System for identifying and adjusting ineffective cardiac resynchronization therapy

Abstract

An implantable medical device system and method for delivering cardiac resynchronization therapy (CRT) pacing includes: in response to delivered CRT pacing, determining that capture associated with the delivered CRT pacing is ineffective. Determining a cause of the ineffective capture, and if the determined cause of the ineffective capture is loss of capture, adjusting a safety margin; and if the determined cause of the ineffective capture is delayed left ventricular (LV) depolarization, adjusting LV pre-excitation. Monitoring changes in effective cardiac resynchronization therapy can be used to confirm that adjustments to the CRT pacing are effective in resolving the ineffective capture.

Description

[0001] The disclosure herein relates to systems and methods for the delivery of cardiac pacing therapy, and more particularly, to the delivery of cardiac resynchronization therapy. Background Art

[0002] During normal sinus rhythm (NSR), the heartbeat is regulated by electrical signals generated by the sinoatrial (SA) node located in the wall of the right atrium. Each atrial depolarization signal generated by the SA node spreads across the atria (causing depolarization and contraction of the atria) and reaches the atrioventricular (AV) node. The AV node responds by propagating the ventricular depolarization signal through the bundle of His of the ventricular septum and then to the bundle branches and Purkinje muscle fibers of the right and left ventricles.

[0003] Cardiac resynchronization pacing devices operate by delivering pacing stimuli 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 stimulus 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. For various reasons, a cardiac pacing system may not achieve effective capture of the ventricles. For example, the pacing leads and / or electrodes may not be placed in the optimal position. Sensed atrioventricular delay (SAV), paced atrioventricular delay (PAV), and right ventricular pre-excitation may also affect whether the ventricles are effectively captured. In addition, after the medical device has been implanted, the pacing leads may migrate or shift. Summary of the invention

[0004] The exemplary systems, methods, and interfaces described herein may be configured as medical device systems and methods for delivering cardiac resynchronization therapy (CRT) pacing to a patient. The delivery of CRT pacing is monitored to determine whether the CRT pacing has effectively captured the patient's heart. During the event of loss of effective capture, the cause of the loss of capture is determined, and if the user has granted the device permission to make automatic changes (i.e., automatic changes have been enabled), adjustments to the CRT pacing are automatically made. For example, when the cause of ineffective capture is determined to be loss of capture, the safety margin associated with the delivered pacing can be increased, and if increasing the safety margin does not resolve the ineffective capture, a determination can be made as to whether there is a very low effective CRT percentage. If it is determined that there is a low effective CRT percentage, the delivery of pacing can be switched to a minimum ventricular pacing mode, and an alarm can be generated. If the left ventricular capture management feature is not enabled, no changes are made to the pacing, but an alarm or observation of the event is generated.

[0005] When the cause of ineffective capture is determined to be delayed left ventricular depolarization (i.e., due to the lead being positioned within scar tissue or within latent or inactive tissue), left ventricular pre-excitation can be increased. If the increase in LV pre-excitation does not resolve the ineffective capture, the LV pre-excitation is adjusted back to the baseline LV pre-excitation, and if the vector adjustment feature is enabled, the vector used to deliver pacing is adjusted. If the adjustment of the vector does not resolve the ineffective capture, a determination can be made as to whether a very low effective CRT percentage exists. If a low effective CRT percentage is determined to exist, the delivery of pacing can be switched to a minimum ventricular pacing mode, and an alarm can be generated.

[0006] In one example, exemplary systems and methods may include an implantable medical device system for delivering cardiac resynchronization therapy (CRT) pacing, the implantable medical device system comprising: an implantable medical device housing; at least one lead having a lead body and capable of being electrically coupled to the housing; a plurality of electrodes positioned along one or both of the device housing and the lead body of the at least one lead to sense cardiac signals of the patient and deliver CRT pacing; and a processor positioned within the housing and configured to: determine, in response to the delivered CRT pacing, that capture associated with the delivered CRT pacing is ineffective, determine a cause of the ineffective capture, and adjust a safety margin in response to the determined cause of the ineffective capture being loss of capture, and adjust LV pre-excitation in response to the determined cause of the ineffective capture being delayed left ventricular (LV) depolarization.

[0007] In at least one example, a method of delivering cardiac resynchronization therapy (CRT) pacing includes: determining, in response to the delivered CRT pacing, that capture associated with the delivered CRT pacing is ineffective; determining a cause of the capture ineffectiveness; and adjusting a safety margin in response to the determined cause of the capture ineffectiveness being loss of capture, and adjusting LV pre-excitation in response to the determined cause of the capture ineffectiveness being delayed left ventricular (LV) depolarization.

[0008] In another example, a non-transitory computer-readable medium stores instructions that cause an implantable medical device to perform a method comprising: determining, in response to delivered CRT pacing, that capture associated with the delivered CRT pacing is ineffective; determining a cause of the capture ineffectiveness; and adjusting a safety margin in response to the determined cause of the capture ineffectiveness being loss of capture and adjusting LV pre-excitation in response to the determined cause of the capture ineffectiveness being delayed left ventricular (LV) depolarization.

[0009] The above summary of the invention is not intended to describe every embodiment or every implementation of the present disclosure. A more complete understanding will become apparent and understandable by referring to the following detailed description obtained in conjunction with the accompanying drawings and the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is a conceptual diagram illustrating an exemplary therapy system including an exemplary implantable medical device (IMD) that may be used to deliver pacing therapy to a patient according to an embodiment of the present disclosure.

[0011] Figure 2 yes Figure 1 A more detailed conceptual diagram of an exemplary IMD.

[0012] Figure 3A is an exemplary IMD (e.g. Figure 1-Figure 2 Block diagram of IMD).

[0013] Figure 3B is Figure 2 Yet another block diagram of an embodiment of an IMD (e.g., IPG) circuitry and associated leads employed in a system of providing three sensing channels and corresponding pacing channels that selectively function in a ventricular pacing mode to provide ventricular capture verification.

[0014] Figure 4 is a flow chart of an exemplary method for determining whether electrical stimulation effectively captured a ventricle.

[0015] Figure 5 Graphically depicts support Figure 4 The flow chart depicts the data of the effective capture test.

[0016] Figure 6 Graphically depicts the Figure 4 Flowchart of the data used where no effective capture occurred.

[0017] Figures 7A-7C Graphically depicts support Figure 4 The flow chart depicts the data of the effective capture test.

[0018] Figure 8 is a flow chart of another exemplary method for automatically adjusting settings on an implantable medical device to more effectively capture a ventricle. Fig. 9 is a flow chart of an exemplary method of delivering cardiac resynchronization therapy in an implantable medical device according to examples of the present disclosure. DETAILED DESCRIPTION

[0019] In the following detailed description of the illustrative embodiments, reference is made to the accompanying drawings, which form a part of the embodiments and in which are shown by way of illustration specific embodiments that can be practiced. It should be understood that other embodiments can be used and structural changes can be made without departing from (e.g., still falling within) the scope of the present disclosure presented herein.

[0020] Will refer to Figure 1-Figure 8 to describe exemplary systems and methods. 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 possible embodiments of such methods and systems using the combination 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. Still further, it will be appreciated that the timing of the processes herein and the sizes and shapes of the various elements may be modified and still fall within the scope of the present disclosure, but certain timings, one or more shapes and / or sizes, or types of elements may be advantageous relative to other timings, shapes and / or sizes, and types of elements.

[0021] Various exemplary systems, methods, and interfaces described herein may be configured as medical device systems and methods for delivering cardiac resynchronization therapy (CRT) pacing to a patient. The delivery of CRT pacing is monitored to determine whether the CRT pacing has effectively captured the patient's heart. During the event of a loss of effective capture, the cause of the loss of capture is determined, and if the capture management feature is enabled, adjustments to the CRT pacing are automatically made. For example, when the cause of ineffective capture is determined to be loss of capture, the pacing output (amplitude, pulse width, or both) may be increased. In another example, the safety margin associated with the delivered pacing may be increased. If increasing the pacing output or increasing the safety margin does not resolve the ineffective capture, a determination may be made as to whether there is a very low effective CRT percentage. If it is determined that there is a low effective CRT percentage, the delivery of the pacing may be switched to a minimum ventricular pacing mode, and an alarm may be generated. If the left ventricular capture management feature is not enabled, no changes are made to the pacing, but an alarm or observation of the event is generated.

[0022] When the cause of ineffective capture is determined to be delayed left ventricular depolarization (i.e., due to the lead being positioned within scar tissue or within latent or inactive tissue), left ventricular pre-excitation can be increased. If the increase in LV pre-excitation does not resolve the ineffective capture, the LV pre-excitation is adjusted back to the baseline LV pre-excitation, and if the vector adjustment feature is enabled, the vector used to deliver pacing is adjusted. If the adjustment to the vector does not resolve the ineffective capture, a determination can be made as to whether a very low effective CRT percentage exists. If a low effective CRT percentage is determined to exist, the delivery of pacing can be switched to a minimum ventricular pacing mode, and an alarm can be generated.

[0023] Figure 1 is a conceptual diagram illustrating an exemplary therapy system 10 that may be used to deliver pacing therapy to a patient 14. Patient 14 may be, but is not necessarily, a human. Therapy 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.

[0024] 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, 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 into 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 into the coronary sinus 30 to a region 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 into the right atrium 26 of the heart 12.

[0025] 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.

[0026] 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.

[0027] Figure 2 is shown in more detail Figure 1 1 and 10. 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.

[0028] Each of leads 18, 20, 22 includes an elongated insulated lead body that may carry a plurality of conductors (e.g., concentrically coiled conductors, straight conductors, etc.) separated from one another by a separator (e.g., a tubular insulating sheath). In the example shown, bipolar electrodes 40, 42 are positioned near 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.

[0029] 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.

[0030] 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 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, 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 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.

[0031] As reference Figure 3A-3B As described in further detail, housing 60 may enclose a therapy delivery module that 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 combination 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 combination with housing electrode 58 to form an RV elongate, coil, or defibrillation electrode to housing electrode vector).

[0032] Figure 1-Figure 2 The configuration of the exemplary treatment system 10 shown in is only one example. In other examples, instead of Figure 1 The transvenous leads 18, 20, 22 shown or other than Figure 1 In addition to the transvenous leads 18, 20, 22 shown, the treatment system may include epicardial leads and / or patch electrodes. Further, in one or more embodiments, the IMD 16 need not be implanted in the patient 14. For example, the IMD 16 can deliver defibrillation shocks and other treatments to the heart 12 via percutaneous leads that extend through the skin of the patient 14 to various locations inside or outside the heart 12. In one or more embodiments, the system 10 may employ wireless pacing (e.g., using energy transmission to a pacing component(s) within the heart via ultrasound, inductive coupling, RF, etc.) and sensing cardiac actuation using electrodes on the can / housing and / or on subcutaneous leads.

[0033] In other examples of therapy systems that provide electrical stimulation therapy to heart 12, such therapy systems may include any suitable number of leads coupled to IMD 16, and each of the leads may extend to any location within or near heart 12. For example, other examples of therapy systems may include, for example, Figure 1-Figure 2Still further, other therapy systems may include a single lead extending from IMD 16 into right atrium 26 or right ventricle 28, or two leads extending into a respective one of right atrium 26 and right ventricle 28.

[0034] Figure 3A is a functional block diagram of one exemplary configuration of IMD 16. As shown, IMD 16 may include a control module 81, a therapy delivery module 84 (eg, which may include a stimulation generator), a sensing module 86, and a power source 90.

[0035] 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 and 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. Memory 82 includes computer instructions related to capture management. An exemplary capture management module (such as left ventricular capture management (LVCM)) is briefly described in U.S. Pat. No. 7,684,863, which is incorporated herein by reference. With respect to the delivery of pacing stimulation, capture management algorithms generally focus on adequate energy delivery of pacing stimulation.

[0036] 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.

[0037] 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 selected one or more 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 electrode polarity specified by selected one or more 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 .

[0038] 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).

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] If the IMD 16 is configured to generate and deliver pacing pulses to the heart 12, the 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 the processor 80 (such as a microprocessor), and / or a software module executed by a component of the processor 80 (which may be a microprocessor or an 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 disabled 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.

[0044] 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.

[0045] 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. Control 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.

[0046] 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.

[0047] 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 transmit a warning or alarm if the pacing therapy becomes ineffective or less effective (e.g., does not have a predetermined level of effectiveness).

[0048] 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.

[0049] The pacing (e.g., LV and / or BV pacing) rate or percentage (which is typically the number of paced beats divided by the total number of beats, often expressed as a percentage of the total number of beats) can be a useful metric for assessing the effectiveness of CRT, but in many cases it can be misleading because a high pacing rate or percentage may not necessarily mean that the CRT is effective if, for example, ventricular pacing fails to properly change the pattern of electrical excitation. Automated beat-by-beat analysis of evoked responses (e.g., paced QRS complexes) in the monitored EGM signal can be used to determine whether the paced beats were effectively paced, thereby providing a higher resolution for the pacing rate. For example, beats that were paced but determined to be ineffectively paced (e.g., depending on the degree of fusion between intrinsic excitation and paced excitation, etc.) can be excluded from the pacing rate, thereby providing a more accurate measure of pacing efficacy and / or efficiency, which can be referred to as a pacing effectiveness rate.

[0050] The feature-based classification can enable beat-by-beat rhythm classification in devices (e.g., IMD 16) that employ cardiac pacing (e.g., left ventricular fusion pacing, biventricular pacing, etc.) and can add value to the device by providing useful diagnostic indicators to physicians. The computational cost involved in such feature-based beat-by-beat classification can be minimal and can be used in devices (such as those described herein). Figure 1-3B For example, the exemplary methods described herein may combine algebraic operations and comparisons and / or may require a single normalization per beat, compared to the multiple intensive mathematical operations and normalizations typically required for detailed template matching algorithms.

[0051] Figure 3B is yet another embodiment of a functional block diagram of IMD 16 . Figure 3B The bipolar RA lead 22, bipolar RV lead 18, and bipolar LV CS lead 20 are depicted without the LA CS pace / sense electrodes 28 and 30 coupled to the IPG circuit 31 having programmable modes and parameters of a biventricular DDD / R type 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 the digital controller / timer circuit 83, the output amplifier circuit 51, the sense amplifier circuit 55, the RF telemetry transceiver 41, the activity sensor circuit 35, and a number of other circuits and components described below.

[0052] 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.

[0053] If the IPG is programmed for rate response mode, the signals output by one or more physiological sensors are used as a rate control parameter (RCP) to derive the physiological escape interval. 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 rate 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.

[0054] 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).

[0055] 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 typically operated in a reduced power consumption mode and is interrupt driven. The microprocessor 80 is awakened in response to defined interrupt events, which may include an A-trigger (TIRG) signal, an RV-trigger signal, a LV-trigger 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. In addition, 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.

[0056] 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.

[0057] 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.

[0058] 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).

[0059] The post-event timer 374 counts down the post-ventricular time period after an RV-event or LV-event or RV-trigger or the 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), but 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 which may follow an 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, may begin at the end of V-pacing which may follow a 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 the RCP(s) and / or as a function of the intrinsic atrial rate.

[0060] 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 corresponds to 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), the timeout of the A-RVp delay and the timeout of the A-LVp delay being 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).

[0061] 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 LA pacing pulse generator, if provided), RV pacing pulse generator, and 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.

[0062] The sense amplifier circuit 55 includes sense amplifiers corresponding to any of those currently employed in contemporary cardiac pacemakers for atrial and ventricular pacing and sensing. As described in the above-referenced, commonly assigned '324 patent, 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 amplifiers use high gain to amplify low amplitude signals and rely 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.

[0063] The sense amplifier is typically decoupled from the sense electrode during blanking periods 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 selected pairs of lead conductors and IND_tank electrodes 20 from the inputs of the RA sense amplifier (and LA sense amplifier, if provided), RV sense amplifier, and LV sense amplifier during ABP, PVABP, and VBP. The sense amplifier circuit 55 also includes a switching circuit for coupling selected sensing electrode lead conductors and IND_tank electrodes 20 to the RA sense amplifier (and LA sense amplifier, if provided), RV sense amplifier, and 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 accomplishing RA, LA, RV, and LV sensing along the desired unipolar and bipolar sensing vectors.

[0064] A right atrial depolarization or P wave in the RA-sense signal sensed by the RA sense amplifier results in an RA-event signal that is 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 that is 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 that is 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 that is 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.

[0065] 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 morphological waveform corresponding to a pacing event for one or more monitored electrical vectors of a patient's heart. As used herein, a sensed morphological 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 morphological waveform can be caused, for example, by delivery of a pacing stimulus and / or intrinsic conduction.

[0066] Figure 4A diagnostic method 500 for determining pacing effectiveness for CRT pacing is depicted. Specifically, morphological features after delivery of a pacing event are compared to an absolute level (i.e., a threshold value that is not patient-specific). For example, the exemplary systems and methods described herein monitor one or more electrical vectors of a patient's heart during pacing therapy, analyzing whether each pacing event has a predetermined level of effectiveness. In one or more embodiments, during LV-only pacing or biventricular (BV) pacing in CRT, morphological features of the LV electrode-RV coil vector are evaluated. An exemplary LV electrode-RV coil vector may include an electrode pair, such as an LV tip (e.g., electrode 46) to an RV coil (e.g., electrode 62), or an LV annulus (e.g., electrode 54) to an RV coil (e.g., electrode 62). It is advantageous to select a monitoring vector that includes an LV pacing cathode and another electrode (such as an RV coil or an IMD 16 housing or shell). For example, if LV pacing occurs at the LV tip, a monitoring vector of Lv tip-Rv coil or Lv tip-device housing is preferably used.

[0067] At box 502, a determination is made as to whether the current or most recent ventricular event is a paced event. If the device has not delivered a paced event, then the "no" path is followed, returning to box 502 to continue checking for the next paced event. If a paced event has occurred, then the "yes" path continues to optional box 504 so that the electrogram data from the monitoring vector can be stored in memory. Box 504 is optional because the data storage can occur automatically independent of the computer instructions set forth in method 500. Figure 5 , exemplary EGM data resulting from a pacing event is depicted in . As shown, an electrical stimulus (e.g., a biventricular pacing pulse) is delivered to cardiac tissue via a medical electrical lead at time = 0, while the data is sampled at an exemplary sampling frequency of 180 Hz (5.56 ms per sample). Immediately prior to the delivery of the pacing stimulus, a baseline data value (BL) is sensed that serves as a reference value. Figure 5 In the example of , the device holds a baseline data value during the blanking period immediately before and after the delivery of a pacing stimulus, and thus the BL may also be sensed during the hold period (i.e., immediately after the delivery of a pacing stimulus). For example, the BL EGM amplitude is -1, and the minimum EGM amplitude is -110, where the unit is equal to the least significant bit (LSB) voltage of the analog-to-digital converter (ADC). As an illustration, if the full-scale voltage range of the ADC is 8 millivolts (mV), and the ADC has an 8-bit resolution, then the LSB voltage is 8*1000 / (2 8-1) = 31.3 microvolts (μV). The timing of the minimum amplitude occurs at 6 time samples (i.e., 33.4 milliseconds (ms)) from the time the pacing stimulus is initially delivered to the cardiac tissue. After delivery of the pacing stimulus, the maximum EGM amplitude is 99, and the timing of the maximum amplitude is 14 time samples (i.e., 78.4 ms).

[0068] Morphological features are parsed from the EGM and used to determine whether pacing has effectively captured the ventricle. Exemplary morphological features include the maximum value (Max), the timing of the maximum value (Tmax), the minimum value (Min), the timing of the minimum value (Tmin), and the baseline value (BL) of the EGM amplitude when delivering pacing. The morphological features are evaluated within a time window of a pre-specified width (i.e., 200ms) from the start of delivering pacing.

[0069] To determine whether the pacing stimulus effectively captured the ventricle, the sensed data is evaluated according to one or more of the mathematical relationships embodied at blocks 506, 508, 510, 516, 518, and 520. At block 506, a determination is made as to whether a first condition relative to effective capture is satisfied. The first condition, presented below, subtracts Tmin from Tmax, and then determines whether the result is greater than a predetermined threshold (T), such as 30 ms. The equation for the first condition is as follows:

[0070] Tmax-Tmin>30ms

[0071] If Tmax-Tmin is not greater than 30 ms, the "no" path continues to box 514, where the pacing stimulus is declared ineffective in capturing the ventricle. Conversely, if Tmax-Tmin>30 ms, the "yes" path continues to box 508. Since Tmax-Tmin is equal to 78.4-33.4 ms (equal to 45 ms), Figure 5 The presented data provides an example of this condition being met. At block 508, a determination is made as to whether the second condition is met. The equation for the second condition is as follows: LL<|Max-BL| / |BL-Min| <UL。

[0072] The lower limit (LL) and upper limit (UL) are associated with the upper and lower ratio limits of the morphological feature, respectively. An exemplary LL may be 0.2 and be in the range of 0.1 to 0.33, and an exemplary UL may be 5.0 and be in the range of 3.0 to 10.0. Preferably, LL is set to 0.125 and UL is set to 8.0.

[0073] The maximum value (Max) and the minimum value (Min) are associated with specific EGM morphological characteristics such as amplitude. The ratio |Max-BL| / |BL-Min| comprises the absolute value of Max-BL divided by the absolute value of BL-Min. If the second condition at box 508 is not met, the "No" path continues to box 518, in which a determination is made as to whether (|Max-BL| / |Min-BL|)≤LL. If (|Max-BL| / |Min-BL|)≤LL is not met, the "No" path continues to box 514, and it is declared that the ventricular pacing stimulation did not induce effective capture of the ventricle. Conversely, the "Yes" path from box 518 continues to box 520, in which a determination is made as to whether BL is less than |Min / 8|. If BL is not less than |Min / 8|, the "No" path from box 520 continues to box 514, in which the electrical stimulation is declared to have ineffectively captured the ventricle. If BL is less than |Min / 8|, the “yes” path continues to optional block 510 .

[0074] The "yes" path from box 508 also continues to box 510, which determines whether Tmin is less than a preselected value, such as 60ms. The preselected value can be any value between 40ms-80ms. If Tmin is not less than 60ms, the "no" path continues to optional box 516, where another determination is made as to whether Max-Min is greater than 3.5mV. If Max-Min is greater than 3.5mV, then there is effective capture, and the "yes" path continues to box 512, where ventricular stimulation is declared to have captured the ventricles. The "no" path from box 516 continues to box 514, where a determination is made that ventricular stimulation was determined not to have effectively captured the ventricles.

[0075] Returning to block 510, if Tmin is less than 60 ms, the "yes" path continues to block 512 where valid capture is asserted. Each time valid capture is asserted at block 512, the valid capture counter is incremented by one. During valid capture monitoring, the valid capture counter is continuously maintained and updated. Valid capture monitoring determines whether the pacing stimulus is valid or invalid. Valid capture monitoring tracks the response from the cardiac tissue during pacing therapy.

[0076] Effective capture monitoring may be performed continuously, or more preferably periodically (e.g., 100 beats / hour (hr), once daily, etc.) to conserve battery life. Preferably, effective capture monitoring is performed at 100 beats per hour and consists of normal pacing timing (rather than ideal timing conditions for ECT). Effective capture monitoring (i.e., 100 beats per hour) is reported to the user as a percentage of effective capture beats. The user may apply any selection of thresholds of interest (e.g., 90%, etc.).

[0077] After the monitoring period, a measure of effective capture may be calculated by dividing the effective capture counter by the total number of paced beats. The method then returns to block 502 to monitor for the next pacing event.

[0078] To determine whether effective LV capture can occur under ideal conditions, an effective capture test (ECT) is performed periodically (e.g., daily, etc.) or in response to continued observation of ineffective capture, under the guidance of the user (e.g., while the patient is sleeping, such as at night). Typically, ideal conditions involve delivery of pacing stimulation with sufficient amplitude and duration.

[0079] The results of ECT may be used to explain the ineffective capture observed throughout the day. For example, if the LV lead is displaced, if scar tissue develops at the site of LV pacing, or if BV pacing involves substantial preexcitation of the RV, then effective LV capture may not be achieved even under ideal conditions.

[0080] ECT testing can be performed for LV-only pacing or BV pacing. The manner in which ECT is performed depends on whether the patient is experiencing atrial fibrillation (AF). AF typically causes the pacing behavior to switch to a pacing mode that does not track atrial activation (e.g., DDI, DDIR, VVI, or VVIR pacing modes). When not in AF, the device typically operates in a pacing mode that tracks atrial activation, such that SAV and PAV are the relevant pacing timing parameters. For example, if the patient is no longer in AF, only LV pacing is performed with a very short PAV (e.g., 10 ms) or SAV (e.g., 10 ms). Alternatively, if the patient is experiencing AF, only LV pacing is performed with an overdrive rate. Test beats (e.g., 5 test beats, etc.) are delivered to the ventricles to track the atrial activation according to the PAV. Figure 4 The criteria presented in the accompanying text determine whether the ventricle is effectively captured. For example, if 75% of the test beats (such as 4 out of 5 beats) are effectively captured, then the ECT is passed for that day. Passing the ECT for that day means that effective capture is possible at least under ideal conditions.

[0081] The BV test follows the LV test. For the BV test, if the patient is not in AF, a very short PAV or SAV and the currently programmed VV delay are used, while if the patient is in AF, an overdrive rate is employed. Likewise, 5 test beats are delivered with BV pacing, and 4 of the 5 must pass effective LV capture. If the morphological characteristics satisfy the effective capture test (ECT), then either the LV pacing beat or the BV pacing beat is considered to provide effective capture. The ECT may include one, two, or three of the following relationships:

[0082] Tmax-Tmin>30 ms (1)

[0083] 0.2<|Max-BL| / |BL-Min|<5 or (|Max-BL| / |Min-BL|≤LL and BL<|Min / 8|) and (2)

[0084] Tmin<60 ms or Max-Min>3.5 mV (3)

[0085] All timing parameters are measured from the time the pace is delivered.

[0086] Table 1 summarizes the diagnostic data of the exemplary method 500. Two different examples of diagnostic data (eg Figure 5 and Figure 6 ) depicts the R wave of the QRS complex from the cardiac cycle. The R wave, the depolarization of the ventricles, typically has a greater amplitude than any other wave of the cardiac cycle and is characterized by a rapid excursion from and back to the baseline.

[0087] Figure 5 shows a negative deflection before a positive deflection, while Figure 6 shows a positive deflection preceding a negative deflection in the signal. A negative deflection occurs when the curve drops below the baseline. A negative deflection indicates that the recorded far-field wave is traveling away from one of the electrodes on the lead. In contrast, Figure 6 As shown, a positive deflection occurs when the curve rises above the baseline. A positive deflection means that the recorded far-field waves are traveling toward the electrode.

[0088] Now turn to the application of ECT standards. Figure 4 506, 508 and 510, so Figure 5 The pacing data presented in delivers effective pacing to capture the ventricle. Since Tmax-Tmin is no greater than 30 ms with respect to block 506, Figure 6 The pacing data presented in the ECT data did not effectively capture the ventricle. Table 1 lists the ECT criteria and Figure 5 and Figure 6 Each result of the pacing data is presented in .

[0089] Table 1

[0090]

[0091] The conditions that classify a paced beat as effectively captured or ineffectively captured can be conveniently displayed as a two-dimensional scatter plot. Figures 7A-7C Supported by Figure 4 The conditions found in the flowchart. Figure 7A-7BThe LV apex-RV coil EGM is depicted. The EGM amplitude extends from -128 to 128 along the Y axis, while the X axis extends from 0 to 0.2 seconds. Data such as BL, Min, Max, Tmin, Tmax are displayed for each stimulus and compared to the criteria for effective capture. The data is then mapped to Figure 7C As shown, according to Fig. 7A The stimulus delivered, effectively captured exists within the framed area, and as Figure 7B Ineffective capture induced by delivered electrical stimulation exists outside the boxed region. Note that the third criterion for effective capture (Tmin<60ms or Max-Min>3.5mV) is not included in this graphical depiction and is not necessary for effective capture determination in one or more other embodiments.

[0092] Figure 8 is a flow chart of an exemplary method of delivering cardiac resynchronization therapy in an implantable medical device according to an example of the present disclosure. Figure 8 As shown, during the delivery of cardiac resynchronization therapy according to an example of the present disclosure, the processor 80 determines whether the effective capture caused by the delivered CRT pacing is less than a predetermined threshold for a latest time period (e.g., 5 days) (box 902). As described above, the exemplary predetermined threshold can be set to 80%, and can be in the range of, for example, 98% to 50%. In addition, although the latest time period can be set to 5 days, it should be understood that the latest time period can be between 1 hour and 14 days. In another example, the predetermined threshold can be related to the percentage of CRT pacing delivered. For example, if 90% of CRT pacing is delivered, but only 80% is effective, this 10% "delta" can be compared to the percentage delta threshold.

[0093] Processor 80 accesses the cause of ineffective capture from memory 82 (block 904). For example, an example method for determining loss of capture or latency as a cause of ineffective capture is described in U.S. Pat. No. 9,320,905 to Ghosh et al., which is incorporated by reference in its entirety. In another example according to the present disclosure, to determine loss of capture as a cause of ineffective capture, processor 80 may determine whether the difference between the percentage of V paced (VP) beats and the percentage of effective CRT during a predetermined time period is greater than or equal to a difference threshold, such as, for example, 5% during the most recent 24 hour period.

[0094] If the difference between the percentage of V paced (VP) beats and the percentage of effective CRT is greater than or equal to the difference threshold, processor 80 may also determine whether at least one of two additional requirements is met. For example, processor 80 may further determine whether (1) a predetermined time period (such as, for example, 14 days) has expired since implantation, the LCVM capture threshold has been unavailable for a predetermined number of days (such as, for example, 9 of the last 14 days), and the LVCM capture threshold has been unavailable for the last day, or whether (2) for the current LV path and LV pulse width, the difference between the minimum LVCM capture threshold and the maximum LVCM capture threshold is greater than or equal to a minimum / maximum difference threshold, such as, for example, the current amplitude safety margin minus 25 volts, over a predetermined number of days (such as, for example, 14 days).

[0095] In this way, according to one example, if processor 80 determines that the difference between the percentage of V paced (VP) beats and the percentage of effective CRT is greater than or equal to a difference threshold, and at least one of additional requirement (1) and additional requirement (2) is met, the cause of ineffective capture (box 904) can be determined as loss of capture (box 906).

[0096] When the cause of ineffective capture is determined to be lost capture (block 906), processor 80 determines whether the LVCM feature is turned on or enabled, and whether the LV safety margin has been programmed to "auto" (block 908). If the LVCM is determined to be not enabled ("No" in block 908), processor 80 may generate an alarm or observation for the determined ineffective capture (block 910) and repeat the process by determining whether effective capture is less than a predetermined threshold (block 902) after the next time period expires.

[0097] If the LVCM is determined to be enabled ("yes" in box 908), the processor 80 may increase the baseline safety margin of the amplitude to a predetermined level of amplitude that exceeds that required for ventricular capture, such as, for example, 0.5 volts (box 912). In additional examples, the safety margin may be pulse width, or a combination of amplitude and pulse width. In another example, the processor may execute a capture management algorithm to determine an adjusted capture threshold if the LVCM is determined to be enabled ("yes" in box 908). When pacing is delivered using the adjusted safety margin or the adjusted capture threshold, the processor 80 then determines whether ineffective capture has been resolved (box 914). For example, to confirm that the adjustment to the safety margin is effective in resolving ineffective capture, the processor 80 may monitor the pacing therapy for a predetermined period of time, such as, for example, 24 hours, and determine whether there is a change in effective CRT during the 24-hour period. As another example, to determine a change in the effective CRT, after waiting a predetermined number of beats (e.g., such as two beats) to enable the device to switch to the adjusted output, a predetermined number of subsequent beats are subsequently analyzed to obtain the effective CRT during the 24 hour period, such as, for example, 5 beats.

[0098] In one example, if it is determined that less than 4 of 5 subsequent beats result in effective capture, it is determined that no change has occurred, and thus the ineffective capture has not been resolved ("No" in box 914). The initial programming is reset (box 915), including resetting the LV safety margin or capture threshold from the adjusted value to the initial value and resetting the VV delay or LV pacing vector as appropriate, and the process is repeated by determining whether the effective capture is less than the predetermined threshold after the next time period expires (box 902). On the other hand, if it is determined that 4 or more of the 5 beats result in effective capture, it is determined that a change has occurred, and thus the ineffective capture has been resolved ("Yes" in box 914). As a result, pacing therapy is continued to be delivered with the adjusted LV safety margin or capture threshold, and the process is repeated by determining whether the effective capture is less than the predetermined threshold after the next time period expires (box 902). In one example, the safety margin or capture threshold may be reset subsequently when the LVCM or LV safety margin is reprogrammed.

[0099] In this way, if the cause of ineffective capture is determined to be lost capture, the processor 80 can adjust the safety margin or capture threshold from the baseline setting, and return to the baseline safety margin if the ineffective capture is not resolved using the adjusted safety margin or capture threshold. In addition, if it is determined that the LVCM is not enabled or disabled, the processor 80 simply generates an alarm or observation without making any adjustments.

[0100] According to one example, to determine delayed depolarization as a cause of ineffective capture (block 922), i.e., due to the lead being positioned within scar tissue or within latent or inactive tissue, the processor 80 may determine whether a predetermined number of delayed depolarization requirements are met. For example, the delayed depolarization requirements may include (1) the CRT of the device is programmed for adaptive biventricular pacing therapy or adaptive biventricular and left ventricular pacing therapy, and the CRT of the device includes control for VV delay. In addition, the requirements may include (2) CRT pacing is effective for 4 of 5 LV-only pacing cycles, and Tmin>100 ms (>13 samples) for at least 4 of 5 LV-only pacing cycles, and (3) the difference between the percentage of ventricular pacing during a predetermined time period and the percentage of effective CRT is greater than or equal to a threshold, such as, for example, 5% over a 24-hour period.

[0101] In this manner, according to one example, if the processor 80 determines that the delayed depolarization requirements (1)-(3) are met, the cause of ineffective capture (box 904) is determined to be delayed LV depolarization (box 922), and as a result, the latent remediation flag is set and the processor 80 increases LV pre-excitation from a baseline value to an adjusted value (box 924). For example, the processor 80 may stop automatic control of the VV delay (e.g., according to an algorithm that routinely updates the VV delay) and cause the VV delay to be increased by a predetermined value to a maximum value, such as, for example, increasing the VV delay by 20 ms up to a maximum value of 60 ms. In another example, an offset may be applied to the VV delay determined by the automatic algorithm. For example, if the CRT algorithm selects a VV delay of 20, this new feature will automatically increase the VV delay to 40 ms.

[0102] After initially increasing the VV delay by 20 ms, a determination is made as to whether the ineffective capture has been resolved as a result of the use of increased LV pre-excitation (block 926). For example, to confirm that the adjustment to LV pre-excitation was effective in resolving the ineffective capture, the processor 80 may monitor the pacing therapy for a predetermined period of time, such as, for example, 24 hours, and determine whether there is a change in effective CRT during the 24 hour period. As another example, the processor 80 may analyze a predetermined number of subsequently delivered pacing beats, such as, for example, five delivered pacing beats, and determine whether these beats resulted in effective capture.

[0103] In one example, if it is determined that four of the five subsequent delivered beats result in effective capture, then the ineffective capture is determined to be resolved ("Yes" in box 926), and increased LV pre-excitation is confirmed and the process is repeated (box 902), wherein CRT pacing is delivered with an adjusted VV delay for a predetermined period of time, such as, for example, 24 hours. If it is determined that less than four of the five subsequent delivered beats result in effective capture, and the current VV delay is less than 60 ms, the VV delay is again increased by 20 ms, and the next five paced beats are analyzed to obtain effective capture, and the process is repeated. On the other hand, if it is determined that less than four of the five subsequent delivered pacing result in effective capture, and the current VV delay is not less than 60 ms, then it is determined that the ineffective capture is not resolved ("No" in box 926), control of the VV delay is resumed by the CRT algorithm, the latent remediation flag is removed, and the latent remediation flag is delayed for a period of time, such as, for example, 24 hours.

[0104] In this way, if a change in effective CRT is determined to have occurred and therefore ineffective capture is determined to have been addressed by adjustment of LV pre-excitation ("yes" in box 926), the process is repeated for CRT delivered with adjusted LV pre-excitation to determine whether effective capture is less than a predetermined threshold after the expiration of the next time period (box 902).

[0105] On the other hand, if it is determined that no change in effective CRT has occurred, and therefore it is determined that ineffective capture has not been resolved by adjustment of LV excitation ("No" in block 926), processor 80 returns the adjusted LV pre-excitation to the baseline LV pre-excitation and determines whether the current device setting indicates that LV pacing vector adjustment is allowed (block 928). If the current device setting indicates that vector adjustment is not allowed ("No" in block 928), the initial programming is reset (block 915), including resetting the LV safety margin from the adjusted value to the initial value and resetting the VV delay or LV pacing vector as appropriate, and the process is repeated by determining whether effective capture is less than a predetermined threshold after the expiration of the next time period (block 902).

[0106] If the current device settings indicate that vector adjustment is allowed ("yes" in box 928), the processor 80 causes the device to switch the sensing vector from the baseline sensing vector formed between the electrodes 40, 42, 44, 46, 48, 50, 58 to another sensing vector formed between the electrodes 40, 42, 44, 46, 48, 50, 58 (box 930), and when delivering pacing using the adjusted pacing vector, determine whether ineffective capture has been resolved (box 932). For example, to confirm that the adjustment to the pacing vector is effective in resolving ineffective capture, the processor 80 can monitor the pacing therapy and determine whether there is a change in effective CRT, as described above. If it is determined that a change in effective CRT has occurred, and therefore ineffective capture is determined to be resolved ("yes" in box 932), the process is repeated by determining whether effective capture is less than a predetermined threshold after the next time period expires (box 902).

[0107] On the other hand, if it is determined that no change in effective CRT has occurred and therefore that ineffective capture has not been resolved ("No" in box 932), processor 80 adjusts the pacing vector back to the baseline pacing vector and resets the initial programming (box 915), and repeats the process by determining whether effective capture is less than a predetermined threshold (box 902) after the next time period expires.

[0108] In this way, if the cause of ineffective capture is determined to be delayed LV depolarization, the processor 80 can adjust LV pre-excitation from the baseline LV pre-excitation setting, and if the ineffective capture is not resolved due to the adjusted LV pre-excitation, return LV pre-excitation to the baseline setting. The processor 80 then determines whether the current device setting indicates that vector adjustment is allowed, and if it is determined that vector adjustment is indicated as allowed, the processor 80 can switch the current pacing vector from the baseline pacing vector to the adjusted pacing vector, and subsequently determine whether the ineffective capture is resolved due to the adjustment of the pacing vector.

[0109] Fig. 9 is a flow chart of an exemplary method of delivering cardiac resynchronization therapy in an implantable medical device according to examples of the present disclosure. Fig. 9 The method includes all the features of the method of claim 8, which will not be repeated here for the sake of brevity. However, Fig. 9 The example differs in that Fig. 9 Examples of include additional features for determining whether ineffective capture is resolved when loss of capture is determined to be the cause of ineffective capture. In one example, such additional features may indicate increased concern for LV loss of capture indicating an increased level of LV capture failure resulting in harmful RV-only pacing.

[0110] Specifically, if Fig. 9As shown, if the invalid capture is not resolved by adjusting the safety margin or capture threshold ("No" in block 914), or if the vector adjustment is not allowed ("No" in block 928), or if the invalid capture is not resolved ("No" in block 932), the processor 80 may determine whether the determined effective CRT is less than the minimum effective CRT threshold (block 916). If the current determined effective CRT is not less than the minimum effective CRT threshold ("No" in block 916), the process is repeated by determining whether the effective capture is less than a predetermined threshold after the next time period expires (block 902). Although the use of a minimum delta between the delivered CRT and the effective CRT is described, in another example, the determination may be associated with a larger delta between the delivered CRT and the effective CRT.

[0111] In one example, the processor 916 can make a determination (box 916) whether the determined effective CRT is less than a minimum effective CRT threshold based on multiple characteristics, such as (1) whether the effective CRT is determined to be less than a predetermined percentage within a given time period, such as, for example, 10% of the effective CRT during a recent day, (2) the LV pacing vector has not been adjusted within a predetermined time period (such as, for example, 48 hours), (3) the effective CRT is greater than a predetermined threshold within a given number of days, such as, for example, greater than 50% of the effective CRT for one or more of the last 3 days, and (4) a valid CRT episode is determined within a given time period (such as, for example, 5 days).

[0112] If all of the additional features (1)-(4) are not satisfied, it is determined that the currently determined effective CRT is not less than the minimum effective CRT threshold ("No" in block 916), and the process is repeated by determining whether the effective capture is less than the predetermined threshold after the next time period expires (block 902). On the other hand, if all of the additional features (1)-(4) are satisfied, the currently determined effective CRT is determined to be less than the minimum effective CRT threshold ("Yes" in block 916), processor 80 may switch the pacing mode to a minimum ventricular pacing (MVP) mode (block 918), generate an alarm or observation for the determined ineffective capture (block 920), and repeat the process by determining whether the effective capture is less than the predetermined threshold after the next time period expires (block 902).

[0113] MVP operates by reducing unnecessary right ventricular pacing to promote intrinsic conduction. During an MVP mode protocol, atrial-only pacing is delivered unless an intrinsic ventricular event is not sensed. When a ventricular event is not sensed between two consecutive atrial events, a ventricular backup pacing pulse can be delivered after the second atrial event to avoid another asystolic cardiac cycle. When a specified number of atrial-only pacing cycles occur without a sensed ventricular event, the pacing device will switch to dual-chamber pacing mode and deliver atrial and ventricular pacing pulses coordinated with the programmed atrial-ventricular (AV) delay.

[0114] In this way, if the cause of ineffective capture is determined to be loss of capture, the processor 80 can adjust the safety margin from the baseline setting, and if the ineffective capture is not resolved using the adjusted safety margin, return to the baseline safety margin and determine whether there is a very low percentage of effective CRT at the baseline setting. If it is determined that there is a very low percentage of effective CRT at the baseline setting, the processor 80 can switch the current LV pacing to MVP mode and generate an alarm. If it is determined that the LVCM is not enabled or turned off, the processor 80 simply generates an alarm or observes without making any adjustments.

[0115] If the cause of the ineffective capture is determined to be delayed LV depolarization, the processor 80 may adjust the LV pre-excitation from the baseline LV pre-excitation setting, and if the ineffective capture is not resolved due to the adjusted LV pre-excitation, return the LV pre-excitation to the baseline setting. The processor 80 then determines whether the current device setting indicates that vector adjustment is allowed, and if it is determined that the vector adjustment is indicated as allowed, the processor 80 may switch the current pacing vector from the baseline pacing vector to the adjusted pacing vector, and subsequently determine whether the ineffective capture is resolved due to the adjustment of the pacing vector. On the other hand, if the vector adjustment is not indicated as allowed, the processor 80 may determine whether there is a very low percentage of effective CRT at the baseline settings. If it is determined that there is a very low percentage of effective CRT at the baseline settings, the processor 80 may switch the current LV pacing to MVP mode and generate an alarm. If it is determined that the LVCM is not enabled or disabled, the processor 80 simply generates an alarm or observation without making any adjustments.

[0116] The techniques described in the present disclosure (including those attributable to IMD 16, programmer 24, processor 80, and / or constituent components) may be implemented, at least in part, in hardware, software, firmware, or any combination thereof. For example, aspects of the 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, as well as 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.

[0117] 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 components, software components, or may be integrated in common or separate hardware or software components.

[0118] 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.

[0119] 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.

[0120] The illustrated embodiment

[0121] Embodiment 1: An implantable medical device system for delivering cardiac resynchronization therapy (CRT) pacing, comprising: an implantable medical device housing; at least one lead having a lead body and capable of being electrically coupled to the housing; a plurality of electrodes positioned along one or both of the device housing and the lead body of at least one lead to sense cardiac signals of the patient and deliver CRT pacing; and a processor positioned within the housing and configured to: in response to the delivered CRT pacing, determine that capture associated with the delivered CRT pacing is ineffective; determine a cause of ineffective capture; and in response to the determined cause of ineffective capture being loss of capture, adjust one of a safety margin and a capture threshold; and in response to the determined cause of ineffective capture being delayed left ventricular (LV) depolarization, adjust LV pre-excitation.

[0122] Embodiment 2: The system of embodiment 1, wherein the processor is configured to: determine whether a left ventricular capture management (LVCM) feature is enabled, generate an alarm in response to LVCM not being enabled, and adjust one of a safety margin and a capture threshold in response to the LVCM feature being enabled.

[0123] Embodiment 3: The system of any of embodiments 1 and 2, wherein the processor is configured to: determine whether a change in effective CRT has occurred in response to CRT pacing being delivered after performing one of an adjustment to a safety margin and a capture threshold and an adjustment to LV preexcitation; determine that ineffective capture has been resolved in response to determining that a change in effective CRT has occurred; and determine that ineffective capture has not been resolved in response to determining that a change in effective CRT has not occurred.

[0124] Embodiment 4: The system of any of Embodiments 1-3, wherein the processor is configured to: adjust LV pre-excitation from baseline LV pre-excitation to adjusted LV pre-excitation; determine whether ineffective capture is resolved in response to CRT pacing being delivered with adjusted LV pre-excitation; adjust LV pre-excitation from adjusted LV pre-excitation to baseline LV pre-excitation in response to determining that ineffective capture is not resolved; determine whether a vector adjustment feature associated with adjusting a vector for delivering CRT pacing is enabled in response to determining that ineffective capture is not resolved; and adjust the vector for delivering CRT pacing in response to determining that the vector adjustment feature is enabled.

[0125] Embodiment 5, the system of embodiment 4, wherein the processor is configured to: in response to determining that the vector adjustment feature is not enabled, determine whether the ineffective CRT is less than a minimum effective CRT threshold; and in response to the effective CRT being less than the minimum effective CRT threshold, switch to a minimum ventricular pacing mode and generate at least one of an alarm and an observation of a determination of ineffective capture.

[0126] Example 6: The system of Example 4, wherein the processor is configured to: determine whether ineffective capture is resolved in response to CRT pacing with an adjusted vector being delivered; determine whether the effective CRT is less than a minimum effective CRT threshold in response to ineffective capture not being resolved in response to CRT pacing with an adjusted vector being delivered; and switch to minimum ventricular pacing mode in response to the effective CRT being less than the minimum effective CRT threshold and generate at least one of an alarm and an observation of the determination of ineffective capture.

[0127] Embodiment 7: The system of any of Embodiments 1-6, wherein the processor is configured to: adjust the safety margin from a baseline safety margin to an adjusted safety margin; determine whether ineffective capture is resolved in response to CRT pacing with the adjusted safety margin being delivered; adjust the safety margin from the adjusted safety margin to the baseline safety margin in response to determining that ineffective capture is not resolved; determine whether the effective CRT is less than a minimum effective CRT threshold in response to ineffective capture being delivered and not resolved; and switch to a minimum ventricular pacing mode in response to the effective CRT being less than the minimum effective CRT threshold and generate at least one of an alarm and an observation of the determination of ineffective capture.

[0128] Embodiment 8: The system of embodiment 7, wherein the processor is configured to: determine whether a left ventricular capture management (LVCM) feature is enabled, generate an alarm in response to the LVCM not being enabled, and adjust the safety margin in response to the LVCM feature being enabled.

[0129] Embodiment 9: The system of any of Embodiments 1-8, wherein adjusting the safety margin comprises adjusting the safety margin from a baseline safety margin to an adjusted safety margin, and adjusting LV pre-excitation comprises: adjusting LV pre-excitation from a baseline LV pre-excitation to an adjusted LV pre-excitation, and the processor is configured to: determine whether ineffective capture is resolved in response to CRT pacing with the adjusted LV pre-excitation being delivered; adjust LV pre-excitation from the adjusted LV pre-excitation to the baseline LV pre-excitation in response to determining that ineffective capture is not resolved in response to CRT pacing with the adjusted LV pre-excitation being delivered; determine whether a vector adjustment feature associated with adjusting a vector for delivering CRT pacing is enabled in response to ineffective capture being not resolved in response to CRT pacing with the adjusted LV pre-excitation being delivered; A vector adjustment feature is enabled and a vector for delivering CRT pacing is adjusted; in response to CRT pacing with the adjusted vector being delivered, determining whether ineffective capture is resolved; in response to CRT pacing with an adjusted safety margin being delivered, determining whether ineffective capture is resolved; in response to ineffective capture being delivered and not resolved in response to CRT pacing with the adjusted safety margin being delivered, adjusting the safety margin from the adjusted safety margin to a baseline safety margin; in response to ineffective capture being delivered and not resolved in response to CRT pacing with the adjusted safety margin being delivered, determining whether the effective CRT is less than a minimum effective CRT threshold; and in response to the effective CRT being less than the minimum effective CRT threshold, switching to a minimum ventricular pacing mode and generating at least one of an alarm and an observation of a determination of ineffective capture.

[0130] Example 10: The system of Example 9, wherein the processor is configured to: determine whether the effective CRT is less than a minimum effective CRT threshold in response to the vector adjustment feature not being enabled; and switch to a minimum ventricular pacing mode in response to the effective CRT being less than the minimum effective CRT threshold, and generate at least one of an alarm and an observation of a determination of ineffective capture.

[0131] Example 11: The system of Example 10, wherein the processor is configured to: determine whether a left ventricular capture management (LVCM) feature is enabled, generate an alarm in response to the LVCM not being enabled, and adjust the safety margin in response to the LVCM feature being enabled.

[0132] Example 12: A method of delivering cardiac resynchronization therapy (CRT) pacing, comprising: in response to the delivered CRT pacing, determining that capture associated with the delivered CRT pacing is ineffective; determining a reason for the ineffective capture; and in response to the determined reason for the ineffective capture being loss of capture, adjusting one of a safety margin and a capture threshold, and in response to the determined reason for the ineffective capture being delayed left ventricular (LV) depolarization, adjusting LV pre-excitation.

[0133] Example 13: The method of Example 12 further comprises: determining whether a left ventricular capture management (LVCM) feature is enabled; generating an alarm in response to LVCM not being enabled; and adjusting one of a safety margin and a capture threshold in response to the LVCM feature being enabled.

[0134] Example 14: The method of any one of Examples 12 and 13, further comprising: determining whether a change in effective CRT occurs in response to CRT pacing being delivered after performing an adjustment to one of the safety margin and the capture threshold and one of the adjustments to LV preexcitation; determining that ineffective capture is resolved in response to determining that a change in effective CRT occurs; and determining that ineffective capture is not resolved in response to determining that a change in effective CRT does not occur.

[0135] Example 15: The method of any one of Examples 12-14, further comprising: adjusting LV pre-excitation from baseline LV pre-excitation to adjusted LV pre-excitation; in response to CRT pacing with adjusted LV pre-excitation being delivered, determining whether ineffective capture is resolved; in response to determining that ineffective capture is not resolved, adjusting LV pre-excitation from adjusted LV pre-excitation to baseline LV pre-excitation; in response to determining that ineffective capture is not resolved, determining whether a vector adjustment feature associated with adjusting a vector for delivering CRT pacing is enabled; and in response to determining that the vector adjustment feature is enabled, adjusting the vector for delivering CRT pacing.

[0136] Example 16: The method of Example 15 further includes: in response to determining that the vector adjustment feature is not enabled, determining whether the ineffective CRT is less than the minimum effective CRT threshold; and in response to the effective CRT being less than the minimum effective CRT threshold, switching to the minimum ventricular pacing mode and generating at least one of an alarm and an observation of the determination of ineffective capture.

[0137] Example 17: The method of Example 15 further includes: determining whether ineffective capture is resolved in response to CRT pacing with an adjusted vector being delivered; determining whether the effective CRT is less than a minimum effective CRT threshold in response to ineffective capture not being resolved in response to CRT pacing with an adjusted vector being delivered; and switching to minimum ventricular pacing mode in response to the effective CRT being less than the minimum effective CRT threshold and generating at least one of an alarm and an observation of the determination of ineffective capture.

[0138] Example 18: The method of any of Examples 12-17, further comprising: adjusting the safety margin from a baseline safety margin to an adjusted safety margin; determining whether ineffective capture is resolved in response to CRT pacing with the adjusted safety margin being delivered; adjusting the safety margin from the adjusted safety margin to the baseline safety margin in response to determining that ineffective capture is not resolved; determining whether the effective CRT is less than a minimum effective CRT threshold in response to ineffective capture being delivered and not resolved; and switching to a minimum ventricular pacing mode in response to the effective CRT being less than the minimum effective CRT threshold and generating at least one of an alarm and an observation of the determination of ineffective capture.

[0139] Example 19: The method of Example 18, further comprising: determining whether a left ventricular capture management (LVCM) feature is enabled; generating an alarm in response to the LVCM not being enabled; and adjusting the safety margin in response to the LVCM feature being enabled.

[0140] Embodiment 20: The method of any of Embodiment 12, wherein adjusting the safety margin comprises adjusting the safety margin from a baseline safety margin to an adjusted safety margin, and adjusting LV pre-excitation comprises adjusting LV pre-excitation from a baseline LV pre-excitation to an adjusted LV pre-excitation, the method further comprising: in response to CRT pacing with adjusted LV pre-excitation being delivered, determining whether ineffective capture is resolved; in response to determining that ineffective capture is not resolved in response to CRT pacing with adjusted LV pre-excitation being delivered, adjusting LV pre-excitation from the adjusted LV pre-excitation to the baseline LV pre-excitation; in response to determining that ineffective capture is not resolved in response to CRT pacing with adjusted LV pre-excitation being delivered, determining whether a vector adjustment feature associated with adjusting a vector for delivering CRT pacing is enabled; in response to determining that ineffective capture is not resolved in response to CRT pacing with adjusted LV pre-excitation being delivered; A vector adjustment feature is enabled to adjust a vector for delivering CRT pacing; in response to CRT pacing with the adjusted vector being delivered, determining whether ineffective capture is resolved; in response to CRT pacing with the adjusted safety margin being delivered, determining whether ineffective capture is resolved; in response to ineffective capture being delivered and not resolved in response to CRT pacing with the adjusted safety margin being delivered, adjusting the safety margin from the adjusted safety margin to a baseline safety margin; in response to ineffective capture being delivered and not resolved in response to CRT pacing with the adjusted safety margin being delivered, determining whether the effective CRT is less than a minimum effective CRT threshold; and in response to the effective CRT being less than the minimum effective CRT threshold, switching to a minimum ventricular pacing mode and generating at least one of an alarm and an observation of a determination of ineffective capture.

[0141] Example 21: The method of Example 20 further includes: in response to the vector adjustment feature not being enabled, determining whether the effective CRT is less than a minimum effective CRT threshold; and in response to the effective CRT being less than the minimum effective CRT threshold, switching to a minimum ventricular pacing mode and generating at least one of an alarm and an observation of a determination of ineffective capture.

[0142] Embodiment 22: The method of any one of Embodiments 20 and 21, further comprising: determining whether a left ventricular capture management (LVCM) feature is enabled; generating an alarm in response to the LVCM not being enabled; and increasing the safety margin in response to the LVCM feature being enabled.

[0143] Embodiment 23: A non-transitory computer-readable medium storing instructions that cause an implantable medical device to perform a method comprising: determining, in response to delivered CRT pacing, that capture associated with the delivered CRT pacing is ineffective; determining a cause of ineffective capture; and adjusting one of a safety margin and a capture threshold in response to the determined cause of ineffective capture being loss of capture, and adjusting LV pre-excitation in response to the determined cause of ineffective capture being delayed left ventricular (LV) depolarization.

Claims

1. An implantable medical device system for delivering cardiac resynchronization therapy (CRT) pacing, comprising: Implantable medical device housing; at least one lead having a lead body and capable of being electrically coupled to the housing; a plurality of electrodes positioned along one or both of the device housing and the lead body of the at least one lead to sense cardiac signals of the patient and deliver the CRT pacing; as well as a processor positioned within the housing and configured to: In response to the delivered CRT pace, determining that capture associated with the delivered CRT pace is ineffective; Determine why the capture was ineffective; as well as In response to determining that the cause of ineffective capture is loss of capture, one of a safety margin and a capture threshold is adjusted, and in response to the determined cause of ineffective capture being delayed left ventricular (LV) depolarization, LV pre-excitation is adjusted by modifying a VV delay of CRT pacing.

2. The system according to claim 1, characterized in that The processor is configured to determine whether a left ventricular capture management (LVCM) feature is enabled, generate an alarm in response to the LVCM not being enabled, and adjust the one of the safety margin and the capture threshold in response to the LVCM feature being enabled.

3. The system according to any one of claims 1 to 2, characterized in that: The processor is configured to: determine whether a change in effective CRT has occurred in response to the CRT pacing being delivered after performing one of adjusting the one of the safety margin and the capture threshold and adjusting the LV pre-excitation; determine that ineffective capture is resolved in response to determining that the change in effective CRT has occurred; And in response to determining that a change in the effective CRT has not occurred, determining that ineffective capture has not been resolved.

4. The system according to any one of claims 1 to 2, characterized in that: The processor is configured to: adjust the LV pre-excitation from a baseline LV pre-excitation to an adjusted LV pre-excitation; in response to the CRT pacing being delivered with the adjusted LV pre-excitation, determine whether ineffective capture is resolved; in response to determining that ineffective capture is not resolved, adjust the LV pre-excitation from the adjusted LV pre-excitation to the baseline LV pre-excitation; responsive to ineffective capture being determined as unresolved, determining whether a vector adjustment feature associated with adjusting a vector used to deliver the CRT pace is enabled; And in response to the vector adjustment feature being determined to be enabled, adjusting the vector used to deliver the CRT pacing.

5. The system according to claim 4, characterized in that The processor is configured to: in response to determining that the vector adjustment feature is not enabled, determine whether the effective CRT is less than a minimum effective CRT threshold; and in response to the effective CRT being less than the minimum effective CRT threshold, switch to a minimum ventricular pacing mode and generate at least one of an alarm and an observation of a determination of ineffective capture.

6. The system according to claim 4, characterized in that The processor is configured to: determine whether ineffective capture is resolved in response to the CRT pacing with the adjusted vector being delivered; determine whether effective CRT is less than a minimum effective CRT threshold in response to ineffective capture not being resolved in response to the CRT pacing with the adjusted vector being delivered; And in response to the effective CRT being less than the minimum effective CRT threshold, switching to a minimum ventricular pacing mode and generating at least one of an alarm and an observation of a determination of ineffective capture.

7. The system according to any one of claims 1 to 2, characterized in that: The processor is configured to: adjust the safety margin from a baseline safety margin to an adjusted safety margin; determine whether ineffective capture is resolved in response to the CRT pacing being delivered with the adjusted safety margin; and adjust the safety margin from the adjusted safety margin to the baseline safety margin in response to determining that ineffective capture is not resolved; determining whether an effective CRT is less than a minimum effective CRT threshold in response to ineffective capture being delivered and not being resolved in response to said CRT pacing having said adjusted safety margin; And in response to the effective CRT being less than the minimum effective CRT threshold, switching to a minimum ventricular pacing mode and generating at least one of an alarm and an observation of a determination of ineffective capture.

8. The system according to claim 7, characterized in that The processor is configured to determine whether a left ventricular capture management (LVCM) feature is enabled, generate an alarm in response to the LVCM not being enabled, and adjust the safety margin in response to the LVCM feature being enabled.

9. The system according to any one of claims 1 to 2, characterized in that: adjusting the safety margin comprises adjusting the safety margin from a baseline safety margin to an adjusted safety margin, and adjusting LV pre-excitation comprises adjusting the LV pre-excitation from a baseline LV pre-excitation to an adjusted LV pre-excitation, and the processor is configured to: determine whether ineffective capture is resolved in response to the CRT pacing being delivered with the adjusted LV pre-excitation; adjust the LV pre-excitation from the adjusted LV pre-excitation to the baseline LV pre-excitation in response to determining that ineffective capture is not resolved in response to the CRT pacing being delivered with the adjusted LV pre-excitation; determining whether a vector adjustment feature associated with adjusting a vector for delivering the CRT pacing is enabled in response to ineffective capture being delivered and not resolved in response to the CRT pacing with the adjusted LV preexcitation being delivered; adjusting the vector for delivering the CRT pacing in response to determining that the vector adjustment feature is enabled; determining whether ineffective capture is resolved in response to the CRT pacing with the adjusted vector being delivered; determining whether ineffective capture is resolved in response to the CRT pacing with the adjusted safety margin being delivered; adjusting the safety margin from the adjusted safety margin to the baseline safety margin in response to ineffective capture being delivered and not resolved in response to the CRT pacing with the adjusted safety margin being delivered; determining whether an effective CRT is less than a minimum effective CRT threshold in response to ineffective capture being delivered and not being resolved in response to said CRT pacing having said adjusted safety margin; And in response to the effective CRT being less than the minimum effective CRT threshold, switching to a minimum ventricular pacing mode and generating at least one of an alarm and an observation of a determination of ineffective capture.

10. The system according to claim 9, characterized in that The processor is configured to: in response to the vector adjustment feature being not enabled, determine whether the effective CRT is less than the minimum effective CRT threshold; and in response to the effective CRT being less than the minimum effective CRT threshold, switch to a minimum ventricular pacing mode and generate at least one of an alarm and an observation of a determination of ineffective capture.

11. The system according to claim 10, characterized in that The processor is configured to determine whether a left ventricular capture management (LVCM) feature is enabled, generate an alarm in response to the LVCM not being enabled, and adjust the safety margin in response to the LVCM feature being enabled.

12. A computer-readable medium comprising instructions stored thereon, which when executed by a processor included in the system causes the processor to perform operations as defined in any one of claims 1-11.

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