Patent Description:
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. A system for leadless cardiac resynchronization therapy is known from <CIT>.

The invention is defined by independent claims <NUM> and <NUM>. In the following the methods are not claimed as such but can be useful for understanding the invention. 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 <NUM> 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 <NUM>, <NUM>, <NUM>, or <NUM>. 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. <NUM> V above thresholds, etc) for delivering pacing therapy.

In one example, a method of monitoring capture management in a left ventricular leadless pacing device, which does not form part of the invention, 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.

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

Exemplary systems and methods shall be described with reference to <FIG>. 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 <NUM> window.

<FIG> is a conceptual drawing illustrating an example system <NUM> that includes a subcutaneous device (SD) <NUM> (e.g. SICD, loop recorder (i.e. REVEAL®) etc.) implanted exterior to a rib cage of patient <NUM> and a leadless pacing device (LPD) <NUM> implanted within the left ventricle <NUM> of patient <NUM>. The SD <NUM> can 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 <CIT>. In the example of <FIG>, system <NUM> includes LPD <NUM> and SD <NUM>. External programmer <NUM> may be configured to communicate with one or both of LPD <NUM> and SD <NUM>. Generally, there are no wires or other direct electrical (e.g., hardwired) connections between SD <NUM> and LPD <NUM>. In this manner, any communication between SD <NUM> and LPD <NUM> may be described as "wireless" communication. Patient <NUM> is ordinarily, but not necessarily, a human patient.

Exemplary SD <NUM> includes a housing <NUM> configured to be subcutaneously implanted outside the rib cage of patient <NUM>. The subcutaneous implantation location may be anterior to the cardiac notch, for example. In addition, housing <NUM> may carry three subcutaneous electrodes 34A-34C (collectively "electrodes <NUM>"). In other examples, housing <NUM> may carry fewer or greater than three electrodes. Lead <NUM> may be configured to couple to housing <NUM> and extend from housing <NUM> to a different subcutaneous location within patient <NUM>. For example, lead <NUM> may be tunneled laterally and posteriorly to the back of patient <NUM> at a location adjacent to a portion of a latissimus dorsi muscle. Lead <NUM> may carry electrode coil <NUM> along a length of lead <NUM> and sensing electrode <NUM> at a distal end of lead <NUM>. SD <NUM> may be configured such that heart <NUM> may be disposed at least partially between housing <NUM> and electrode coil <NUM> of lead <NUM>. In some examples, lead <NUM> may carry two or more electrode coils <NUM> and/or two or more sensing electrodes <NUM>.

SD <NUM> may contain, within housing <NUM>, 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 LPD <NUM> to apply appropriate electrical stimuli (e.g. pacing and/or anti-tachyarrhythmia shock therapy (e.g., defibrillation or cardioversion shocking pulses)) to heart <NUM>. SD <NUM> also may be configured to apply pacing pulses via one or more electrodes <NUM>. SD <NUM> may be configured to apply the anti-tachyarrhythmia shock pulses between coil electrode <NUM> and one or more of electrodes <NUM> and/or the electrically conductive housing <NUM> (e.g., an additional can electrode) of SD <NUM>. SD <NUM> may be configured to communicate with programmer <NUM> via an RF communication link, inductive coupling, or some other wireless communication protocol.

SD <NUM> differs from traditionally used ICDs in that housing <NUM> may be larger in size than the housing of a traditional ICD to accommodate larger capacity batteries, for example. In addition, SD <NUM> may be implanted subcutaneously whereas a traditional ICD may be implanted under muscle or deeper within patient <NUM>. In other examples, housing <NUM> may be shaped or sized differently to be implanted subcutaneously instead of under a muscle or within deep tissue. Moreover, SD <NUM> does not include leads configured to be placed in the bloodstream (e.g., endocardial or epicardial leads). Instead, SD <NUM> may be configured to carry one or more electrodes (e.g., electrodes <NUM>) on housing <NUM> together with one or more subcutaneous leads (e.g., lead <NUM>) that carry defibrillation coil electrode <NUM> and sensing electrode <NUM>. In other examples, lead <NUM> may include additional electrodes. These subcutaneously implanted electrodes of SD <NUM> may 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 SD <NUM> may be varied for different applications or patients. Although SD <NUM> is generally described as including one or more electrodes, SD <NUM> may typically include at least two electrodes to deliver an electrical signal (e.g., therapy) and/or provide at least one sensing vector. Other exemplary SDs <NUM> can be used in combination with LPD <NUM>. For example, SD <NUM> includes intravenously implanted device (IID), an ICD or a pacemaker or any other suitable device.

System <NUM> also includes one or more LPDs, such as LPD <NUM>. LPD <NUM> may be, for example, an implantable leadless pacing device (e.g., a pacemaker, cardioverter, and/or defibrillator) that provides electrical signals to heart <NUM> via electrodes carried on the housing of LPD <NUM>. In the example of <FIG>, LPD <NUM> is implanted within left ventricle <NUM> of heart <NUM> to sense electrical activity of heart <NUM> and/or deliver electrical stimulation, e.g., CRT such as fusion pacing, to heart <NUM>. Fusion pacing involves left ventricle (LV) <NUM> only pacing with an electrode on the LPD <NUM> in coordination with the intrinsic right ventricle (RV) activation. Alternatively, fusion pacing can involve pacing the RV with an electrode on the LPD <NUM> in coordination with the intrinsic LV activation. In this scenario, the LPD <NUM> is placed within the right ventricle <NUM>.

LPD <NUM> is schematically shown in <FIG> attached to a wall of the left ventricle <NUM> via one or more fixation elements (e.g. tines, helix etc.) that penetrate the tissue. These fixation elements may secure LPD <NUM> to the cardiac tissue and retain an electrode (e.g., a cathode or an anode) in contact with the cardiac tissue. LPD <NUM> may 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 heart <NUM>. Since LPD <NUM> includes two or more electrodes carried on the exterior housing of LPD <NUM>, no other leads or structures need to reside in other chambers of heart <NUM>. However, in other examples, system <NUM> may include additional LPDs within respective chambers of heart <NUM> (e.g., left atrium <NUM>, right atrium <NUM>).

Using the electrodes carried on the housing of LPD <NUM>, LPD <NUM> may be capable sensing intrinsic electrical signals, e.g., an electrocardiogram (ECG). SD <NUM> may similarly sense intrinsic electrical signals from the sensing vectors of electrodes <NUM>, <NUM>, and <NUM>. These intrinsic signals may be electrical signals generated by cardiac muscle and indicative of depolarizations and repolarizations of heart <NUM> at various times during the cardiac cycle. LPD <NUM> may generate an electrogram from these cardiac signals that may be used by LPD <NUM> to detect cardiac conditions (e.g. ventricular dyssynchrony, arrhythmias, such as tachyarrhythmias), or identify other cardiac events, e.g., ventricle depolarizations or atrium depolarizations. LPD <NUM> may 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, LPD <NUM> may be configured to communicate with external programmer <NUM>. The configurations of electrodes used by LPD <NUM> for sensing and pacing may be typically considered bipolar but unipolar may also be used.

External programmer <NUM> may be configured to communicate with one or both of SD <NUM> and LPD <NUM>. In examples where external programmer <NUM> only communicates with one of SD <NUM> and LPD <NUM>, the non-communicative device may receive instructions from or transmit data to the device in communication with programmer <NUM>. In some examples, programmer <NUM> comprises a handheld computing device, computer workstation, or networked computing device. Programmer <NUM> may include a user interface that receives input from a user. In other examples, the user may also interact with programmer <NUM> remotely via a networked computing device. The user may interact with programmer <NUM> to communicate with LPD <NUM> and/or SD <NUM>. For example, the user may interact with programmer <NUM> to send an interrogation request and retrieve therapy delivery data, update therapy parameters that define therapy, manage communication between LPD <NUM> and/or SD <NUM>, or perform any other activities with respect to LPD <NUM> and/or SD <NUM>. Although the user is a physician, technician, surgeon, electrophysiologist, or other healthcare professional, the user may be patient <NUM> in some examples.

Programmer <NUM> may also allow the user to define how LPD <NUM> and/or SD <NUM> senses electrical signals (e.g., ECGs), detects cardiac conditions (e.g. ventricular dyssynchrony, arrhythmias etc.), delivers therapy, and communicates with other devices of system <NUM>. For example, programmer <NUM> may be used to change detection parameters. In another example, programmer <NUM> may be used to manage therapy parameters that define therapies such as CRT. Moreover, programmer <NUM> may be used to alter communication protocols between LPD <NUM> and SD <NUM>. For example, programmer <NUM> may instruct LPD <NUM> and/or SD <NUM> to switch between one-way and two-way communication and/or change which of LPD <NUM> and/or SD <NUM> are tasked with initial detection of a cardiac condition.

Programmer <NUM> may communicate with LPD <NUM> and/or SD <NUM> via 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, programmer <NUM> may include a programming head that may be placed proximate to the patient's body near the LPD <NUM> and/or SD <NUM> implant site in order to improve the quality or security of communication between LPD <NUM> and/or SD <NUM> and programmer <NUM>.

LPD <NUM> and SD <NUM> may 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. LPD <NUM> and SD <NUM> may be configured to communicate with each other provide alternative electrical stimulation therapies.

Although LPD <NUM> may at least partially determine whether or not LPD <NUM> delivers CRT or another therapy to patient <NUM>, LPD <NUM> may perform one or more functions in response to receiving a request from SD <NUM> and without any further analysis by LPD <NUM>. In this manner, SD <NUM> may act as a master device and LPD <NUM> may act as a slave device. In this configuration, LPD <NUM> passively senses. Specifically, a VVT mode is employed as a trigger mode to pace in synchrony. In one or more embodiments, the LPD <NUM> can be configured to actively sense.

<FIG> are conceptual drawings illustrating different views of SD <NUM> of <FIG>. <FIG> is a top view of SD <NUM>, and <FIG> is a front view of SD <NUM>. In the example of <FIG>, housing <NUM> may be constructed as an ovoid with a substantially kidney-shaped profile. The ovoid shape of housing <NUM> may promote ease of subcutaneous implantation and may minimize patient discomfort during normal body movement and flexing of the thoracic musculature. In other examples, housing <NUM> may be constructed with different shapes intended for different implant locations and/or to house different components, subcutaneous leads, or configurations for electrodes <NUM> <FIG>.

Housing <NUM> may contain the electronic circuitry of SD <NUM>. Header <NUM> and connector <NUM> may provide an electrical connection between distal electrode coil <NUM> and distal sensing electrode <NUM> of lead <NUM> and the circuitry within housing <NUM>. Subcutaneous lead <NUM> may include distal defibrillation coil electrode <NUM>, distal sensing electrode <NUM>, insulated flexible lead body <NUM> and proximal connector pin <NUM>. Distal sensing electrode <NUM> may be sized appropriately to match the sensing impedance of electrodes 34A-34C to be used in combination.

In some examples, electrodes <NUM> are each welded into place on a flattened periphery of housing <NUM> and are connected to electronic circuitry inside housing <NUM>. Electrodes <NUM> may be constructed of flat plates, or alternatively, spiral electrodes (as described in <CIT>) and mounted in a non-conductive surround shroud (as described in <CIT> and <CIT>). Electrodes <NUM> shown in <FIG> may be positioned on housing <NUM> to form orthogonal signal vectors. However, electrodes <NUM> may be positioned to form any non-orthogonal signal vectors in other examples. In addition, housing <NUM> may include fewer or greater than three electrodes. Moreover, housing <NUM> may be configured as an electrically conductive surface and operate as an electrode. Housing <NUM> may be referred to as a "can electrode" or used as an indifferent electrode. In some examples, housing <NUM> may be used as an electrode with coil electrode <NUM> during delivery of (electrical stimuli e.g. pacing pulses, anti-tachyarrhythmia shock).

<FIG> is a conceptual drawing illustrating example LPD <NUM> of <FIG>. As shown in <FIG>, LPD <NUM> includes case <NUM>, cap <NUM>, electrode <NUM>, electrode <NUM>, fixation mechanisms <NUM>, flange <NUM>, and opening <NUM>. Together, case <NUM> and cap <NUM> may be considered the housing of LPD <NUM>. In this manner, case <NUM> and cap <NUM> may enclose and protect the various electrical components within LPD <NUM>. Case <NUM> may enclose substantially all of the electrical components, and cap <NUM> may seal case <NUM> and create the hermetically sealed housing of LPD <NUM>. Although LPD <NUM> is generally described as including one or more electrodes, LPD <NUM> may typically include at least two electrodes (e.g., electrodes <NUM> and <NUM>) to deliver an electrical signal (e.g., therapy such as CRT) and/or provide at least one sensing vector. Electrodes <NUM> and <NUM> are carried on the housing created by case <NUM> and cap <NUM>. In this manner, electrodes <NUM> and <NUM> may be considered leadless electrodes. In the example of <FIG>, electrode <NUM> is disposed on the exterior surface of cap <NUM>.

Electrode <NUM> may be a circular electrode positioned to contact cardiac tissue upon implantation. Electrode <NUM> may be a ring or cylindrical electrode disposed on the exterior surface of case <NUM>. Both case <NUM> and cap <NUM> may be electrically insulating. Electrode <NUM> may be used as a cathode and electrode <NUM> may be used as an anode, or vice versa, for delivering CRT or other appropriate cardiac therapy (ATP, shock etc.). However, electrodes <NUM> and <NUM> may be used in any stimulation configuration. In addition, electrodes <NUM> and <NUM> may be used to detect intrinsic electrical signals from cardiac muscle. In other examples, LPD <NUM> may include three or more electrodes, where each electrode may deliver therapy and/or detect intrinsic signals. CRT delivered by LPD <NUM> may be considered to be "painless" to patient <NUM> or even undetectable by patient <NUM> since the electrical stimulation occurs very close to or at cardiac muscle and at relatively low energy levels compared with alternative devices.

Fixation mechanisms <NUM> may attach LPD <NUM> to cardiac tissue. Fixation mechanisms <NUM> may be active fixation tines, screws, clamps, adhesive members, or any other types of attaching a device to tissue. As shown in the example of <FIG>, fixation mechanisms <NUM> may be constructed of a memory material that retains a preformed shape. During implantation, fixation mechanisms <NUM> may be flexed forward to pierce tissue and allowed to flex back towards case <NUM>. In this manner, fixation mechanisms <NUM> may be embedded within the target tissue.

Flange <NUM> may be provided on one end of case <NUM> to enable tethering or extraction of LPD <NUM>. For example, a suture or other device may be inserted around flange <NUM> and/or through opening <NUM> and attached to tissue. In this manner, flange <NUM> may provide a secondary attachment structure to tether or retain LPD <NUM> within heart <NUM> if fixation mechanisms <NUM> fail. Flange <NUM> and/or opening <NUM> may also be used to extract LPD <NUM> once the LPD needs to be explanted (or removed) from patient <NUM> if such action is deemed necessary.

In another example, LPD <NUM> may be configured to be implanted external to heart <NUM>, e.g., near or attached to the epicardium of heart <NUM>. An electrode carried by the housing of the fusion pacing LPD <NUM> may 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, SD <NUM> may communicate with one or more leadless or leaded devices implanted internal or external to heart <NUM>.

<FIG> is a functional block diagram illustrating an example configuration of SD <NUM> of <FIG>. In the illustrated example, SD <NUM> includes a processor <NUM>, memory <NUM>, shock module <NUM>, signal generator <NUM>, sensing module <NUM>, telemetry module <NUM>, communication module <NUM>, activity sensor <NUM>, and power source <NUM>. Memory <NUM> includes computer-readable instructions that, when executed by processor <NUM>, cause SD <NUM> and processor <NUM> to perform various functions attributed to SD <NUM> and processor <NUM> herein (e.g., detection of ventricular dyssynchrony, communication with LPD <NUM>, and/or delivery of anti-tachyarrhythmia shock therapy, if needed). Memory <NUM> may include any volatile, non-volatile, magnetic, optical, or electrical media, such as a random access memory (RAM), read-only memory (ROM), non-volatile RAM (NVRAM), electrically-erasable programmable ROM (EEPROM), flash memory, or any other digital or analog media.

Processor <NUM> may include any one or more of a microprocessor, a controller, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or equivalent discrete or analog logic circuitry. In some examples, processor <NUM> may include multiple components, such as any combination of one or more microprocessors, one or more controllers, one or more DSPs, one or more ASICs, or one or more FPGAs, as well as other discrete or integrated logic circuitry. The functions attributed to processor <NUM> herein may be embodied as software, firmware, hardware or any combination thereof.

Processor <NUM> controls signal generator <NUM> to deliver stimulation therapy to heart <NUM> according to a therapy parameters, which may be stored in memory <NUM>. For example, processor <NUM> may control signal generator <NUM> to 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 generator <NUM> may deliver electrical pulses to heart <NUM> via electrodes <NUM>, <NUM>, and/or <NUM>. In addition, housing <NUM> may be configured as an electrode and coupled to signal generator <NUM> and/or sensing module <NUM>. SD <NUM> may use any combination of electrodes to deliver anti-tachycardia therapy and/or detect electrical signals from patient <NUM>. However, in general, coil electrode <NUM> may be used to deliver an anti-tachyarrhythmia shock, if necessary.

Signal generator <NUM> may also include shock module <NUM>. Shock module <NUM> may include circuitry and/or capacitors required to deliver an anti-tachyarrhythmia shock. For example, signal generator <NUM> may charge shock module <NUM> to prepare for delivering a shock. Shock module <NUM> may then discharge to enable signal generator <NUM> to deliver the shock to patient <NUM> via one or more electrodes. In other examples, shock module <NUM> may be located within SD <NUM> but outside of signal generator <NUM>.

Signal generator <NUM> is electrically coupled to electrodes <NUM>, <NUM>, and <NUM>. In the illustrated example, signal generator <NUM> is configured to generate and deliver electrical stimuli (e.g. anti-tachyarrhythmia shock therapy) to heart <NUM>. For example, signal generator <NUM> may, using shock module <NUM>, deliver shocks to heart <NUM> via a subset of electrodes <NUM>, <NUM>, and <NUM>. In some examples, signal generator <NUM> may 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 generator <NUM> may include a switch module and processor <NUM> may 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 module <NUM> may be configured to monitor signals from at least one of electrodes <NUM>, <NUM>, and <NUM> in order to monitor electrical activity of heart <NUM>, 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 module <NUM> may 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, processor <NUM> may select the electrodes that function as sense electrodes, i.e., select the sensing configuration, via the switch module within sensing module <NUM>. Sensing module <NUM> may 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 processor <NUM>, e.g., as described in <CIT> and is entitled, "APPARATUS FOR MONITORING ELECTRICAL PHYSIOLOGIC SIGNALS". Processor <NUM> may control the functionality of sensing module <NUM> by providing signals via a data/address bus.

Processor <NUM> may 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 processor <NUM> components, such as a microprocessor, or a software module executed by a component of processor <NUM>, which may be a microprocessor or ASIC. The timing and control module may implement programmable counters. If SD <NUM> is configured to generate and deliver pacing pulses to heart <NUM>, 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 processor <NUM> may 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 module <NUM> for a time interval during and after delivery of electrical stimulation to heart <NUM>. The durations of these intervals may be determined by processor <NUM> in response to stored data in memory <NUM>. The timing and control module of processor <NUM> may also determine the amplitude of the cardiac pacing pulses.

Interval counters implemented by the timing and control module of processor <NUM> may be reset upon sensing of R-waves and P-waves with detection channels of sensing module <NUM>. The value of the count present in the interval counters when reset by sensed R-waves and P-waves may be used by processor <NUM> to 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 memory <NUM>. In some examples, processor <NUM> may 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 module <NUM> may be used to detect communication signals from LPD <NUM>. LPD <NUM> may not include telemetry circuitry. Instead, LPD <NUM> may generate electrical signals via one or more electrodes with amplitudes and/or patterns representative of information to be sent to SD <NUM>. The electrical signals may be carried by pacing pulses or separate communication signals configured to be detected by SD <NUM>. In this manner, communication module <NUM> may be configured to monitor signals sensed by sensing module <NUM> and determine when a communication message is received from LPD <NUM>.

In other examples, SD <NUM> may also transmit communication messages to LPD <NUM> using electrical signals from one or more of electrodes <NUM>, <NUM>, and <NUM>. In this case, communication module <NUM> may be coupled to signal generator <NUM> to control the parameters of generated electrical signals or pulses. Alternatively, processor <NUM> may detect communications via sensing module <NUM> and/or generate communications for deliver via signal generator <NUM>. Although communication module <NUM> may be used to communicate using electrical signals via electrodes <NUM>, <NUM> and <NUM>, communication module <NUM> may alternatively or in addition use wireless protocols such as RF telemetry to communicate with LPD <NUM> or other medical devices. In some examples, telemetry module <NUM> may include this wireless communication functionality.

Memory <NUM> may 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 patient <NUM>. Memory <NUM> may 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, memory <NUM> may also store communications transmitted to and/or received from LPD <NUM>.

Activity sensor <NUM> may be contained within the housing of SD <NUM> and include one or more accelerometers or other devices capable of detecting motion and/or position of SD <NUM>. For example, activity sensor <NUM> may include a <NUM>-axis accelerometer that is configured to detect accelerations in any direction in space. Accelerations detected by activity sensor <NUM> may be used by processor <NUM> to identify potential noise in signals detected by sensing module <NUM> and/or confirm the detection of arrhythmias or other patient conditions.

Telemetry module <NUM> includes any suitable hardware, firmware, software or any combination thereof for communicating with another device, such as programmer <NUM> (<FIG>). As described herein, telemetry module <NUM> may transmit generated or received arrhythmia data, therapy parameter values, communications between SD <NUM> and LPD <NUM>, or any other information. For example, telemetry module <NUM> may transmit information representative of sensed physiological data such as R-R intervals or any other data that may be used by LPD <NUM> to determine a condition of patient <NUM>. Telemetry module <NUM> may also be used to receive updated therapy parameters from programmer <NUM>. Under the control of processor <NUM>, telemetry module <NUM> may receive downlink telemetry from and send uplink telemetry to programmer <NUM> with the aid of an antenna, which may be internal and/or external. Processor <NUM> may provide the data to be uplinked to programmer <NUM> and the control signals for the telemetry circuit within telemetry module <NUM>, e.g., via an address/data bus. In some examples, telemetry module <NUM> may provide received data to processor <NUM> via a multiplexer. In some examples, SD <NUM> may signal programmer <NUM> to further communicate with and pass the alert through a network such as the Medtronic CareLink® Network developed by Medtronic, Inc. , of Minneapolis, MN, or some other network linking patient <NUM> to a clinician. SD <NUM> may spontaneously transmit the diagnostic information to the network or in response to an interrogation request from a user.

Power source <NUM> may be any type of device that is configured to hold a charge to operate the circuitry of SICD. Power source <NUM> may be provided as a rechargeable or non-rechargeable battery. In other examples, power source <NUM> may also incorporate an energy scavenging system that stores electrical energy from movement of SD <NUM> within patient <NUM>.

There may be numerous variations to the configuration of SD <NUM>, as described herein. In the examples of <FIG>, and <FIG>, SD <NUM> may include housing <NUM> configured to be implanted in patient <NUM> external to a rib cage of patient <NUM>, one or more electrodes (e.g., electrodes <NUM>, <NUM>, and <NUM>) configured to be disposed external to the rib cage, and shock module <NUM> configured to at least partially deliver anti-tachyarrhythmia shock therapy to patient <NUM> via the one or more electrodes.

SD <NUM> may also include communication module <NUM> configured to transmit and/or receive communication messages between LPD <NUM> configured to be implanted within heart <NUM> of patient <NUM> and a sensing module <NUM> configured to sense an electrical signal from heart <NUM> of patient <NUM> via the one or more electrodes. Further, SD <NUM> may include one or more processors <NUM> configured to detect a ventricular dyssynchrony within the sensed electrical signal and determine, based on the detected ventricular dyssynchrony, to deliver CRT to patient <NUM> to treat the detected ventricular dyssynchrony. Processor <NUM> may also be configured to transmit, via communication module <NUM> and prior to delivering CRT, a communication message to LPD <NUM> requesting LPD <NUM> deliver fusion pacing to heart <NUM> of patient <NUM>.

<FIG> is a functional block diagram illustrating an example configuration of LPD <NUM> of <FIG>. In the illustrated example, LPD <NUM> includes a processor <NUM>, memory <NUM>, signal generator <NUM>, sensing module <NUM>, shock detector <NUM>, activity sensor <NUM>, telemetry module <NUM>, and power source <NUM>. Memory <NUM> includes computer-readable instructions that, when executed by processor <NUM>, cause LPD <NUM> and processor <NUM> to perform various functions attributed to LPD <NUM> and processor <NUM> herein (e.g., detecting ventricular dyssnchrony, arrhythmias, communicating with SD <NUM>, and delivering anti-tachycardia pacing and post-shock pacing). Memory <NUM> may include any volatile, non-volatile, magnetic, optical, or electrical media, such as a random access memory (RAM), read-only memory (ROM), non-volatile RAM (NVRAM), electrically-erasable programmable ROM (EEPROM), flash memory, or any other digital or analog media.

Processor <NUM> controls signal generator <NUM> to deliver stimulation therapy to heart <NUM> according to a therapy parameters, which may be stored in memory <NUM>. For example, processor <NUM> may control signal generator <NUM> to deliver electrical pulses with the amplitudes, pulse widths, frequency, or electrode polarities specified by the therapy parameters. In this manner, signal generator <NUM> may deliver pacing pulses (e.g., fusion pacing) to heart <NUM> via electrodes <NUM> and <NUM>. Although LPD <NUM> may only include two electrodes, e.g., electrodes <NUM> and <NUM>, LPD <NUM> may utilize three or more electrodes in other examples. LPD <NUM> may use any combination of electrodes to deliver therapy and/or detect electrical signals from patient <NUM>.

Signal generator <NUM> is electrically coupled to electrodes <NUM> and <NUM> carried on the housing of LPD <NUM>. In the illustrated example, signal generator <NUM> is configured to generate and deliver electrical stimulation therapy to heart <NUM>. For example, signal generator <NUM> may deliver pulses to a portion of cardiac muscle within heart <NUM> via electrodes <NUM> and <NUM>. In some examples, signal generator <NUM> may 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 LPD <NUM> is generally described has delivering pacing pulses, LPD <NUM> may deliver cardioversion or defibrillation pulses in other examples.

Fusion pacing may be delivered to patient <NUM> as 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 generator <NUM> may also include circuitry for measuring the capture threshold of one or both electrodes <NUM> and <NUM>. The capture threshold may indicate the voltage necessary to induce depolarization of the surrounding cardiac muscle. For example, signal generator <NUM> may measure the voltage of pacing signals needed to induce synchronized ventricular contractions. In examples in which LPD <NUM> includes more than two electrodes, signal generator <NUM> may include a switch module and processor <NUM> may 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, processor <NUM> may withhold delivery of therapeutic pacing. In addition, processor <NUM> may transmit communication to SD <NUM> if pacing cannot be delivered.

Electrical sensing module <NUM> monitors signals from at least one of electrodes <NUM> and <NUM> in order to monitor electrical activity of heart <NUM>, 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 module <NUM> may 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, processor <NUM> may select the electrodes that function as sense electrodes, i.e., select the sensing configuration, via the switch module within sensing module <NUM>. Sensing module <NUM> may 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 processor <NUM>, e.g., as described in <CIT> and is entitled, "APPARATUS FOR MONITORING ELECTRICAL PHYSIOLOGIC SIGNALS". Processor <NUM> may control the functionality of sensing module <NUM> by providing signals via a data/address bus.

Processor <NUM> may 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 processor <NUM> components, such as a microprocessor, or a software module executed by a component of processor <NUM>, which may be a microprocessor or ASIC. The timing and control module may implement programmable counters. If LPD <NUM> is configured to generate and deliver pacing pulses to heart <NUM>, 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 <CIT>, or in <CIT>.

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

Memory <NUM> may 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 patient <NUM>. In the example of <FIG>, memory <NUM> may store sensed ECGs, detected arrhythmias, communications from SD <NUM>, and therapy parameters. In other examples, memory <NUM> may act as a temporary buffer for storing data until it can be uploaded to SD <NUM>, another implanted device, or programmer <NUM>.

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

Telemetry module <NUM> includes any suitable hardware, firmware, software or any combination thereof for communicating with another device, such as programmer <NUM> or SD <NUM> (<FIG>). Under the control of processor <NUM>, telemetry module <NUM> may receive downlink telemetry from and send uplink telemetry to programmer <NUM> with the aid of an antenna, which may be internal and/or external. Processor <NUM> may provide the data to be uplinked to programmer <NUM> and the control signals for the telemetry circuit within telemetry module <NUM>, e.g., via an address/data bus. In some examples, telemetry module <NUM> may provide received data to processor <NUM> via a multiplexer.

In some examples, LPD <NUM> may signal programmer <NUM> to further communicate with and pass the alert through a network such as the Medtronic CareLink® Network developed by Medtronic, Inc. , of Minneapolis, MN, or some other network linking patient <NUM> to a clinician. LPD <NUM> may spontaneously transmit information to the network or in response to an interrogation request from a user.

In other examples, processor <NUM> may be configured to transmit information to another device, such as SD <NUM> using electrodes <NUM> and <NUM>. For example, processor <NUM> may control signal generator <NUM> to 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, processor <NUM> may cause telemetry module <NUM> to transmit information representative of sensed physiological data such as R-R intervals or any other data that may be used by SD <NUM> to determine a condition of patient <NUM> (e.g., whether or not patient <NUM> is experiencing ventricular dyssynchrony). The communication may be in the form of dedicated communication signals.

Alternatively, processor <NUM> may communicate with SD <NUM> by delivering pacing pulses at specific intervals that would be identifiable by SD <NUM> as non-physiologic and intended to convey information. In other words, these pulses intended for communication with SD <NUM>. SD <NUM> may 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. SD <NUM> may detect the intervals between these pulses as code for specific messages from LPD <NUM>. For example, the pacing pulses may be varied and/or repeated in certain patterns detectable by SD <NUM> and still therapeutic. LPD <NUM> may also be configured to detect such communication messages via electrodes <NUM> and <NUM>. Processor <NUM> may monitor sensing module <NUM> for such communications. Alternatively, LPD <NUM> may include a communication module, similar to communication module <NUM> of <FIG>, to detect any communications received via sensing module <NUM>. In any example, LPD <NUM> may be configured for one-way communication to or from another device such as SD <NUM> or two-way communication with another device such as SD <NUM> using any type of communication protocol.

Power source <NUM> may be any type of device that is configured to hold a charge to operate the circuitry of LPD <NUM>. Power source <NUM> may be provided as a rechargeable or non-rechargeable battery. In other example, power source <NUM> may incorporate an energy scavenging system that stores electrical energy from movement of LPD <NUM> within patient <NUM>.

There may be numerous variations to the configuration of LPD <NUM>, as described herein. In one example, LPD <NUM> includes a housing configured to be implanted within heart <NUM> of patient <NUM>, one or more electrodes (e.g., electrodes <NUM> and <NUM>) coupled to the housing, fixation mechanism <NUM> configured to attach the housing to tissue of heart <NUM>, sensing module <NUM> configured to sense an electrical signal from heart <NUM> of patient <NUM> via the one or more electrodes, and signal generator <NUM> configured to deliver therapy to heart <NUM> of patient <NUM> via the one or more electrodes. LPD <NUM> may also include processor <NUM> configured to receive a communication message from SD <NUM> requesting LPD <NUM> deliver CRT to heart <NUM>, where SD <NUM> is configured to be implanted exterior to a rib cage of patient <NUM>. Processor <NUM> may also be configured to determine, based on the sensed electrical signal, whether to deliver CRT to heart <NUM>, and, in response to the determination, command signal generator <NUM> to deliver the CRT therapy. Processor <NUM> may also be configured to control signal generator <NUM> to deliver post-shock pacing to patient <NUM> in response to shock detector <NUM> detecting an anti-tachyarrhythmia shock.

<FIG> is a functional block diagram illustrating an example configuration of external programmer <NUM> of <FIG>. As shown in <FIG>, programmer <NUM> may include a processor <NUM>, memory <NUM>, user interface <NUM>, telemetry module <NUM>, and power source <NUM>. Programmer <NUM> may be a dedicated hardware device with dedicated software for programming of LPD <NUM> and/or SD <NUM>. Alternatively, programmer <NUM> may be an off-the-shelf computing device running an application that enables programmer <NUM> to program LPD <NUM> and/or SD <NUM>.

A user may use programmer <NUM> to configure the operational parameters of and retrieve data from LPD <NUM> and/or SD <NUM> (<FIG>). In one example, programmer <NUM> may communicate directly to both LPD <NUM> and SD <NUM>. In other examples, programmer may communicate to one of LPD <NUM> or SD <NUM>, and that device may relay any instructions or information to or from the other device. The clinician may interact with programmer <NUM> via user interface <NUM>, 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 SD <NUM> indicating that a shock has been delivered, any other therapy has been delivered, or any problems or issues related to the treatment of patient <NUM>.

Processor <NUM> can take the form one or more microprocessors, DSPs, ASICs, FPGAs, programmable logic circuitry, or the like, and the functions attributed to processor <NUM> herein may be embodied as hardware, firmware, software or any combination thereof. Memory <NUM> may store instructions that cause processor <NUM> to provide the functionality ascribed to programmer <NUM> herein, and information used by processor <NUM> to provide the functionality ascribed to programmer <NUM> herein. Memory <NUM> may 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. Memory <NUM> may 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 programmer <NUM> is used to program therapy for another patient.

Programmer <NUM> may communicate wirelessly with LPD <NUM> and/or SD <NUM>, such as using RF communication or proximal inductive interaction. This wireless communication is possible through the use of telemetry module <NUM>, which may be coupled to an internal antenna or an external antenna. An external antenna that is coupled to programmer <NUM> may correspond to the programming head that may be placed over heart <NUM> or the location of the intend implant, as described above with reference to <FIG>. Telemetry module <NUM> may be similar to telemetry modules <NUM> and <NUM> of respective <FIG> and <FIG>.

Telemetry module <NUM> may 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 programmer <NUM> and another computing device include RF communication according to the <NUM> 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 programmer <NUM> may be a networked device such as a server capable of processing information retrieved from LPD <NUM>. In other examples, LPD <NUM> may not use a shock detector to time the beginning or ending of post-shock pacing. Instead, LPD <NUM> may determine when to deliver post-shock pacing based on a command from SD <NUM>. For example, SD <NUM> may determine that a shock will be delivered and transmit a shock imminent command to LPD <NUM>. In response to receiving the shock imminent command, LPD <NUM> may enter a shock state for a predetermined period of time. This predetermined period of time may be stored in memory <NUM> or sent along with the shock imminent command from SD <NUM>. 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, LPD <NUM> may exit the shock state and enter a post-shock pacing state in which LPD <NUM> delivers post-shock pacing and/or first determines whether post-shock pacing is needed.

<FIG> is 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 in <FIG>, according to one example, during monitoring of capture management in a leadless pacing device, the leadless pacing device senses, via electrodes <NUM>, <NUM> and sensing module <NUM>, an intrinsic cardiac signal, i.e., corresponding to systole under conditions of stable, non-tachyarrhythmia cardiac rhythm, Block <NUM>. The processor <NUM> of the pacing device <NUM> determines the occurrence of an intrinsic P-wave event, Block <NUM>, based either on a signal sensed by the sensor <NUM> of the leadless pacing device <NUM>, or based on a signal sensed by an extravascular ICD, such as subcutaneous device <NUM>, and received from the extravascular ICD via the telemetry module <NUM> of the leadless pacing device <NUM>. Based on the determined intrinsic P-wave event, Block <NUM>, the processor <NUM> of the pacing device <NUM> determines an intrinsic electromechanical interval associated with the intrinsic P-wave event, Block <NUM>, 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 device <NUM> delivering ventricular pacing therapy via electrodes <NUM>, <NUM>, Block <NUM>. 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 processor <NUM> determines timing of a V-pace event, Block <NUM>, and based on the determined V-pace event, Block <NUM>, determines a V-pace to electromechanical response interval, Block <NUM>, described below. A determination is then made, based on the determined intrinsic electromechanical interval, Block <NUM>, and the determined V-pace to electromechanical response interval, Block <NUM>, as to whether capture is detected, Block <NUM>, described below.

If capture is detected, Yes in Block <NUM>, the processor <NUM> adjusts the pacing parameter, Block <NUM>, and the process, Blocks <NUM>-<NUM>, is repeated with the pacing device <NUM> delivering pacing therapy, Block <NUM>, using the adjusted pacing parameter, Block <NUM>. In one example, the processor <NUM> may adjust the pacing parameter, Block <NUM>, by reducing the pacing parameter by a predetermined step until lack of capture is detected, Yes in Block <NUM>. 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. <NUM> V) and during capture management routine this parameter may be reduced in steps of <NUM> V.

Once lack of capture is no longer detected, NO in Block <NUM>, the processor <NUM> stores the pacing parameter, Block <NUM>, in the memory <NUM> of the pacing device <NUM> so 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 Block <NUM>, the processor <NUM> may 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 <NUM> volt above the threshold, for example, for delivering the pacing therapy.

<FIG> is 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 in <FIG>, according to one example, in order to determine the intrinsic electromechanical interval, Block <NUM> of <FIG>, the processor <NUM> senses a cardiac signal <NUM> via electrodes <NUM>, <NUM> and an electromechanical signal, <NUM>, such as an accelerometer signal, via sensor <NUM>, and determines the occurrence of an intrinsic P-wave <NUM> based either on the sensed cardiac signal <NUM> or the sensed electromechanical signal <NUM>.

For example, in order to determine the intrinsic P-wave <NUM>, the processor <NUM> may determine the occurrence of intrinsic P-wave <NUM> base on the cardiac signal <NUM> sensed via electrodes <NUM>, <NUM> of the device, or based on the cardiac signal <NUM> being sensed by an extravascular ICD, such as subcutaneous device <NUM>, and received from the extravascular ICD via the telemetry module <NUM> of the leadless pacing device <NUM>. For example, the processor <NUM> may determine the occurrence of an intrinsic ventricular event <NUM> and use an offset interval <NUM> to identify the intrinsic P-wave <NUM>.

Once the intrinsic P-wave <NUM> is determined, the processor <NUM> determines a maximum <NUM> of the sensed electromechanical signal <NUM> that occurs within a time window that extends a predetermined time period <NUM> from the sensed intrinsic P-wave <NUM>. An intrinsic electromechanical interval <NUM>, such as an AV interval for example, is identified as the time period extending from the intrinsic P-wave <NUM> and the determined maximum <NUM> of the electromechanical signal.

<FIG> is 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 in <FIG>, according to one example, in order to determine the V-pace to electromechanical response interval, Block <NUM> of <FIG>, the processor <NUM> senses a cardiac signal <NUM> via electrodes <NUM>, <NUM> and an electromechanical signal, <NUM>, such as an accelerometer signal, via sensor <NUM>, and determines the occurrence of a V-pace event <NUM> based either on the sensed cardiac signal <NUM> sensed directly by the pacing device <NUM> via electrodes <NUM>, <NUM>, or a sensed cardiac signal being sensed by an extravascular ICD, such as subcutaneous device <NUM>, and received from the extravascular ICD via the telemetry module <NUM> of the leadless pacing device <NUM>.

Once the V-pace event <NUM> is determined to occur, the processor <NUM> determines a maximum <NUM> of the sensed electromechanical signal <NUM> that occurs within a time window that extends a predetermined time period <NUM> from the sensed V-pace event. Exemplary values of this time-window may be <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>. 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. <NUM>%)of that interval. For example, if successive atrial sensing events occur at interval of <NUM>, then this window will be <NUM>% of <NUM> = <NUM>. A V-pace to electromechanical response interval <NUM> is identified as the time period that extends from the sensed V-pace event <NUM> to the determined maximum <NUM> of the electromechanical signal <NUM>.

In this way, during the determination as to whether capture is detected, Block <NUM> of <FIG>, the processor <NUM> determines whether the intrinsic electromechanical interval <NUM> is greater than the V-pace to electromechanical response interval <NUM>. If the intrinsic electromechanical interval <NUM> is greater than the V-pace to electromechanical response interval <NUM>, left ventricular capture is detected, Yes in Block <NUM>. If the intrinsic electromechanical interval <NUM> is not greater than the V-pace to electromechanical response interval <NUM>, left ventricular capture is not detected, No in Block <NUM>. In one example, a constant time interval associated with the V-pace to electromechanical response interval <NUM>, such as <NUM>, <NUM>, <NUM> or <NUM> for example, may be utilized so that the processor <NUM> determines whether the intrinsic electromechanical interval <NUM> is greater than the V-pace to electromechanical response interval <NUM> plus the constant time interval. If the intrinsic electromechanical interval <NUM> is greater than the V-pace to electromechanical response interval <NUM> plus the constant time interval, left ventricular capture is detected, Yes in Block <NUM>. If the intrinsic electromechanical interval <NUM> is not greater than the V-pace to electromechanical response interval <NUM> plus the constant time interval, left ventricular capture is not detected, No in Block <NUM>.

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 patient <NUM>.

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 system <NUM> may not be limited to treatment of a human patient. In alternative examples, system <NUM> may 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.

The techniques described in this disclosure, including those attributed to SD <NUM>, LPD <NUM>, programmer <NUM>, and various constituent components, may be implemented, at least in part, in hardware, software, firmware or any combination thereof. For example, various 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 combinations of such components, embodied in programmers, such as physician or patient programmers, stimulators, remote servers, or other devices.

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 SD <NUM>, LPD <NUM> and/or programmer <NUM>.

The techniques described in this disclosure may also be embodied or encoded in an article of manufacture including a computer-readable storage medium encoded with instructions. Instructions embedded or encoded in an article of manufacture including a computer-readable storage medium encoded, may cause one or more programmable processors, or other processors, to implement one or more of the techniques described herein, such as when instructions included or encoded in the computer-readable storage medium are executed by the one or more processors. Example computer-readable storage media may include random access memory (RAM), read only memory (ROM), programmable read only memory (PROM), erasable programmable read only memory (EPROM), electronically erasable programmable read only memory (EEPROM), flash memory, a hard disk, a compact disc ROM (CD-ROM), a floppy disk, a cassette, magnetic media, optical media, or any other computer readable storage devices or tangible computer readable media.

Claim 1:
A left ventricular leadless pacing device, comprising:
one or more electrodes (<NUM>, <NUM>) to sense a cardiac signal;
an electromechanical sensor (<NUM>) to sense an electromechanical signal; and
a processor (<NUM>) 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.