered to the patient. The initial cardiac conduction system ATP pulse set may include a first cardiac conduction system ATP pulse, or pace, delivered early in the cycle length of the ventricular tachycardia to provide, or allow, maximum control over the cardiac conduction system by “winning the race” against the ventricular tachycardia wavefronts for control of sites near the critical features of re-entrant circuits as will be described further herein. Further, for example, the initial cardiac conduction system ATP pulse set may include a second cardiac conduction system ATP pulse, or pace, following the first cardiac conduction system ATP pulse delivered early in the cycle length of the ventricular tachycardia to maximally advance the next wavefront towards the refractory tail of the ventricular tachycardia wave as will be described further herein. If the ventricular tachycardia has not ceased or been terminated after the first and second cardiac conductionsystem ATP pulses, a second cardiac conduction system ATP pulse set including three cardiac conduction system ATP pulses may be delivered as well as a third cardiac conduction system ATP pulse set including more than three cardiac conduction system ATP pulses if the second cardiac conduction system ATP pulse set does not cease or terminate that ventricular tachycardia as will be described further herein.

[0010] An illustrative implantable medical device includes, among other things, a computing apparatus comprising processing circuitry and operably coupled to one or more implantable electrodes. The one or more implantable electrodes includes at least a cardiac conduction system pacing electrode positionable proximate a portion of the patient’s cardiac conduction system. The computing apparatus is configured to provide cardiac conduction system antitachycardia pacing therapy (ATP) using the cardiac conduction system pacing electrode. The cardiac conduction system ATP includes monitoring electrical activity of the patient’s heart using the one or more implantable electrodes, determining a cardiac cycle time based on the monitored electrical activity, and delivering an initial cardiac conduction system ATP pulse set comprising three or less cardiac conduction system ATP pulses. The three or less ATP pulses of the initial cardiac conduction system ATP pulse set include a first cardiac conduction system ATP pulse to the patient’s cardiac conduction system using the cardiac conduction system pacing electrode after a first period of time following an intrinsic cardiac activation. The first period of time is based on the cardiac cycle time and configured to provide maximal capture of the cardiac conduction system. The three or less ATP pulses of the initial cardiac conduction system ATP pulse set further includes a second cardiac conduction system ATP pulse to the patient’s cardiac conduction system using the cardiac conduction system pacing electrode after a second period of time based on the cardiac cycle time and following the first cardiac conduction system ATP pulse.

[0011] An illustrative method includes monitoring electrical activity of a patient’s heart using one or more implantable electrodes, determining a cardiac cycle time based on the monitored electrical activity, and delivering an initial cardiac conduction system ATP pulse set comprising three or less cardiac conduction system ATP pulses. The three or less ATP pulses of the initial cardiac conduction system ATP pulse set include a first cardiac conduction system ATP pulse to the patient’s cardiac conduction system using a cardiac conduction system pacing electrode positioned proximate a portion of the patient’s cardiacconduction system after a first period of time following an intrinsic cardiac activation. The first period of time is based on the cardiac cycle time and configured to provide maximal capture of the cardiac conduction system. The three or less ATP pulses of the initial cardiac conduction system ATP pulse set further includes a second cardiac conduction system ATP pulse to the patient’s cardiac conduction system using the cardiac conduction system pacing electrode after a second period of time based on the cardiac cycle time and following the first cardiac conduction system ATP pulse.

[0012] The above summary is not intended to describe each embodiment or every implementation of the present disclosure. A more complete understanding will become apparent and appreciated by referring to the following detailed description and claims taken in conjunction with the accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG. l is a schematic diagram of a heart and conduction system of a patient.

[0014] FIG. 2A is a conceptual diagram illustrating an illustrative therapy system that is configured to provide cardiac conduction system pacing therapy to the His bundle using a lead placed in the right atrium.

[0015] FIG. 2B is a more detailed conceptual diagram showing the illustrative therapy system of FIG. 2 A.

[0016] FIG. 3 A is a conceptual diagram illustrating an illustrative therapy system that is configured to provide cardiac conduction system pacing therapy to the left bundle branch using a lead placed in the right ventricle.

[0017] FIG. 3B is a close-up view of the lead in the patient’s heart of FIG. 3 A.

[0018] FIG. 4 is a functional block diagram illustrating an example of a configuration of an implantable medical device of FIGS. 2 A and 2B.

[0019] FIG. 5 is a block diagram of an illustrative method of antitachycardia pacing therapy for cardiac conduction system pacing therapy that may be utilized by the devices of FIGS. 2-4.

[0020] FIG. 6A are graphs of 12-lead electrocardiograph (ECG) signals over a first cardiac cycle where a first cardiac conduction system ATP pulse is delivered to the cardiac conduction system in a first simulation.

[0021] FIG. 6B are graphs of 12-lead ECG signals over a second cardiac cycle where a second cardiac conduction system ATP pulse is delivered to the cardiac conduction system in the first simulation.

[0022] FIG. 6C are graphs of 12-lead ECG signals over a third cardiac cycle where a third cardiac conduction system ATP pulse is delivered to the cardiac conduction system in the first simulation.

[0023] FIG. 7A are graphs of 12-lead ECG signals over a first cardiac cycle where a first cardiac conduction system ATP pulse is delivered to the cardiac conduction system in a second simulation.

[0024] FIG. 7B are graphs of 12-lead ECG signals over a second cardiac cycle where a second cardiac conduction system ATP pulse is delivered to the cardiac conduction system in the second simulation.

[0025] FIG. 8A are graphs of 12-lead ECG signals over a first cardiac cycle where a first cardiac conduction system ATP pulse is delivered to the cardiac conduction system in a third simulation.

[0026] FIG. 8B are graphs of 12-lead ECG signals over a second cardiac cycle where a second cardiac conduction system ATP pulse is delivered to the cardiac conduction system in the third simulation.

[0027] FIG. 8C are graphs of 12-lead ECG signals over a third cardiac cycle where a third cardiac conduction system ATP pulse is delivered to the cardiac conduction system in the third simulation.DETAILED DESCRIPTION

[0028] In the following detailed description of illustrative embodiments, reference is made to the accompanying figures of the drawing which form a part hereof, and in which are shown, by way of illustration, specific embodiments which may be practiced. It is to be understood that other embodiments may be utilized, and structural changes may be made without departing from (e.g., still falling within) the scope of the disclosure presented hereby.

[0029] Illustrative devices and methods shall be described with reference to FIGS.1-8. It will be apparent to one skilled in the art that elements or processes from one embodiment may be used in combination with elements or processes of the other embodiments, and that the possible embodiments of such devices and methods using combinations of features set forth herein is not limited to the specific embodiments shown in the Figures and / or described herein. Further, it will be recognized that the embodiments described herein may include many elements that are not necessarily shown to scale. Still further, it will be recognized that timing of the processes and the size and shape of various elements herein may be modified but still fall within the scope of the present disclosure, although certain timings, one or more shapes and / or sizes, or types of elements, may be advantageous over others.

[0030] FIG. 1 depicts a schematic diagram of a heart 12 and FIGS. 2-4 depict conceptual diagrams showing illustrative therapy systems that may be used to provide therapy to the heart 12 of a patient 14. The patient 14 ordinarily, but not necessarily, will be a human. As shown in FIGS. 2 A and 2B, the therapy system 10 may include IMD 16, which is coupled to three leads 18, 20, 23, and a programmer 24. The IMD 16 may be, for example, an implantable pacemaker, cardioverter, and / or defibrillator that provides electrical pulses to the heart 12 via electrodes coupled to one or more of the leads 18, 20, 23. Further non-limiting examples of the IMD 16 include the following: a pacemaker with a medical lead; an implantable cardioverter-defibrillator (ICD); an intracardiac device; a leadless pacing device (LPD); a subcutaneous ICD (S-ICD); and a subcutaneous medical device (e.g., inserted monitoring device, etc.).

[0031] The leads 18, 20, 23 may extend into the heart 12 of the patient 14 to sense electrical activity of the heart 12 and / or deliver electrical stimulation to the heart 12. In the example shown in FIG. 2A, the right ventricular lead 18 extends through one or more veins (not shown), the superior vena cava (not shown), and the right atrium 26, and into the right ventricle 28. The left ventricular coronary sinus lead 20 extends through one or more veins, the vena cava, the right atrium 26, and into the coronary sinus 30 to a region adjacent to the free wall of the left ventricle 32 of the heart 12. The cardiac conduction system pacing therapy lead 23 (e.g., left bundle branch pacing lead, right bundle branch pacing lead, His-bundle pacing lead, etc.) extends through one or more veins and the vena cava, and into the right atrium 26 of heart 12 to pace the cardiac conduction system (e.g.,through triangle of Koch region, within the septal wall, proximate and / or in direct contact with the left bundle branch 8a, proximate and / or in direct contact with the right bundle branch 8b, proximate and / or in direct contact with the His bundle 13, etc.). In some embodiments, the cardiac conduction system pacing therapy lead 23 may be positioned within about 1 millimeter of a portion of the cardiac conduction system such as, e.g., the His bundle 13, the left bundle branch 8a, the right bundle branch 8b, etc. In one or more embodiments, a cardiac conduction system therapy lead may be further positioned, or located, through the tricuspid valve into the right ventricle 28 and implanted in the interventricular septum (VS), e.g., about 1 to 2 centimeters in an apical direction as will be described further herein with reference to FIGS. 3A and 3B. One example of a cardiac conduction system pacing therapy lead (e.g., a His Bundle or left bundle branch lead) can be the OMNIASECURE™. The OMNIASECURE™ lead includes a sense and defibrillation coil conductor and a pace cable conductor and does not include, or define, a lumen. One example of a cardiac conduction system pacing therapy lead (e.g., a His lead) can be the SELECT SECURE™ 3830. A description of the SELECT SECURE™ 3830 may be described in the Medtronic model SELECTSECURE™ 3830 manual (2013), incorporated herein by reference in its entirety. The SELECTSESURE™ 3830 lead includes two conductors without lumens.

[0032] As used herein, cardiac conduction system pacing therapy refers to any pacing therapy configured to deliver pacing therapy (e.g., pacing pulses, electrical stimulation, etc.) to the cardiac conduction system including, e.g., the His bundle 13, the left bundle branch 8a, the right bundle branch 8b, etc. As used herein, the term “activation” refers to a sensed or paced event. For example, an atrial activation may refer to an atrial sense or event (As) or an atrial pace or artifact of atrial pacing (Ap). As will be described herein, an atrial sense may be detected, or identified, in one or more various signals monitored using one or more various devices or sensors located in one or more various locations. For example, an atrial sense may be detected in a near-field electrical signal from an electrode positioned in the right atrium. Further, for example, an atrial sense may be detected in a far-field electrical signal from an electrode positioned outside of the right atrium such as in the right ventricle or ventricular septum. Still, for example, an atrial sense may be detected in a far-field signal from a mechanical cardiac activation sensor such as an accelerometer or microphone (e.g., a heart sound sensor) positionedoutside of the right atrium such as in the right ventricle or ventricular septum or another portion of the patient’s body (e.g., within the can or housing of an IMD positioned outside of the patient’s heart). Similarly, a ventricular activation may refer to a ventricular sense or event (Vs) or a ventricular pace or artifact of ventricular pacing (Vp), which may be described as ventricular stimulation pulses. In some embodiments, an activation interval can be detected from As or Ap to Vs or Vp, as well as Vp to Vs. In particular, activation intervals may include a pacing (Ap or Vp) to ventricular interval (left ventricular or right ventricular sense) or an atrial-sensing (As) to ventricular-sensing interval (left ventricular or right ventricular).

[0033] Illustrative IMDs may be described as delivering one or both of conventional pacing therapy and cardiac conduction system pacing therapy. Conventional, or traditional, pacing therapy may be described as delivering pacing pulses into myocardial tissue that is not part of the cardiac conduction system of the patient’s heart such that, e.g., the pacing pulses trigger electrical activation that propagates primarily from one myocardial cell to another myocardial cell (also referred to as “cell-to-cell”) as opposed to propagating within the cardiac conduction system prior to the myocardial tissue. For instance, conventional pacing therapy may deliver pacing pulses directly into the muscular heart tissue (i.e., myocardial tissue) that is to be depolarized to provide the contraction of the heart. For example, conventional left ventricular pacing therapy may utilize a left ventricular coronary sinus lead 20 that is implanted so as to extend through one or more veins, the vena cava, the right atrium 26, and into the coronary sinus 30 to a region adjacent to the free wall of the left ventricle 32 of the heart 12 so as to deliver pacing pulses to the myocardial tissue of the free wall of the left ventricle 32.

[0034] Illustrative leads and electrodes used to form pacing vectors are shown and described in U.S. Pat. No. 11,850,431, U.S. Pat. No. 8,355,784 B2, and U.S. Pat. No. 8,126,546, each of which are incorporated by reference in their entireties.

[0035] Additionally, the pacing therapy leads 18, 20, 23 may be utilized to deliver left ventricle or left ventricular septal pacing to the ventricular septal wall. At least one of pacing therapy leads 18, 20, 23 may extend through one or more veins, the vena cava, right atrium 26, and into the coronary sinus 30 to a region adjacent to the septal wall of left ventricle 32 of heart 12.

[0036] Illustrative cardiac conduction system pacing therapy may be described in, for example, U.S. Pat. No. 11,207,529 entitled “His Bundle and Bundle Branch Pacing Adjustment” issued on December 28, 2021, which is incorporated herein by reference in its entirety. Illustrative left ventricular septal pacing may be described in, for example, U.S. Pat. No. 11,633,607 entitled “AV Synchronous Septal Pacing” issued on April 25, 2023, which is incorporated herein by reference in its entirety.

[0037] One or more elongated conductors of any of the leads 18, 20, 23 may extend through a hermetic feedthrough assembly, and within an insulative tubular member of the respective lead, and may electrically couple an electrical pulse generator (contained within housing) to one or more electrodes such as, e.g., ring electrodes, tips electrodes, helical electrodes, etc. The conductors may be formed by one or more electrically conductive wires comprising, for example, MP35N alloy known to those skilled in the art, in a coiled or cabled configuration, and the insulative tubular member may be any suitable medical grade polymer, for example, polyurethane, silicone rubber, or a blend thereof. According to one or more illustrative embodiments, the flexible lead body may extend a pre-specified length (e.g., about 10 centimeters (cm) to about 20 cm, or about 15 to 20 cm) from a proximal end to a distal end. The lead body may be less than about 7 French (FR) but typically in the range of about 3 FR to 4 FR in size. In one or more embodiments, about 2 FR size to about 3 FR size lead body is employed.

[0038] Cardiac conduction system pacing may include at least one of His bundle pacing and left and / or right bundle branch pacing. Bundle branch pacing may bypass the pathological region and may have a low and stable pacing threshold. In some embodiments, only one of the left bundle branch or the right bundle branch may be paced using one or more pacing leads. In further embodiments, both bundle branches may be paced at the same time (e.g., dual bundle branch pacing), which may mimic intrinsic activation propagation via the His bundle-Purkinje conduction system, e.g., paced activation propagates via both bundle branches to both ventricles for synchronized contraction. His bundle pacing, on the other hand, typically paces the His bundle proximal to the bundle branches. In some embodiments, the IMD 16 may include one, two, or more electrodes located in one or more bundle branches configured for bundle branch pacing.

[0039] In some embodiments, the IMD 16 may be an intracardiac pacemaker or leadless pacing device (LPD) configured to pace one or more portions of the cardiacconduction system such as the His bundle. As used herein, “leadless” refers to a device being free of a lead extending out of the heart 12. In other words, a leadless device may have a lead that does not extend from outside of the heart to inside of the heart. Some leadless devices may be introduced through a vein, but once implanted, the leadless devices are free of, or may not include, any transvenous lead and may be configured to provide cardiac therapy without using any transvenous lead. In one or more embodiments, an illustrative LPD for bundle pacing does not use a lead to operably connect to an electrode disposed proximate to the septum when a housing of the device is positioned in the atrium. A leadless electrode may be leadlessly coupled to the housing of the medical device without using a lead between the electrode and the housing.

[0040] The IMD 16 may sense electrical signals attendant to the depolarization and repolarization of the heart 12 via various electrodes as shown in FIG. 2B coupled to at least one of leads 18, 20, 23. In some examples, the IMD 16 provides pacing pulses to the heart 12 based on the electrical signals sensed within the heart 12. The configurations of the electrodes used by the IMD 16 for sensing and pacing may be unipolar or bipolar.

[0041] The IMD 16 may also provide defibrillation therapy and / or cardioversion therapy via electrodes located on at least one of the leads 18, 20, 23. For example, the IMD 16 may detect atrial arrhythmias of heart 12, such as atrial fibrillation of the atria 26, 33, ventricular tachycardia of the ventricles 28, 32, ventricular fibrillation of the ventricles 28, 32, etc. and then may deliver antitachycardia pacing therapy and / or defibrillation therapy to the heart 12 in the form of electrical pulses. In some examples, the IMD 16 may be programmed to deliver a progression of therapies, e.g., pulses with increasing energy levels, until the arrhythmia of the heart 12 is stopped. The IMD 16 may detect the arrythmias employing one or more arrythmia detection techniques known in the art.

[0042] In some examples, the programmer 24 as shown in FIG. 2A may be a handheld computing device or a computer workstation or a mobile phone. The programmer 24 may include a user interface that receives input from a user. The user interface may include, for example, a keypad and a display, which may for example, be a cathode ray tube (CRT) display, a liquid crystal display (LCD) or light emitting diode (LED) display. The keypad may take the form of an alphanumeric keypad or a reduced set of keys associated with particular functions. The programmer 24 can additionally or alternatively include a peripheral pointing device, such as a mouse, via which a user mayinteract with the user interface. In some embodiments, a display of the programmer 24 may include a touch screen display, and a user may interact with the programmer 24 via the display. Through the graphical user interface on the programmer 24, a user may configure one or more pacing therapies, select one or more pacing modes, etc. A user, such as a physician, technician, or other clinician, may interact with the programmer 24 to communicate with the IMD 16. For example, the user may interact with the programmer 24 to retrieve physiological or diagnostic information from the IMD 16. Additionally, a user may also interact with the programmer 24 to program the IMD 16, e.g., select values for operational parameters of the IMD 16. The IMD 16 and programmer 24 may communicate via wireless communication using any techniques known in the art.Examples of communication techniques may include, for example, low frequency or radiofrequency (RF) telemetry, but other techniques are also contemplated. In some examples, the programmer 24 may include a programming head that may be placed proximate to the patient’s body near the IMD 16 implant site in order to improve the quality or security of communication between the IMD 16 and the programmer 24.

[0043] As used herein, the term “far-field” electrical signal refers to the result of measuring cardiac activity using a sensor, such as an electrode, positioned outside of an area of interest. For example, a far-field electrical signal representing electrical activity of a chamber of interest of the patient’s heart may be measured from an electrode positioned in an adjacent chamber (i.e., a chamber different from than that of the chamber of interest that is next to or near the chamber of interest). More specifically, for example, atrial electrical activity, or electrical activity originating one or more both atria, representative of depolarization of the one or both atria may be monitored in a far-field electrical signal measured using an electrode positioned outside of the right atrium such as in the right or left ventricle, or in the ventricular septum. As used herein, the term “near-field” electrical signal refers to the result of measuring cardiac activity using a sensor, such as an electrode, positioned near an area of interest. For example, an electrical signal measured from an electrode positioned on the left side of the patient’s ventricular septum is one example of a near-field electrical signal of the patient’s LV.

[0044] P-wave timing is the time at which a P-wave is detected. Typically, P-wave timing includes using the maximal first derivative of a P-wave upstroke (or the time of the maximal P-wave value). P-wave timing is also used in the device marker channel toindicate the time of the P-wave or the time of atrial activation. P-wave timing may be determined using near-field signals obtained by sensors (e.g., electrodes, accelerometers, heart sound sensors, etc.) positioned in the atria (e.g., the right atrium) and / or far-field near-field signals obtained by sensors (e.g., electrodes, accelerometers, heart sound sensors, etc.) positioned outside of the atria (e.g., the right atrium) such as in the right ventricle and / or ventricular septum.

[0045] R-wave timing is the time at which the QRS complex is detected.Typically, R-wave timing includes using the maximal first derivative of an R-wave upstroke (or the time of the maximal R-wave value). R-wave timing is also used in the device marker channel to indicate the time of the R-wave or the time of ventricular activation.

[0046] FIG. 2B is a conceptual diagram illustrating the IMD 16 and the leads 18, 20, 23 of the therapy system 10 in greater detail. The three chamber IMD 16 may be used for cardiac rhythm therapy and defibrillation or cardioversion therapy (CRT-D). The leads 18, 20, 23 may be electrically coupled to a stimulation generator, a sensing module, or other modules of IMD 16 via connector block 34. In some examples, proximal ends of leads 18, 20, 23 may include electrical contacts that electrically couple to respective electrical contacts within the connector block 34. In addition, in some examples, the leads 18, 20, 23 may be mechanically coupled to the connector block 34 with the aid of set screws, connection pins, or another suitable mechanical coupling mechanism.

[0047] Each of the leads 18, 20, 23 includes an elongated, insulative lead body, which may carry any number of concentric coiled conductors separated from one another by tubular, insulative sheaths. In the illustrated example, an optional pressure sensor 38 and bipolar electrodes 40 and 42 are located proximate to a distal end of the right ventricular lead 18. In addition, the bipolar electrodes 44 and 46 are located proximate to a distal end of the left ventricular lead 20 and bipolar electrodes 48 and 50 are located proximate to a distal end of cardiac conduction pacing lead 23. The cardiac conduction system pacing electrode 50 may be used for pacing and / or sensing of the cardiac conduction system tissue (e.g., His bundle or bundle branch tissue). Thus, the cardiac conduction system pacing electrode 50 may be positionable proximate the portion of the cardiac conduction system such as the His bundle or bundle branch tissue so as to deliver cardiac conduction system pacing therapy thereto. In some embodiments, the cardiacconduction system pacing electrode 50 is implanted through myocardial tissue to be positioned proximate (e.g., touching, in contact with, etc.) the cardiac conduction system to be able to deliver pacing pulses into the cardiac conduction system.

[0048] In FIG. 2B, the pressure sensor 38 is disposed in right ventricle 28 and may respond to an absolute pressure inside right ventricle 28. The pressure sensor 38 may be, for example, a capacitive or piezoelectric absolute pressure sensor. In other examples, the pressure sensor 38 may be positioned within other regions of the heart 12 and may monitor pressure within one or more of the other regions of the heart 12, or the pressure sensor 38 may be positioned elsewhere within or proximate to the cardiovascular system of the patient 14 to monitor cardiovascular pressure associated with mechanical contraction of the heart. Optionally, a pressure sensor in the pulmonary artery can be used that is in communication with the IMD 16.

[0049] The electrodes 40, 44, and 48 may take the form of ring electrodes, and the electrodes 42, 46, and 50 may take the form of extendable and / or fixed helix tip electrodes mounted within the insulative electrode heads 52, 54 and 56, respectively. Each of the electrodes 40, 42, 44, 46, 48, and 50 may be electrically coupled to a respective one of the coiled conductors within the lead body of its associated lead 18, 20, 23, and thereby coupled to respective ones of the electrical contacts on the proximal end of the leads 18, 2023.

[0050] The electrodes 40, 42, 44, 46, 48, 50 may sense electrical signals attendant to the depolarization and repolarization of the heart 12. The electrical signals are conducted to the IMD 16 via the respective leads 18, 20, 23. In some examples, the IMD 16 also delivers pacing pulses via the electrodes 40, 42, 44, 46, 48, 50 to cause depolarization of cardiac tissue of heart 12. In some examples, as illustrated in FIG. 2B, the IMD 16 may include one or more housing electrodes, such as housing electrode 58, which may be formed integrally with an outer surface of a hermetically sealed housing 60 of the IMD 16 or otherwise coupled to the housing 60. In some examples, the housing electrode 58 may be defined by an uninsulated portion of an outward facing portion of the housing 60 of the IMD 16. Other divisions between insulated and uninsulated portions of housing 60 may be employed to define two or more housing electrodes. In some examples, the housing electrode 58 includes substantially all of the housing 60. Any of the electrodes 40, 42, 44, 46, 48, 50 may be used for unipolar sensing or pacing in combination with thehousing electrode 58 or for bipolar sensing with two electrodes in the same pacing lead. In one or more embodiments, the housing 60 may enclose a stimulation generator (see FIG.4) that generates cardiac pacing pulses and defibrillation or cardioversion shocks, as well as a sensing module for monitoring the patient’s heart rhythm.

[0051] The leads 18, 20, 23 may also include elongated electrodes 62, 64, 66, respectively, which may take the form of a coil. The IMD 16 may deliver defibrillation shocks to the heart 12 via any combination of the elongated electrodes 62, 64, 66, and the housing electrode 58. The electrodes 58, 62, 64, 66 may also be used to deliver cardioversion pulses to the heart 12. The electrodes 62, 64, 66 may be fabricated from any suitable electrically conductive material, such as, but not limited to, platinum, platinum alloy or other materials known to be usable in implantable defibrillation electrodes.

[0052] Although the example shown in FIGS. 2 A and 2B shows a three-chamber system, it is be understood the present disclosure contemplates using dual chamber therapy systems or a single-chamber therapy systems. For example, an illustrative system may utilize the IMD 16 configured to deliver, or perform, dual chamber pacing with leads implanted within the right ventricle 28 and the right atrium 26 to pace one or more portions of the cardiac conduction system such as the His bundle or one or both bundle branches, respectively. Further, for example, an illustrative system may utilize the IMD 16 configured to deliver, or perform, single-chamber pacing with a single lead, such as lead 23, implanted in the right atrium 26 to pace one or more portions of the cardiac conduction system such as the His bundle or one or both bundle branches, respectively.

[0053] The cardiac conduction system pacing lead 23 may be include an electrode 50 in the form of a helix (also referred to as a helical electrode) that may be positioned proximate to, near, adjacent to, or in, area or portions of the cardiac conduction system such as, e.g., ventricular septum, triangle of Koch, the His bundle, left right bundle branch tissues, and / or right bundle branch tissue. The cardiac conduction system pacing lead 23 may be configured as a bipolar lead or as a quadripolar lead that may be used with a pacemaker device, a CRT-P device or a CRT-ICD.

[0054] FIGS. 3A and 3B show the patient’s heart 12 implanted with an implantable medical electrical lead 723 coupled to an IMD 716 to deliver bundle branch pacing according to one example of an IMD system 710. FIG. 3B is a close-up view of lead 723 in the patient’s heart 12 of FIG. 3A. In some embodiments, the electrical lead 723may be the only lead implanted in the heart 12. In other embodiments as discussed herein, there may be multiple leads implanted in the heart 12. The one or more implantable electrodes may include a pacing electrode implantable proximate the cardiac conduction system or may be implantable in the ventricular septum (VS), to deliver cardiac conduction system pacing therapy, for examples.

[0055] In one embodiment, the lead 723 may be configured for dual bundle branch pacing, and the lead 723 may be the same as or similar to lead 23 shown in FIGS.2A and 2B) except that the lead 723 is implanted near the bundle branches in the ventricular septum (VS) from the right ventricle 28 instead of, for example, the His bundle 13. As illustrated, the lead 723 is implanted in the septal wall, or ventricular septum, from the right ventricle 28 toward the left ventricle 32. The lead 723 may not pierce through the wall of the left ventricle 32 or extend into the left ventricular chamber. An electrode 752 and a tissue-piercing electrode 761 may be disposed on a distal end portion of the lead 723, which may also be described as a shaft. The electrode 752 and the tissue-piercing electrode 761 may be the same as or similar to electrode and tissue-piercing electrode 50 shown in FIG. 2B except that the electrode 752 is configured as a cathode electrode to sense or pace the right bundle branch and the electrode 761 is configured to sense or pace the left bundle branch, for example, during dual bundle branch pacing. Accordingly, the electrode 752 may be implanted near right bundle branch 8b, and the electrode 761 may be implanted near the left bundle branch 8a. The electrode 761 may be described as a unipolar cathode electrode, which may be implanted on the left side of the patient’s ventricular septum. The electrode 752 may be described as a unipolar cathode electrode, which may be implanted on the right side of the patient’s ventricular septum.

[0056] During dual bundle branch pacing, both the electrode 752 and the electrode 761 may each deliver a cathodal pulse to achieve synchronized activation, or excitation, of the right bundle branch 8b and the left bundle branch 8a, which may result in synchronized activation of the right ventricle 28 and the left ventricle 32. In some embodiments, the pulses may be delivered at the same time to achieve synchrony. In other embodiments, the pulses may be delivered with a delay to achieve synchrony.

[0057] Although the lead 723 as shown in configured for dual bundle branch pacing using the electrodes 752, 761, it is to be understood that the lead 723 or leads similar thereto are considered herein that may only include one of the electrode 752and the electrode 761, and thus, only configured to deliver cardiac conduction system pacing therapy to one of the right bundle branch and the left bundle branch.

[0058] Additionally, the lead 723 may include a right atrial electrode 770 disposed more proximal to the electrode 752 and the electrode 761 along the lead 723. The right atrial electrode 770 may be positioned in or near the right atrium 26 and may function as an anode for cathodal pulses from the electrode 752 and / or the electrode 761. Further, the right atrial electrode 770 may provide atrial sensing to, e.g., sense atrial depolarizations or activations, to sense or detect atrial fibrillation, etc. Although the lead 723 as shown includes the right atrial electrode 770, it is to be understood that the lead 723 may not include the right atrial electrode 770, and instead, only include one or both of the electrode 752 and the electrode 761.

[0059] Additionally, the device system 710 may include a mechanical cardiac activation sensor 751 coupled to the lead 723 as shown in FIG. 3B. As shown in this embodiment, when the distal end of the lead 723 is implanted through the right ventricle 28 into the ventricular septum, the mechanical cardiac activation sensor 751 may be positioned in the right ventricle 28. The mechanical cardiac activation sensor 751 may be a motion sensor (e.g., an accelerometer) and / or a heart sound sensor (e.g., a microphone) that may be used to determined atrial activation or depolarization (e.g., atrial kick) so as to be used to deliver atrioventricular timed cardiac conduction system pacing therapy. In other words, the device system 710 may be configured to monitor mechanical activity of the patient’s heart using the mechanical cardiac activation sensor, determine atrial activation based on the monitored mechanical activity, and deliver cardiac conduction system pacing using the cardiac conduction system pacing electrode based on the determined atrial activation. Additionally, in one or more embodiments, the mechanical cardiac activation sensor 751 may be located in a housing of the IMD 716, which not be located within the heart of the patient. For example, the house of the IMD 716 may be positioned subcutaneously with the body of the patient. Furthermore, if the device system 710 includes a leadless device, the mechanical cardiac activation sensor 751 may be located in a housing of the leadless device implanted in the right ventricle 28.

[0060] Furthermore, atrial activations determined using the mechanical cardiac activation sensor 751 may be used in conjunction with atrial activations determined using near-field or far-field electrical activity. In at least one embodiment, theatrial activations determined using the mechanical cardiac activation sensor 751 may be used to confirm atrial activations determined using near-field or far-field electrical activity, or vice versa.

[0061] Although the illustrative system 710 show in FIGS. 3A and 3B includes a single lead, it is to be understood that the system may include two leads or three leads in various configures to provide traditional pacing and cardiac conduction system pacing therapy. For example, the illustrative system 710 may include one or both of leads 18, 20 of system 10. Moreover, the configuration of therapy systems 10, 710 illustrated in FIGS. 2 and 3 are merely examples. In other examples, a therapy system may include epicardial leads and / or patch electrodes instead of or in addition to the transvenous leads 18, 20, 23 or other configurations shown or described herein or incorporated by reference. Further, the IMDs 16, 716 need not be implanted within patient 14. As such, it is to be understood that the illustrative therapy systems described herein may include any suitable number of leads coupled to IMDs 16, 716, and each of the leads may extend to any location within or proximate to the heart 12. For example, illustrative therapy systems may include three transvenous leads located as illustrated in FIGS. 2 A and 2B, a single transvenous lead located as illustrated in FIGS. 3 A and 3B, or two transvenous leads.

[0062] FIG. 4 is a functional block diagram of one example configuration of the IMD 16. Although the IMD 16 of FIG. 4 is described in terms of the systems shown in FIGS. 2A and 2B, it is to be understood that the IMD 716 may be substantially similar to the IMD 16, and as such, the IMD 716 may include any or all of the described functionality with respect to the functional block diagram of IMD 16.

[0063] The IMD 16 includes a processor 80, a memory 82, a stimulation generator 84 (e.g., electrical pulse generator or signal generating circuit), a sensing module 86 (e.g., sensing circuit), a telemetry module 88, and a power source 90. In other words, the IMD 16 includes computing apparatus, and the computing apparatus includes processing circuitry. The computing apparatus, including processing circuitry, may include one or more of the processor 80, the memory 82, the stimulation generator 84, the sensing module 86, the telemetry module 88, and the power source 90 as well as any other components used to interconnect such elements and / or provide the functionality described herein. One or more components of the IMD 16, such as the processor 80, may be contained within a housing of the IMD 16 (e.g., within a housing of a pacemaker). Thetelemetry module 88, the sensing module 86, or both the telemetry module 88 and the sensing module 86 may be included in a communication interface. The memory 82 includes computer-readable instructions that, when executed by the processor 80, cause the IMD 16 and the processor 80 to perform various functions attributed to the IMD 16 and the processor 80 herein. The memory 82 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 media.

[0064] The processor 80 may include any one or more of a microprocessor, a controller, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or equivalent discrete or integrated logic circuitry. In some examples, processor 80 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 80 herein may be embodied as software, firmware, hardware or any combination thereof. The processor 80 controls the stimulation generator 84 to, for example, deliver antitachycardia pacing therapy to the heart 12 according to a selected method, process, or algorithm, which may be stored in the memory 82, and based on various sensing (e.g., atrial depolarizations or activations, ventricular atrial depolarizations or activations, cycle length, heartrate, P-wave-to-R-wave intervals, etc.). Specifically, the processor 80 may control the stimulation generator 84 to deliver electrical pulses with amplitudes, pulse widths, frequency, or electrode polarities specified by the selected one or more therapy programs and therapy modes.

[0065] In some embodiments, the lead 23 may be operably coupled to the electrode 50, which may be used to monitor or pace the right atrium. The stimulation generator 84 may be electrically coupled to the electrodes 40, 42, 44, 46, 48, 50, 58, 62, 64, and 66, e.g., via conductors of the respective lead 18, 20, 23 or, in the case of housing electrode 58, via an electrical conductor disposed within the housing 60 of the IMD 16. The stimulation generator 84 may be configured to generate and deliver electrical stimulation therapy to the heart 12. For example, the stimulation generator 84 may deliver defibrillation shocks to the heart 12 via at least two of the electrodes 58, 62, 64, 66. The stimulation generator 84 may deliver pacing pulses via the ring electrodes 40, 44, 48coupled to the leads 18, 20, 23, respectively, and / or the helical electrodes 42, 46, 50 of the leads 18, 20, or 23, respectively. The cardiac conduction system pacing therapy can be delivered through the cardiac conduction system lead 23 that is connected to an atrial, right ventricular, or left ventricular connection port of the connector block 34. In some embodiments, the cardiac conduction system pacing therapy can be delivered through the leads 18 and / or 23. In some examples, the stimulation generator 84 delivers pacing, antitachycardia pacing therapy, cardioversion, or defibrillation stimulation in the form of electrical pulses. In other examples, the stimulation generator 84 may deliver one or more of these types of stimulation in the form of other signals, such as sine waves, square waves, or other substantially continuous time signals.

[0066] The stimulation generator 84 may include a switch module and the processor 80 may use the switch module to select, e.g., via a data / address bus, which of the available electrodes are used to deliver defibrillation shocks or pacing pulses. The switch module may include a switch array, switch matrix, multiplexer, or any other type of switching device suitable to selectively couple stimulation energy to selected electrodes.

[0067] The sensing module 86 monitors signals from at least one of the electrodes 40, 42, 44, 46, 48, 50, 58, 62, 64, 66 in order to monitor electrical activity of the heart 12, e.g., via electrical signals, such as electrocardiogram (ECG) signals and / or electrograms (EGMs). The sensing module 86 may also include a switch module to select which of the available electrodes are used to sense the heart activity. In some examples, the processor 80 may select the electrodes that function as sense electrodes via the switch module within the sensing module 86, e.g., by providing signals via a data / address bus. In some examples, the sensing module 86 includes one or more sensing channels, each of which may include an amplifier. In response to the signals from the processor 80, the switch module may couple the outputs from the selected electrodes to one of the sensing channels.

[0068] In some examples, one channel of the sensing module 86 may include an R-wave amplifier that receives signals from the electrodes 44, 46, which are used for pacing and sensing proximate to the left ventricle 32 of the heart 12. Another channel may include another R-wave amplifier that receives signals from the electrodes 40, 42, which are used for pacing and sensing in the right ventricle 28 of the heart 12. In some examples, the R-wave amplifiers may take the form of an automatic gain-controlled amplifier thatprovides an adjustable sensing threshold as a function of the measured R-wave amplitude of the heart rhythm.

[0069] In addition, in some examples, one channel of the sensing module 86 may include a P-wave amplifier that receives signals from electrodes the 48, 50, which are used for pacing and sensing in the right atrium 26 of heart 12. In some examples, the P-wave amplifier may take the form of an automatic gain-controlled amplifier that provides an adjustable sensing threshold as a function of the measured P-wave amplitude of the heart rhythm. Examples of R-wave and P-wave amplifiers are described in U.S. Patent No. 5,117,824 to Keimel et al., which issued on June 2, 1992, and is entitled, “APPARATUS FOR MONITORING ELECTRICAL PHYSIOLOGIC SIGNALS,” and is incorporated herein by reference in its entirety. Other amplifiers may also be used. Furthermore, in some examples, one or more of the sensing channels of the sensing module 86 may be selectively coupled to the housing electrode 58, or one or more of the elongated electrodes 62, 64, 66, with or instead of one or more of the electrodes 40, 42, 44, 46, 48, 50, e.g., for unipolar sensing of R- waves or P-waves in any of the chambers 26, 28, or 32 of the heart 12.

[0070] In some examples, the sensing module 86 includes a channel that includes an amplifier with a relatively wider pass band than the R-wave or P-wave amplifiers or a high-resolution amplifier with relatively narrow-pass band for His bundle or bundle branch potential recording. Signals from the selected sensing electrodes that are selected for coupling to this wide-band amplifier may be provided to a multiplexer, and thereafter converted to multi-bit digital signals by an analog-to-digital converter for storage in the memory 82 as an electrogram (EGM). In some examples, the storage of such EGMs in the memory 82 may be under the control of a direct memory access circuit. The processor 80 may employ digital signal analysis techniques to characterize the digitized signals stored in memory 82 to detect and classify the patient’s heart rhythm from the electrical signals. The processor 80 may detect and classify the heart rhythm of the patient 14 by employing any of the numerous signal processing methodologies known in the art.

[0071] If the IMD 16 is configured to generate and deliver pacing pulses to the heart 12, the processor 80 may include pacer timing and control module, which may be embodied as hardware, firmware, software, or any combination thereof. The pacer timing and control module may include a dedicated hardware circuit, such as an ASIC, separatefrom other the processor 80 components, such as a microprocessor, or a software module executed by a component of the processor 80, which may be a microprocessor or ASIC.

[0072] Intervals defined by the pacer timing and control module may include cycle length of ventricular tachycardia, atrial and ventricular pacing escape intervals, refractory periods during which sensed P-waves and R-waves are ineffective to restart timing of the escape intervals, and the pulse widths of the pacing pulses. As another example, the pace timing and control module may define a blanking time period and provide signals from sensing module 86 to blank one or more channels, e.g., amplifiers, for a period during and after delivery of electrical stimulation to the heart 12. The durations of these intervals may be determined by the processor 80 in response to stored data in the memory 82. The pacer timing and control module may also determine the amplitude of the cardiac pacing pulses.

[0073] During pacing, escape interval counters within the pacer timing / control module may be reset upon sensing of R-waves and P-waves. The stimulation generator 84 may include pacer output circuits that are coupled, e.g., selectively by a switching module, to any combination of the electrodes 40, 42, 44, 46, 48, 50, 58, 62, or 66 appropriate for delivery of a bipolar or unipolar pacing pulse to one of the chambers of the heart 12. The processor 80 may reset the escape interval counters upon the generation of pacing pulses by stimulation generator 84, and thereby control the basic timing of cardiac pacing functions, including anti-tachyarrhythmia pacing.

[0074] In some examples, the processor 80 may operate as an interrupt driven device, and is responsive to interrupts from pacer timing and control module, where the interrupts may correspond to the occurrences of sensed P-waves and R-waves and the generation of cardiac pacing pulses. Any necessary mathematical calculations to be performed by the processor 80 and any updating of the values or intervals controlled by the pacer timing and control module of the processor 80 may take place following such interrupts. A portion of the memory 82 may be configured as a plurality of recirculating buffers, capable of holding series of measured intervals, which may be analyzed by the processor 80 in response to the occurrence of a pace or sense interrupt to determine whether the patient’s heart 12 is presently exhibiting atrial or ventricular tachyarrhythmia.

[0075] The telemetry module 88 includes any suitable hardware, firmware, software or any combination thereof for communicating with another device, such as the programmer 24. Under the control of the processor 80, the telemetry module 88 mayreceive downlink telemetry from and send uplink telemetry to the programmer 24 with the aid of an antenna, which may be internal and / or external. The processor 80 may provide the data to be uplinked to the programmer 24 and the control signals for the telemetry circuit within the telemetry module 88, e.g., via an address / data bus. In some examples, the telemetry module 88 may provide received data to the processor 80 via a multiplexer.

[0076] The various components of the IMD 16 are coupled to the power source 90, which may include a rechargeable or non-rechargeable battery. A non-rechargeable battery may be selected to last for several years, while a rechargeable battery may be inductively charged from an external device, e.g., on a daily or weekly basis.

[0077] The illustrative devices and methods described herein may provide antitachycardia pacing therapy for cardiac conduction system pacing therapy. An illustrative method 100 of antitachycardia pacing therapy for cardiac conduction system pacing therapy that may be utilized by the devices of FIGS. 2-4 is depicted in FIG. 5. As shown, the method 100 may monitor cardiac activity 102. In particular, the method 100 may be performed by an IMD using one or more implantable electrodes to sense cardiac electrical activity of a patient’s heart 102. In particular, for example, one or more both of intrinsic atrial depolarizations or activations and intrinsic ventricular depolarizations or activations may be monitored 192 to be used to detect ventricular tachycardia 104.Although an arrow is shown extending from monitoring cardiac activity 102 to detecting ventricular tachycardia 104, it is to be understood that the method 100 may continuously monitor cardiac activity 102. In other words, monitoring cardiac activity 102 will not cease, or stop, during the remainder of the processes of method 100.

[0078] Ventricular tachycardia may be detected 104 according to a detection protocol, process, or algorithm implemented by the computing apparatus of the IMD. It is to be understood that the illustrative devices and methods of providing antitachycardia pacing therapy for cardiac conduction system pacing therapy presented herein is not limited to use with a particular ventricular tachycardia detection protocol, process, or algorithm. In one embodiment, the R-R interval (e.g., the duration between R-waves or ventricular activations) may be monitored using one or more implantable or external electrodes and compared to a ventricular tachycardia threshold value. For example, if the R-R interval (e.g., a median R-R interval, an average R-R interval, etc.) is less than or equal to the ventricular tachycardia threshold value for a selected number of cardiaccycles, then it may be determined that the patient is undergoing ventricular tachycardia. Illustrative ventricular tachycardia detection protocols, processes, or algorithms may be described in U.S. Pat. No. 9,808,637 issued on November 7, 2017, and U.S. Pat. No. 8,521,269 issued on August 27, 2013, each of which are incorporated by reference herein in their entireties.

[0079] If ventricular tachycardia is not detected 104, then the method 100 may return to only monitoring cardiac activity 102. If ventricular tachycardia is detected 104, then the method 100 may continue to provide antitachycardia pacing (ATP) therapy 120. As described herein, the illustrative ATP therapy 120 may be configured to leverage the unique properties of the cardiac conduction system and have demonstrated in computational models the ability to terminate ventricular tachycardia in two to three paces as opposed to eight or more paces as often used in traditional antitachycardia pacing therapy delivered to myocardial tissue.

[0080] The ATP therapy 120 includes determining a cardiac cycle time 105 and delivering an initial cardiac conduction system ATP pulse set 106 to the patient’s cardiac conduction system. The cardiac cycle time, or cycle time of the ventricular tachycardia is the time between consecutive ventricular depolarizations or R-waves during the ventricular tachycardia. The cardiac cycle time may be an aggregate of a plurality of cardiac cycle times monitored, or measured, of a monitoring time period. For example, the cardiac cycle time may be an average of cardiac cycle times monitored over 5 seconds.

[0081] The initial cardiac conduction system ATP pulse set 106 may include between two and four cardiac conduction system ATP pulses. In a two-pulse embodiment, the initial cardiac conduction system ATP pulse set 106 includes only two cardiac conduction system ATP pulses. In other words, the initial cardiac conduction system ATP pulse set consists essentially of two cardiac conduction system ATP pulses in this two-pulse embodiment. Thus, no other cardiac conduction system ATP pulses other than a first cardiac conduction system ATP pulse and a second cardiac conduction system ATP pulse may be delivered during the two-pulse embodiment prior to pausing the ATP pulses to monitor intrinsic cardiac electrical activity to determine whether the ventricular tachycardia persists.

[0082] In a two-pulse embodiment, a first cardiac conduction system ATP pulse of the initial cardiac conduction system ATP pulse set 106 may be delivered to the patient’scardiac conduction system using a cardiac conduction system pacing electrode positioned proximate a portion of the patient’s cardiac conduction system such as, e.g., the bundle of His, left bundle branch, or right bundle branch as show in described with respect to FIGS.2 and 3. The first cardiac conduction system ATP pulse interval or timing is selected to be near the minimum refractory period of the cardiac conduction system that allows for cardiac conduction system capture thereby allowing maximum control over the cardiac conduction system by “winning the race” against the ventricular tachycardia wavefronts for control of sites near the critical features of re-entrant circuit (e.g., entrances and exits), which may be described as being opposite that of traditional antitachycardia pacing therapy delivered to myocardial tissue, where a rapid first cardiac conduction system ATP pulse provides little overall value in the eventual termination of the ventricular tachycardia. Moreover, and in other words, the first cardiac conduction system ATP pulse interval or timing being near the minimum refractory period may target the Purkinje-myocardial junctions (PMJs) that are closer to the exit, or more in general, to target PMJs that are closer to the critical ventricular tachycardia sites, which will be the sites to recover first due to retrograde propagation of the ventricular tachycardia into the PMJs early in the prior cardiac cycle.

[0083] The first cardiac conduction system ATP pulse may be timed with respect to the previous ventricular activation, or R-wave, which may be sensed from the ongoing monitoring of cardiac activity 102. For example, the first cardiac conduction system ATP pulse may be delivered after a first period of time following an intrinsic cardiac, or ventricular, activation that is based on a minimum refractory period of the cardiac conduction system.

[0084] In one embodiment, the first period of time may be further based on the cardiac cycle time, or cycle time of the ventricular tachycardia. For example, the first period of time may be between about 50% of the cardiac cycle time and about 75% of the cardiac cycle time. In one embodiment, the first period of time is 57% of the cardiac cycle time as will be described herein with respect to the simulations of FIGS. 6 and 7. In another embodiment, the first period of time is 68% of the cardiac cycle time as will be described herein with respect to the simulations of FIG. 8. In one or more embodiments, the first period of time is less than or equal to 70% of the cardiac cycle time, less than or equal to 65% of the cardiac cycle time, less than or equal to 60% of the cardiac cycle time,or less than or equal to 55% of the cardiac cycle time and / or greater than or equal to 45% of the cardiac cycle time, greater than or equal to 50% of the cardiac cycle time, greater than or equal to 57% of the cardiac cycle time, or greater than or equal to 63% of the cardiac cycle time.

[0085] The initial cardiac conduction system ATP pulse set 106 further includes a second cardiac conduction system ATP pulse delivered to the patient’s cardiac conduction system following the first cardiac conduction system ATP pulse. The second cardiac conduction system ATP pulse may be delivered using a cardiac conduction system pacing electrode positioned proximate a portion of the patient’s cardiac conduction system such as, e.g., the bundle of His, left bundle branch, or right bundle branch as show in described with respect to FIGS. 2 and 3, and may be the same or different electrode that was used to deliver the initial cardiac conduction system ATP pulse set 106. The second cardiac conduction system ATP pulse interval or timing may be increased from the first cardiac conduction system ATP pulse interval or timing to allow consistent capture of the conduction system but kept short enough to maximally advance the next wavefront towards the refractory tail of the ventricular tachycardia wave. Moreover, and in other words, the second cardiac conduction system ATP pulse interval or timing is still below the ventricular tachycardia cycle length but will allow conduction through the cardiac conduction system to interact with retrograde to target the Purkinje-myocardial junctions (PMJs) and able push the wavefront to the tail.

[0086] The second cardiac conduction system ATP pulse may be timed with respect to the previous first cardiac conduction system ATP pulse 106. For example, the second cardiac conduction system ATP pulse may be delivered after a second period of time following the first cardiac conduction system ATP pulse 106. Similar to the first period of time, the second period of time may be based on the cardiac cycle time, or cycle time of the ventricular tachycardia, which is the time between consecutive ventricular depolarizations or R-waves. In one embodiment, the second period of time is greater than the first period of time. For example, the second period of time may be between about 60% of the cardiac cycle time and about 85% of the cardiac cycle time. In one embodiment, the second period of time is 76% of the cardiac cycle time as will be described herein with respect to the simulation of FIG. 6. In another embodiment, the second period of time is 71% of the cardiac cycle time as will be described herein withrespect to the simulation of FIG. 7. In another embodiment, the second period of time is 77% of the cardiac cycle time as will be described herein with respect to the simulation of FIG. 8. In one or more embodiments, the second period of time is less than or equal to 85% of the cardiac cycle time, less than or equal to 80% of the cardiac cycle time, or less than or equal to 75% of the cardiac cycle time and / or greater than or equal to 60% of the cardiac cycle time, greater than or equal to 65% of the cardiac cycle time, or greater than or equal to 70% of the cardiac cycle time.

[0087] The ATP therapy 120 may then determine whether the initial cardiac conduction system ATP pulse set 106 (e.g., first and the second cardiac conduction system ATP pulses) terminated or ceased the ventricular tachycardia 110. To determine whether the initial cardiac conduction system ATP pulse set 106 terminated or ceased the ventricular tachycardia 110, the intrinsic electrical activity of the patient’s heart may be monitored following the initial cardiac conduction system ATP pulse set 106 and the monitored intrinsic electrical activity may be analyzed in the same or similar fashion as in process 104 described herein. In other words, the ATP therapy 120 may be paused and the intrinsic electrical activity of the patient’s heart may be analyzed to determine whether the method 100 should continue the ATP therapy 120.

[0088] If ventricular tachycardia is not detected 110, then the method 100 may return to only monitoring cardiac activity 102. If ventricular tachycardia is still detected 110, then the method 100 may continue providing ATP therapy 120. More specifically, the ATP therapy 120 may further include delivering a second cardiac conduction system ATP pulse set 112. The second cardiac conduction system ATP pulse set 112 may include first and second cardiac conduction system ATP pulses that are substantially similar to the first and second cardiac conduction system ATP pulses of the initial cardiac conduction system ATP pulse set 106, and thus, are not described further herein. The second cardiac conduction system ATP pulse set 112, however, includes, a third cardiac conduction system ATP pulse delivered to the patient’s cardiac conduction system following the second cardiac conduction system ATP pulse. The third cardiac conduction system ATP pulse may be delivered using a cardiac conduction system pacing electrode positioned proximate a portion of the patient’s cardiac conduction system such as, e.g., the bundle of His, left bundle branch, or right bundle branch as show in described with respect to FIGS.2 and 3, and may be the same or different electrode that was used to deliver the first andsecond cardiac conduction system ATP pulses of the initial cardiac conduction system ATP pulse set 106. The third cardiac conduction system ATP pulse interval or timing may be increased from the first cardiac conduction system ATP pulse interval or timing and increased from or similar to the second cardiac conduction system ATP pulse interval or timing to continue advancement of the wavefront but reduce the risk of accelerating the ventricular tachycardia due to multiple, very-rapid paces.

[0089] The third cardiac conduction system ATP pulse of the second cardiac conduction system ATP pulse set 112 may be timed with respect to the second cardiac conduction system ATP pulse of the second cardiac conduction system ATP pulse set 112. For example, the third cardiac conduction system ATP pulse of the second cardiac conduction system ATP pulse set 112 may be delivered after a third period of time following the second cardiac conduction system ATP pulse. Similar to the first and second periods of time, the third period of time may be based on the cardiac cycle time, or cycle time of the ventricular tachycardia, which is the time between consecutive ventricular depolarizations or R-waves. In one embodiment, the third period of time is greater than one or both of the first and second periods of time. For example, the third period of time may be between about 75% of the cardiac cycle time and about 95% of the cardiac cycle time. In one embodiment, the third period of time is 94% of the cardiac cycle time. In one embodiment, the third period of time is 81% of the cardiac cycle time as will be described herein with respect to the simulation of FIG. 6. In another embodiment, the third period of time is 80% of the cardiac cycle time as will be described herein with respect to the simulation of FIG. 8. In one or more embodiments, the third period of time is less than or equal to 95% of the cardiac cycle time, less than or equal to 93% of the cardiac cycle time, less than or equal to 90% of the cardiac cycle time, less than or equal to 88% of the cardiac cycle time, or less than or equal to 85% of the cardiac cycle time and / or greater than or equal to 75% of the cardiac cycle time, greater than or equal to 77% of the cardiac cycle time, or greater than or equal to 80% of the cardiac cycle time.

[0090] The ATP therapy 120 may then again determine whether the second cardiac conduction system ATP pulse set 112 (e.g., the first, second, and third cardiac conduction system ATP pulses), terminated or ceased the ventricular tachycardia 114. To determine whether the second cardiac conduction system ATP pulse set 112 terminated or ceased the ventricular tachycardia 114, the intrinsic electrical activity of the patient’s heart may bemonitored following the second cardiac conduction system ATP pulse set 112 and the monitored intrinsic electrical activity may be analyzed in the same or similar fashion as in process 104 described herein. In other words, the ATP therapy 120 may be paused and the intrinsic electrical activity of the patient’s heart may be analyzed to determine whether the method 100 should continue the ATP therapy 120.

[0091] If ventricular tachycardia is not detected 114, then the method 100 may return to only monitoring cardiac activity 102. If ventricular tachycardia is still detected 114, then the method 100 may continue providing ATP therapy 120. More specifically, the ATP therapy 120 may further include delivering a third cardiac conduction system ATP pulse set 116. The third cardiac conduction system ATP pulse set 116 may include first, second, and third cardiac conduction system ATP pulses that are substantially similar to the first, second, and third cardiac conduction system ATP pulses of the second cardiac conduction system ATP pulse set 112, and thus, are not described further herein. The third cardiac conduction system ATP pulse set 116, however, includes a plurality of tertiary cardiac conduction system ATP pulses following the third cardiac conduction system ATP pulse. The plurality of tertiary cardiac conduction system ATP pulses may include between 3 pulses and 8 pulses. In one embodiment, the plurality of tertiary cardiac conduction system ATP pulses of the third cardiac conduction system ATP pulse set 116 includes 5 pulses.

[0092] The plurality of tertiary cardiac conduction system ATP pulses may be delivered using a cardiac conduction system pacing electrode positioned proximate a portion of the patient’s cardiac conduction system such as, e.g., the bundle of His, left bundle branch, or right bundle branch as show in described with respect to FIGS. 2 and 3, and may be the same or different electrode that was used to deliver the initial and second cardiac conduction system ATP pulse sets 106, 112. The plurality of tertiary cardiac conduction system ATP pulses intervals or timing may be similar to intervals or timing employed by the third cardiac conduction system ATP pulse, and thus, the plurality of tertiary cardiac conduction system ATP pulses may employ conservative intervals or timing. In one embodiment, the plurality of tertiary cardiac conduction system ATP pulses may be delivered according to the third period of time previously described herein, each ATP pulse timed according to the previously delivered ATP pulse.

[0093] In another embodiment, each of the plurality of tertiary cardiac conduction system ATP pulses may be delivered according to a tertiary period of time following the previous ATP pulse. The tertiary period of time may be between about 80% of the cardiac cycle time and about 95% of the cardiac cycle time. In one or more embodiments, the tertiary period of time is less than or equal to 95% of the cardiac cycle time, less than or equal to 90% of the cardiac cycle time, or less than or equal to 88% of the cardiac cycle time and / or greater than or equal to 80% of the cardiac cycle time, greater than or equal to 82% of the cardiac cycle time, or greater than or equal to 85% of the cardiac cycle time.

[0094] In another embodiment, each of the plurality of tertiary cardiac conduction system ATP pulses may be delivered in a sequential fashion where the tertiary period of time is decremented for each sequential tertiary cardiac conduction system ATP pulse (or each cycle). The decrement may be a fixed period of time or a percentage. For example, the decrement may be 20 milliseconds (ms) or 10%. In other words, the tertiary time periods may decrement in an iterative manner for each of the plurality of tertiary cardiac conduction system ATP pulses.

[0095] Upon the completion of the ATP therapy 120, the method 100 may continue to monitor cardiac activity 102 and determine, or detect, ventricular tachycardia 104. In one embodiment, if the ventricular tachycardia 104 is not terminated or ceased by the ATP therapy 120, then the ATP therapy 120 may be repeated one or more times. In one embodiment, if the ventricular tachycardia 104 is not terminated or ceased by the ATP therapy 120, then the method 100 may provide alternative ventricular tachycardia therapy such as, e.g., cardioversion / defibrillation using a coil electrode, which may be delivered by the same IMD that provided the ATP therapy 120.

[0096] As described herein with respect the embodiment of FIG. 5, the initial cardiac conduction system ATP pulse set 106 includes two cardiac conduction system ATP pulses and the second cardiac conduction system ATP pulse set 112 includes three cardiac conduction system ATP pulses. It is to be understood that each of the initial and second cardiac conduction system ATP pulse sets may include between two and five cardiac conduction system ATP pulses.

[0097] For example, the initial cardiac conduction system ATP pulse set 106 may include only three cardiac conduction system ATP pulses in the same or similar fashion to the second cardiac conduction system ATP pulse set 112. In such three-pulse embodiment,the initial cardiac conduction system ATP pulse set 106 includes only three cardiac conduction system ATP pulses. In other words, the initial cardiac conduction system ATP pulse set 106 would consist essentially of three cardiac conduction system ATP pulses in this three-pulse embodiment. Thus, no other cardiac conduction system ATP pulses other than a first cardiac conduction system ATP pulse, a second cardiac conduction system ATP pulse, and a third cardiac conduction system ATP pulse may be delivered during the three-pulse embodiment of the initial cardiac conduction system ATP pulse set 106 prior to pausing the ATP pulses to monitor intrinsic cardiac electrical activity to determine whether the ventricular tachycardia persists.

[0098] Further, for example, the second cardiac conduction system ATP pulse set 1112 may include only two cardiac conduction system ATP pulses in the same or similar fashion to the initial cardiac conduction system ATP pulse set 106. In such two-pulse embodiment, the second cardiac conduction system ATP pulse set 112 includes only two cardiac conduction system ATP pulses. In other words, the second cardiac conduction system ATP pulse set 112 would consist essentially of two cardiac conduction system ATP pulses in this two-pulse embodiment. Thus, no other cardiac conduction system ATP pulses other than a first cardiac conduction system ATP pulse and a second cardiac conduction system ATP pulse may be delivered during the two-pulse embodiment of the second cardiac conduction system ATP pulse set 112 prior to pausing the ATP pulses to monitor intrinsic cardiac electrical activity to determine whether the ventricular tachycardia persists.

[0099] When using far-field electrograms (EGM) to monitor cardiac activity, the illustrative devices and methods may take into account ventricular-to-cardiac conduction system time to estimate the refractory state of the cardiac conduction system (as, e.g., the electrical signals of the local myocardium “dominate” the small electrical signals of the cardiac conduction system). In this way, the illustrative devices and methods may alter the timing of the first cardiac conduction system ATP pulse, or pace, relative to the ventricular myocardial electrogram such that the synchronization point of the first cardiac conduction system ATP pulse is based on the determined, or estimated, activation time of the conduction system at the pacing site. Thus, the timing of the first cardiac conduction system ATP pulse is shifted by a selected amount or percentage to account for the ventricular-to-cardiac conduction system time. For example, the cardiac cycle length ofthe ventricular tachycardia may be decreased by about 30 milliseconds (ms) to about 150 ms relative to the onset of the R-wave in the local electrogram or far-field electrogram. In one embodiment, the cardiac cycle length of the desired first pacing cycle may be decreased by 60 ms from the onset of the R-wave in the far-field EGM.

[0100] Also, timing of the first and second cardiac conduction system ATP pulses, or paces, can be adjusted based on the T-wave of a far-field EGM or ECG. In one embodiment, each of the first and second cardiac conduction system ATP pulses, or paces, may be initiated, or delivered, late in the T-wave to maximize the advancement of the wave front. For example, each of the first and second cardiac conduction system ATP pulses, or paces, may be delivered in response to expiration of the first and second time periods, respectively, or a time point within the T-wave of the present cardiac cycle. In one embodiment, the first period of time, upon which the first cardiac conduction system ATP pulse would be delivered, is set based on the center of area of the T-wave, with an offset to place the pacing period at approximately one half of the interval from the T-wave center of area to the end of the T-wave of the ventricular tachycardia cycle. This offset from the center of area may be determined using an averaged T-wave from more than one cycle of the VT. The second period of time, upon which the second cardiac conduction system ATP pulse would be delivered, is a set period after the T-wave provoked by first cardiac conduction system ATP pulse has reached peak amplitude and begins to decline between about 20 ms to about 80 ms.

[0101] Still further, changes in paced R-wave width may be monitored and widened R-waves may indicate that the pacing overdrive is not sufficiently fast to maximally control the conduction. In this way, the timing of the ATP pulses may be accelerated (e.g., shortened) in response to R-wave width being greater than or equal to a R-wave threshold value. The R-wave threshold value may be between about 110 ms and about 200 ms.

[0102] Results from three simulations of the illustrative devices and methods to deliver antitachycardia pacing therapy for cardiac conduction system pacing therapy to terminate a simulated ventricular tachycardia are shown in FIGS. 6-8. In particular, graphs of 12-lead electrocardiograph (ECG) signals over three cardiac cycles where first, second, and third cardiac conduction system ATP pulses are delivered to the cardiac conductionsystem in a first simulation are shown in FIGS. 6A-6C. The ATP pulse is indicated by the vertical line extending between the X-axis and the top of each graph.

[0103] The first cardiac conduction system ATP pulse shown in the graphs of FIG.6A was delivered after a first period of time following an intrinsic ventricular activation that was 57% of the cycle length of the ventricular tachycardia. The second cardiac conduction system ATP pulse shown in the graphs of FIG. 6B was delivered after a second period of time following the first cardiac conduction system ATP pulse that was 76% of the cycle length of the ventricular tachycardia. The third cardiac conduction system ATP pulse shown in the graphs of FIG. 6C was delivered after a third period of time following the second cardiac conduction system ATP pulse that was 81% of the cycle length of the ventricular tachycardia. In this simulation depicted with respect to FIGS. 6A-6C, the ventricular tachycardia was ceased after the third cardiac conduction system ATP pulse.

[0104] Graphs of 12-lead electrocardiograph (ECG) signals over three cardiac cycles where first and second cardiac conduction system ATP pulses are delivered to the cardiac conduction system in a second simulation are shown in FIGS. 7 A and 7B. The ATP pulse is indicated by the vertical line extending between the X-axis and the top of each graph. The first cardiac conduction system ATP pulse shown in the graphs of FIG.7A was delivered after a first period of time following an intrinsic ventricular activation that was 57% of the cycle length of the ventricular tachycardia. The second cardiac conduction system ATP pulse shown in the graphs of FIG. 7B was delivered after a second period of time following the first cardiac conduction system ATP pulse that was 71% of the cycle length of the ventricular tachycardia. In this simulation depicted with respect to FIGS. 7A and 7B, the ventricular tachycardia was ceased after the second cardiac conduction system ATP pulse.

[0105] Graphs of 12-lead electrocardiograph (ECG) signals over three cardiac cycles where first, second, and third cardiac conduction system ATP pulses are delivered to the cardiac conduction system in a first simulation are shown in FIGS. 8A-8C. The first cardiac conduction system ATP pulse shown in the graphs of FIG. 8 A was delivered after a first period of time following an intrinsic ventricular activation that was 68.4% of the cycle length of the ventricular tachycardia. The second cardiac conduction system ATP pulse shown in the graphs of FIG. 8B was delivered after a second period of timefollowing the first cardiac conduction system ATP pulse that was 77% of the cycle length of the ventricular tachycardia. The third cardiac conduction system ATP pulse shown in the graphs of FIG. 8C was delivered after a third period of time following the second cardiac conduction system ATP pulse that was 80% of the cycle length of the ventricular tachycardia. In this simulation depicted with respect to FIGS. 8A-8C, the ventricular tachycardia was ceased after the third cardiac conduction system ATP pulse.

[0106] Thus, the illustrative ATP devices, methods, and protocols may be described as being specifically geared to leverage the cardiac conduction system. Such illustrative ATP devices methods, and protocols utilize a short first coupling interval (i.e., the first period of time), which is valuable in cardiac conduction system pacing therapy but not for standard myocardial antitachycardia pacing therapy. Further, a moderate second coupling interval (i.e., the second period of time) is based on the refractory period properties of the specialized conduction system. Further, the illustrative ATP devices methods, and protocols may be able to minimize paces used (two to three paces), which may lower the risk of acceleration or induction of ventricular fibrillation. Further, as described herein, if the first three ATP pulse do not terminate the ventricular tachycardia, the illustrative ATP devices methods, and protocols may fall back to a longer conservative train of ATP pulses. Additionally, the illustrative ATP devices methods, and protocols may be guided by far-field EGM / ECG, allowing for a fully-automatic functionality.ILLUSTRATIVE EXAMPLES

[0107] While the present disclosure is not so limited, an appreciation of various aspects of the disclosure will be gained through a discussion of the specific illustrative examples provided below. Various modifications of the illustrative examples, as well as additional examples of the disclosure, will become apparent herein.

[0108] Example Exl: An implantable medical device comprising:a computing apparatus comprising processing circuitry and operably coupled to one or more implantable electrodes comprising a cardiac conduction system pacing electrode positionable proximate a portion of the patient’s cardiac conduction system, wherein the computing apparatus is configured to provide cardiac conduction system antitachycardia pacing therapy (ATP) using the cardiac conduction system pacing electrode, wherein the cardiac conduction system ATP comprises:monitoring electrical activity of the patient’s heart using the one or more implantable electrodes;determining a cardiac cycle time based on the monitored electrical activity; and delivering an initial cardiac conduction system ATP pulse set comprising three or less cardiac conduction system ATP pulses, wherein the three or less ATP pulses of the initial cardiac conduction system ATP pulse set comprise:a first cardiac conduction system ATP pulse to the patient’s cardiac conduction system using the cardiac conduction system pacing electrode after a first period of time following an intrinsic cardiac activation, wherein the first period of time is based on the cardiac cycle time and configured to provide maximal capture of the cardiac conduction system; anda second cardiac conduction system ATP pulse to the patient’s cardiac conduction system using the cardiac conduction system pacing electrode after a second period of time based on the cardiac cycle time and following the first cardiac conduction system ATP pulse.

[0109] Example Ex2: A method comprising:monitoring electrical activity of a patient’s heart using one or more implantable electrodes;determining a cardiac cycle time based on the monitored electrical activity; and delivering an initial cardiac conduction system ATP pulse set comprising three or less cardiac conduction system ATP pulses, wherein the three or less ATP pulses of the initial cardiac conduction system ATP pulse set comprise:a first cardiac conduction system ATP pulse to the patient’s cardiac conduction system using a cardiac conduction system pacing electrode positioned proximate a portion of the patient’s cardiac conduction system after a first period of time following an intrinsic cardiac activation, wherein the first period of time is based on the cardiac cycle time and configured to provide maximal capture of the cardiac conduction system; anda second cardiac conduction system ATP pulse to the patient’s cardiac conduction system using the cardiac conduction system pacing electrode after a second period of time based on the cardiac cycle time following the first cardiac conduction system ATP pulse.

[0110] Example Ex3: The device as in Example Exl or the method as in Example Ex2, wherein the cardiac conduction system pacing electrode is configured to deliver the cardiac conduction system ATP to the left bundle branch of the patient’s heart.

[0111] Example Ex4: The device as in Example Exl or the method as in Example Ex2, wherein the cardiac conduction system pacing electrode is configured to deliver the cardiac conduction system ATP to the His bundle of the patient’s heart.

[0112] Example Ex5: The device or method as in any one of Examples Exl-Ex4, wherein the one or more implantable electrodes are included on one of a single-chamber leadless pacing device, a lead, and a multi-chamber pacing device.

[0113] Example Ex6: The device or method as in any one of Examples Exl-Ex5, wherein the second period of time is greater than the first period of time.

[0114] Example Ex7: The device or method as in any one of Examples Exl-Ex6, wherein the first period of time is less than or equal to 70% of the cardiac cycle time.

[0115] Example Ex8: The device or method as in any one of Examples Exl-Ex6, wherein the first period of time is less than or equal to 60% of the cardiac cycle time.

[0116] Example Ex9: The device or method as in any one of Examples Exl-Ex8, wherein the second period of time is less than or equal to 80% of the cardiac cycle time.

[0117] Example ExlO: The device or method as in any one of Examples Exl-Ex8, wherein the second period of time is greater than 70% of the cardiac cycle time.

[0118] Example Exl 1 : The device or method as in any one of Examples Exl-ExlO, wherein the cardiac cycle time is adjusted to account for ventricular-to-cardiac conduction system delay prior to be using to determine the first and second periods of time.

[0119] Example Exl2: The device or method as in any one of Examples Exl-Exl 1, wherein one or both of the first and second periods of time is adjusted based on intrinsic T-wave in the monitored electrical activity.

[0120] Example Exl3: The device or method as in any one of Examples Exl-Exl2, wherein the three or less ATP pulses of the initial cardiac conduction system ATP pulse set further comprise a third cardiac conduction system ATP pulse to the patient’s cardiac conduction system using the cardiac conduction system pacing electrode after a third period of time based on the cardiac cycle time and following the second cardiac conduction system ATP pulse.

[0121] Example Exl4: The device or method as in any one of Examples Exl-Exl2, wherein the cardiac conduction system ATP further comprises:determining that the ventricular tachycardia has not ceased in response to the first cardiac conduction system ATP pulse set based on monitored intrinsic electrical activity of the patient’s heart; anddelivering a second cardiac conduction system ATP pulse set in response to determining that the ventricular tachycardia has not ceased in response to the initial cardiac conduction system ATP pulse set, the second cardiac conduction system ATP pulse set consists essentially ofthe first cardiac conduction system ATP pulse to the patient’s cardiac conduction system using the cardiac conduction system pacing electrode after the first period of time following another intrinsic cardiac activation;the second cardiac conduction system ATP pulse to the patient’s cardiac conduction system using the cardiac conduction system pacing electrode after the second period of time following the first cardiac conduction system ATP pulse; anda third cardiac conduction system ATP pulse to the patient’s cardiac conduction system using the cardiac conduction system pacing electrode after a third period of time following the second cardiac conduction system ATP pulse.

[0122] Example Exl5: The device or method as in any one of Example Exl3 and Example Exl4, wherein the third period of time is greater than the second period of time.

[0123] Example Exl6: The device or method as in any one of Examples Exl3- Exl5, wherein the third period of time is greater than or equal to 80% of a cardiac cycle time.

[0124] Example Exl7: The device or method as in any one of Examples Exl3- Exl5, wherein the third period of time is less than or equal to 94% of a cardiac cycle time.

[0125] Example Exl8: The device or method as in any one of Examples Exl4- Exl7, wherein the cardiac conduction system ATP further comprises:determining that the ventricular tachycardia has not ceased in response to the second cardiac conduction system ATP pulse set based on monitored intrinsic electrical activity of the patient’s heart; anddelivering a cardiac conduction system third cardiac conduction system ATP pulse set in response to determining that the ventricular tachycardia has not ceased in response to the second cardiac conduction system ATP pulse set, the third cardiac conduction system ATP pulse set comprising:the first cardiac conduction system ATP pulse to the patient’s cardiac conduction system using the cardiac conduction system pacing electrode after the first period of time following another intrinsic cardiac activation;the second cardiac conduction system ATP pulse to the patient’s cardiac conduction system using the cardiac conduction system pacing electrode after the second period of time following the first cardiac conduction system ATP pulse;the third cardiac conduction system ATP pulse to the patient’s cardiac conduction system using the cardiac conduction system pacing electrode after the third period of time following the second cardiac conduction system ATP pulse; anda plurality of tertiary cardiac conduction system ATP pulses to the patient’s cardiac conduction system using the cardiac conduction system pacing electrode according to a tertiary period of time following the third cardiac conduction system ATP pulse.

[0126] This disclosure has been provided with reference to illustrative embodiments and examples and is not meant to be construed in a limiting sense. As described previously, one skilled in the art will recognize that other various illustrative applications may use the techniques as described herein to take advantage of the beneficial characteristics of the devices and methods described herein. Various modifications of the illustrative embodiments and examples will be apparent upon reference to this description.

[0127] In one or more examples, the described techniques 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 a hardware-based processing unit. Computer-readable media may include non-transitory computer-readable 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).

[0128] 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 physical structure suitablefor implementation of the described techniques. Also, the techniques could be fully implemented in one or more circuits or logic elements.

[0129] All references and publications cited herein are expressly incorporated herein by reference in their entirety for all purposes, except to the extent any aspect directly contradicts this disclosure.

[0130] All scientific and technical terms used herein have meanings commonly used in the art unless otherwise specified. The definitions provided herein are to facilitate understanding of certain terms used frequently herein and are not meant to limit the scope of the present disclosure.

[0131] Unless otherwise indicated, all numbers expressing feature sizes, amounts, and physical properties used in the specification and claims may be understood as being modified either by the term “exactly” or “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the foregoing specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by those skilled in the art utilizing the teachings disclosed herein or, for example, within typical ranges of experimental error.

[0132] The recitation of numerical ranges by endpoints includes all numbers subsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5) and any range within that range. Herein, the terms “up to” or “no greater than” a number (e.g., up to 50) includes the number (e.g., 50), and the term “no less than” a number (e.g., no less than 5) includes the number (e.g., 5).

[0133] The terms “coupled” or “connected” refer to elements being attached to each other either directly (in direct contact with each other) or indirectly (having one or more elements between and attaching the two elements). Either term may be modified by “operatively” and “operably,” which may be used interchangeably, to describe that the coupling or connection is configured to allow the components to interact to carry out at least some functionality (for example, a mobile user device may be operatively coupled to a cellular network transmit data to or receive data therefrom).

[0134] Reference to “one embodiment,” “an embodiment,” “certain embodiments,” or “some embodiments,” etc., means that a particular feature, configuration, composition, or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. Thus, the appearances of suchphrases in various places throughout are not necessarily referring to the same embodiment of the disclosure. Furthermore, the particular features, configurations, compositions, or characteristics may be combined in any suitable manner in one or more embodiments.

[0135] As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” encompass embodiments having plural referents, unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term “or” is generally employed in its sense including “and / or” unless the content clearly dictates otherwise.

[0136] As used herein, “have,” “having,” “include,” “including,” “comprise,” “comprising” or the like are used in their open-ended sense, and generally mean “including, but not limited to.” Further, wherever embodiments are described herein with the language “have,” “has,” “having,” “include,” “includes,” “including,” “comprise,” “comprises,” “comprising” and the like, otherwise analogous embodiments described in terms of “consisting of’ and / or “consisting essentially of’ are also provided. The term “consisting of’ means including, and limited to, that which follows the phrase “consisting of.” That is, “consisting of’ indicates that the listed elements are required or mandatory, and that no other elements may be present. The term “consisting essentially of’ indicates that any elements listed after the phrase are included, and that other elements than those listed may be included provided that those elements do not interfere with or contribute to the activity or action specified in the disclosure for the listed elements.

[0137] The term “and / or” means one or all of the listed elements or a combination of at least two of the listed elements.

[0138] The phrases “at least one of,” “comprises at least one of,” and “one or more of’ followed by a list refers to any one of the items in the list and any combination of two or more items in the list.

Claims

CLAIMSWhat is claimed:

1. An implantable medical device comprising:a computing apparatus comprising processing circuitry and operably coupled to one or more implantable electrodes comprising a cardiac conduction system pacing electrode positionable proximate a portion of the patient’s cardiac conduction system, wherein the computing apparatus is configured to provide cardiac conduction system antitachycardia pacing therapy (ATP) using the cardiac conduction system pacing electrode, wherein the cardiac conduction system ATP comprises:monitoring electrical activity of the patient’s heart using the one or more implantable electrodes;determining a cardiac cycle time based on the monitored electrical activity; anddelivering an initial cardiac conduction system ATP pulse set comprising three or less cardiac conduction system ATP pulses, wherein the three or less ATP pulses of the initial cardiac conduction system ATP pulse set comprise:a first cardiac conduction system ATP pulse to the patient’s cardiac conduction system using the cardiac conduction system pacing electrode after a first period of time following an intrinsic cardiac activation, wherein the first period of time is based on the cardiac cycle time and configured to provide maximal capture of the cardiac conduction system; and a second cardiac conduction system ATP pulse to the patient’s cardiac conduction system using the cardiac conduction system pacing electrode after a second period of time based on the cardiac cycle time and following the first cardiac conduction system ATP pulse.

2. The device as in claim 1, wherein the cardiac conduction system pacing electrode is configured to deliver the cardiac conduction system ATP to the left bundle branch of the patient’s heart.

3. The device as in claim 1, wherein the cardiac conduction system pacing electrode is configured to deliver the cardiac conduction system ATP to the His bundle of the patient’s heart.

4. The device as in any one of claims 1-3, wherein the one or more implantable electrodes are included on one of a single-chamber leadless pacing device, a lead, and a multi-chamber pacing device.

5. The device as in any one of claims 1-4, wherein the second period of time is greater than the first period of time.

6. The device as in any one of claims 1-5, wherein the first period of time is less than or equal to 70% of the cardiac cycle time.

7. The device as in any one of claims 1-6, wherein the first period of time is less than or equal to 60% of the cardiac cycle time.

8. The device as in any one of claims 1-8, wherein the second period of time is less than or equal to 80% of the cardiac cycle time.

9. The device as in any one of claims 1-8, wherein the second period of time is greater than 70% of the cardiac cycle time.

10. The device as in any one of claims 1-9, wherein the cardiac cycle time is adjusted to account for ventricular-to-cardiac conduction system delay prior to be using to determine the first and second periods of time.

11. The device as in any one of claims 1-10, wherein one or both of the first and second periods of time is adjusted based on intrinsic T-wave in the monitored electrical activity.

12. The device as in any one of claims 1-11, wherein the three or less ATP pulses of the initial cardiac conduction system ATP pulse set further comprise a third cardiac conduction system ATP pulse to the patient’s cardiac conduction system using the cardiac conduction system pacing electrode after a third period of time based on the cardiac cycle time and following the second cardiac conduction system ATP pulse.

13. The device as in any one of claims 1-11, wherein the cardiac conduction system ATP further comprises:determining that the ventricular tachycardia has not ceased in response to the first cardiac conduction system ATP pulse set based on monitored intrinsic electrical activity of the patient’s heart; anddelivering a second cardiac conduction system ATP pulse set in response to determining that the ventricular tachycardia has not ceased in response to the initial cardiac conduction system ATP pulse set, the second cardiac conduction system ATP pulse set consists essentially of:the first cardiac conduction system ATP pulse to the patient’s cardiac conduction system using the cardiac conduction system pacing electrode after the first period of time following another intrinsic cardiac activation;the second cardiac conduction system ATP pulse to the patient’s cardiac conduction system using the cardiac conduction system pacing electrode after the second period of time following the first cardiac conduction system ATP pulse; anda third cardiac conduction system ATP pulse to the patient’s cardiac conduction system using the cardiac conduction system pacing electrode after a third period of time following the second cardiac conduction system ATP pulse.

14. The device as in any one of claims 12 and 13, wherein the third period of time is greater than the second period of time, greater than or equal to 80% of a cardiac cycle time, orless than or equal to 94% of a cardiac cycle time.

15. The device as in any one of claims 13-14, wherein the cardiac conduction system ATP further comprises:determining that the ventricular tachycardia has not ceased in response to the second cardiac conduction system ATP pulse set based on monitored intrinsic electrical activity of the patient’s heart; anddelivering a cardiac conduction system third cardiac conduction system ATP pulse set in response to determining that the ventricular tachycardia has not ceased in response to the second cardiac conduction system ATP pulse set, the third cardiac conduction system ATP pulse set comprising:the first cardiac conduction system ATP pulse to the patient’s cardiac conduction system using the cardiac conduction system pacing electrode after the first period of time following another intrinsic cardiac activation;the second cardiac conduction system ATP pulse to the patient’s cardiac conduction system using the cardiac conduction system pacing electrode after the second period of time following the first cardiac conduction system ATP pulse;the third cardiac conduction system ATP pulse to the patient’s cardiac conduction system using the cardiac conduction system pacing electrode after the third period of time following the second cardiac conduction system ATP pulse; anda plurality of tertiary cardiac conduction system ATP pulses to the patient’s cardiac conduction system using the cardiac conduction system pacing electrode according to a tertiary period of time following the third cardiac conduction system ATP pulse.

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