Capture management in leadless cardiac pacing device

Capture management in a left ventricular leadless pacing device that includes determining an intrinsic P-wave of a sensed cardiac signal, sensing an electromechanical signal from an electromechanical sensor of the pacing device, and determining an intrinsic electromechanical atrioventricular interval of the sensed electromechanical signal in response to the sensed P-wave. Ventricular pacing is delivered via the one or more electrodes of the pacing device, and a ventricular pacing (V-pace) event is determined in response to the delivered ventricular pacing, and a V-pace to electromechanical response interval is determined in response to the V-pace event. A determination as to capture is detected is made in response to the intrinsic electromechanical atrioventricular interval and the V-pace to electromechanical response interval, and a pacing parameter is determined in response to determining whether capture is detected.

The disclosure herein relates to an implantable leadless cardiac pacing device, and in particular to a method and apparatus for monitoring of capture management in a left ventricular leadless pacing device using an electromechanical response signal.

BACKGROUND

In the normal human heart, the sinus node, generally located near the junction of the superior vena cava and the right atrium, constitutes the primary natural pacemaker initiating rhythmic electrical excitation of the heart chambers. The cardiac impulse arising from the sinus node is transmitted to the two atrial chambers causing a depolarization and the resulting atrial chamber contractions. The excitation pulse is further transmitted to and through the ventricles via the atrioventricular (AV) node and a ventricular conduction system causing a depolarization and the resulting ventricular chamber contractions.

Disruption of this natural pacemaker and conduction system as a result of aging or disease can be treated by artificial cardiac pacing. For example, one or more heart chambers may be electrically paced depending on the location and severity of the conduction disorder. Cardiac therapy, such as cardiac resynchronization therapy (CRT), may correct symptoms of electrical dyssynchrony of a patient's heart by providing pacing therapy to one or both ventricles or atria, e.g., by providing pacing to encourage earlier activation of the left or right ventricles. By pacing the ventricles, the ventricles may be controlled such that they contract in synchrony.

Cardiac resynchronization pacing devices operate by either delivering pacing stimulus to both ventricles or to one ventricle with the desired result of a more or less simultaneous mechanical contraction and ejection of blood from the ventricles. Ideally, each pacing pulse stimulus delivered to a ventricle evokes a response from the ventricle. Delivering electrical stimuli that causes the ventricle to respond is commonly referred to as capturing a ventricle.

Current implantable pacemakers and implantable cardioverter defibrillators (ICDs) are available for delivering electrical stimulation therapies to a patient's heart, such as cardiac resynchronization therapy (CRT). Medical device technology advancement has led toward smaller and smaller implantable devices. Recently, this reduction in size has resulted in the introduction of leadless intracardiac pacemakers that can be implanted directly in a heart chamber. Left ventricular capture management is an important feature for CRT since it helps to ensure that the outputs of the pacing parameters maintain consistent left ventricular pacing. While conventional left ventricular capture management in conventional pacemakers and ICDs is based on right ventricular sensing and atrial pacing, such right ventricular sensing and atrial pacing are not available in a leadless pacing device positioned in a left ventricle of a patient's heart.

SUMMARY

A leadless pacing device may include an integrated accelerometer whose signal can be representative of various mechanical events that occur during the contraction/relaxation cycle of a ventricle of the patient's heart. The time-intervals between these various mechanical events are reflective of cardiac mechanical function and may potentially be used as diagnostic metrics for cardiac dyssynchrony. The present disclosure relates to left capture management in a left ventricular leadless pacemaker that includes defining an intrinsic electromechanical atrioventricular (AV) interval (IEMAVI) as the timing interval between an atrial sensing event (sensed by an accelerometer of the leadless acing device or sensed by an extravascular ICD vector) and the mechanical response as measured by the peak of the accelerometer signal corresponding to systole under conditions of stable non-tachy rhythms. Since the largest peak in the accelerometer signal will correspond to the ventricular systole for patients who have intrinsic AV conduction, the IEMAVI may be determined using a window of the accelerometer signal extending from the intrinsic atrial sense event, such as a 450 ms window.

During capture management, ventricular pacing may be delivered by the left ventricular leadless device simultaneously with an atrial sensing event at a given pacing output, and the ventricular pace to electromechanical response interval (Vp-EMI) may be measured in the same way. Left ventricular capture is detected if IEMAVI>Vp-EMI+a constant-time interval. Example values for the constant time interval may be 20 ms, 30 ms, 40 ms, or 50 ms. The capture management routine may start with the highest pacing output parameters and then step down the outputs till lack of capture is detected. In this way the device may determine pacing thresholds and set margins for appropriate pacing outputs (e.g. 1 V above thresholds, etc) for delivering pacing therapy.

In one example, a method of monitoring capture management in a left ventricular leadless pacing device comprises sensing a cardiac signal via one or more electrodes of the pacing device; determining an intrinsic P-wave of the sensed cardiac signal; sensing an electromechanical signal from an electromechanical sensor of the pacing device, such as an accelerometer signal; determining an intrinsic electromechanical atrioventricular interval of the sensed electromechanical signal in response to the sensed intrinsic P-wave; delivering ventricular pacing via the one or more electrodes of the pacing device; determining a ventricular pacing (V-pace) event in response to the delivered ventricular pacing; determining a V-pace to electromechanical response interval in response to the V-pace event; determining whether capture is detected in response to the intrinsic electromechanical atrioventricular interval and the V-pace to electromechanical response interval; and determining a pacing parameter in response to determining whether capture is detected.

In another example, a left ventricular leadless pacing device comprises: one or more electrodes to sense a cardiac signal; an electromechanical sensor, such as an accelerometer, to sense an electromechanical signal, and a processor configured to determine an intrinsic P-wave of the sensed cardiac signal, determine an intrinsic electromechanical atrioventricular interval in response to the sensed intrinsic P-wave, deliver ventricular pacing via the one or more electrodes, determine a ventricular pacing (V-pace) event in response to the delivered ventricular pacing, determine a V-pace to electromechanical response interval in response to the V-pace event, determine whether capture is detected in response to the intrinsic electromechanical atrioventricular interval and the V-pace to electromechanical response interval, and determine a pacing parameter in response to determining whether capture is detected.

In another example, a non-transitory computer readable medium storing instructions which cause a left ventricular leadless pacing device to perform a method that comprises: sensing a cardiac signal via one or more electrodes of the pacing device; determining an intrinsic P-wave of the sensed cardiac signal; sensing an electromechanical signal from an electromechanical sensor of the pacing device, such as an accelerometer; determining an intrinsic electromechanical atrioventricular interval of the sensed electromechanical signal in response to the sensed intrinsic P-wave; delivering ventricular pacing via the one or more electrodes of the pacing device; determining a ventricular pacing (V-pace) event in response to the delivered ventricular pacing; determining a V-pace to electromechanical response interval in response to the V-pace event; determining whether capture is detected in response to the intrinsic electromechanical atrioventricular interval and the V-pace to electromechanical response interval; and determining a pacing parameter in response to determining whether capture is detected.

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

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Exemplary systems and methods shall be described with reference toFIGS. 1-9. It will be apparent to one skilled in the art that elements or processes from one embodiment may be used in combination with elements or processes of the other embodiments, and that the possible embodiments of such methods and systems using combinations of features set forth herein is not limited to the specific embodiments shown in the Figures and/or described herein. Further, it will be recognized that the embodiments described herein may include many elements that are not necessarily shown to scale. Still further, it will be recognized that timing of the processes and the size and shape of various elements herein may be modified but still fall within the scope of the present disclosure, although certain timings, one or more shapes and/or sizes, or types of elements, may be advantageous over others.

The exemplary system, device and methods described herein relates to left capture management in a left ventricular leadless pacemaker that includes defining an intrinsic electromechanical atrioventricular (AV) interval (IEMAVI) as the timing interval between an atrial sensing event (sensed by an accelerometer of the leadless acing device or sensed by an extravascular ICD vector) and the mechanical response as measured by the peak of the accelerometer signal corresponding to systole under conditions of stable non-tachy rhythms. Since the largest peak in the accelerometer signal will correspond to the ventricular systole for patients who have intrinsic AV conduction, the IEMAVI may be determined using a window of the accelerometer signal extending from the intrinsic atrial sense event, such as a 450 ms window.

During capture management, ventricular pacing may be delivered by the left ventricular leadless device simultaneously with an atrial sensing event at a given pacing output, and the ventricular pace to electromechanical response interval (Vp-EMI) may be measured in the same way. Left ventricular capture is detected if IEMAVI>Vp-EMI+a constant-time interval. Example values for the constant time interval may be 20 ms, 30 ms, 40 ms, or 50 ms. The capture management routine may start with the highest pacing output parameters and then step down the outputs till lack of capture is detected. In this way the device may determine pacing thresholds and set margins for appropriate pacing outputs (e.g. 1 V above thresholds, etc) for delivering pacing therapy.

FIG. 1is a conceptual drawing illustrating an example system10that includes a subcutaneous device (SD)30(e.g. SICD, loop recorder (i.e. REVEAL®) etc.) implanted exterior to a rib cage of patient14and a leadless pacing device (LPD)16implanted within the left ventricle24of patient14. The SD30can be implanted external to a rib cage and within the vasculature. Additionally or alternatively, an implantable medical device can be implanted substernally/retrosternally, as described in U.S. Patent Application 61/819,946, entitled “IMPLANTABLE MEDICAL DEVICE SYSTEM HAVING IMPLANTABLE CARDIAC DEFIBRILLATOR SYSTEM AND SUBSTERNAL LEADLESS PACING DEVICE” filed May 6, 2013, incorporated by reference in its entirety. In the example ofFIG. 1, system10includes LPD16and SD30. External programmer20may be configured to communicate with one or both of LPD16and SD30. Generally, there are no wires or other direct electrical (e.g., hardwired) connections between SD30and LPD16. In this manner, any communication between SD30and LPD16may be described as “wireless” communication. Patient14is ordinarily, but not necessarily, a human patient.

Exemplary SD30includes a housing32configured to be subcutaneously implanted outside the rib cage of patient14. The subcutaneous implantation location may be anterior to the cardiac notch, for example. In addition, housing32may carry three subcutaneous electrodes34A-34C (collectively “electrodes34”). In other examples, housing32may carry fewer or greater than three electrodes. Lead36may be configured to couple to housing32and extend from housing32to a different subcutaneous location within patient14. For example, lead36may be tunneled laterally and posteriorly to the back of patient14at a location adjacent to a portion of a latissimus dorsi muscle. Lead36may carry electrode coil38along a length of lead36and sensing electrode40at a distal end of lead36. SD30may be configured such that heart12may be disposed at least partially between housing30and electrode coil38of lead36. In some examples, lead36may carry two or more electrode coils38and/or two or more sensing electrodes40.

SD30may contain, within housing32, signal processing and therapy delivery circuitry to detect cardiac conditions (e.g., ventricular dyssnchrony, arrhythmias such as bradycardia and tachycardia conditions etc.) and to communicate with LPD16to apply appropriate electrical stimuli (e.g. pacing and/or anti-tachyarrhythmia shock therapy (e.g., defibrillation or cardioversion shocking pulses)) to heart12. SD30also may be configured to apply pacing pulses via one or more electrodes34. SD30may be configured to apply the anti-tachyarrhythmia shock pulses between coil electrode38and one or more of electrodes34and/or the electrically conductive housing32(e.g., an additional can electrode) of SD30. SD30may be configured to communicate with programmer20via an RF communication link, inductive coupling, or some other wireless communication protocol.

SD30differs from traditionally used ICDs in that housing32may be larger in size than the housing of a traditional ICD to accommodate larger capacity batteries, for example. In addition, SD30may be implanted subcutaneously whereas a traditional ICD may be implanted under muscle or deeper within patient14. In other examples, housing32may be shaped or sized differently to be implanted subcutaneously instead of under a muscle or within deep tissue. Moreover, SD30does not include leads configured to be placed in the bloodstream (e.g., endocardial or epicardial leads). Instead, SD30may be configured to carry one or more electrodes (e.g., electrodes34) on housing32together with one or more subcutaneous leads (e.g., lead36) that carry defibrillation coil electrode38and sensing electrode40. In other examples, lead36may include additional electrodes. These subcutaneously implanted electrodes of SD30may be used to provide therapies similar to that of traditional ICDs without invasive vascular leads. In other examples, the exact configuration, shape, and size of SD30may be varied for different applications or patients. Although SD30is generally described as including one or more electrodes, SD30may typically include at least two electrodes to deliver an electrical signal (e.g., therapy) and/or provide at least one sensing vector. Other exemplary SDs30can be used in combination with LPD16. For example, SD30includes intravenously implanted device (IID), an ICD or a pacemaker or any other suitable device.

System10also includes one or more LPDs, such as LPD16. LPD16may be, for example, an implantable leadless pacing device (e.g., a pacemaker, cardioverter, and/or defibrillator) that provides electrical signals to heart12via electrodes carried on the housing of LPD16. In the example ofFIG. 1, LPD16is implanted within left ventricle16of heart12to sense electrical activity of heart12and/or deliver electrical stimulation, e.g., CRT such as fusion pacing, to heart12. Fusion pacing involves left ventricle (LV)24only pacing with an electrode on the LPD16in coordination with the intrinsic right ventricle (RV) activation. Alternatively, fusion pacing can involve pacing the RV with an electrode on the LPD16in coordination with the intrinsic LV activation. In this scenario, the LPD16is placed within the right ventricle18.

LPD16is schematically shown inFIG. 1attached to a wall of the left ventricle24via one or more fixation elements (e.g. tines, helix etc.) that penetrate the tissue. These fixation elements may secure LPD16to the cardiac tissue and retain an electrode (e.g., a cathode or an anode) in contact with the cardiac tissue. LPD16may also include one or more motion sensors (e.g., accelerometers) configured to detect and/or confirm cardiac conditions (e.g. ventricular dyssynchrony, tachyarrhythmias etc.) from these mechanical motions of heart12. Since LPD16includes two or more electrodes carried on the exterior housing of LPD16, no other leads or structures need to reside in other chambers of heart12. However, in other examples, system10may include additional LPDs within respective chambers of heart12(e.g., left atrium26, right atrium22).

Using the electrodes carried on the housing of LPD16, LPD16may be capable sensing intrinsic electrical signals, e.g., an electrocardiogram (ECG). SD30may similarly sense intrinsic electrical signals from the sensing vectors of electrodes34,38, and40. These intrinsic signals may be electrical signals generated by cardiac muscle and indicative of depolarizations and repolarizations of heart12at various times during the cardiac cycle. LPD16may generate an electrogram from these cardiac signals that may be used by LPD16to detect cardiac conditions (e.g. ventricular dyssynchrony, arrhythmias, such as tachyarrhythmias), or identify other cardiac events, e.g., ventricle depolarizations or atrium depolarizations. LPD16may also measure impedances of the carried electrodes and/or determine capture thresholds of those electrodes intended to be in contact with cardiac tissue. In addition, LPD16may be configured to communicate with external programmer20. The configurations of electrodes used by LPD16for sensing and pacing may be typically considered bipolar but unipolar may also be used.

External programmer20may be configured to communicate with one or both of SD30and LPD16. In examples where external programmer20only communicates with one of SD30and LPD16, the non-communicative device may receive instructions from or transmit data to the device in communication with programmer20. In some examples, programmer20comprises a handheld computing device, computer workstation, or networked computing device. Programmer20may include a user interface that receives input from a user. In other examples, the user may also interact with programmer20remotely via a networked computing device. The user may interact with programmer20to communicate with LPD16and/or SD30. For example, the user may interact with programmer20to send an interrogation request and retrieve therapy delivery data, update therapy parameters that define therapy, manage communication between LPD16and/or SD30, or perform any other activities with respect to LPD16and/or SD30. Although the user is a physician, technician, surgeon, electrophysiologist, or other healthcare professional, the user may be patient14in some examples.

Programmer20may also allow the user to define how LPD16and/or SD30senses electrical signals (e.g., ECGs), detects cardiac conditions (e.g. ventricular dyssynchrony, arrhythmias etc.), delivers therapy, and communicates with other devices of system10. For example, programmer20may be used to change detection parameters. In another example, programmer20may be used to manage therapy parameters that define therapies such as CRT. Moreover, programmer20may be used to alter communication protocols between LPD16and SD30. For example, programmer20may instruct LPD16and/or SD30to switch between one-way and two-way communication and/or change which of LPD16and/or SD30are tasked with initial detection of a cardiac condition.

Programmer20may communicate with LPD16and/or SD30via wireless communication using any techniques known in the art. Examples of communication techniques may include, for example, radiofrequency (RF) telemetry, but other techniques are also contemplated. In some examples, programmer20may include a programming head that may be placed proximate to the patient's body near the LPD16and/or SD30implant site in order to improve the quality or security of communication between LPD16and/or SD30and programmer20.

LPD16and SD30may engage in communication to facilitate the appropriate detection of ventricular dyssynchrony and/or delivery of CRT. The communication may include one-way communication in which one device is configured to transmit communication messages and the other device is configured to receive those messages. The communication may instead include two-way communication in which each device is configured to transmit and receive communication messages. LPD16and SD30may be configured to communicate with each other provide alternative electrical stimulation therapies.

Although LPD16may at least partially determine whether or not LPD16delivers CRT or another therapy to patient14, LPD16may perform one or more functions in response to receiving a request from SD30and without any further analysis by LPD16. In this manner, SD30may act as a master device and LPD16may act as a slave device. In this configuration, LPD16passively senses. Specifically, a VVT mode is employed as a trigger mode to pace in synchrony. In one or more embodiments, the LPD16can be configured to actively sense.

FIGS. 2A and 2Bare conceptual drawings illustrating different views of SD30ofFIG. 1.FIG. 2Ais a top view of SD30, andFIG. 2Bis a front view of SD30. In the example ofFIGS. 2A and 2B, housing32may be constructed as an ovoid with a substantially kidney-shaped profile. The ovoid shape of housing32may promote ease of subcutaneous implantation and may minimize patient discomfort during normal body movement and flexing of the thoracic musculature. In other examples, housing32may be constructed with different shapes intended for different implant locations and/or to house different components, subcutaneous leads, or configurations for electrodes34FIG. 2B.

Housing32may contain the electronic circuitry of SD30. Header48and connector46may provide an electrical connection between distal electrode coil38and distal sensing electrode40of lead36and the circuitry within housing32. Subcutaneous lead36may include distal defibrillation coil electrode38, distal sensing electrode40, insulated flexible lead body42and proximal connector pin44. Distal sensing electrode40may be sized appropriately to match the sensing impedance of electrodes34A-34C to be used in combination.

In some examples, electrodes34are each welded into place on a flattened periphery of housing32and are connected to electronic circuitry inside housing32. Electrodes34may be constructed of flat plates, or alternatively, spiral electrodes (as described in U.S. Pat. No. 6,512,940, incorporated herein in its entirety) and mounted in a non-conductive surround shroud (as described in U.S. Pat. Nos. 6,522,915 and 6,622,046, both incorporated herein in their entirety). Electrodes34shown inFIG. 2Bmay be positioned on housing32to form orthogonal signal vectors. However, electrodes34may be positioned to form any non-orthogonal signal vectors in other examples. In addition, housing32may include fewer or greater than three electrodes. Moreover, housing32may be configured as an electrically conductive surface and operate as an electrode. Housing32may be referred to as a “can electrode” or used as an indifferent electrode. In some examples, housing32may be used as an electrode with coil electrode38during delivery of (electrical stimuli e.g. pacing pulses, anti-tachyarrhythmia shock).

FIG. 3is a conceptual drawing illustrating example LPD16ofFIG. 1. As shown inFIG. 3, LPD16includes case50, cap58, electrode60, electrode52, fixation mechanisms62, flange54, and opening56. Together, case50and cap58may be considered the housing of LPD16. In this manner, case50and cap58may enclose and protect the various electrical components within LPD16. Case50may enclose substantially all of the electrical components, and cap58may seal case50and create the hermetically sealed housing of LPD16. Although LPD16is generally described as including one or more electrodes, LPD16may typically include at least two electrodes (e.g., electrodes52and60) to deliver an electrical signal (e.g., therapy such as CRT) and/or provide at least one sensing vector. Electrodes52and60are carried on the housing created by case50and cap58. In this manner, electrodes52and60may be considered leadless electrodes. In the example ofFIG. 3, electrode60is disposed on the exterior surface of cap58.

Electrode60may be a circular electrode positioned to contact cardiac tissue upon implantation. Electrode52may be a ring or cylindrical electrode disposed on the exterior surface of case50. Both case50and cap58may be electrically insulating. Electrode60may be used as a cathode and electrode52may be used as an anode, or vice versa, for delivering CRT or other appropriate cardiac therapy (ATP, shock etc.). However, electrodes52and60may be used in any stimulation configuration. In addition, electrodes52and60may be used to detect intrinsic electrical signals from cardiac muscle. In other examples, LPD16may include three or more electrodes, where each electrode may deliver therapy and/or detect intrinsic signals. CRT delivered by LPD16may be considered to be “painless” to patient14or even undetectable by patient14since the electrical stimulation occurs very close to or at cardiac muscle and at relatively low energy levels compared with alternative devices.

Fixation mechanisms62may attach LPD16to cardiac tissue. Fixation mechanisms62may be active fixation tines, screws, clamps, adhesive members, or any other types of attaching a device to tissue. As shown in the example ofFIG. 3, fixation mechanisms62may be constructed of a memory material that retains a preformed shape. During implantation, fixation mechanisms62may be flexed forward to pierce tissue and allowed to flex back towards case50. In this manner, fixation mechanisms62may be embedded within the target tissue.

Flange54may be provided on one end of case50to enable tethering or extraction of LPD16. For example, a suture or other device may be inserted around flange54and/or through opening56and attached to tissue. In this manner, flange54may provide a secondary attachment structure to tether or retain LPD16within heart12if fixation mechanisms62fail. Flange54and/or opening56may also be used to extract LPD16once the LPD needs to be explanted (or removed) from patient14if such action is deemed necessary.

In another example, LPD16may be configured to be implanted external to heart12, e.g., near or attached to the epicardium of heart12. An electrode carried by the housing of the fusion pacing LPD16may be placed in contact with the epicardium and/or one or more electrodes placed in contact with the epicardium at locations sufficient to provide therapy (e.g., on external surfaces of the left and/or right ventricles). In any example, SD30may communicate with one or more leadless or leaded devices implanted internal or external to heart12.

FIG. 4is a functional block diagram illustrating an example configuration of SD30ofFIG. 1. In the illustrated example, SD30includes a processor70, memory72, shock module75, signal generator76, sensing module78, telemetry module74, communication module80, activity sensor82, and power source84. Memory72includes computer-readable instructions that, when executed by processor70, cause SD30and processor70to perform various functions attributed to SD30and processor70herein (e.g., detection of ventricular dyssynchrony, communication with LPD16, and/or delivery of anti-tachyarrhythmia shock therapy, if needed). Memory72may include any volatile, non-volatile, magnetic, optical, or electrical media, such as a random access memory (RAM), read-only memory (ROM), non-volatile RAM (NVRAM), electrically-erasable programmable ROM (EEPROM), flash memory, or any other digital or analog media.

Processor70controls signal generator76to deliver stimulation therapy to heart12according to a therapy parameters, which may be stored in memory72. For example, processor70may control signal generator76to deliver electrical pulses (e.g., shock pulses) with the amplitudes, pulse widths, frequency, or electrode polarities specified by the therapy parameters. In this manner, signal generator76may deliver electrical pulses to heart12via electrodes34,38, and/or40. In addition, housing30may be configured as an electrode and coupled to signal generator76and/or sensing module78. SD30may use any combination of electrodes to deliver anti-tachycardia therapy and/or detect electrical signals from patient14. However, in general, coil electrode38may be used to deliver an anti-tachyarrhythmia shock, if necessary.

Signal generator76may also include shock module75. Shock module75may include circuitry and/or capacitors required to deliver an anti-tachyarrhythmia shock. For example, signal generator76may charge shock module75to prepare for delivering a shock. Shock module75may then discharge to enable signal generator76to deliver the shock to patient14via one or more electrodes. In other examples, shock module75may be located within SD30but outside of signal generator76.

Signal generator76is electrically coupled to electrodes34,38, and40. In the illustrated example, signal generator76is configured to generate and deliver electrical stimuli (e.g. anti-tachyarrhythmia shock therapy) to heart12. For example, signal generator76may, using shock module75, deliver shocks to heart12via a subset of electrodes34,38, and40. In some examples, signal generator76may deliver pacing stimulation, and cardioversion or defibrillation shocks in the form of electrical pulses. In other examples, signal generator may deliver one or more of these types of stimulation or shocks in the form of other signals, such as sine waves, square waves, or other substantially continuous time signals.

Signal generator76may include a switch module and processor70may use the switch module to select, e.g., via a data/address bus, which of the available electrodes are used to deliver shock and/or pacing pulses. The switch module may include a switch array, switch matrix, multiplexer, or any other type of switching device suitable to selectively couple stimulation energy to selected electrodes.

Electrical sensing module78may be configured to monitor signals from at least one of electrodes34,38, and40in order to monitor electrical activity of heart12, impedance, or other electrical phenomenon. Sensing may be done to determine heart rates or heart rate variability, or to detect arrhythmias (e.g., tachyarrhythmia) or other electrical signals. Sensing module78may also include a switch module to select which of the available electrodes are used to sense the heart activity, depending upon which electrode combination, or electrode vector, is used in the current sensing configuration. In examples with several electrodes, processor70may select the electrodes that function as sense electrodes, i.e., select the sensing configuration, via the switch module within sensing module78. Sensing module78may include one or more detection channels, each of which may be coupled to a selected electrode configuration for detection of cardiac signals via that electrode configuration. Some detection channels may be configured to detect cardiac events, such as P- or R-waves, and provide indications of the occurrences of such events to processor70, e.g., as described in U.S. Pat. No. 5,117,824 to Keimel et al., which issued on Jun. 2, 1992 and is entitled, “APPARATUS FOR MONITORING ELECTRICAL PHYSIOLOGIC SIGNALS,” and is incorporated herein by reference in its entirety. Processor70may control the functionality of sensing module78by providing signals via a data/address bus.

Processor70may include a timing and control module, which may be embodied as hardware, firmware, software, or any combination thereof. The timing and control module may comprise a dedicated hardware circuit, such as an ASIC, separate from other processor70components, such as a microprocessor, or a software module executed by a component of processor70, which may be a microprocessor or ASIC. The timing and control module may implement programmable counters. If SD30is configured to generate and deliver pacing pulses to heart12, such counters may control the basic time intervals associated with DDD, VVI, DVI, VDD, AAI, DDI, DDDR, VVIR, DVIR, VDDR, AAIR, DDIR and other modes of pacing.

Intervals defined by the timing and control module within processor70may include atrial and ventricular pacing escape intervals, refractory periods during which sensed P-waves and R-waves are ineffective to restart timing of the escape intervals, and the pulse widths of the pacing pulses. As another example, the timing and control module may withhold sensing from one or more channels of sensing module78for a time interval during and after delivery of electrical stimulation to heart12. The durations of these intervals may be determined by processor70in response to stored data in memory72. The timing and control module of processor70may also determine the amplitude of the cardiac pacing pulses.

Interval counters implemented by the timing and control module of processor70may be reset upon sensing of R-waves and P-waves with detection channels of sensing module78. The value of the count present in the interval counters when reset by sensed R-waves and P-waves may be used by processor70to measure the durations of R-R intervals, P-P intervals, P-R intervals and R-P intervals, which are measurements that may be stored in memory72. In some examples, processor70may determine that ventricular dyssynchrony has occurred based on AV interval and P-wave width measurements. Ventricular dyssynchrony is automatically addressed by updating AV delays every minute based on AV interval and P-wave width measurements.

In some examples, communication module80may be used to detect communication signals from LPD16. LPD16may not include telemetry circuitry. Instead, LPD16may generate electrical signals via one or more electrodes with amplitudes and/or patterns representative of information to be sent to SD30. The electrical signals may be carried by pacing pulses or separate communication signals configured to be detected by SD30. In this manner, communication module80may be configured to monitor signals sensed by sensing module78and determine when a communication message is received from LPD16.

In other examples, SD30may also transmit communication messages to LPD16using electrical signals from one or more of electrodes34,38, and40. In this case, communication module80may be coupled to signal generator76to control the parameters of generated electrical signals or pulses. Alternatively, processor70may detect communications via sensing module78and/or generate communications for deliver via signal generator76. Although communication module80may be used to communicate using electrical signals via electrodes34,38and40, communication module80may alternatively or in addition use wireless protocols such as RF telemetry to communicate with LPD16or other medical devices. In some examples, telemetry module74may include this wireless communication functionality.

Memory72may be configured to store a variety of operational parameters, therapy parameters, sensed and detected data, and any other information related to the monitoring, therapy and treatment of patient14. Memory72may store, for example, thresholds and parameters indicative of cardiac conditions such as ventricular dyssynchrony and/or therapy parameter values that at least partially define delivered CRT such as fusion pacing. In some examples, memory72may also store communications transmitted to and/or received from LPD16.

Activity sensor82may be contained within the housing of SD30and include one or more accelerometers or other devices capable of detecting motion and/or position of SD30. For example, activity sensor82may include a 3-axis accelerometer that is configured to detect accelerations in any direction in space. Accelerations detected by activity sensor82may be used by processor70to identify potential noise in signals detected by sensing module78and/or confirm the detection of arrhythmias or other patient conditions.

Telemetry module74includes any suitable hardware, firmware, software or any combination thereof for communicating with another device, such as programmer20(FIG. 1). As described herein, telemetry module74may transmit generated or received arrhythmia data, therapy parameter values, communications between SD30and LPD16, or any other information. For example, telemetry module74may transmit information representative of sensed physiological data such as R-R intervals or any other data that may be used by LPD16to determine a condition of patient14. Telemetry module74may also be used to receive updated therapy parameters from programmer20. Under the control of processor70, telemetry module74may receive downlink telemetry from and send uplink telemetry to programmer20with the aid of an antenna, which may be internal and/or external. Processor70may provide the data to be uplinked to programmer20and the control signals for the telemetry circuit within telemetry module74, e.g., via an address/data bus. In some examples, telemetry module74may provide received data to processor70via a multiplexer. In some examples, SD30may signal programmer20to further communicate with and pass the alert through a network such as the Medtronic CareLink® Network developed by Medtronic, Inc., of Minneapolis, Minn., or some other network linking patient14to a clinician. SD30may spontaneously transmit the diagnostic information to the network or in response to an interrogation request from a user.

Power source84may be any type of device that is configured to hold a charge to operate the circuitry of SICD. Power source84may be provided as a rechargeable or non-rechargeable battery. In other examples, power source84may also incorporate an energy scavenging system that stores electrical energy from movement of SD30within patient14.

There may be numerous variations to the configuration of SD30, as described herein. In the examples ofFIGS. 2A, 2B, and 4, SD30may include housing32configured to be implanted in patient14external to a rib cage of patient14, one or more electrodes (e.g., electrodes34,38, and40) configured to be disposed external to the rib cage, and shock module75configured to at least partially deliver anti-tachyarrhythmia shock therapy to patient14via the one or more electrodes.

SD30may also include communication module80configured to transmit and/or receive communication messages between LPD16configured to be implanted within heart12of patient14and a sensing module78configured to sense an electrical signal from heart12of patient14via the one or more electrodes. Further, SD30may include one or more processors70configured to detect a ventricular dyssynchrony within the sensed electrical signal and determine, based on the detected ventricular dyssynchrony, to deliver CRT to patient14to treat the detected ventricular dyssynchrony. Processor70may also be configured to transmit, via communication module80and prior to delivering CRT, a communication message to LPD16requesting LPD16deliver fusion pacing to heart12of patient14.

FIG. 5is a functional block diagram illustrating an example configuration of LPD16ofFIG. 1. In the illustrated example, LPD16includes a processor90, memory92, signal generator96, sensing module98, shock detector99, activity sensor100, telemetry module94, and power source102. Memory92includes computer-readable instructions that, when executed by processor90, cause LPD16and processor90to perform various functions attributed to LPD16and processor90herein (e.g., detecting ventricular dyssnchrony, arrhythmias, communicating with SD30, and delivering anti-tachycardia pacing and post-shock pacing). Memory92may include any volatile, non-volatile, magnetic, optical, or electrical media, such as a random access memory (RAM), read-only memory (ROM), non-volatile RAM (NVRAM), electrically-erasable programmable ROM (EEPROM), flash memory, or any other digital or analog media.

Processor90controls signal generator96to deliver stimulation therapy to heart12according to a therapy parameters, which may be stored in memory92. For example, processor90may control signal generator96to deliver electrical pulses with the amplitudes, pulse widths, frequency, or electrode polarities specified by the therapy parameters. In this manner, signal generator96may deliver pacing pulses (e.g., fusion pacing) to heart12via electrodes52and60. Although LPD16may only include two electrodes, e.g., electrodes52and60, LPD16may utilize three or more electrodes in other examples. LPD16may use any combination of electrodes to deliver therapy and/or detect electrical signals from patient14.

Signal generator96is electrically coupled to electrodes52and60carried on the housing of LPD16. In the illustrated example, signal generator96is configured to generate and deliver electrical stimulation therapy to heart12. For example, signal generator96may deliver pulses to a portion of cardiac muscle within heart12via electrodes52and60. In some examples, signal generator96may deliver pacing stimulation in the form of electrical pulses. In other examples, signal generator may deliver one or more of these types of stimulation in the form of other signals, such as sine waves, square waves, or other substantially continuous time signals. Although LPD16is generally described has delivering pacing pulses, LPD16may deliver cardioversion or defibrillation pulses in other examples.

Fusion pacing may be delivered to patient14as defined by a set of parameters. These parameters may include pulse intervals, pulse width, current and/or voltage amplitudes, and durations for each pacing mode.

Signal generator96may also include circuitry for measuring the capture threshold of one or both electrodes52and60. The capture threshold may indicate the voltage necessary to induce depolarization of the surrounding cardiac muscle. For example, signal generator96may measure the voltage of pacing signals needed to induce synchronized ventricular contractions. In examples in which LPD16includes more than two electrodes, signal generator96may include a switch module and processor90may use the switch module to select, e.g., via a data/address bus, which of the available electrodes are used to deliver pacing pulses. The switch module may include a switch array, switch matrix, multiplexer, or any other type of switching device suitable to selectively couple stimulation energy to selected electrodes. In the instance that the capture threshold exceeds useable limits, processor90may withhold delivery of therapeutic pacing. In addition, processor90may transmit communication to SD30if pacing cannot be delivered.

Electrical sensing module98monitors signals from at least one of electrodes52and60in order to monitor electrical activity of heart12, impedance, or other electrical phenomenon. Sensing may be done to determine heart rates or heart rate variability, or to detect ventricular dyssynchrony, arrhythmias (e.g., tachyarrhythmias) or other electrical signals. Sensing module98may also include a switch module to select which of the available electrodes (or electrode polarity) are used to sense the heart activity, depending upon which electrode combination, or electrode vector, is used in the current sensing configuration. In examples with several electrodes, processor90may select the electrodes that function as sense electrodes, i.e., select the sensing configuration, via the switch module within sensing module98. Sensing module98may include one or more detection channels, each of which may be coupled to a selected electrode configuration for detection of cardiac signals via that electrode configuration. Some detection channels may be configured to detect cardiac events, such as P- or R-waves, and provide indications of the occurrences of such events to processor90, e.g., as described in U.S. Pat. No. 5,117,824 to Keimel et al., which issued on Jun. 2, 1992 and is entitled, “APPARATUS FOR MONITORING ELECTRICAL PHYSIOLOGIC SIGNALS,” and is incorporated herein by reference in its entirety. Processor90may control the functionality of sensing module98by providing signals via a data/address bus.

Processor90may include a timing and control module, which may be embodied as hardware, firmware, software, or any combination thereof. The timing and control module may comprise a dedicated hardware circuit, such as an ASIC, separate from other processor90components, such as a microprocessor, or a software module executed by a component of processor90, which may be a microprocessor or ASIC. The timing and control module may implement programmable counters. If LPD16is configured to generate and deliver pacing pulses to heart12, such counters may control the basic time intervals associated with DDD, VVI, DVI, VDD, AAI, DDI, DDDR, VVIR, DVIR, VDDR, AAIR, DDIR and other modes of pacing. Example LPDs that may deliver pacing using such modes are described in U.S. patent application Ser. No. 13/665,492 to Bonner et al., entitled, “LEADLESS PACEMAKER SYSTEM,” and filed on Oct. 31, 2012, or in U.S. patent application Ser. No. 13/665,601 to Bonner et al., entitled, “LEADLESS PACEMAKER SYSTEM,” and filed on Oct. 31, 2012. U.S. patent application Ser. No. 13/665,492 to Bonner et al. and U.S. patent Ser. No. 13/665,601 to Bonner et al. are both incorporated herein by reference in their entireties.

In addition to detecting and identifying specific types of cardiac rhythms (types of cardiac events), sensing module98may also sample the detected intrinsic signals to generate an electrogram or other time-based indication of cardiac events. Processor90may also be able to coordinate the delivery of pacing pulses from different LPDs implanted in different chambers of heart12, such as an LPD implanted in the other ventricle. For example, processor90may identify delivered pulses from other LPDs via sensing module98and updating pulse timing. In other examples, LPDs may communicate with each other via telemetry module94and/or instructions over a carrier wave (such as a stimulation waveform).

Memory92may be configured to store a variety of operational parameters, therapy parameters, sensed and detected data, and any other information related to the therapy and treatment of patient14. In the example ofFIG. 5, memory92may store sensed ECGs, detected arrhythmias, communications from SD30, and therapy parameters. In other examples, memory92may act as a temporary buffer for storing data until it can be uploaded to SD30, another implanted device, or programmer20.

Activity sensor100may be contained within the housing of LPD16and include one or more accelerometers or other devices capable of detecting motion and/or position of LPD16. For example, activity sensor100may include a 3-axis accelerometer that is configured to detect accelerations in any direction in space. Specifically, the 3-axis accelerator may be used to detect LPD16motion that may be indicative of cardiac events and/or noise. For example, processor16may monitor the accelerations from activity sensor100to confirm or detect arrhythmias. Since LPD16may move with a chamber wall of heart12, the detected changes in acceleration may also be indicative of contractions. Therefore, LPD16may be configured to identify heart rates and confirm ventricular dyssynchrony sensed via sensing module98.

Telemetry module94includes any suitable hardware, firmware, software or any combination thereof for communicating with another device, such as programmer20or SD30(FIG. 1). Under the control of processor90, telemetry module94may receive downlink telemetry from and send uplink telemetry to programmer20with the aid of an antenna, which may be internal and/or external. Processor90may provide the data to be uplinked to programmer20and the control signals for the telemetry circuit within telemetry module94, e.g., via an address/data bus. In some examples, telemetry module94may provide received data to processor90via a multiplexer.

In some examples, LPD16may signal programmer20to further communicate with and pass the alert through a network such as the Medtronic CareLink® Network developed by Medtronic, Inc., of Minneapolis, Minn., or some other network linking patient14to a clinician. LPD16may spontaneously transmit information to the network or in response to an interrogation request from a user.

In other examples, processor90may be configured to transmit information to another device, such as SD30using electrodes52and60. For example, processor90may control signal generator96to generate electrical signals representative of commands such as the detection of ventricular dyssynchrony, confirmation that ventricular dyssynchrony has been detected, a request to monitor electrical signals for ventricular dyssynchrony, or even signals to “wake up” an SICD in a sleep mode. In other examples, processor90may cause telemetry module94to transmit information representative of sensed physiological data such as R-R intervals or any other data that may be used by SD30to determine a condition of patient14(e.g., whether or not patient14is experiencing ventricular dyssynchrony). The communication may be in the form of dedicated communication signals.

Alternatively, processor90may communicate with SD30by delivering pacing pulses at specific intervals that would be identifiable by SD30as non-physiologic and intended to convey information. In other words, these pulses intended for communication with SD30. SD30may be configured to identify, or distinguish, these pulses from signals indicative of normal or non-normal heart beats, signals indicative of ectopic or non-ectopic heart beats, signals indicative of noise (e.g., skeletal muscle noise), or any other signals indicative of typically physiological or therapeutic electrical signals. The communication pulses may or may not be therapeutic pulses or signals. SD30may detect the intervals between these pulses as code for specific messages from LPD16. For example, the pacing pulses may be varied and/or repeated in certain patterns detectable by SD30and still therapeutic. LPD16may also be configured to detect such communication messages via electrodes52and60. Processor90may monitor sensing module98for such communications. Alternatively, LPD16may include a communication module, similar to communication module80ofFIG. 4, to detect any communications received via sensing module98. In any example, LPD16may be configured for one-way communication to or from another device such as SD30or two-way communication with another device such as SD30using any type of communication protocol.

Power source102may be any type of device that is configured to hold a charge to operate the circuitry of LPD16. Power source102may be provided as a rechargeable or non-rechargeable battery. In other example, power source102may incorporate an energy scavenging system that stores electrical energy from movement of LPD16within patient14.

There may be numerous variations to the configuration of LPD16, as described herein. In one example, LPD16includes a housing configured to be implanted within heart12of patient14, one or more electrodes (e.g., electrodes52and60) coupled to the housing, fixation mechanism62configured to attach the housing to tissue of heart12, sensing module98configured to sense an electrical signal from heart12of patient14via the one or more electrodes, and signal generator96configured to deliver therapy to heart12of patient14via the one or more electrodes. LPD16may also include processor90configured to receive a communication message from SD30requesting LPD16deliver CRT to heart12, where SD30is configured to be implanted exterior to a rib cage of patient14. Processor90may also be configured to determine, based on the sensed electrical signal, whether to deliver CRT to heart12, and, in response to the determination, command signal generator96to deliver the CRT therapy. Processor90may also be configured to control signal generator96to deliver post-shock pacing to patient14in response to shock detector99detecting an anti-tachyarrhythmia shock.

FIG. 6is a functional block diagram illustrating an example configuration of external programmer20ofFIG. 1. As shown inFIG. 6, programmer20may include a processor110, memory112, user interface114, telemetry module116, and power source118. Programmer20may be a dedicated hardware device with dedicated software for programming of LPD16and/or SD30. Alternatively, programmer20may be an off-the-shelf computing device running an application that enables programmer20to program LPD16and/or SD30.

A user may use programmer20to configure the operational parameters of and retrieve data from LPD16and/or SD30(FIG. 1). In one example, programmer20may communicate directly to both LPD16and SD30. In other examples, programmer may communicate to one of LPD16or SD30, and that device may relay any instructions or information to or from the other device. The clinician may interact with programmer20via user interface114, which may include display to present graphical user interface to a user, and a keypad or another mechanism for receiving input from a user. In addition, the user may receive an alert or notification from SD30indicating that a shock has been delivered, any other therapy has been delivered, or any problems or issues related to the treatment of patient14.

Processor110can take the form one or more microprocessors, DSPs, ASICs, FPGAs, programmable logic circuitry, or the like, and the functions attributed to processor110herein may be embodied as hardware, firmware, software or any combination thereof. Memory112may store instructions that cause processor110to provide the functionality ascribed to programmer20herein, and information used by processor110to provide the functionality ascribed to programmer20herein. Memory112may include any fixed or removable magnetic, optical, or electrical media, such as RAM, ROM, CD-ROM, hard or floppy magnetic disks, EEPROM, or the like. Memory112may also include a removable memory portion that may be used to provide memory updates or increases in memory capacities. A removable memory may also allow patient data to be easily transferred to another computing device, or to be removed before programmer20is used to program therapy for another patient.

Programmer20may communicate wirelessly with LPD16and/or SD30, such as using RF communication or proximal inductive interaction. This wireless communication is possible through the use of telemetry module116, which may be coupled to an internal antenna or an external antenna. An external antenna that is coupled to programmer20may correspond to the programming head that may be placed over heart12or the location of the intend implant, as described above with reference toFIG. 1. Telemetry module116may be similar to telemetry modules74and94of respectiveFIGS. 4 and 5.

Telemetry module116may also be configured to communicate with another computing device via wireless communication techniques, or direct communication through a wired connection. Examples of local wireless communication techniques that may be employed to facilitate communication between programmer20and another computing device include RF communication according to the 802.11 or Bluetooth specification sets, infrared communication, e.g., according to the IrDA standard, or other standard or proprietary telemetry protocols. An additional computing device in communication with programmer20may be a networked device such as a server capable of processing information retrieved from LPD16. In other examples, LPD16may not use a shock detector to time the beginning or ending of post-shock pacing. Instead, LPD16may determine when to deliver post-shock pacing based on a command from SD30. For example, SD30may determine that a shock will be delivered and transmit a shock imminent command to LPD16. In response to receiving the shock imminent command, LPD16may enter a shock state for a predetermined period of time. This predetermined period of time may be stored in memory92or sent along with the shock imminent command from SD30. The predetermined period of time may have a sufficient duration such that any shock would be delivered prior to the predetermined period expiring. In response to the predetermined period elapsing, LPD16may exit the shock state and enter a post-shock pacing state in which LPD16delivers post-shock pacing and/or first determines whether post-shock pacing is needed.

FIG. 7is a flowchart of a method of monitoring capture management in a left ventricular leadless pacing device according to an example of the present disclosure. As illustrated inFIG. 7, according to one example, during monitoring of capture management in a leadless pacing device, the leadless pacing device senses, via electrodes52,60and sensing module98, an intrinsic cardiac signal, i.e., corresponding to systole under conditions of stable, non-tachyarrhythmia cardiac rhythm, Block200. The processor90of the pacing device16determines the occurrence of an intrinsic P-wave event, Block202, based either on a signal sensed by the sensor100of the leadless pacing device16, or based on a signal sensed by an extravascular ICD, such as subcutaneous device30, and received from the extravascular ICD via the telemetry module94of the leadless pacing device16. Based on the determined intrinsic P-wave event, Block202, the processor90of the pacing device16determines an intrinsic electromechanical interval associated with the intrinsic P-wave event, Block204, described below.

In this way, during a capture management procedure, in order to generate pacing parameters that maintain desired consistent left ventricular pacing from a left ventricular leadless pacing device positioned within the left chamber of a patient's heart, the capture management routine begins by the pacing device16delivering ventricular pacing therapy via electrodes52,60, Block206. The ventricular pacing therapy may be delivered simultaneously with an atrial sense event at a given pacing output. For example, the ventricular pacing therapy may be delivered using initial predetermined pacing parameters, such as an initial atrial ventricular (AV) interval for example, which controls the timing of ventricular pacing pulses relative to an atrial depolarization, intrinsic or paced. The processor90determines timing of a V-pace event, Block208, and based on the determined V-pace event, Block208, determines a V-pace to electromechanical response interval, Block210, described below. A determination is then made, based on the determined intrinsic electromechanical interval, Block204, and the determined V-pace to electromechanical response interval, Block210, as to whether capture is detected, Block212, described below.

If capture is detected, Yes in Block212, the processor90adjusts the pacing parameter, Block214, and the process, Blocks206-212, is repeated with the pacing device16delivering pacing therapy, Block206, using the adjusted pacing parameter, Block214. In one example, the processor90may adjust the pacing parameter, Block214, by reducing the pacing parameter by a predetermined step until lack of capture is detected, Yes in Block212. For example, the pacing parameter may include a pacing voltage whose initial value may be the maximum pacing voltage output from the device (e.g. 6.0 V) and during capture management routine this parameter may be reduced in steps of 0.5 V.

Once lack of capture is no longer detected, NO in Block212, the processor90stores the pacing parameter, Block216, in the memory92of the pacing device16so that pacing therapy may be subsequently delivered using pacing settings associated with the stored pacing parameter.

In one example, based on the pacing parameter setting or settings that were being utilized during delivery of the pacing therapy at the time when capture was no longer detected, No on Block212, the processor90may determine the pacing threshold based on the settings used just prior to when capture was no longer detected, and set margins for desired pacing outputs, such as 1 volt above the threshold, for example, for delivering the pacing therapy.

FIG. 8is a graphical representation of determining of an intrinsic electromechanical interval for a method of monitoring capture management in a left ventricular leadless pacing device according to an example of the present disclosure. As illustrated inFIG. 8, according to one example, in order to determine the intrinsic electromechanical interval, Block204ofFIG. 7, the processor90senses a cardiac signal340via electrodes52,60and an electromechanical signal,342, such as an accelerometer signal, via sensor100, and determines the occurrence of an intrinsic P-wave344based either on the sensed cardiac signal340or the sensed electromechanical signal342.

For example, in order to determine the intrinsic P-wave344, the processor90may determine the occurrence of intrinsic P-wave344base on the cardiac signal340sensed via electrodes52,60of the device, or based on the cardiac signal340being sensed by an extravascular ICD, such as subcutaneous device30, and received from the extravascular ICD via the telemetry module94of the leadless pacing device16. For example, the processor90may determine the occurrence of an intrinsic ventricular event346and use an offset interval348to identify the intrinsic P-wave344.

Once the intrinsic P-wave344is determined, the processor90determines a maximum350of the sensed electromechanical signal342that occurs within a time window that extends a predetermined time period352from the sensed intrinsic P-wave344. An intrinsic electromechanical interval354, such as an AV interval for example, is identified as the time period extending from the intrinsic P-wave344and the determined maximum350of the electromechanical signal.

FIG. 9is a graphical representation of determining of a ventricular-pace event to electromechanical interval for a method of monitoring capture management in a left ventricular leadless pacing device according to an example of the present disclosure. As illustrated inFIG. 9, according to one example, in order to determine the V-pace to electromechanical response interval, Block210ofFIG. 7, the processor90senses a cardiac signal340via electrodes52,60and an electromechanical signal,342, such as an accelerometer signal, via sensor100, and determines the occurrence of a V-pace event364based either on the sensed cardiac signal340sensed directly by the pacing device16via electrodes52,60, or a sensed cardiac signal being sensed by an extravascular ICD, such as subcutaneous device30, and received from the extravascular ICD via the telemetry module94of the leadless pacing device16.

Once the V-pace event364is determined to occur, the processor90determines a maximum366of the sensed electromechanical signal342that occurs within a time window that extends a predetermined time period368from the sensed V-pace event. Exemplary values of this time-window may be 250 ms, 300 ms, 350 ms, 400 ms, 450 ms, 500 ms. In one embodiment this time-window may be adjusted depending on the heart rate or interval between successive cardiac depolarization—the time window may be set to a certain percentage (e.g. 50%) of that interval. For example, if successive atrial sensing events occur at interval of 900 ms, then this window will be 50% of 900=450 ms. A V-pace to electromechanical response interval370is identified as the time period that extends from the sensed V-pace event364to the determined maximum366of the electromechanical signal342.

In this way, during the determination as to whether capture is detected, Block212ofFIG. 7, the processor90determines whether the intrinsic electromechanical interval354is greater than the V-pace to electromechanical response interval358. If the intrinsic electromechanical interval354is greater than the V-pace to electromechanical response interval370, left ventricular capture is detected, Yes in Block212. If the intrinsic electromechanical interval354is not greater than the V-pace to electromechanical response interval370, left ventricular capture is not detected, No in Block212. In one example, a constant time interval associated with the V-pace to electromechanical response interval370, such as 20 ms, 30 ms, 40 ms or 50 ms for example, may be utilized so that the processor90determines whether the intrinsic electromechanical interval354is greater than the V-pace to electromechanical response interval370plus the constant time interval. If the intrinsic electromechanical interval354is greater than the V-pace to electromechanical response interval370plus the constant time interval, left ventricular capture is detected, Yes in Block212. If the intrinsic electromechanical interval354is not greater than the V-pace to electromechanical response interval370plus the constant time interval, left ventricular capture is not detected, No in Block212.

The systems and techniques described herein may be generally related to cooperative monitoring of a patient and/or therapy delivery to the patient using multiple implanted devices such as an SD and an LPD. In one example, the SD and LPD may detect the functions of each other and/or communicate to coordinate monitoring and therapy such as CRT. However, the SD and LPD may coordinate other monitoring and therapy features. For example, using the communication techniques described herein, prior to either the SD or LPD delivering therapy, sensed data from both devices may be used to determine if the therapy should be delivered. In some examples, the SD or the LPD may be configured to override the other device in situations in which there is a discrepancy between whether or not physiological condition is occurring. In any case, the SD and LPD may be configured to function together to monitor and/or provide therapy to patient14.

The techniques described herein may provide for a SD and LPD to operate cooperatively within a patient to monitor the heart for arrhythmias and deliver appropriate therapy to treat any detected arrhythmias. For example, an SD and LPD may detect ventricular dyssynchrony and deliver CRT. Wireless communication between the SD implanted external of the rib cage and one or more LPDs implanted within the heart may provide various ECG or EGM sensing vectors.

The disclosure also contemplates computer-readable storage media comprising instructions to cause a processor to perform any of the functions and techniques described herein. The computer-readable storage media may take the example form of any volatile, non-volatile, magnetic, optical, or electrical media, such as a RAM, ROM, NVRAM, EEPROM, or flash memory. The computer-readable storage media may be referred to as non-transitory. A programmer, such as patient programmer or clinician programmer, or other computing device may also contain a more portable removable memory type to enable easy data transfer or offline data analysis.

In addition, it should be noted that system400may not be limited to treatment of a human patient. In alternative examples, system400may be implemented in non-human patients, e.g., primates, canines, equines, pigs, and felines. These other animals may undergo clinical or research therapies that may benefit from the subject matter of this disclosure.

Such hardware, software, firmware may be implemented within the same device or within separate devices to support the various operations and functions described in this disclosure. For example, any of the techniques or processes described herein may be performed within one device or at least partially distributed amongst two or more devices, such as between SD30, LPD16and/or programmer20. In addition, any of the described units, modules or components may be implemented together or separately as discrete but interoperable logic devices. Depiction of different features as modules or units is intended to highlight different functional aspects and does not necessarily imply that such modules or units must be realized by separate hardware or software components. Rather, functionality associated with one or more modules or units may be performed by separate hardware or software components, or integrated within common or separate hardware or software components.

In some examples, a computer-readable storage medium comprises non-transitory medium. The term “non-transitory” may indicate that the storage medium is not embodied in a carrier wave or a propagated signal. In certain examples, a non-transitory storage medium may store data that can, over time, change (e.g., in RAM or cache). Various examples have been described for detecting arrhythmias and delivering anti-tachycardia therapy via a subcutaneous implantable cardioverter defibrillator and/or a leadless pacing device. Any combination of the described operations or functions is contemplated. These and other examples are within the scope of the following claims.

ILLUSTRATIVE EMBODIMENTS

A method of monitoring capture management in a left ventricular leadless pacing device, comprising:sensing a cardiac signal via one or more electrodes of the pacing device;determining an intrinsic P-wave of the sensed cardiac signal;sensing an electromechanical signal from an electromechanical sensor of the pacing device;determining an intrinsic electromechanical atrioventricular interval of the sensed electromechanical signal in response to the sensed intrinsic P-wave;delivering ventricular pacing via the one or more electrodes of the pacing device;determining a ventricular pacing (V-pace) event in response to the delivered ventricular pacing;determining a V-pace to electromechanical response interval in response to the V-pace event;determining whether capture is detected in response to the intrinsic electromechanical atrioventricular interval and the V-pace to electromechanical response interval; anddetermining a pacing parameter in response to determining whether capture is detected.

The method of embodiment 1, wherein the electromechanical sensor comprises an accelerometer.

The method of any of embodiments 1-2, further comprising:determining a maximum of the electromechanical signal in response to the intrinsic P-wave; anddetermining the intrinsic electromechanical atrioventricular interval in response to the determined maximum of the electromechanical signal.

The method of any of embodiments 1-2, further comprising:determining a maximum of the electromechanical signal in response to in response to the determined V-pace event; anddetermining the V-pace to electromechanical response interval in response to the determined maximum of the electromechanical signal.

The method of any of embodiments 1-4, further comprising:determining capture as being detected in response to the intrinsic electromechanical atrioventricular interval being greater than the V-pace to electromechanical response interval; anddetermining capture as not being detected in response to the intrinsic electromechanical atrioventricular interval not being greater than the V-pace to electromechanical response interval.

The method of any of embodiments 1-4, further comprising:determining capture as being detected in response to the intrinsic electromechanical atrioventricular interval being greater than a sum of the V-pace to electromechanical response interval and a predetermined time interval; anddetermining capture as not being detected in response to the intrinsic electromechanical atrioventricular interval not being greater than the sum of the V-pace to electromechanical response interval and the predetermined time interval.

The method of any of embodiments 1-6, further comprising:reducing the pacing parameter by a predetermined step in response to capture being detected until lack of capture is detected; anddetermining a pacing threshold based on parameter settings used prior to when capture was no longer detected and setting pacing output margins relative to the threshold for subsequent delivery the ventricular pacing therapy in response to capture not being detected.

The method of any of embodiments 1-2, further comprising:sensing an electromechanical signal from an electromechanical sensor of the pacing device;determining the intrinsic P-wave in response to the cardiac signal;determining a first maximum of the electromechanical signal in response to the intrinsic P-wave;determining the intrinsic electromechanical atrioventricular interval in response to the determined first maximum of the electromechanical signal;determining a second maximum of the electromechanical signal in response to in response to the determined V-pace event; anddetermining the V-pace to electromechanical response interval in response to the determined second maximum of the electromechanical signal.

The method of embodiment 8, further comprising:determining a first time window extending a predetermined time period from the intrinsic P-wave, wherein the first maximum of the electromechanical signal is determined within the first time window; anddetermining a second time window extending a predetermined time period from the intrinsic V-pace event, wherein the second maximum of the electromechanical signal is determined within the second time window.

The method of embodiment 8, further comprising:determining capture as being detected in response to the intrinsic electromechanical atrioventricular interval being greater than a sum of the V-pace to electromechanical response interval and a predetermined time interval; anddetermining capture as not being detected in response to the intrinsic electromechanical atrioventricular interval not being greater than the sum of the V-pace to electromechanical response interval and the predetermined time interval.

The method of embodiment 8, further comprising:reducing the pacing parameter by a predetermined step until lack of capture is detected in response to capture being detected; anddetermining a pacing threshold based on parameter settings used prior to when capture was no longer detected and setting pacing output margins relative to the threshold for subsequent delivery the ventricular pacing therapy in response to capture not being detected.

A left ventricular leadless pacing device, comprising:one or more electrodes to sense a cardiac signal;an electromechanical sensor to sense an electromechanical signal; anda processor configured to determine an intrinsic P-wave of the sensed cardiac signal, determine an intrinsic electromechanical atrioventricular interval in response to the sensed intrinsic P-wave, deliver ventricular pacing via the one or more electrodes, determine a ventricular pacing (V-pace) event in response to the delivered ventricular pacing, determine a V-pace to electromechanical response interval in response to the V-pace event, determine whether capture is detected in response to the intrinsic electromechanical atrioventricular interval and the V-pace to electromechanical response interval, and determine a pacing parameter in response to determining whether capture is detected.

The device of embodiment 12, wherein the electromechanical sensor comprises an accelerometer.

The device of any of embodiments 12-13, wherein the processor is configured determine a maximum of the sensed electromechanical signal in response to the intrinsic P-wave and determine the intrinsic electromechanical atrioventricular interval in response to the determined maximum of the electromechanical signal.

The device of any of embodiments 12-13, wherein the processor is further configured to determine a maximum of the electromechanical signal in response to in response to the determined V-pace event and determine the V-pace to electromechanical response interval in response to the determined maximum of the electromechanical signal.

The device of any of embodiments 12-16, wherein the processor is configured to determine capture as being detected in response to the intrinsic electromechanical atrioventricular interval being greater than the V-pace to electromechanical response interval, and determine capture as not being detected in response to the intrinsic electromechanical atrioventricular interval not being greater than the V-pace to electromechanical response interval.

The device of any of embodiments 12-16, wherein the processor is configured to determine capture as being detected in response to the intrinsic electromechanical atrioventricular interval being greater than a sum of the V-pace to electromechanical response interval and a predetermined time interval, and determine capture as not being detected in response to the intrinsic electromechanical atrioventricular interval not being greater than the sum of the V-pace to electromechanical response interval and the predetermined time interval.

The device of any of embodiments 12-16, wherein the processor is configured to reduce the pacing parameter by a predetermined step until lack of capture is detected in response to capture being detected, and determine a pacing threshold based on parameter settings used prior to when capture was no longer detected and setting pacing output margins relative to the threshold for subsequent delivery the ventricular pacing therapy in response to capture not being detected.

The device of any of embodiments 12-13, wherein the processor is configured to determine a first maximum of the electromechanical signal in response to the intrinsic P-wave, determine the intrinsic electromechanical atrioventricular interval in response to the determined first maximum of the electromechanical signal, determine a second maximum of the electromechanical signal in response to in response to the determined V-pace event, and determine the V-pace to electromechanical response interval in response to the determined second maximum of the electromechanical signal.

The device of any of embodiments 12-19, wherein the processor is configured to determine a first time window extending a predetermined time period from the intrinsic P-wave, determine the first maximum of the electromechanical signal within the first time window, determine a second time window extending a predetermined time period from the intrinsic V-pace event and determine the second maximum of the electromechanical signal within the second time window.

The device of any of embodiments 12-20, wherein the processor is configured to determine capture as being detected in response to the intrinsic electromechanical atrioventricular interval being greater than a sum of the V-pace to electromechanical response interval and a predetermined time interval, and determine capture as not being detected in response to the intrinsic electromechanical atrioventricular interval not being greater than the sum of the V-pace to electromechanical response interval and the predetermined time interval.

The device of any of embodiments 12-21, wherein the processor is configured to reduce the pacing parameter by a predetermined step in response to capture being detected until lack of capture is detected and determine a pacing threshold based on parameter settings used prior to when capture was no longer detected and setting pacing output margins relative to the threshold for subsequent delivery the ventricular pacing therapy in response to capture not being detected.

A non-transitory computer readable medium storing instructions which cause a left ventricular leadless pacing device to perform a method comprising:sensing a cardiac signal via one or more electrodes of the pacing device;determining an intrinsic P-wave of the sensed cardiac signal;sensing an electromechanical signal from an electromechanical sensor of the pacing device;determining an intrinsic electromechanical atrioventricular interval of the sensed electromechanical signal in response to the sensed intrinsic P-wave;delivering ventricular pacing via the one or more electrodes of the pacing device;determining a ventricular pacing (V-pace) event in response to the delivered ventricular pacing;determining a V-pace to electromechanical response interval in response to the V-pace event;determining whether capture is detected in response to the intrinsic electromechanical atrioventricular interval and the V-pace to electromechanical response interval; anddetermining a pacing parameter in response to determining whether capture is detected.