Monitoring of His bundle capture during ventricular pacing therapy

Abstract

Methods and systems for delivering cardiac pacing therapy, including sensing a cardiac signal via an electrode of an atrial lead, and determining the occurrence of one of an intrinsic atrial depolarization event and a paced atrial depolarization event for a current cardiac cycle in response to the sensed cardiac signal. In response to the determined occurrence of the depolarization event, delivering a first pacing therapy during the current cardiac cycle, and comparing the amplitude of the cardiac signal after the delivered first pacing therapy in the current cardiac cycle to a predetermined amplitude threshold. In response to the amplitude not being more negative than the predetermined amplitude threshold, delivering a second pacing therapy via a left ventricular lead in the same cardiac cycle and after the delivered first pacing therapy, and in response to the amplitude being more negative than the predetermined amplitude threshold, not delivering the second pacing therapy.

Description

[0001] This application claims the benefit of U.S. Patent Application No. 15 / 928,753, filed on March 22, 2018, which is incorporated herein by reference in its entirety. Technical Field

[0002] The present disclosure relates to cardiac pacing methods and systems, and more particularly to methods and apparatus for delivering continuous ventricular pacing therapy in an implantable medical device. Background Art

[0003] Cardiac resynchronization therapy devices operate by delivering pacing stimulation to both ventricles or to one ventricle, achieving the desired result of more or less simultaneous mechanical contraction and ejection of blood from the ventricles. Ideally, each pacing pulse stimulation delivered to the ventricles induces a response from the ventricles. Delivering electrical stimulation that causes the ventricles to respond is generally referred to as capturing the ventricles.

[0004] For a variety of reasons, a cardiac pacing system may not effectively capture a ventricle. For example, the pacing lead and / or electrodes may not be placed in an optimal position. Sensed atrioventricular delay (SAV), paced atrioventricular delay (PAV), right ventricular pre-excitation may also affect whether the ventricle is effectively captured. In addition, the pacing lead may migrate or shift after the medical device has been implanted. It is desirable to develop additional systems and methods that automatically determine optimal effective capture of the ventricle. Summary of the invention

[0005] The present disclosure relates to methods and apparatus for delivering His bundle pacing to produce more standardized and physiological excitation of a patient's heart. The pacing device includes pacing leads extending from the pacing device, the pacing leads leading to specified locations in the atria, AV septum, and one or both ventricles of the heart. The distal ends of the pacing leads include electrodes for sensing cardiac signals and for delivering electrical impulses or pacing therapy. The pacing leads leading to the atria and ventricles are programmed to deliver electrical pulses on a demand mode basis if no natural electrical signals are measured within a predetermined time period.

[0006] Immediately after sensing atrial activity, a pacing lead positioned along the AV septum delivers continuous electrical pulses to the His bundle. These electrical pulses then travel through the right and left bundle branches and reach the Purkinje fibers, causing the ventricles to depolarize and contract. By delivering such His bundle pacing to stimulate the natural conduction system, the ventricles contract in a more coordinated manner, thereby improving cardiac output and performance, compared to delivering ventricular pacing directly to one of the left and right ventricles, thereby improving cardiac output and performance. However, while His bundle pacing tends to result in more standardized contractions compared to delivering pacing directly within the ventricles, certain factors associated with His bundle pacing (such as an increased tendency for threshold changes and an increased tendency for contact problems to occur) tend to make maintaining capture during His bundle pacing a more significant challenge. At the same time, current indications appear to suggest that in order to optimize the effectiveness of resynchronization therapy, it is desirable to deliver pacing therapy as close to 100% of the time as possible. Therefore, any percentage loss of delivered pacing (such as when pacing does not result in cardiac capture) can be considered less than optimal.

[0007] In an implantable medical device according to an example of the present disclosure, an atrial lead is positioned near the AV node / high septum region to deliver His bundle pacing therapy, and a second lead may be located in the right ventricle or in the left ventricle. The implantable medical device determines on a beat-by-beat basis whether the delivered His bundle pacing has captured the patient's heart. If the His bundle pacing therapy does not capture the patient's heart for the current cardiac cycle or heartbeat, the device delivers pacing therapy via other ventricular leads during the same cardiac cycle with a pre-specified delay from the delivered His bundle pacing, thereby resolving the loss of capture from the His bundle pacing during the same cardiac cycle and providing continuous pacing therapy to the patient. On the other hand, if the His bundle pacing captures the patient's heart, delivery of pacing therapy from the other ventricular leads is inhibited, thereby promoting His bundle pacing and more physiological excitation of the ventricles.

[0008] According to one example of the present disclosure, a method for delivering cardiac pacing therapy to a patient includes: sensing a cardiac signal of the patient; determining, in response to the sensed cardiac signal, the occurrence of one of an intrinsic atrial depolarization event and a paced atrial depolarization event of a current cardiac cycle; delivering a first pacing therapy during the current cardiac cycle in response to the determined occurrence of the depolarization event; comparing the amplitude of the cardiac signal after the delivered first pacing therapy in the current cardiac cycle with a predetermined amplitude threshold; and determining, in response to the comparison, whether to deliver a second pacing therapy in the current cardiac cycle and after the delivered first pacing therapy.

[0009] According to another example of the present disclosure, a system for delivering cardiac pacing therapy to a patient includes: a first cardiac lead, the first cardiac lead having a distal end; at least one electrode positioned at the distal end of the first cardiac lead, for sensing a cardiac signal of the patient and delivering a first cardiac pacing therapy; a second cardiac lead, the second cardiac lead having a distal end; at least one electrode positioned at the distal end of the second cardiac lead, for delivering a second cardiac pacing therapy; and a processor, the processor being configured to: determine the occurrence of one of an intrinsic atrial depolarization event and a paced atrial depolarization event of a current cardiac cycle in response to a sensed cardiac signal, deliver the first pacing therapy via the at least one electrode of the first cardiac lead during the current cardiac cycle in response to the determined occurrence of the depolarization event, compare the amplitude of the cardiac signal after the delivered first pacing therapy within the current cardiac cycle with a predetermined amplitude threshold, and determine, in response to the comparison, whether to deliver the second pacing therapy via the at least one electrode of the second cardiac lead within the current cardiac cycle and after the delivered first pacing therapy.

[0010] In another example of the present disclosure, a non-transitory computer-readable medium stores instructions that cause a cardiac medical device to perform a method including: sensing a cardiac signal of the patient; determining, in response to the sensed cardiac signal, the occurrence of one of an intrinsic atrial depolarization event and a paced atrial depolarization event of a current cardiac cycle; delivering a first pacing therapy during the current cardiac cycle in response to the determined occurrence of the depolarization event; comparing the amplitude of the cardiac signal after the delivered first pacing therapy within the current cardiac cycle with a predetermined amplitude threshold; and determining, in response to the comparison, whether to deliver a second pacing therapy within the current cardiac cycle and after the delivered first pacing therapy. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is a schematic diagram of an exemplary cardiac therapy delivery system that may be used to deliver pacing therapy in accordance with the present disclosure.

[0012] Figure 2 is shown in more detail Figure 1 Schematic diagram of an exemplary cardiac therapy delivery system.

[0013] Figure 3 is an exemplary functional block diagram of an exemplary configuration of an implantable medical device according to examples of the present disclosure.

[0014] Figure 4 is an exemplary functional block diagram of a circuit system of an implantable medical device according to the present disclosure.

[0015] Figure 5 is a flow chart of a method for delivering pacing therapy according to an example of the present disclosure.

[0016] Fig. 6A -C is a graphical representation of the delivery of pacing therapy according to an example of the present disclosure. DETAILED DESCRIPTION

[0017] It will be apparent to those skilled in the art that elements or processes from one embodiment may be used in combination with elements or processes of other embodiments, and that possible embodiments of such methods, devices, and systems using the combinations of features set forth herein are not limited to the specific embodiments shown in the drawings and / or described herein. Further, it will be appreciated that the embodiments described herein may include many elements that are not necessarily shown to scale.

[0018] Figure 1 is a schematic diagram of an exemplary cardiac therapy delivery system that may be used to deliver pacing therapy according to the present disclosure. Therapy delivery system 10 may include an implantable medical device 16 (IMD) that may be coupled to leads 18, 20, 22 and a programmer 24. IMD 16 may be, for example, an implantable pacemaker, cardioverter, and / or defibrillator that provides electrical signals to heart 12 of patient 14 via electrodes coupled to one or more of leads 18, 20, 22. Patient 14 may be, but is not necessarily, a human.

[0019] Leads 18, 20, 22 extend into heart 12 of patient 14 to sense electrical activity of heart 12 and / or deliver electrical stimulation to heart 12. Figure 1 In the example shown in , the right ventricular (RV) lead 18 extends through one or more veins (not shown), the superior vena cava (not shown), and the right atrium 26, and enters the right ventricle 28. The left ventricular (LV) coronary sinus lead 20 extends through one or more veins, the vena cava, the right atrium 26, and enters the coronary sinus 30 to reach the area adjacent to the free wall of the left ventricle 32 of the heart 12. The right atrial (RA) lead 22 extends through one or more veins and the vena cava, and enters the right atrium 26 of the heart 12. As described below, in one example, the atrial lead 22 is positioned near the AV node / septum area for delivery of His bundle pacing, and at least one ventricular lead 18 is positioned in the right ventricle or the ventricular lead 20 is positioned in the left ventricle.

[0020] IMD 16 may sense electrical signals associated with depolarization and repolarization of heart 12, etc., via electrodes coupled to at least one of leads 18, 20, 22. In some examples, IMD 16 provides pacing therapy (e.g., pacing pulses) to heart 12 based on the electrical signals sensed within heart 12. IMD 16 is operable to adjust one or more parameters associated with pacing therapy, such as, for example, pulse width, amplitude, voltage, pulse train length, etc. Further, IMD 16 is operable to deliver pacing therapy using various electrode configurations, which may be unipolar or bipolar. IMD 16 may also provide defibrillation therapy and / or cardioversion therapy via electrodes located on at least one of leads 18, 20, 22. Further, IMD 16 may detect arrhythmias of heart 12 (e.g., fibrillation of ventricles 28, 32) and deliver defibrillation therapy to heart 12 in the form of electrical pulses. In some examples, IMD 16 may be programmed to deliver progressive therapy (eg, pulses having increasing energy levels) until the fibrillation of heart 12 ceases.

[0021] In some examples, programmer 24 may be a handheld computing device or computer workstation that may be used by a user (such as a physician, a technician, another clinician, and / or a patient) to communicate with (e.g., program) IMD 16. For example, a user may interact with programmer 24 to retrieve information about one or more detected or indicated faults within IMD 16 and / or associated with delivered pacing therapy. IMD 16 and programmer 24 may communicate via wireless communications using any technique known in the art. Examples of communications techniques may include, for example, low frequency or radio frequency (RF) telemetry, although other techniques are also contemplated.

[0022] Figure 2 is shown in more detail Figure 1 Schematic diagram of an exemplary cardiac therapy delivery system of IMD 16. Leads 18, 20, 22 may be electrically coupled to a therapy delivery module (e.g., for delivering pacing therapy), a sensing module (e.g., one or more electrodes for sensing or monitoring electrical activity of heart 12 for determining effectiveness of pacing therapy), and / or any other module of IMD 16 via connector block 34. In some examples, proximal ends of leads 18, 20, 22 may include electrical contacts that are electrically coupled to corresponding electrical contacts in connector block 34 of IMD 16. Additionally, in some examples, leads 18, 20, 22 may be mechanically coupled to connector block 34 by means of set screws, connecting pins, or another suitable mechanical coupling mechanism.

[0023] Each of leads 18, 20, 22 includes an elongated insulated lead body that may carry a plurality of conductors (e.g., concentric coil conductors, straight conductors, etc.) separated from one another by insulation (e.g., a tubular insulating sheath). In the example shown, bipolar electrodes 40, 42 are positioned proximate the distal end of lead 18. Additionally, bipolar electrodes 44, 46 are positioned proximate the distal end of lead 20, and bipolar electrodes 48, 50 are positioned proximate the distal end of lead 22.

[0024] Electrodes 40, 44, 48 may take the form of ring electrodes, and electrodes 42, 46, 50 may take the form of extendable spiral tip electrodes telescopically mounted within insulating electrode heads 52, 54, 56, respectively. Each of electrodes 40, 42, 44, 46, 48, 50 may be electrically coupled to a respective one of the conductors (e.g., spiral and / or straight) within the lead body of its associated lead 18, 20, 22, and thereby coupled to a respective one of the electrical contacts on the proximal end of the lead 18, 20, 22.

[0025] Electrodes 40, 42, 44, 46, 48, 50 may further be used to sense electrical signals (e.g., morphological waveforms within an electrogram (EGM)) associated with depolarization and repolarization of heart 12. These sensed electrical signals are conducted to IMD 16 via corresponding leads 18, 20, 22. In some examples, IMD 16 may also deliver pacing pulses via electrodes 40, 42, 44, 46, 48, 50 to cause depolarization of cardiac tissue of the patient's heart 12. In some examples, such as Figure 2 As shown in , IMD 16 includes one or more housing electrodes, such as housing electrode 58, which may be integrally formed with or otherwise coupled to an outer surface of a housing 60 (e.g., a hermetically sealed housing) of IMD 16. Any of electrodes 40, 42, 44, 46, 48, 50 may be used in combination with housing electrode 58 for unipolar sensing or pacing. In other words, any of electrodes 40, 42, 44, 46, 48, 50, 58 may be used in combination to form a sensing vector, e.g., a sensing vector that may be used to assess and / or analyze the effectiveness of a pacing therapy. Examples of sensing and pacing configurations may be seen in connection with U.S. Patent Application No. 61 / 580,058, filed on December 23, 2011 and assigned to the assignee of the present invention, the disclosure of which is incorporated herein by reference in its entirety, as modified by preferably using the LV apex (i.e., electrode 46)-Rv coil (i.e., electrode 62) for pacing vectors and sensing vectors. It is generally understood by those skilled in the art that other electrodes may be selected as pacing and sensing vectors. Electrodes 44 and 64 are referred to as third and fourth LV electrodes in the claims.

[0026] As reference Figure 3 and Figure 4 As further described in detail, housing 60 may enclose a therapy delivery module, which may include a stimulation generator for generating cardiac pacing pulses and defibrillation or cardioversion shocks, and a sensing module for monitoring the patient's heart rhythm. Leads 18, 20, 22 may also include elongated electrodes 62, 64, 66, respectively, which may take the form of coils. IMD 16 may deliver defibrillation shocks to heart 12 via any combination of elongated electrodes 62, 64, 66 and housing electrodes 58. Electrodes 58, 62, 64, 66 may also be used to deliver cardioversion pulses to heart 12. Further, electrodes 62, 64, 66 may be made of any suitable conductive material, such as, but not limited to, platinum, platinum alloys, and / or other materials known to be useful for implantable defibrillation electrodes. Because electrodes 62, 64, 66 are generally not configured to deliver pacing therapy, any of electrodes 62, 64, 66 may be used to sense electrical activity during pacing therapy (e.g., for analyzing pacing therapy effectiveness) and may be used in conjunction with any of electrodes 40, 42, 44, 46, 48, 50, 58. In at least one embodiment, RV elongate electrode 62 may be used to sense electrical activity of the patient's heart during delivery of pacing therapy (e.g., in conjunction with housing electrode 58 to form an RV elongate, coil, or defibrillation electrode to housing electrode vector).

[0027] Figure 1-2 The configuration of the exemplary therapy delivery system 10 shown in is only one example. In one example, the atrial lead 22 is positioned near the AV node / septum region for delivery of His bundle pacing, and the ventricular lead 18 is positioned in the right ventricle or the ventricular lead 20 is positioned in the left ventricle, or both ventricular leads 18 and 20 may be included, as described below. In addition, as described below, the electrode 50 of the lead 22 may take the form of a spiral tip electrode to enable the lead to be fixedly engaged near the AV node / septum region for delivery of His bundle pacing.

[0028] Figure 3 is a functional block diagram of an exemplary configuration of an implantable medical device according to an example of the present disclosure. Figure 3As shown, IMD 16 may include control module 81, therapy delivery module 84 (e.g., which may include a stimulation generator), sensing module 86, and power supply 90. Control module 81 may include processor 80, memory 82, and telemetry module 88. Memory 82 may include computer-readable instructions that, when executed, for example, by processor 80, cause IMD 16 and / or control module 81 to perform various functions described herein as being attributed to IMD 16 and / or control module 81. Further, memory 82 may include any volatile, nonvolatile, magnetic, optical, and / or electrical media, such as random access memory (RAM), read-only memory (ROM), nonvolatile RAM (NVRAM), electrically erasable programmable ROM (EEPROM), flash memory, and / or any other digital media. As will be described in detail below, memory 82 includes computer instructions related to capture management (including methods of capture management according to the present disclosure).

[0029] The processor 80 of the control module 81 may include any one or more of the following: a microprocessor, a controller, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), and / or an equivalent discrete or integrated logic circuit system. In some examples, the processor 80 may include multiple components, such as any combination of the following: one or more microprocessors, one or more controllers, one or more DSPs, one or more ASICs, and / or one or more FPGAs, and other discrete or integrated logic circuit systems. The functions attributed to the processor 80 herein may be embodied as software, firmware, hardware, or any combination thereof.

[0030] Control module 81 may control therapy delivery module 84 to deliver therapy (e.g., electrical stimulation therapy such as pacing) to heart 12 according to one or more selected therapy programs that may be stored in memory 82. More specifically, control module 81 (e.g., processor 80) may control therapy delivery module 84 to deliver electrical stimulation, such as, for example, pacing pulses having an amplitude, pulse width, frequency, or polarity of electrodes specified by one or more selected therapy programs (e.g., a pacing therapy program, a pacing recovery program, a capture management program, etc.). As shown, therapy delivery module 84 is electrically coupled to electrodes 40, 42, 44, 46, 48, 50, 58, 62, 64, 66, e.g., via conductors of respective leads 18, 20, 22 or, in the case of housing electrode 58, via electrical conductors disposed within housing 60 of IMD 16. Therapy delivery module 84 may be configured to generate and deliver electrical stimulation therapy, such as pacing therapy, to heart 12 using one or more of electrodes 40 , 42 , 44 , 46 , 48 , 50 , 58 , 62 , 64 , 66 .

[0031] For example, therapy delivery module 84 may deliver pacing stimulation (e.g., pacing pulses) via ring electrodes 40, 44, 48 coupled to leads 18, 20, and 22, respectively, and / or helical tip electrodes 42, 46, and 50 of leads 18, 20, and 22, respectively. Further, for example, therapy delivery module 84 may deliver a defibrillation shock to heart 12 via at least two of electrodes 58, 62, 64, 66. In some examples, therapy delivery module 84 may be configured to deliver pacing, cardioversion, or defibrillation stimulation in the form of electrical pulses. In other examples, therapy delivery module 84 may be configured to deliver one or more of these types of stimulation in the form of other signals (e.g., sine waves, square waves, and / or other substantially continuous time signals).

[0032] The IMD 16 may further include a switch module 85, and the control module 81 (e.g., the processor 80) may use the switch module 85 to select, for example, via a data / address bus, which of the available electrodes are used to deliver therapy (such as pacing pulses for pacing therapy), or which of the available electrodes are used for sensing. The switch module 85 may include a switch array, a switch matrix, a multiplexer, or any other type of switch device suitable for selectively coupling the sensing module 86 and / or the therapy delivery module 84 to one or more selected electrodes. More specifically, the therapy delivery module 84 may include a plurality of pacing output circuits. The switch module 85 may be used, for example, to selectively couple each of the plurality of pacing output circuits to one or more of the electrodes 40, 42, 44, 46, 48, 50, 58, 62, 64, 66 (e.g., a pair of electrodes for delivering therapy to a pacing vector). That is, the switch module 85 may be used to selectively couple each electrode to one of the pacing output circuits of the therapy delivery module.

[0033] The sensing module 86 is coupled (e.g., electrically coupled) to a sensing device, which, as well as additional sensing devices, may include electrodes 40, 42, 44, 46, 48, 50, 58, 62, 64, 66 to monitor the electrical activity of the heart 12, such as electrocardiogram (ECG) / electrogram (EGM) signals, etc. The ECG / EGM signals may be used to analyze a plurality of pacing events. More specifically, one or more morphological features of each pacing event within the ECG / EGM signals may be used to determine whether each pacing event has a predetermined level of effectiveness. ECG / EGM signals can be further used to monitor heart rate (HR), heart rate variability (HRV), heart rate oscillations (HRT), deceleration / acceleration ability, incidence of deceleration sequences, T wave alternans (TWA), P wave to P wave interval (also known as PP interval or AA interval), R wave to R wave interval (also known as RR interval or VV interval), P wave to QRS complex interval (also known as PR interval, AV interval or PQ interval), QRS complex morphology, ST segment (i.e., the segment connecting the QRS complex and T wave), T wave changes, QT interval, electrical vector, etc.

[0034] The switch module 85 can also be used with the sensing module 86 to select which of the available electrodes to use, for example, to sense electrical activity of the patient's heart (e.g., using any combination of electrodes 40, 42, 44, 46, 48, 50, 58, 62, 64, 66 to sense one or more electrical vectors of the patient's heart). In some examples, the control module 81 can select the electrodes to use as sensing electrodes via the switch module within the sensing module 86 (e.g., by providing a signal via a data / address bus). In some examples, the sensing module 86 can include one or more sensing channels, each of which can include an amplifier.

[0035] In some examples, the sensing module 86 includes a channel that includes an amplifier having a relatively wider passband than an R-wave or P-wave amplifier. Signals from selected sensing electrodes selected for coupling to the wideband amplifier may be provided to a multiplexer and subsequently converted to a multi-bit digital signal by an analog-to-digital converter for storage as an EGM in the memory 82. In some examples, the storage of such EGMs in the memory 82 may be under the control of a direct memory access circuit. The control module 81 (e.g., using the processor 80) may employ digital signal analysis techniques to characterize the digitized signals stored in the memory 82 to analyze and / or classify one or more morphological waveforms of the EGM signal to determine the effectiveness of the pacing therapy. For example, the processor 80 may be configured to determine or obtain one or more features of one or more sensed morphological waveforms within one or more electrical vectors of the patient's heart and store the one or more features in the memory 82 for use in determining the effectiveness of the pacing therapy at a later time.

[0036] If IMD 16 is configured to generate and deliver pacing pulses to heart 12, control module 81 may include a pacemaker timing and control module, which may be implemented as hardware, firmware, software, or any combination thereof. The pacemaker timing and control module may include one or more dedicated hardware circuits (such as ASICs) separate from processor 80 (such as a microprocessor), and / or a software module executed by a component of processor 80 (which may be a microprocessor or ASIC). The pacemaker timing and control module may include a programmable counter that controls the basal time intervals associated with DDD, VVI, DVI, VDD, AAI, DDI, DDDR, VVIR, DVIR, VDDR, AAIR, DDIR, and other modes of single-chamber pacing and dual-chamber pacing. In the aforementioned pacing modes, "D" may indicate dual chamber, "V" may indicate ventricle, "I" may indicate inhibited pacing (e.g., no pacing), and "A" may indicate atrium. The first letter in the pacing mode may indicate the chamber that is paced, the second letter may indicate the chamber in which the electrical signal is sensed, and the third letter may indicate the chamber in which the response to the sensing is provided.

[0037] Intervals defined by the pacemaker timing and control module within the control module 81 may include atrial and ventricular pacing escape intervals, refractory periods during which sensed P and R waves are ineffective for restarting the timing of escape intervals, and / or pulse widths of pacing pulses. As another example, the pacemaker timing and control module may define blanking periods and provide signals based on the sensing module 86 to blank one or more channels (e.g., amplifiers) for a period of time during and after the delivery of electrical stimulation to the heart 12. The duration of these intervals may be determined in response to data stored in the memory 82. The pacemaker timing and control module of the control module 81 may also determine the amplitude of the cardiac pacing pulses.

[0038] During pacing, an escape interval counter within the pacemaker timing / control module may be reset when R and P waves are sensed. Therapy delivery module 84 (e.g., including a stimulation generator) may include one or more pacing output circuits that are selectively coupled, for example, via switch module 85, to any combination of electrodes 40, 42, 44, 46, 48, 50, 58, 62, or 66 suitable for delivering bipolar or unipolar pacing pulses to one of the chambers of heart 12. Processing module 81 may reset the escape interval counter when a pacing pulse is generated by therapy delivery module 84, and thereby control basic timing of cardiac pacing functions including anti-tachyarrhythmia pacing.

[0039] In some examples, the control module 81 may operate as an interrupt driven device and may respond to interrupts from the pacemaker timing and control module, wherein the interrupts may correspond to the occurrence of sensed P and R waves and the generation of cardiac pacing pulses. Any necessary mathematical calculations may be performed by the processor 80, and any updates to values ​​or intervals controlled by the pacemaker timing and control module may occur following such interrupts. A portion of the memory 82 may be configured as a plurality of recirculating buffers that can store a series of measured intervals that may be analyzed by, for example, the processor 80 in response to the occurrence of a pacing or sensing interrupt to determine whether the patient's heart 12 is currently exhibiting an atrial or ventricular tachyarrhythmia.

[0040] The telemetry module 88 of the control module 81 may include a device for communicating with a device such as the one described herein. Figure 1 The processor 80 may include any suitable hardware, firmware, software, or any combination thereof, for communicating with another device such as the programmer 24 described herein. For example, under the control of the processor 80, the telemetry module 88 may receive downlink telemetry from the programmer 24 and send uplink telemetry to the programmer 24 with the aid of an antenna (which may be an internal and / or external antenna). The processor 80 may provide data to be transmitted to the programmer 24 via an uplink and control signals for telemetry circuits within the telemetry module 88, for example, via an address / data bus. In some examples, the telemetry module 88 may provide the received data to the processor 80 via a multiplexer. In at least one embodiment, the telemetry module 88 may be configured to send a warning or alarm if the pacing therapy becomes ineffective or less effective (e.g., does not have a predetermined level of effectiveness).

[0041] The various components of IMD 16 are further coupled to a power source 90, which may include rechargeable and non-rechargeable batteries. Non-rechargeable batteries may be selected to last for several years, while rechargeable batteries may be inductively charged from an external device, for example, daily or weekly.

[0042] Figure 4 is an exemplary functional block diagram of a circuit system of an implantable medical device according to the present disclosure. Figure 4The bipolar RA lead 22, bipolar RV lead 18, and bipolar LV CS lead 20 are depicted coupled to an implantable pulse generator (IPG) circuit 31 without the LA CS pace / sense electrodes 28 and 30, the implantable pulse generator circuit 31 having a biventricular DDD / R type programmable mode and parameters known in the pacing art. In turn, the sensor signal processing circuit 43 is indirectly coupled to the timing circuit 83 and to the microcomputer circuit system 33 via a data and control bus. The IPG circuit 31 is shown in a functional block diagram generally divided into the microcomputer circuit 33 and the pacing circuit 83. The pacing circuit 83 includes a digital controller / timer circuit 83, an output amplifier circuit 51, a sense amplifier circuit 55, an RF telemetry transceiver 41, an activity sensor circuit 35, and a number of other circuits and components described below.

[0043] Crystal oscillator circuit 47 provides a basic timing clock for pacing circuit 320, while battery 29 provides power. Power-on reset circuit 45 responds to initial connection of the circuit to the battery for defining initial operating conditions, and similarly responds to detection of a low battery condition to reset the operating state of the device. Reference mode circuit 37 generates a stable voltage reference and current for analog circuits within pacing circuit 320, while analog-to-digital converter ADC and multiplexer circuit 39 digitizes the analog signals and voltages to provide real-time telemetry of cardiac signals from sense amplifier 55 for uplink transmission via RF transmitter and receiver circuit 41. Voltage reference and bias circuit 37, ADC and multiplexer 39, power-on reset circuit 45, and crystal oscillator circuit 47 may correspond to any of those currently used in currently commercially available implantable cardiac pacemakers.

[0044] If the IPG is programmed for frequency response mode, the signals output by one or more physiological sensors are used as frequency control parameters (RCP) to derive physiological escape intervals. For example, the escape interval is adjusted in proportion to the patient's activity level obtained in the patient activity sensor (PAS) circuit 35 in the depicted exemplary IPG circuit 31. The patient activity sensor 316 is coupled to the IPG housing and may take the form of a piezoelectric crystal transducer well known in the art, and its output signal is processed and used as the RCP. The sensor 316 generates electrical signals in response to sensed physical activity, which are processed by the activity circuit 35 and provided to the digital controller / timer circuit 83. The activity circuit 35 and the associated sensor 316 may correspond to the circuit systems disclosed in U.S. Patents Nos. 5,052,388 and 4,428,378. Similarly, the present invention may be practiced in conjunction with alternative types of sensors such as oxygenation sensors, pressure sensors, pH sensors, and respiration sensors (all of which are known to provide frequency response pacing capabilities). Alternatively, the QT time may be used as a rate-indicating parameter, in which case no additional sensor is required. Similarly, the present invention may also be practiced in non-rate-responsive pacemakers.

[0045] Data transmission to and from the external programmer is accomplished by means of a telemetry antenna 57 and an associated RF transceiver 41, which serves to both demodulate received downlink telemetry and transmit uplink telemetry. As is well known in the pacing art, uplink telemetry capability will typically include the ability to transmit stored digital information (e.g., operating modes and parameters, EGM histograms, and other events, as well as real-time EGMs of atrial and / or ventricular electrical activity and marker channel pulses indicating the occurrence of sensed and paced depolarizations in the atria and ventricles).

[0046] The microcomputer 33 includes a microprocessor 80 and an associated system clock, and includes on-processor RAM and ROM chips 82A and 82B, respectively. In addition, the microcomputer circuit 33 includes a separate RAM / ROM chip 82C to provide additional memory capacity. The microprocessor 80 is usually operated in a reduced power consumption mode and is interrupt driven. The microprocessor 80 is awakened in response to a defined interrupt event, which may include an A-trigger (A-TIRG) signal, an RV-trigger (RV-TIRG) signal, a LV-trigger (LV-TIRG) signal generated by a timer in the digital timer / controller circuit 83, and an A-event signal, an RV-event signal, and a LV-event signal generated by the sense amplifier circuit 55, etc. The specific values ​​of the intervals and delays for the countdown (timeout) performed by the digital controller / timer circuit 83 are controlled by the microcomputer circuit 33 via the data and control bus 306 according to the programmed-in parameter values ​​and operating mode. Furthermore, if programmed to operate as a rate-responsive pacemaker, a timed interrupt may be provided, for example, every cycle or every two seconds, to allow the microprocessor to analyze the activity sensor data and update the basic AA, VA, or VV escape intervals (as applicable). In addition, the microprocessor 80 may also be used to define variable, actionable AV delay intervals and the energy delivered to each ventricle.

[0047] In one embodiment, microprocessor 80 is a custom microprocessor adapted to fetch and execute instructions stored in RAM / ROM unit 314 in a conventional manner. However, it is contemplated that other implementations may be suitable for practicing the present invention. For example, an off-the-shelf commercially available microprocessor or microcontroller, or a custom dedicated hard-wired logic or state machine type circuit may perform the functions of microprocessor 80.

[0048] The digital controller / timer circuit 83 operates under the overall control of the microcomputer 33 to control timing and other functions within the pacing circuit 320 and includes a set of timing circuits and associated logic circuits, certain of which are depicted that are relevant to the present invention. The depicted timing circuits include a URI / LRI timer 83A, a VV delay timer 83B, an intrinsic interval timer 83C for timing past V-event to V-event intervals or V-event to A-event intervals or VV conduction intervals, an escape interval timer 83D for timing AA, VA and / or VV pacing escape intervals, an AV delay interval timer 83E for timing the A-LVp delay (or A-RVp delay) from a preceding A-event or A-trigger, a post-ventricular timer 374 for timing post-ventricular time periods, and a date / time clock 376.

[0049] The AV delay interval timer 83E is loaded with the appropriate delay interval for one ventricular chamber (i.e., A-RVp delay or A-LVp delay determined using known methods) for counting down from the start of a preceding A-pacing or A-event. The interval timer 83E triggers pacing stimulus delivery and may be based on one or more prior cardiac cycles (or based on a data set empirically derived for a given patient).

[0050] A post-event timer 374 counts down a post-ventricular time period after an RV-event or LV-event or RV-trigger or a post-atrial time period after an A-event or A-trigger. The duration of the post-event time period may also be selected as a programmable parameter stored in the microcomputer 33. The post-ventricular time period includes the PVARP, the post-atrial ventricular blanking period (PAVBP), the ventricular blanking period (VBP), the post-ventricular atrial blanking period (PVARP), and the ventricular refractory period (VRP), although other time periods may also be appropriately defined based at least in part on the operating circuitry employed in the pacing engine. The post-atrial time period includes the atrial refractory period (ARP) (during which the A-event is ignored for the purpose of resetting any AV delay) and the atrial blanking period (ABP) (during which atrial sensing is disabled). It should be noted that the start of the post-atrial time period and AV delay may begin substantially simultaneously with the start or end of each A-event or A-trigger, or in the case of an A-trigger, may begin at the end of A-pacing after the A-trigger. Similarly, the start of the post-ventricular time period and VA escape interval may begin substantially simultaneously with the start or end of a V-event or V-trigger, or in the case of a V-trigger, at the end of V-pacing after the V-trigger. The microprocessor 80 also optionally calculates the AV delay, post-ventricular time period, and post-atrial time period as a function of the sensor-based escape interval established in response to one or more RCPs and / or with the intrinsic atrial rate.

[0051] The output amplifier circuit 51 includes an RA pacing pulse generator (and a LA pacing pulse generator, if LA pacing is provided), an RV pacing pulse generator, and an LV pacing pulse generator, or any of those currently used in commercially available cardiac pacemakers that provide atrial and ventricular pacing. To trigger the generation of RV-pacing or LV-pacing pulses, the digital controller / timer circuit 83 generates an RV-trigger signal upon timeout of the A-RVp delay (in the case of RV preexcitation) or generates an LV-trigger upon timeout of the A-LVp delay (in the case of LV preexcitation), which is provided by the AV delay interval timer 83E (or the VV delay timer 83B). Similarly, at the end of the VA escape interval timed by the escape interval timer 83D, the digital controller / timer circuit 83 generates an RA-trigger signal that triggers the output of an RA-pacing pulse (or an LA-trigger signal that triggers the output of an LA-pacing pulse, if provided).

[0052] The output amplifier circuit 51 includes switching circuitry for coupling selected pacing electrode pairs from between the lead conductors and the IND_CAN electrode 20 to the RA pacing pulse generator (and the LA pacing pulse generator, if provided), the RV pacing pulse generator, and the LV pacing pulse generator. The pacing / sense electrode pair selection and control circuit 53 selects the lead conductors and associated pacing electrode pairs to be coupled to the atrial and ventricular output amplifiers within the output amplifier circuit 51 for accomplishing RA, LA, RV, and LV pacing.

[0053] The sense amplifier circuit 55 contains sense amplifiers corresponding to any of those currently employed in contemporary cardiac pacemakers for atrial and ventricular pacing and sensing. It has been common in the art to use very high impedance P-wave and R-wave sense amplifiers to amplify the voltage difference signal generated across the sensing electrode pair by the passage of the cardiac depolarization wavefront. The high impedance sense amplifier uses high gain to amplify low amplitude signals and relies on passband filters, time domain filtering, and amplitude threshold comparisons to distinguish the P-wave or R-wave from background electrical noise. The digital controller / timer circuit 83 controls the sensitivity setting of the atrial and ventricular sense amplifiers 55.

[0054] The sense amplifier is typically decoupled from the sense electrode during a blanking period before, during, and after delivery of a pacing pulse to any of the pacing electrodes of the pacing system to avoid saturation of the sense amplifier. The sense amplifier circuit 55 includes a blanking circuit for decoupling the selected lead conductor pairs and the IND_CAN electrode 20 from the inputs of the RA sense amplifier (and the LA sense amplifier, if provided), the RV sense amplifier, and the LV sense amplifier during ABP, PVABP, and VBP. The sense amplifier circuit 55 also includes a switching circuit for coupling the selected sensing electrode lead conductors and the IND_CAN electrode 20 to the RA sense amplifier (and the LA sense amplifier, if provided), the RV sense amplifier, and the LV sense amplifier. Again, the sense electrode selection and control circuit 53 selects the conductors and associated sensing electrode pairs to be coupled to the atrial and ventricular sense amplifiers within the output amplifier circuit 51 and the sense amplifier circuit 55 for completing RA, LA, RV, and LV sensing along the desired unipolar and bipolar sensing vectors.

[0055] A right atrial depolarization or P wave in the RA-sense signal sensed by the RA sense amplifier results in an RA-event signal transmitted to the digital controller / timer circuit 83. Similarly, a left atrial depolarization or P wave in the LA-sense signal sensed by the LA sense amplifier (if provided) results in an LA-event signal transmitted to the digital controller / timer circuit 83. A ventricular depolarization or R wave in the RV-sense signal sensed by the ventricular sense amplifier results in an RV-event signal transmitted to the digital controller / timer circuit 83. Similarly, a ventricular depolarization or R wave in the LV-sense signal sensed by the ventricular sense amplifier results in an LV-event signal transmitted to the digital controller / timer circuit 83. The RV-event signal, the LV-event signal, as well as the RA-event signal, the LA-sense signal may be refractory or non-refractory, and may be inadvertently triggered by an electrical noise signal or an abnormally conducted depolarization wave, rather than a true R-wave or P-wave.

[0056] The exemplary methods and / or devices described herein can track or monitor the effectiveness of pacing therapy by analyzing one or more features of a sensed morphology waveform corresponding to a pacing event for one or more monitored electrical vectors of a patient's heart. As used herein, a sensed morphology waveform can correspond to a pacing event occurring within a predetermined or selected time period or sensing window (e.g., 200 milliseconds) after delivery of a pacing stimulus. The sensed morphology waveform can be caused, for example, by delivery of a pacing stimulus and / or intrinsic conduction.

[0057] The present disclosure relates to methods and apparatus for delivering His bundle pacing to produce more standardized and physiological excitation of a patient's heart. The pacing device includes pacing leads extending from the pacing device, the pacing leads leading to specified locations in the atria, AV septum, and one or both ventricles of the heart. The distal ends of the pacing leads include electrodes for sensing cardiac signals and for delivering electrical pulses or pacing therapy. The pacing leads leading to the atria and ventricles are programmed to deliver electrical pulses on a demand mode basis if no natural electrical signals are measured within a predetermined time period.

[0058] Immediately after atrial activity is sensed, a pacing lead positioned along the AV septum delivers continuous electrical pulses to the His bundle. These electrical pulses then travel through the right and left bundle branches and reach the Purkinje fibers, causing the ventricles to depolarize and contract. By delivering such His bundle pacing to stimulate the natural conduction system, the ventricles contract in a more coordinated manner, thereby improving cardiac output and performance, compared to delivering ventricular pacing directly to one of the left and right ventricles, thereby improving cardiac output and performance. However, while His bundle pacing tends to result in more standardized contractions compared to delivering pacing directly within the ventricles, certain factors associated with His bundle pacing (such as an increased tendency for threshold changes, and an increased tendency for contact problems to occur) tend to make maintaining capture during His bundle pacing a more significant challenge. At the same time, current indications appear to suggest that in order to optimize the effectiveness of resynchronization therapy, it is desirable to deliver pacing therapy as close to 100% of the time as possible. Therefore, any percentage loss of delivered pacing (such as when pacing does not result in cardiac capture) can be considered less than optimal.

[0059] According to an implantable medical device of an example of the present disclosure, an atrial lead is positioned near the AV node / high septum region to deliver His bundle pacing therapy, and a second lead may be positioned in the right ventricle or in the left ventricle. The implantable medical device determines on a beat-by-beat basis whether the delivered His bundle pacing has captured the patient's heart. If the His bundle pacing therapy has not captured the patient's heart for the current cardiac cycle or heartbeat, the device delivers pacing therapy via other ventricular leads during the same cardiac cycle with a pre-specified delay from the delivered His bundle pacing, thereby resolving the loss of capture from the His bundle pacing during the same cardiac cycle and providing continuous pacing therapy to the patient. On the other hand, if the His bundle pacing captures the patient's heart, delivery of pacing therapy from the other ventricular leads is inhibited, thereby promoting His bundle pacing and more physiological excitation of the ventricles.

[0060] Figure 5is a flow chart of a method for delivering pacing therapy according to an example of the present disclosure. In one example, atrial lead 22 is positioned near the AV node / septum region for delivery of His bundle pacing via electrodes via tip electrode 50 and ring electrode 48, and ventricular lead 18 may be positioned in the right ventricle or ventricular lead 20 may be positioned in the left ventricle, or both ventricular lead 18 may be positioned in the right ventricle and ventricular lead 20 may be positioned in the left ventricle. Figure 5 As shown, during the delivery of pacing therapy according to an example of the present disclosure, near-field cardiac signals can be sensed via the tip electrode 50 and the ring electrode 48 of the atrial lead 22 (box 200). The processor 80 processes the sensed cardiac signals and determines the location of the P wave of the sensed cardiac signals (box 202). The processor 80 causes His bundle pacing to be delivered via the tip electrode 50 and the ring electrode 48 of the atrial lead 22 based on the determined location of the P wave (box 202). For example, as described below, the processor 80 can cause such His bundle pacing to be delivered with a predetermined time delay from the P wave. When delivering His bundle pacing (box 204), the processor 80 determines the amplitude of the signal sensed for the same cardiac cycle that occurs immediately after the blanking period associated with the delivered His bundle pacing (box 206) and determines whether the amplitude is less than an amplitude threshold (box 208), as described below.

[0061] If it is determined that the post-pacing blanking amplitude for the current cardiac cycle is less than the amplitude threshold (yes in box 208), it is determined that capture has occurred for the His bundle pacing therapy delivered for the current cardiac cycle (box 210), and the process is repeated for the next cardiac cycle (box 200). If it is determined that the post-pacing blanking amplitude for the current cardiac cycle is not less than the amplitude threshold (no in box 208), it is determined that capture has not occurred for the His bundle pacing therapy currently delivered (box 212). When capture does not occur as a result of the delivered His bundle pacing (box 212), the processor 80 causes ventricular pacing to be delivered in the same cardiac cycle via the bipolar electrodes 40, 42 positioned proximate to the distal end of the right ventricular lead 18 or the bipolar electrodes 44, 46 positioned proximate to the distal end of the left ventricular lead 20 (box 214).

[0062] In this manner, an implantable medical device or implantable medical device system may include an atrial lead positioned near the AV node / high septal region to deliver His bundle pacing therapy, and a second lead positioned in at least the right ventricle or the left ventricle. A processor 80 of the implantable medical device determines for a given cardiac cycle whether the delivered His bundle pacing captured the patient's heart for that cardiac cycle. If during a given single cardiac cycle, the processor 80 determines that the His bundle pacing therapy did not capture the heart, the processor 80 causes ventricular pacing to be delivered in the same cardiac cycle with a pre-specified delay from the His bundle pacing delivered during that cycle. If the processor 80 determines that the His bundle pacing captured the patient's heart, delivery of pacing therapy from the other ventricular leads is suppressed by the processor 80, and the process is repeated for delivery of His bundle pacing for the next cardiac cycle. The process is then repeated for the next cardiac cycle. Thus, the present disclosure reduces instances where His bundle pacing does not capture the heart by delivering ventricular pacing within the same cardiac cycle, rather than allowing loss of capture to occur and adjusting parameters to account for the loss of capture in a subsequent cardiac cycle, thereby resulting in more continuous resynchronization pacing therapy being delivered to the patient.

[0063] Fig. 6A -C is a graphical representation of the delivery of pacing therapy according to an example of the present disclosure. Fig. 6A As shown, during the delivery of pacing therapy, the processor 80 senses the cardiac signal 300 via the tip electrode 50 and the ring electrode 48 of the atrial lead 22 and determines the location of the P wave 302 of the sensed signal 300. Once the location of the P wave 302 is determined, the processor 80 delivers His bundle pacing via the tip electrode 50 and the ring electrode 48 of the atrial lead 22 positioned along the His bundle. The His bundle pacing is delivered at a predetermined time period or AV delay or interval 304 after the P wave 302. If the delivered His bundle pacing results in capture of the heart, the delivered His bundle pacing is followed by an induced response 306 that occurs within a predetermined time period 308 after the delivery of the His bundle pacing.

[0064] like Fig. 6A and Figure 6B As shown, during delivery of His bundle pacing via the tip electrode 50 and the ring electrode 48 of the atrial lead 22, when the delivered His bundle pacing results in capture of the patient's heart (i.e., an induced response 306 occurs), a negative amplitude induced response 310 of the signal 300 relative to a baseline 312 of the signal 300 occurs after the delivered His bundle pacing. Figure 6C As shown, when the delivered His bundle pacing does not result in capture of the patient's heart, such negative amplitude induced response 310 of signal 300 relative to baseline 312 of signal 300 does not occur following the delivered His bundle pacing.

[0065] The time period 314 between the P wave 302 and the evoked response 306 of His bundle pacing is patient specific and may depend on a programmed paced AV interval, which is typically programmed to a value between 60 ms and 150 ms in the absence of intrinsic ventricular conduction (e.g., due to AV block), or may be set to a percentage of the patient's intrinsic AV interval (i.e., the timing between an atrial event and the patient's intrinsic conduction) in the presence of a patient's intrinsic AV conduction. Example AV intervals may be programmed, for example, to be at least 45 ms, at least 50 ms, at least 55 ms, at least 60 ms, at least 65 ms prior to an intrinsic ventricular event in the presence of a patient's intrinsic AV conduction. Thus, in an example where the intrinsic AV interval for a patient is set to 200 ms, the processor 80 may determine the time period or delay 304 after the P wave 302 for delivering His bundle pacing as a percentage of the intrinsic AV interval (such as, for example, 40%), such that the His bundle pacing is delivered at least a certain time period (such as, for example, at least 60 ms) before the intrinsic ventricular event. Thus, in one example, the processor 80 may deliver His bundle pacing 80 ms (40% of 200 ms = 80 ms) after the determined P wave 302, resulting in an AV delay 304 of 80 ms.

[0066] like Figure 6B As shown, after delivering the His bundle pacing, the processor 80 waits for a predetermined time period 316 after the delivered His bundle pacing, which time period 316 is referred to as a blanking period. The time period 316 associated with the blanking period is generally programmable and can be set to 20 ms in one example. Once the blanking period 316 expires, the processor 80 determines whether the amplitude 310 extending from the baseline 312 of the sensed signal 300 is more negative than a predetermined amplitude threshold 320 (such as, for example, -5 millivolts) during a time period 322 extending after the end 318 of the blanking period 316. Exemplary values ​​for the time period 322 for determining whether the amplitude is more negative than the amplitude threshold can be, for example, between 5 ms and 20 ms.

[0067] like Figure 6B As shown in the example of , when the amplitude 310 of the sensed signal 300 relative to the baseline 312 within the time period 322 is more negative than the predetermined amplitude threshold 320, the processor 80 determines that the delivered His bundle pacing resulted in cardiac capture and repeats the process for delivering His bundle pacing during the next cardiac cycle. Figure 6CAs shown in the example of , when the processor 80 determines that the amplitude 310 of the sensed signal 300 relative to the baseline 312 within the time period 322 after the blanking period 316 is not more negative than the predetermined amplitude threshold 320, the processor 80 determines that the delivered His bundle pacing will likely not result in capturing the heart. Therefore, the processor 80 delivers a ventricular pacing signal via one of the left ventricular lead 20 and the right ventricular lead 18 within a time period 324 (which may be between 5 ms and 10 ms) after the expiration of the time period 322 or the end of the time period 322 for the same cardiac cycle. Therefore, after delivering the His bundle pacing, if the delivered His bundle pacing is likely to fail to capture the patient's heart, a ventricular pacing event and a resulting pacing induced response 326 are generated in the same cardiac cycle, resulting in the delivery of continuous pacing therapy. A second pacing therapy (i.e., ventricular pacing therapy) can be delivered from one or more pacing leads positioned in a more standard anatomical location within the ventricle, with an output well above the pacing capture threshold for that particular lead (such as, for example, 1 volt above the pacing capture threshold for that lead) to maximize the likelihood of effective capture for that cardiac cycle.

[0068] In this manner, a method for delivering pacing therapy according to an example of the present disclosure may include the processor 80 sensing the cardiac signal 300 via the tip electrode 50 and the ring electrode 48 of the atrial lead 22 and determining the occurrence of the P wave 302 of the current cardiac cycle in response to the sensed cardiac signal. The processor 80: in response to the determined occurrence of the P wave 302, causes a first pacing therapy to be delivered via the tip electrode 50 and the ring electrode 48 of the atrial lead 22 during the current cardiac cycle; compares the amplitude of the cardiac signal after the delivered first pacing therapy in the current cardiac cycle with a predetermined amplitude threshold; and in response to the comparison, delivers a second pacing therapy via the bipolar electrodes 44, 46 positioned proximal to the distal end of the left ventricular lead 20 in the same or current cardiac cycle and after the delivered first pacing therapy.

[0069] For example, processor 80 may compare the amplitude of cardiac signal 300 to an amplitude threshold during a first time period 322 following a blanking period 316 associated with a delivered first pacing therapy, and if the amplitude of the cardiac signal is not more negative than the amplitude threshold 320, deliver a second pacing therapy during a second time interval 324 (which may be, for example, between 5 ms and 10 ms) following the first time period 322, wherein the sum of the AV interval 304 for delivering His bundle pacing, the blanking period 316 following the delivered His bundle pacing, the first time period 322, and the second time period 324 is less than the patient's intrinsic AV interval, or if it is determined that intrinsic AV conduction is not present (e.g., due to atrioventricular block), the sum of the AV interval 304 for delivering His bundle pacing, the blanking period 316 following the delivered His bundle pacing, the first time period 322, and the second time period 324 is less than the first AV interval plus an additional time period (such as, for example, 40 ms).

[0070] Thus, the present disclosure reduces instances of loss of capture during His bundle pacing by delivering ventricular pacing within the cardiac cycle when the His bundle fails to capture for the same cardiac cycle, rather than allowing loss of capture to occur and adjusting parameters to account for the loss of capture in a subsequent cardiac cycle, thereby resulting in more continuous resynchronization pacing therapy being delivered to the patient.

[0071] The techniques described in the present disclosure (including those attributable to IMD 16, programmer 24, or constituent components) may be implemented, at least in part, in hardware, software, firmware, or any combination thereof. For example, aspects of these techniques may be implemented within one or more processors, including one or more microprocessors, DSPs, ASICs, FPGAs, or any other equivalent integrated or discrete logic circuitry, and any combination of such components embodied in a programmer (such as a physician programmer or patient programmer, stimulator, image processing device, or other device). The terms "module," "processor," or "processing circuitry" may generally refer to any of the foregoing logic circuitry, either independently or in combination with other logic circuitry, or any other equivalent circuitry.

[0072] Such hardware, software and / or firmware may be implemented in the same device or in separate devices to support the various operations and functions described in the present disclosure. In addition, any of the described units, modules or components may be implemented together, or may be implemented separately as discrete but interoperable logical devices. Depicting different features as modules or units is intended to emphasize different functional aspects, and does not necessarily imply that such modules or units must be implemented by separate hardware or software components. Instead, the functions associated with one or more modules or units may be performed by separate hardware or software components, or may be integrated in common or separate hardware or software components.

[0073] When implemented in software, the functionality attributed to the systems, devices, and techniques described in this disclosure may be embodied as instructions on a computer-readable medium (such as RAM, ROM, NVRAM, EEPROM, flash memory, magnetic data storage media, optical data storage media, etc.). These instructions may be executed by one or more processors to support one or more aspects of the functionality described in this disclosure.

[0074] The present disclosure has been provided with reference to illustrative embodiments, and the disclosure is not intended to be interpreted in a limiting sense. As previously stated, those skilled in the art will recognize that various other illustrative applications can use the techniques described herein to take advantage of the beneficial properties of the apparatus and methods described herein. Various modifications of the illustrative embodiments and additional embodiments of the present disclosure will be apparent when referring to this specification.

[0075] The illustrated embodiment

[0076] Example 1: A method for delivering cardiac pacing therapy to a patient, comprising:

[0077] sensing a cardiac signal of the patient;

[0078] In response to the sensed cardiac signal, determining the occurrence of one of an intrinsic atrial depolarization event and a paced atrial depolarization event of a current cardiac cycle;

[0079] delivering a first pacing therapy during the current cardiac cycle in response to the determined occurrence of the depolarization event;

[0080] comparing an amplitude of the cardiac signal after the delivered first pacing therapy within the current cardiac cycle to a predetermined amplitude threshold; and

[0081] In response to the comparison, a determination is made whether to deliver a second pacing therapy during the current cardiac cycle and subsequent to the delivered first pacing therapy.

[0082] Example 2: The method of Example 1, wherein the first pacing therapy comprises His bundle pacing and the second pacing therapy comprises ventricular pacing therapy.

[0083] Example 3: The method of any of Examples 1-2, further comprising determining whether intrinsic atrioventricular conduction is absent, wherein the first pacing therapy comprises His bundle pacing and the second pacing therapy comprises ventricular pacing therapy, wherein in response to the absence of intrinsic atrioventricular conduction, His bundle pacing with an AV delay of between approximately 60 ms and 150 ms is delivered.

[0084] Embodiment 4: The method of any one of embodiments 1-3 further comprises:

[0085] responsive to the amplitude being not more negative than the predetermined amplitude threshold, determining to deliver the second pacing therapy; and

[0086] In response to the amplitude being more negative than the predetermined amplitude threshold, a determination is made not to deliver the second pacing therapy.

[0087] Embodiment 5: The method of any one of embodiments 1-4, wherein the predetermined amplitude threshold is approximately -5 millivolts.

[0088] Embodiment 6: The method as described in any one of Embodiments 1-5, further comprising:

[0089] comparing the amplitude of the cardiac signal to the amplitude threshold during a first time period following a blanking period associated with a delivered first pacing therapy; and

[0090] In response to the amplitude of the cardiac signal being not more negative than the amplitude threshold, determining to deliver the second pacing therapy within a second time period after the first time period, wherein a sum of an AV interval, the blanking period, the first time period, and the second time period for delivering the first pacing therapy relative to the determined atrial depolarization event is less than an intrinsic AV interval associated with the patient.

[0091] Example 7: The method described in Example 6 further includes determining whether there is no intrinsic atrioventricular conduction, wherein the first pacing therapy includes His bundle pacing and the second pacing therapy includes ventricular pacing therapy, wherein in response to the absence of intrinsic atrioventricular conduction, the sum of the AV interval, the blanking period, the first time period and the second time period for delivering the first pacing therapy relative to the determined atrial depolarization event is less than the sum of the AV interval and 40ms for delivering the first pacing therapy relative to the determined atrial depolarization event.

[0092] Embodiment 8: The method of embodiment 7, wherein the first time period is between approximately 5 milliseconds and 20 milliseconds and the second time period is between approximately 5 milliseconds and 10 milliseconds.

[0093] Embodiment 9: The method of any one of Embodiments 1-6, further comprising:

[0094] comparing the amplitude of the cardiac signal to the amplitude threshold during a first time period following a blanking period associated with a delivered first pacing therapy;

[0095] responsive to the amplitude of the cardiac signal being not more negative than the amplitude threshold, determining to deliver the second pacing therapy within a second time period after the first time period; and

[0096] In response to the amplitude being more negative than the predetermined amplitude threshold, it is determined not to deliver the second pacing therapy, wherein the first pacing therapy comprises His bundle pacing and the second pacing therapy comprises ventricular pacing therapy.

[0097] Embodiment 10: The method of Embodiment 9, wherein the predetermined amplitude threshold is approximately -5 millivolts.

[0098] Example 11: The method of any of Examples 9-10, wherein the sum of the AV interval for delivering the first pacing therapy relative to the determined atrial depolarization event, the blanking period, the first time period, and the second time period is less than an intrinsic AV interval associated with the patient.

[0099] Embodiment 12. Embodiment 12: The method of embodiment 11, wherein the first time period is between approximately 5 milliseconds and 20 milliseconds and the second time period is between approximately 5 milliseconds and 10 milliseconds.

[0100] Embodiment 13: A system for delivering cardiac pacing therapy to a patient, comprising:

[0101] a first cardiac lead having a distal end;

[0102] at least one electrode positioned at the distal end of the first cardiac lead for sensing cardiac signals of the patient and delivering a first cardiac pacing therapy;

[0103] a second cardiac lead having a distal end;

[0104] at least one electrode positioned at the distal end of the second cardiac lead for delivering a second cardiac pacing therapy; and

[0105] A processor configured to: determine, in response to a sensed cardiac signal, the occurrence of one of an intrinsic atrial depolarization event and a paced atrial depolarization event of a current cardiac cycle; deliver a first pacing therapy via at least one electrode of the first cardiac lead during the current cardiac cycle in response to the determined occurrence of the depolarization event; compare the amplitude of the cardiac signal after the delivered first pacing therapy within the current cardiac cycle with a predetermined amplitude threshold; and determine, in response to the comparison, whether to deliver a second pacing therapy via at least one electrode of the second cardiac lead within the current cardiac cycle and after the delivered first pacing therapy.

[0106] Example 14: The system of Example 13, wherein the first pacing therapy comprises His bundle pacing and the second pacing therapy comprises ventricular pacing therapy.

[0107] Example 15: The system of any of Examples 13-14, wherein the processor is configured to determine whether intrinsic atrioventricular conduction is absent, wherein the first pacing therapy comprises His bundle pacing and the second pacing therapy comprises ventricular pacing therapy, and wherein in response to the absence of intrinsic atrioventricular conduction, the His bundle pacing is delivered with an AV delay of between approximately 60 ms and 150 ms.

[0108] Example 16: The system of any of Examples 13-15, wherein the processor is configured to: determine to deliver the second pacing therapy in response to the amplitude being not more negative than the predetermined amplitude threshold, and determine not to deliver the second pacing therapy in response to the amplitude being more negative than the predetermined amplitude threshold.

[0109] Embodiment 17: The system of Embodiment 16, wherein the predetermined amplitude threshold is approximately -5 millivolts.

[0110] Example 18: The system of any of Examples 13-14, wherein the processor is configured to: compare the amplitude of the cardiac signal to the amplitude threshold during a first time period after a blanking period associated with a delivered first pacing therapy, and in response to the amplitude of the cardiac signal being not more negative than the amplitude threshold, determine to deliver the second pacing therapy during a second time period after the first time period, wherein the sum of the AV interval for delivering the first pacing therapy relative to the determined atrial depolarization event, the blanking period, the first time period, and the second time period is less than an intrinsic AV interval associated with the patient.

[0111] Example 19: The system of Example 18, wherein the processor is configured to: determine whether intrinsic atrioventricular conduction is absent, wherein the first pacing therapy includes His bundle pacing and the second pacing therapy includes ventricular pacing therapy, and wherein in response to the absence of intrinsic atrioventricular conduction, the sum of the AV interval, the blanking period, the first time period, and the second time period for delivering the first pacing therapy relative to the determined atrial depolarization event is less than the sum of the AV interval and 40 ms for delivering the first pacing therapy relative to the determined atrial depolarization event.

[0112] Embodiment 20: The system of any of Embodiments 18-19, wherein the first time period is between approximately 5 milliseconds and 20 milliseconds and the second time period is between approximately 5 milliseconds and 10 milliseconds.

[0113] Example 21: A system as described in any of Examples 18-20, wherein the processor is configured to: compare the amplitude of the cardiac signal to the amplitude threshold during a first time period after a blanking period associated with a delivered first pacing therapy; in response to the amplitude of the cardiac signal being not more negative than the amplitude threshold, determine to deliver the second pacing therapy within a second time period after the first time period; and in response to the amplitude being more negative than the predetermined amplitude threshold, determine not to deliver the second pacing therapy, wherein the first pacing therapy includes His bundle pacing and the second pacing therapy includes ventricular pacing therapy.

[0114] Embodiment 22: The system of Embodiment 21, wherein the predetermined amplitude threshold is approximately -5 millivolts.

[0115] Example 23: The system of any of Examples 20-22, wherein the sum of the AV interval for delivering the first pacing therapy relative to the determined atrial depolarization event, the blanking period, the first time period, and the second time period is less than an intrinsic AV interval associated with the patient.

[0116] Embodiment 24: The system of any of Embodiments 20-23, wherein the first time period is between approximately 5 milliseconds and 20 milliseconds and the second time period is between approximately 5 milliseconds and 10 milliseconds.

[0117] Embodiment 25: A non-transitory computer readable medium storing instructions that cause a cardiac medical device to perform a method comprising:

[0118] sensing a cardiac signal of the patient;

[0119] In response to the sensed cardiac signal, determining the occurrence of one of an intrinsic atrial depolarization event and a paced atrial depolarization event of a current cardiac cycle;

[0120] delivering a first pacing therapy during the current cardiac cycle in response to the determined occurrence of the depolarization event;

[0121] comparing an amplitude of the cardiac signal after the delivered first pacing therapy within the current cardiac cycle to a predetermined amplitude threshold; and

[0122] In response to the comparison, a determination is made whether to deliver a second pacing therapy during the current cardiac cycle and subsequent to the delivered first pacing therapy.

Claims

1. A system for delivering cardiac pacing therapy to a patient, comprising: a first cardiac lead having a distal end; at least one electrode positioned at the distal end of the first cardiac lead for sensing cardiac signals of the patient and delivering a first cardiac pacing therapy; a second cardiac lead having a distal end; at least one electrode positioned at the distal end of the second cardiac lead for delivering a second cardiac pacing therapy; as well as a processor configured to: determine, in response to a sensed cardiac signal, an occurrence of one of an intrinsic atrial depolarization event and a paced atrial depolarization event for a current cardiac cycle; deliver a first pacing therapy via the at least one electrode of the first cardiac lead during the current cardiac cycle in response to the determined occurrence of the depolarization event; compare an amplitude of the cardiac signal within the current cardiac cycle after the delivered first pacing therapy to a predetermined amplitude threshold; and, responsive to the comparing, determining whether to deliver a second pacing therapy via the at least one electrode of the second cardiac lead during the current cardiac cycle and subsequent to the delivered first pacing therapy.

2. The system according to claim 1, characterized in that The first pacing therapy comprises His bundle pacing and the second pacing therapy comprises ventricular pacing therapy.

3. The system according to any one of claims 1 to 2, characterized in that: The processor is configured to determine whether intrinsic atrioventricular conduction is absent, wherein the first pacing therapy comprises His bundle pacing and the second pacing therapy comprises ventricular pacing therapy, and wherein in response to the absence of intrinsic atrioventricular conduction, the His bundle pacing is delivered with an atrioventricular delay of between 60 ms and 150 ms.

4. The system according to any one of claims 1 to 3, characterized in that: The processor is configured to determine to deliver the second pacing therapy in response to the amplitude being not more negative than the predetermined amplitude threshold, and to determine not to deliver the second pacing therapy in response to the amplitude being more negative than the predetermined amplitude threshold.

5. The system as claimed in claim 4, characterized in that The predetermined amplitude threshold is -5 mV.

6. The system according to any one of claims 1 to 5, characterized in that: The processor is configured to compare the amplitude of the cardiac signal to the amplitude threshold during a first time period following a blanking period associated with a delivered first pacing therapy, and in response to the amplitude of the cardiac signal being not more negative than the amplitude threshold, determine to deliver the second pacing therapy during a second time period following the first time period, wherein the sum of the atrioventricular interval for delivering the first pacing therapy relative to a determined atrial depolarization event, the blanking period, the first time period, and the second time period is less than an intrinsic atrioventricular interval associated with the patient.

7. The system according to claim 6, characterized in that The processor is configured to determine whether intrinsic atrioventricular conduction is absent, wherein the first pacing therapy includes His bundle pacing and the second pacing therapy includes ventricular pacing therapy, and wherein in response to the absence of intrinsic atrioventricular conduction, the sum of the atrioventricular interval, the blanking period, the first time period, and the second time period for delivering the first pacing therapy relative to a determined atrial depolarization event is less than the sum of the atrioventricular interval and 40 ms for delivering the first pacing therapy relative to the determined atrial depolarization event.

8. The system according to any one of claims 6 to 7, characterized in that: The first time period is between 5 milliseconds and 20 milliseconds and the second time period is between 5 milliseconds and 10 milliseconds.

9. The system according to any one of claims 1 to 8, characterized in that: The processor is configured to: compare the amplitude of the cardiac signal to the amplitude threshold during a first time period after a blanking period associated with a delivered first pacing therapy; determine to deliver the second pacing therapy within a second time period after the first time period in response to the amplitude of the cardiac signal being not more negative than the amplitude threshold; and determine not to deliver the second pacing therapy in response to the amplitude being more negative than the predetermined amplitude threshold, wherein the first pacing therapy includes His bundle pacing and the second pacing therapy includes ventricular pacing therapy.

10. The system as claimed in claim 9, characterized in that A sum of an atrioventricular interval at which the first pacing therapy is delivered relative to the determined atrial depolarization event, the blanking period, the first time period, and the second time period is less than an intrinsic atrioventricular interval associated with the patient.

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