US20190262617A1 - Generation of diagnostic metrics for use in determining delivery of pacing therapy by a cardiac pacing device - Google Patents

Abstract

A cardiac pacemaker that delivers cardiac pacing therapy that includes delivering the cardiac pacing therapy from a cardiac pacing device, sensing a pacing event from a plurality of electrodes of the pacing device, and sensing an electromechanical signal from an electromechanical sensor of the pacing device. A pre-ejection period is determined in response to the sensed electromechanical signal, and a left ventricular ejection time is determined in response to the sensed electromechanical signal. The pacemaker device performs one or both of adjusting a pacing parameter setting and generating an alert in response to the determined pre-ejection period and the determined left ventricular ejection time.

Description

• The disclosure herein relates to systems and methods for evaluation and adjustment of delivery of a pacing therapy by an implantable cardiac pacing device.
BACKGROUND
• During normal sinus rhythm (NSR), the heart beat is regulated by electrical signals produced by the sino-atrial (SA) node located in the right atrial wall. Each atrial depolarization signal produced by the SA node spreads across the atria, causing the depolarization and contraction of the atria, and arrives at the atrioventricular (A-V) node. The A-V node responds by propagating a ventricular depolarization signal through the bundle of His of the ventricular septum and thereafter to the bundle branches and the Purkinje muscle fibers of the right and left ventricles.
• Leadless pacemakers are used to sense electrical activity and/or deliver therapeutic pacing pulses to the heart. For some patients, one atrial pacemaker may be used in one atrium of the heart. In other patients, multiple leadless pacemakers may be used in at least one atrium and at least one ventricle of the heart. Each leadless pacemaker device typically includes two or more electrodes on its outer housing to deliver therapeutic electrical pulses and/or sense intrinsic depolarizations of the heart. Each leadless pacemaker may be positioned within a chamber of the heart and, in some examples, may be anchored to a wall of the heart via a fixation mechanism.
• Patients with heart failure are often treated with cardiac resynchronization pacing therapy delivered by a pacing device to synchronize contraction/relaxation of a heart that has become asynchronous. It is typically advantageous that parameters associated with the delivered pacing therapy for addressing instances of dyssynchrony of the heart be adjusted in order to manage better outcomes for heart failure patients. In addition, heart failure diagnostics and management are critical for managing delivery of cardiac resynchronization therapy.
SUMMARY
• A leadless pacing device may include an integrated electromechanical sensor, such as an 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 an automated algorithm which can determine certain relevant time-intervals from the accelerometer signal on a beat-by-beat basis. The data may be incorporated in device diagnostics as markers of cardiac mechanical function presented, for example, as a trend-chart over time. If the markers indicate values of the metrics above or below certain thresholds consistently over a period of time, the device may transmit an alert to the clinician. The data may be also used by the device to adjust pacing therapy in patients with a leadless pacing device positioned within the left ventricle for delivering closed loop resynchronization pacing.
• As a result, the present disclosure may address parameters that can be used for managing heart failure in patients to adjust pacing therapy for desired outcomes. In this way, the accelerometer signal of the leadless pacing device provides metrics for heart failure diagnostics and heart failure management. The metrics may also be utilized for adjusting device therapy parameters in a closed loop fashion for optimal cardiac resynchronization.
• The exemplary system, device and methods described herein involve determining relevant timing parameters reflecting different intervals of mechanical events that occur during the cardiac cycle and that are sensed by an activity sensor, such as an accelerometer, located within a leadless pacing device. In one example, the leadless pacing device may be positioned within one or more chambers of a patient's heart, such as within the left ventricle of the patient, for example. The timing parameters may be determined when the pacing device determines that both the heart rate and heart rhythm are regular and are not associated with the occurrence of a tachycardia event, such as when the heart rate is less than 100 beats-per-minute (bpm), for example.
• Based upon the occurrence of either a sensed ventricular event or a paced ventricular event, or sensed ventricular beat, the pacing device may determine a window of an accelerometer signal that extends, relative to the ventricular event for a period of time, such as approximately 260 ms for example. A first peak of a rectified slope of the accelerometer signal (|d(accelerometer)/dt) within the window is determined, and the timing of the first peak of the rectified slope corresponds to a surrogate of the time indicative of early systole, i.e., early contraction of the ventricle. A second peak of the accelerometer signal is also determined within a window that begins 200 ms after the ventricular event and ends 600 ms after the ventricular event. The second peak serves as a fiducial indicative of the end of systole.
• The time period extending from the ventricular event to the first peak is identified as a surrogate measurement of a pre-ejection period (PEP) for the corresponding cardiac cycle, which is typically longer for failing/asynchronous heart function. The time period extending from the first peak to the second peak is identified as a surrogate measurement of an LV ejection time (LVET) for the corresponding cardiac cycle, which is typically longer during normal synchronized pump function and shorter for failing hearts. A ratio r=PEP/LVET may be determined as an indicator of overall cardiac function, with a PEP/LVET having a greater value being associated with higher dyssynchrony and reduced efficiency in the pumping of the heart.
• In one example, the pacing device may periodically or continuously monitor these data on a cycle by cycle basis and generate a trend plot over time showing how the three parameters, PEP, LVET and PEP/LVET vary. In another example, worsening heart failure may be determined o be occurring if two or more of the following occur:
• • i) PEP increases by a certain threshold over the last five days, such as a greater than 20% increase, for example, or increases above a predetermined threshold value, such as 400 ms for example.
  • ii) LVET decreases by a certain threshold over the last five days, such as a greater than 20% decrease, for example, or decreases below a predetermined threshold value, such as 150 ms for example.
  • iii) the ratio r=PEP/LVET increases by a predetermined threshold over the last five days, such as an average increase greater than 20% for example, or increases above a predetermined threshold value, such as 0.5 for example.
• In one example, once worsening heart failure is determined, an alert may be generated by the pacing device. In another example, the pacing device may adjust pacing parameters, such as an AV delay, or a pacing rate for example, resulting in improved synchronization of markers of dyssynchrony, such as PEP increasing or the ratio of PEP/LVET increasing. In another example the pacing device may continue to auto-tune AV delays (i.e., either decreasing or increasing the AV-delay) on a cycle-by-cycle basis to bring the parameter values within certain thresholds as indicated by the markers of dyssynchrony, PEP, LVET and the ratio of PEP/LVET.
• In at least one embodiment, a method of delivering a cardiac pacing therapy may comprise delivering the cardiac pacing therapy from a cardiac pacing device; sensing a pacing event from a plurality of electrodes of the pacing device; sensing an electromechanical signal from an electromechanical sensor of the pacing device; determining a pre-ejection period in response to the sensed electromechanical signal; determining a left ventricular ejection time in response to the sensed electromechanical signal; and performing one or both of adjusting a pacing parameter setting and generating an alert in response to the determined pre-ejection period and the determined left ventricular ejection time.
• In at least one embodiment, a cardiac pacing device for delivering a cardiac therapy may include one or more electrodes for sensing a cardiac event and delivering the pacing therapy; a sensor for sensing an electromechanical signal; and a processor configured to determine a pre-ejection period in response to the sensed electromechanical signal, determine a left ventricular ejection time in response to the sensed electromechanical signal, and perform one or both of adjusting a pacing parameter setting and generating an alert in response to the determined pre-ejection period and the determined left ventricular ejection time.
• In at least one embodiment, an exemplary system may include non-transitory computer readable medium storing instructions which cause a cardiac medical device to perform a method comprising: delivering the cardiac pacing therapy from a cardiac pacing device; sensing a pacing event from a plurality of electrodes of the pacing device; sensing an electromechanical signal from an electromechanical sensor of the pacing device; determining a pre-ejection period in response to the sensed electromechanical signal; determining a left ventricular ejection time in response to the sensed electromechanical signal; and performing one or both of adjusting a pacing parameter setting and generating an alert in response to the determined pre-ejection period and the determined left ventricular ejection time.
• The above summary is not intended to describe each embodiment or every implementation of the present disclosure. A more complete understanding will become apparent and appreciated by referring to the following detailed description and claims taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is a schematic diagram illustrating a cardiac pacing device for delivering a pacing therapy according to an example of the present disclosure.
• FIG. 2 is a conceptual diagram illustrating the example cardiac pacing device ofFIG. 1 according to an example of the present disclosure.
• FIG. 3 is a functional block diagram of an example leadless cardiac pacemaker device according to an example of the present disclosure.
• FIG. 4 is a flowchart of a method of delivering a cardiac pacing therapy according to an example of the present disclosure.
• FIG. 5 is a flowchart of a method of delivering a cardiac pacing therapy according to an example of the present disclosure.
• FIG. 6 is a graphical representation of determining markers of cardiac electromechanical function during delivery of a pacing therapy by a leadless cardiac pacing device, according to an example of the present disclosure.
• FIG. 7 is a flow chart of a method of delivering a cardiac pacing therapy according to an example of the present disclosure.
• FIG. 8 is a flow chart of a method of delivering a cardiac pacing therapy according to an example of the present disclosure.
• FIG. 9 is a flow chart of a method of delivering a cardiac pacing therapy according to an example of the present disclosure.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
• 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 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 involve determining relevant timing parameters reflecting different intervals of mechanical events that occur during the cardiac cycle and that are sensed by an activity sensor, such as an accelerometer, located within a leadless pacing device. In one example, the leadless pacing device may be positioned within one or more chambers of a patient's heart, such as within the left ventricle of the patient, for example. The timing parameters may be determined when the pacing device determines that both the heart rate and heart rhythm are regular and are not associated with the occurrence of a tachycardia event, such as when the heart rate is less than 100 beats-per-minute (bpm), for example.
• Based upon the occurrence of either a sensed ventricular event or a paced ventricular event, or sensed ventricular beat, the pacing device may determine a window of an accelerometer signal that extends, relative to the ventricular event for a period of time, such as approximately 260 ms for example. A first peak of a rectified slope of the accelerometer signal (|d(accelerometer)/dt) within the window is determined, and the timing of the first peak of the rectified slope corresponds to a surrogate of the time indicative of early systole, i.e., early contraction of the ventricle. A second peak of the accelerometer signal is also determined within a window that begins 200 ms after the ventricular event and ends 600 ms after the ventricular event. The second peak serves as a fiducial indicative of the end of systole.
• The time period extending from the ventricular event to the first peak is identified as a surrogate measurement of a pre-ejection period (PEP) for the corresponding cardiac cycle, which is typically longer for failing/asynchronous heart function. The time period extending from the first peak to the second peak is identified as a surrogate measurement of an LV ejection time (LVET) for the corresponding cardiac cycle, which is typically longer during normal synchronized pump function and shorter for failing hearts. A ratio r=PEP/LVET may be determined as an indicator of overall cardiac function, with a PEP/LVET having a greater value being associated with higher dyssynchrony and reduced efficiency in the pumping of the heart.
• In one example, the pacing device may periodically or continuously monitor these data on a cycle by cycle basis and generate a trend plot over time showing how the three parameters, PEP. LVET and PEP/LVET vary. In another example, worsening heart failure may be determined o be occurring if two or more of the following occur:
• • i) PEP increases by a certain threshold over the last five days, such as a greater than 20% increase, for example, or increases above a predetermined threshold value, such as 400 ms for example.
  • ii) LVET decreases by a certain threshold over the last five days, such as a greater than 20% decrease, for example, or decreases below a predetermined threshold value, such as 150 ms for example.
  • iii) the ratio r of the PEP to the LVET, r=PEP/LVET, increases by a predetermined threshold over the last five days, such as an average increase greater than 20% for example, or increases above a predetermined threshold value, such as 0.5 for example.
• In one example, once worsening heart failure is determined, an alert may be generated by the pacing device. In another example, the pacing device may adjust pacing parameters, such as an AV delay, or a pacing rate for example, resulting in improved synchronization if markers of dyssynchrony, such as PEP increasing or the ratio of PEP/LVET increasing. In another example the pacing device may continue to auto-tune AV delays (i.e., either decreasing or increasing the AV-delay) on a cycle-by-cycle basis to bring the parameter values within certain thresholds as indicated by the markers of dyssynchrony, PEP, LVET and the ratio of PEP/LVET.
• FIG. 1 is a schematic diagram illustrating a cardiac pacing device for delivering a pacing therapy according to an example of the present disclosure. As illustrated inFIG. 1, asystem200 for use in evaluation and delivery of pacing therapy according to the present disclosure may include one or moreleadless pacemaker device202 configured to be positioned within either aright atrium204 of aheart206 of apatient208, within aright ventricle210 of thepatient208, or both, as illustrated inFIG. 1. Theleadless pacemaker device202 may be configured to monitor electrical activity of the patient's208heart206 and/or provide electrical therapy to theheart206.
• FIG. 2 is a conceptual diagram illustrating the example cardiac pacing device ofFIG. 1 according to an example of the present disclosure. As illustrated inFIG. 2, theleadless pacemaker device202 includes ahousing220,fixation tines222, aproximal electrode224 and adistal electrode226. Thehousing220 may have a pill-shaped cylindrical form factor in some examples. Thefixation tines222 are configured to connect (e.g., anchor)device202 toheart206, and may be fabricated from a shape memory material, such as Nitinol. In some examples, thefixation tines222 may connect one or bothleadless pacemaker device202 to theheart206 within one or both of thechambers204,210 of theheart206, as illustrated inFIG. 1. In another example, thefixation tines222 may be configured to anchor a singleleadless pacemaker device202 to theheart206 within only theright atrium204. Although theleadless pacemaker device202 includes a plurality offixation tines222 that are configured to anchor theleadless pacemaker device202 to cardiac tissue in theright atrium204, theleft atrium210, or both, it is contemplated that a leadless device according to the present disclosure may be fixed to cardiac tissue using other types of fixation mechanisms.
• Theleadless pacemaker device202 may include one or more electrodes for sensing electrical activity of theheart206 and/or delivering electrical stimulation to theheart206. While theleadless pacemaker device202 shown includes twoelectrodes224,226, more than two electrodes may be included on theleadless pacemaker device202 in other examples.Electrode226 may be referred to as a “tip electrode,” andelectrode224 may be referred to as a “ring electrode.” Thefixation tines222 may anchor theleadless pacemaker device202 to cardiac tissue such that thetip electrode226 maintains contact with the cardiac tissue. Thering electrode224 may be located on thehousing220. For example, thering electrode224 may be a cylindrical electrode that wraps around thehousing220. Although thering electrode224 is illustrated as being a cylindrical electrode that wraps around thehousing220, thering electrode224 may include other geometries. In some examples, thehousing220 may be formed from a conductive material. In these examples, thehousing220 may act as an electrode of theleadless pacemaker device202.
• Thehousing220 houses electronic components of theleadless pacemaker device202. Electronic components may include any discrete and/or integrated electronic circuit components that implement analog and/or digital circuits capable of producing the functions attributed to theleadless pacemaker device202 described herein. For example, thehousing220 may house electronic components that sense electrical activity viaelectrodes224,226 and/or deliver electrical stimulation viaelectrodes224,226. Additionally, thehousing220 may also include memory that includes instructions that, when executed by one or more processing circuits housed within thehousing220, cause theleadless pacemaker device202 to perform various functions attributed to theleadless pacemaker device202 herein. Thehousing220 may also house sensors that sense physiological conditions of thepatient208, such as an accelerometer and/or a pressure sensor.
• In some examples, thehousing220 may house a communication module that enables theleadless pacemaker device202 to communicate with other electronic devices, such as aprogrammer212 or other external patient monitor. In some examples, thehousing220 may house an antenna for wireless communication. Thehousing220 may also include a power source, such as a battery. Electronic components included within thehousing220 are described in further detail hereinafter.
• FIG. 3 is a functional block diagram of an example leadless cardiac pacemaker device according to an example of the present disclosure.FIG. 3 shows a system including aleadless pacemaker device202 positioned in theatrium204 of theheart206, aleadless pacemaker device202 positioned within theventricle210 of theheart206, and aprogrammer212 that may be used to program one or bothleadless pacemaker device202 and/or to retrieve data from one or bothleadless pacemaker device202. Eachleadless pacemaker device202 may include a processor orprocessing module230, memory232 asignal generator module234, anelectrical sensing module236, acommunication module238, asensor240, and a power source242. The power source242 may include a battery, e.g., a rechargeable or non-rechargeable battery.
• The modules included in theleadless pacemaker device202 represent functionality that may be included in each of theleadless pacemaker devices202, and may include any discrete and/or integrated electronic circuit components that implement analog and/or digital circuits capable of producing the functions attributed to the modules herein. For example, the modules may include analog circuits, e.g., amplification circuits, filtering circuits, and/or other signal conditioning circuits. The modules may also include digital circuits, e.g., combinational or sequential logic circuits, memory devices, etc. Memory may include any volatile, non-volatile, magnetic, 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 memory device. Furthermore, memory may include instructions that, when executed by one or more processing circuits, cause the modules to perform various functions attributed to the modules herein.
• The functions attributed to the modules herein may be embodied as one or more processors, hardware, firmware, software, or any combination thereof. Depiction of different features as modules is intended to highlight different functional aspects, and does not necessarily imply that such modules must be realized by separate hardware or software components. Rather, functionality associated with one or more modules may be performed by separate hardware or software components, or integrated within common or separate hardware or software components.
• Theprocessing module230 may communicate with thememory232. Thememory232 may include computer-readable instructions that, when executed by theprocessing module230, cause theprocessing module230 to perform the various functions attributed to theprocessing module230 herein. Thememory232 may include any volatile, non-volatile, magnetic, or electrical media, such as RAM, ROM, NVRAM, EEPROM, Flash memory, or any other digital media. For example, thememory232 may include pacing instructions and values, such as the baseline atrial pacing rate, the baseline atrial pacing interval and the baseline AV interval. The pacing instructions and values may be updated by the programmer212 (FIG. 1). Pacing instructions included in thememory232 may cause theleadless pacemaker device202 to operate as described herein.
• Theprocessing module230 may communicate with thesignal generator module234 and theelectrical sensing module236. Thesignal generator module234 and theelectrical sensing module236 are electrically coupled to theelectrodes224,226. Theelectrical sensing module236 is configured to monitor signals from theelectrodes224,226 in order to monitor electrical activity of theheart206. Thesignal generator module234 is configured to deliver electrical stimulation to one or both of theatrium204 of theheart206 and theventricle210 of theheart206 via theelectrodes224,226.
• Theprocessing module230 may control signal thesignal generator module234 to generate and deliver electrical stimulation to one or both of theatrium204 of theheart206 and theventricle210 of theheart206 via theelectrodes224,226. Electrical stimulation may include pacing pulses. In some examples, electrical stimulation may also include anti-tachycardia pacing (ATP) therapy. Theprocessing module230 may control thesignal generator module234 to deliver electrical stimulation therapy according to one or more atrial or ventricular therapy programs including pacing instructions and values, which may be stored in thememory232.
• Theelectrical sensing module236 may include circuits that acquire electrical signals. Electrical signals acquired by theelectrical sensing module236 may include intrinsic cardiac electrical activity, such as intrinsic atrial and/or intrinsic ventricular cardiac electrical activity. Theelectrical sensing module236 may filter, amplify, and digitize the acquired electrical signals to generate raw digital data. Theprocessing module230 may receive the digitized data generated by theelectrical sensing module236. In some examples, theprocessing module230 may perform various digital signal processing operations on the raw data, such as digital filtering.
• Theprocessing module230 may sense cardiac events based on the data received from theelectrical sensing module236. For example, theprocessing module230 may sense atrial events based on the data received from theelectrical sensing module236. In some examples, theprocessing module230 may sense ventricular activation based on the data received from theelectrical sensing module236. For example, theprocessing module230 may detect FFRWs indicative of ventricular activation based on the data received from theelectrical sensing module236.
• Thesensor240 may comprise at least one of a variety of different sensors. For example, thesensor240 may comprise at least one of a pressure sensor, a heart sounds sensor, and an accelerometer. Thesensor240 may generate signals that indicate at least one of an activity level of thepatient208, a hemodynamic pressure, and heart sounds. Theprocessing module230 may detect, for example, an activity level of thepatient208 based on a sensed accelerometer signal, a hemodynamic pressure signal, and a heart sounds signal based on the signals generated by thesensor240.
• Thecommunication module238 may include any suitable hardware (e.g., an antenna), firmware, software, or any combination thereof for communicating with another device, such as theprogrammer212 or a patient monitor. Under the control of theprocessing module230, thecommunication module238 may receive downlink telemetry from and send uplink telemetry to other devices, such as the programmer212 (FIG. 1) or a patient monitor, with the aid of an antenna included in thecommunication module238. As described herein, a leadless pacing system may coordinate pacing of theheart206 based on sensed cardiac electrical and/or mechanical activity without establishment of a communication link between theleadless pacemaker devices202. Accordingly, thecommunication module238 is not required to include functionality that provides for communication between theleadless pacemaker devices202.
• Theprogrammer212 may be a handheld computing device, desktop computing device, a networked computing device, etc. Theprogrammer212 may include a computer-readable storage medium having instructions that cause a processor of theprogrammer212 to provide the functions attributed to theprogrammer212 in the present disclosure. One or both of theleadless pacemaker devices202 may wirelessly communicate with theprogrammer212. For example, theleadless pacemaker devices202 may transfer data to theprogrammer212 and may receive data from theprogrammer212. Theprogrammer212 may also wirelessly program and/or wirelessly charge theleadless pacemaker devices202.
• Data retrieved from theleadless pacemaker devices202 using theprogrammer212 may include cardiac EGMs stored by theleadless pacemaker devices202 that indicate electrical activity of theheart206 and marker channel data that indicates the occurrence and timing of sensing, diagnosis, and therapy events associated with theleadless pacemaker devices202. Data transferred to theleadless pacemaker devices202 using theprogrammer212 may include, for example, operational programs and/or settings for theleadless pacemaker devices202 that cause theleadless pacemaker devices202 to operate as described herein.
• Theprocessing module230 may control atrial pacing timing based on the detection of ventricular activation events in a variety of different ways. The manner in which theprocessing module230 controls atrial pacing timing may depend on when a ventricular activation event occurs relative to the atrial event that preceded the ventricular activation event. In other words, the manner in which theprocessing module230 controls atrial pacing timing may depend on when processing module detects a FFRW or an S1 heart sound relative to the atrial event that preceded the detected FFRW or the detected S1 heart sound.
• FIG. 4 is a flowchart of a method of delivering a cardiac pacing therapy according to an example of the present disclosure. As illustrated inFIG. 4, a method of delivering a cardiac pacing therapy according to an example of the present disclosure may include initially delivering a pacing therapy viaelectrodes224,226 of thepacing device202,Block300, during a time when processingmodule230 of thepacing device202 determines that the current rate and rhythm of the patient's heart is regular and not presently exhibiting atrial or ventricular tachyarrhythmia, such as when the current heart rate is less than 100 bpm for example. During delivery of the initial pacing therapy, thepacing device202 senses a far-field cardiac signal viaelectrodes224,226 and an electromechanical signal,Block302, such as an accelerometer signal sensed viasensor240. Theprocessing module230 determines, based on the sensed far-field signal, when a ventricular paced (V-Pace) beat occurs,Block304. Once a V-pace beat is determined to occur, theprocessing module230 determines one or more markers of cardiac mechanical function from the sensed electromechanical signal. For example, theprocessing module230 may determine a pre-ejection period (PEP) associated with the current delivered V-pace beat,Block306, and a left ventricular ejection time (LVET) associated with the current delivered V-pace beat,Block308. The determined initial PEP and initial LVET are then stored in thememory232 of thepacing device202,Block310.
• FIG. 5 is a flowchart of a method of delivering a cardiac pacing therapy according to an example of the present disclosure. As illustrated inFIG. 5, once theprocessing module230 determines the initial markers of cardiac electromechanical function, PEP and LVET, during a time when processingmodule230 of thepacing device202 determines that the current rate and rhythm of the patient's heart is regular and not presently exhibiting atrial or ventricular tachyarrhythmia, thepacing device202 subsequently delivers a pacing therapy using initial pacing parameters associated with the pacing therapy delivered during the initial determination of the markers, such as an initial pacing rate and an initial AV interval,Block320.
• During subsequent delivery of the pacing therapy, thepacing device202 senses a far-field cardiac signal viaelectrodes224,226 and an electromechanical signal,Block322, such as an accelerometer signal sensed fromsensor240. Theprocessing module230 determines, based on the far-field signal, when a pacing event, such as a ventricular paced (V-Pace) beat occurs,Block324. Once a V-pace beat is determined to occur, theprocessing module230 determines a pre-ejection period (PEP) associated with the current sensed V-pace beat,Block326, a left ventricular ejection time (LVET) associated with the current sensed V-pace beat,Block328, and updates trends based on the current determined PEP and LVET,Block330. Theprocessing module230 then determines, based on the current PEP and LVET, whether dyssynchrony is occurring,Block332. If dyssynchrony is determined to be occurring, Yes inBlock332, theprocessing module230 adjusts one or more of the pacing parameters of the pacing therapy,Block334, such as an AV-delay or a pacing rate, for example.
• In addition to determining whether dyssynchrony is indicated or determined to occur,Block332, theprocessing module230 may also determine whether worsening heart failure is being indicated based on the current PEP and LVET,Block336. If worsening heart failure is indicated, Yes inBlock336, an alert may be generated by theprocessing module230,Block338, and the process is repeated for the next beat,Block320, using the adjusted parameter setting,Block334, that was adjusted if dyssynchrony was determined to be occurring for the current beat, Yes inBlock332, and using the current, non-adjusted parameter settings if dyssynchrony was not determined to be occurring for the current beat, No inBlock332. On the other hand, if worsening heart failure is not indicated, No inBlock336, an alarm is not generated and the process is repeated for the next beat,Block320, using the adjusted parameter setting,Block334, that was adjusted if dyssynchrony was determined to be occurring for the current beat, Yes inBlock332, and using the current, non-adjusted parameter settings if dyssynchrony was not determined to be occurring for the current beat, No inBlock332.
• While both the determination of dyssynchrony,Block332 and the determination of worsening heart failure,Block336, are included in theFIG. 5, it is understood, that, in one example, during monitoring of the markers of cardiac mechanical function, i.e., PEP and LVET, theprocessing module230 may periodically or continuously generate a trend plot over time indicative of the variation in the markers over time, and only perform the alerting of the patient or a clinician when worsening heart failure is determined to occur. In another example, theprocessing module230 may only periodically or continuously adjust one or more settings of pacing parameters, such as AV-delay or pacing rate, to deliver improved resynchronization if the markers indicate dyssynchrony so as to bring the values of the pacing parameters within certain desired thresholds. In another example, theprocessing module230 may perform both the generation of the alert if worsening heart failure is indicated and the adjusting of the one or more pacing parameters of the delivered pacing therapy if dyssynchrony is determined to occur based on the trend data.
• FIG. 6 is a graphical representation of determining markers of cardiac electromechanical function during delivery of a pacing therapy by a leadless cardiac pacing device, according to an example of the present disclosure. As illustrated inFIG. 6, during delivery of the initial pacing therapy viaelectrodes224,226 theprocessing module230 of thepacing device202 determines a near-field signal400 sensed by sensing electrodes of the pacing device, and anEM signal402 sensed by an EM sensor of the pacing device. Theprocessing module230 identifies timing of the occurrence of a ventricular pace (VP)event404 from the near-field signal400 and determines atime window406 extending a predetermined time period from the sensedVP event404. In one example, the predetermined time period oftime window406 may be approximately 260 ms.
• In addition, theprocessing module230 determines a rectifiedderivative signal408 of theEM signal402 and determines timing indicative of the occurrence of early systole by determining a maximum410 of the rectifiedderivative signal408 that occurs within thetime window406. In addition, theprocessing module230 determines timing indicative of the occurrence of the end of systole by determining a maximum412 of theaccelerometer signal402 that occurs during a second time window having astart point414 located apredetermined distance416 from the sensed V-pace event404 and that extends a predetermined time period from thestart point414. In one example, thestart point414 may be located 200 ms from the V-pace event404 and the second time window may extend a predetermined time period of 600 ms from thestart point414 of the second time window.
• In this way, during initial delivery of pacing therapy determines one or more marker of cardiac mechanical function from the sensed electromechanical signal. For example, once the V-pace event404 is identified, and the maximum410 of the rectifiedderivative signal408 and the maximum412 of theaccelerometer signal402 are determined relative to the V-pace event404, theprocessing module230 may determine a pre-ejection period (PEP)418 extending between the V-pace event404 and the maximum410 of the rectifiedderivative signal408, and a left ventricular ejection time (LVET)420 extending from the maximum410 of the rectifiedderivative signal408 to the maximum412 of theaccelerometer signal402. The determined initial pre-ejection period (PEP)418 and initial left ventricular ejection time (LVET)420 are then stored in thememory232 of thepacing device202.
• FIG. 7 is a flow chart of a method of delivering a cardiac pacing therapy according to an example of the present disclosure. As described above, in one example, during monitoring of the markers of cardiac mechanical function, i.e., PEP and LVET, theprocessing module230 may periodically or continuously generate a trend plot over time indicative of the variation in the markers over time, and only perform the generation of the alert if worsening heart failure is determined to be occurring. In another example, theprocessing module230 may only periodically or continuously adjust one or more settings of pacing parameters, such as AV-delay or pacing rate, by either increasing or decreasing the parameter setting to deliver improved resynchronization if the markers indicate dyssynchrony, so as to bring the values of the pacing parameters within certain desired thresholds. In another example, theprocessing module230 may perform both the generating of the alert of worsening heart failure and the adjusting of the one or more pacing parameters of the delivered pacing therapy based on the updated trend data.
• For example, as illustrated inFIGS. 6 and 7, once the initial pre-ejection period (PEP)418 and initial left ventricular ejection time (LVET)420 have been determined and stored, described above, thepacing device202 subsequently delivers a pacing therapy having the initial pacing parameters settings associated with the pacing therapy delivered by thepacing device202 during the determination of the initial pre-ejection period (PEP)418 and initial left ventricular ejection time (LVET)420, described above. Theprocessing module230 of the pacing202 determines, on a beat-by-beat basis, the pre-ejection period (PEP)418 and initial left ventricular ejection time (LVET)420 associated with each subsequently sensed V-pace event404,Block500, and stores the determined current pre-ejection period (PEP)418 and initial left ventricular ejection time (LVET)420 for each sensed V-pace event404. Theprocessing module230 then updates trend data over time using the currentdetermined PEP418 andLVET420 in such a way as to be indicative of how thePEP418 and LVET420 have varied over time.
• Based on the updated trended data, including the current pre-ejection period (PEP)418 and initial left ventricular ejection time (LVET)420 data, theprocessing module230 determines whether there is a predetermined increase in thePEP418, such as a greater than 20 percent increase on average, over a predetermined number of days, such as 5 days, for example,Block502. If there is an increase in thePEP418, Yes inBlock502, indicating dyssynchrony, the pacing device may adjust one or more pacing parameters of the pacing therapy,Block504, such as the AV-delay or pacing rate, for example. In addition, theprocessing module230 determines whether there is both an increase in thecurrent PEP418 and a decrease in the currentdetermined LVET420 over a predetermined number of days, such as 5 days for example,Block506. If there is both an increase in thecurrent PEP418 and a decrease in the currentdetermined LVET420, Yes inBlock506, changes in trend data are determined to be satisfied,Block508, and therefore worsening heart failure is indicated.
• In response to the indication of worsening heart failure, an alert may be generated, and the process is repeated for the next beat,Block512, using the adjusted parameter setting,Block504, that was adjusted if the predetermined increase in thePEP418 was determined to occur for the current sensed V-pace beat404, Yes inBlock502. On the other hand, the process is repeated for thenext beat Block512 using the current, non-adjusted parameter settings if the predetermined increase in thePEP418 was not determined to occur for the current sensed V-pace beat404, No inBlock502.
• If there is not both an increase in thecurrent PEP418 and a decrease in the currentdetermined LVET420, No inBlock506, theprocessing module230 determines a ratio of thePEP418 and theLVET420,Block514, updates the ratio of thedetermined PEP418 and theLVET420 over multiple sensed V-pace events, and determines whether there is an increase in the ratio of thePEP418 and theLVET420,Block516, indicative of dyssynchrony. In one example, an increase in the ratio of PEP to LVET indicative of dyssynchrony may be determined to occur if the ratio increases by a predetermined threshold over a predetermined number of days. For example, an increase in the ratio may be determined to occur if the ratio increases by more than 20 percent over five days. In another example, an increase in the ratio may be determined to occur if the ratio is greater than a predetermined threshold, such as 0.5, for example.
• If an increase in the ratio of thePEP418 and theLVET420 is not determined to occur, No inBlock516, the process is repeated for the next beat,Block512, using the adjusted parameter setting,Block504, that was adjusted if the predetermined increase in thePEP418 was determined to occur for the current sensed V-pace beat404, Yes inBlock502. On the other hand, the process is repeated for thenext beat Block512 using the current, non-adjusted parameter settings if the predetermined increase in thePEP418 was not determined to occur for the current sensed V-pace beat404, No inBlock502.
• If an increase in the ratio of thePEP418 and theLVET420 is determined to occur, Yes inBlock516, theprocessing module230 may adjust one or more pacing parameters of the pacing therapy,Block518, such as the AV-delay or pacing rate, for example, and a determination is made as to whether there is either an increase in thePEP418 or a decrease in theLVET420,Block520. If there is not one of an increase in thePEP418 or a decrease in theLVET420, No inBlock520, heart failure is not indicated and the process is repeated for the next beat,Block512, using the current, non-adjusted parameter settings, i.e., without any parameter adjustment having been made for the current sensed V-pace event404.
• If there is either an increase in thePEP418 or a decrease in theLVET420, Yes inBlock520, changes in trend data are determined to be satisfied,Block508, and therefore worsening heart failure is indicated. In response to the indication of worsening heart failure, an alert may be generated, and the process is repeated for the next beat,Block512, using the adjusted parameter setting,Block504, that was adjusted if the predetermined increase in thePEP418 was determined to occur for the current sensed V-pace beat404, Yes inBlock502. On the other hand, the process is repeated for thenext beat Block512 using the current, non-adjusted parameter settings if the predetermined increase in thePEP418 was not determined to occur for the current sensed V-pace beat404, No inBlock502.
• In this way, based upon the occurrence of either a sensed ventricular event or a paced ventricular event, or sensed ventricular beat, the pacing device may determine a window of an accelerometer signal that extends, relative to the ventricular event for a period of time, such as approximately 260 ms for example. A first peak of a rectified slope of the accelerometer signal (|d(accelerometer)/dt) within the window is determined, and the timing of the first peak of the rectified slope corresponds to a surrogate of the time indicative of early systole, i.e., early contraction of the ventricle. A second peak of the accelerometer signal is also determined within a window that begins 200 ms after the ventricular event and ends 600 ms after the ventricular event. The second peak serves as a fiducial indicative of the end of systole.
• The time period extending from the ventricular event to the first peak is identified as a surrogate measurement of a pre-ejection period (PEP) for the corresponding cardiac cycle, which is typically longer for failing/asynchronous heart function. The time period extending from the first peak to the second peak is identified as a surrogate measurement of an LV ejection time (LVET) for the corresponding cardiac cycle, which is typically longer during normal synchronized pump function and shorter for failing hearts. A ratio r=PEP/LVET, which serves as an indicator of overall cardiac function, i.e., a greater ratio value being associated with increased dyssynchrony and reduced efficiency, may be determined as an indicator of overall cardiac function, with a PEP/LVET having a greater value being associated with higher dyssynchrony and reduced efficiency in the pumping of the heart.
• In one example, the pacing device may periodically or continuously monitor these data on a cycle by cycle basis and generate a trend plot over time showing how the three parameters, PEP, LVET and PEP/LVET vary. In another example, worsening heart failure may be determined to be occurring if two or more of the following occur:
• • i) PEP increases by a certain threshold over the last five days, such as a greater than 20% increase, for example, or increases above a predetermined threshold value, such as 400 ms for example.
  • ii) LVET decreases by a certain threshold over the last five days, such as a greater than 20% decrease, for example, or decreases below a predetermined threshold value, such as 150 ms for example.
  • iii) the ratio r=PEP/LVET increases by a predetermined threshold over the last five days, such as an average increase greater than 20% for example, or increases above a predetermined threshold value, such as 0.5 for example.
• In one example, once worsening heart failure is determined, an alert may be generated by the pacing device. In another example, theprocessing module230 may adjust pacing parameters, such as an AV delay, or a pacing rate for example, resulting in improved synchronization of markers of dyssynchrony, if either thePEP418 is determined to be increasing or the ratio of PEP/LVET is determined to be increasing. In this way, thepacing device202 may continue to auto-tune AV delays (i.e., either decreasing or increasing the AV-delay) on a cycle-by-cycle basis to bring the parameter values within certain thresholds as indicated by the markers of dyssynchrony, PEP, LVET and the ratio of PEP/LVET.
• FIG. 8 is a flow chart of a method of delivering a cardiac pacing therapy according to an example of the present disclosure. While in the example method of delivering a cardiac pacing therapy described inFIG. 7 includes both adjusting pacing parameters when dyssynchrony is determined to occur and generating an alarm when worsening heart failure is determined, it is understood, that, in one example, theprocessing module230 may periodically or continuously generate a trend plot over time indicative of the variation in the markers of cardiac mechanical function, i.e., PEP and LVET, over time, and perform only the generation of the alert if worsening heart failure determined to be occurring. For example, as illustrated inFIGS. 6 and 8, once the initial pre-ejection period (PEP)418 and initial left ventricular ejection time (LVET)420 have been determined and stored, described above, thepacing device202 subsequently delivers a pacing therapy having the initial pacing parameters settings associated with the pacing therapy delivered by thepacing device202 during the determination of the initial pre-ejection period (PEP)418 and initial left ventricular ejection time (LVET)420, described above. Theprocessing module230 determines, on a beat-by-beat basis, the pre-ejection period (PEP)418, the left ventricular ejection time (LVET)420,Block540, and the ratio of thePEP412 andLVET420,Block542, associated with each subsequently sensed V-pace event404, and updates trend data,Block544, using the currentdetermined PEP418 andLVET420 in such a way as to be indicative of how thePEP418, theLVET420 and a ratio of the PEP and LVET have varied over time.
• Based on the updated trended data,Block544, including the current pre-ejection period (PEP)418 and initial left ventricular ejection time (LVET)420 data, theprocessing module230 determines whether the pre-ejection period (PEP)418 is increasing, whether the left ventricular ejection time (LVET)420 is decreasing, and whether the ratio of thePEP418 and theLVET420 is increasing over multiple sensed V-pace events,Block544. Theprocessing module230 determines whether heart failure is occurring,Block546, based on whether at least two of an increase in the PEP, a decrease in the LVET and an increase in the ratio of thePEP418 and theLVET420 are occurring, indicative of dyssynchrony.
• In one example, an increase in the ratio of PEP to LVET may be determined to occur if the ratio increases by a predetermined threshold over a predetermined number of days. For example, an increase in the ratio may be determined to occur if the ratio increases by more than 20 percent over five days. In another example, an increase in the ratio may be determined to occur if the ratio is greater than a predetermined threshold, such as 0.5, for example. An increase in PEP may be determined to be occurring if there is a predetermined increase in thePEP418, such as a greater than 20 percent increase on average, over a predetermined number of days, such as 5 days, for example. In another example, an increase in PEP may be determined to be occurring if the PEP increases above a predetermined threshold, such as 400 ms, for example. A decrease in LVET may be determined to be occurring if there is a predetermined decrease in the currentdetermined LVET420, such as a greater than 20 percent decrease on average, over a predetermined number of days, such as 5 days for example. In another example, a decrease in LVET may be determined to be occurring if the LVET decreases below a predetermined threshold, such as 150 ms, for example.
• If at least two of an increase in the PEP, a decrease in the LVET and an increase in the ratio of thePEP418 and theLVET420 are not determined to occur and therefore heart failure is not indicated, No inBlock546, the process is repeated for the next beat,Block548. If at least two of an increase in the PEP, a decrease in the LVET and an increase in the ratio of thePEP418 and theLVET420 are determined to occur and therefore heart failure is indicated, Yes inBlock546, theprocessing module230 may generate an alarm,Block550, and the process is repeated for the next beat,Block548.
• In this way, worsening heart failure may be determined to be occurring if two or more of the following occur:
• • i) PEP increases by a certain threshold over the last five days, such as a greater than 20% increase, for example, or increases above a predetermined threshold value, such as 400 ms for example.
  • ii) LVET decreases by a certain threshold over the last five days, such as a greater than 20% decrease, for example, or decreases below a predetermined threshold value, such as 150 ms for example.
  • iii) the ratio r=PEP/LVET increases by a predetermined threshold over the last five days, such as an average increase greater than 20% for example, or increases above a predetermined threshold value, such as 0.5 for example.
• FIG. 9 is a flow chart of a method of delivering a cardiac pacing therapy according to an example of the present disclosure. As illustrated inFIGS. 6 and 9, once the initial pre-ejection period (PEP)418 and initial left ventricular ejection time (LVET)420 have been determined and stored, described above, thepacing device202 subsequently delivers a pacing therapy having the initial pacing parameters settings associated with the pacing therapy delivered by thepacing device202 during the determination of the initial pre-ejection period (PEP)418 and initial left ventricular ejection time (LVET)420, described above. Theprocessing module230 determines, on a beat-by-beat basis, the pre-ejection period (PEP)418, the left ventricular ejection time (LVET)420, and the ratio of thePEP412 andLVET420,Block560, associated with each subsequently sensed V-pace event404, and updates trend data,Block562, using the currentdetermined PEP418 andLVET420 in such a way as to be indicative of how thePEP418 and a ratio of the PEP and LVET have varied over time.
• Based on the updated trended data,Block562, including the current pre-ejection period (PEP)418 and initial left ventricular ejection time (LVET)420 data, theprocessing module230 determines, for the current sensed V-pace event404, whether there is a predetermined increase in thePEP418,Block564. If there is an increase in thePEP418, Yes inBlock564, indicating dyssynchrony, theprocessing module230 may adjust one or more pacing parameters of the pacing therapy,Block566, such as the AV-delay or pacing rate, for example, and the process is repeated for the next beat,Block568.
• If there is not an increase in thePEP418, No inBlock564, theprocessing module230 determines whether the ratio of thePEP418 to theLVET420 has increased,Block570. If an increase in the ratio of thePEP418 to theLVET420 is not determined to occur, No inBlock570, the process is repeated for the next beat,Block568. If an increase in the ratio of thePEP418 to theLVET420 is determined to occur, Yes inBlock570, indicating dyssynchrony, theprocessing module230 may adjust one or more pacing parameters of the pacing therapy,Block566, such as the AV-delay or pacing rate, for example, and the process is repeated for the next beat,Block568. In this way, theprocessing module230 may adjust pacing parameters, such as an AV delay, or a pacing rate for example, resulting in improved synchronization of markers of dyssynchrony, if either thePEP418 is determined to be increasing,Block564, or the ratio of PEP/LVET is determined to be increasing,Block570. As a result, thepacing device202 may continue to auto-tune AV delays (i.e., either decreasing or increasing the AV-delay) on a cycle-by-cycle basis to bring the parameter values within certain thresholds as indicated by the markers of dyssynchrony, PEP and the ratio of PEP/LVET.
• In one example, an increase in the ratio of PEP to LVET may be determined to occur if the ratio increases by a predetermined threshold over a predetermined number of days. For example, an increase in the ratio may be determined to occur if the ratio increases by more than 20 percent over five days. In another example, an increase in the ratio may be determined to occur if the ratio is greater than a predetermined threshold, such as 0.5, for example. An increase in PEP may be determined to be occurring if there is a predetermined increase in thePEP418, such as a greater than 20 percent increase on average, over a predetermined number of days, such as 5 days, for example. In another example, an increase in PEP may be determined to be occurring if the PEP increases above a predetermined threshold, such as 400 ms, for example.
• The techniques described in this disclosure, such as those attributed to thepacing device202, including theprocessing module230, and/or 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, image processing devices, or other devices. The term “module,” “processor,” or “processing circuitry” may generally refer to any of the foregoing logic circuitry, alone or in combination with other logic circuitry, or any other equivalent circuitry.
• Such hardware, software, and/or firmware may be implemented within the same device or within separate devices to support the various operations and functions described in this disclosure. 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.
• When implemented in software, the functionality ascribed to the systems, devices and techniques described in this disclosure may be embodied as instructions on a computer-readable medium such as RAM, ROM, NVRAM, EEPROM, FLASH memory, magnetic data storage media, optical data storage media, or the like. The instructions may be executed by one or more processors to support one or more aspects of the functionality described in this disclosure.
• This disclosure has been provided with reference to illustrative embodiments and is not meant to be construed in a limiting sense. As described previously, one skilled in the art will recognize that other various illustrative applications may use the techniques as described herein to take advantage of the beneficial characteristics of the apparatus and methods described herein. Various modifications of the illustrative embodiments, as well as additional embodiments of the disclosure, will be apparent upon reference to this description.
ILLUSTRATIVE EMBODIMENTSEmbodiment 1
• A method of delivering a cardiac pacing therapy, comprising:
• • delivering the cardiac pacing therapy from a cardiac pacing device;
  • sensing a pacing event from a plurality of electrodes of the pacing device;
  • sensing an electromechanical signal from an electromechanical sensor of the pacing device;
  • determining a pre-ejection period in response to the sensed electromechanical signal;
  • determining a left ventricular ejection time in response to the sensed electromechanical signal; and
  • performing one or both of adjusting a pacing parameter setting and generating an alert in response to the determined pre-ejection period and the determined left ventricular ejection time.
Embodiment 2
• The method ofembodiment 1, further comprising:
• • determining a maximum of a rectified derivative of the EM signal within a first time window extending a predetermined time period from the sensed pacing event; and
  • determining a maximum of the EM signal within a second time window extending from a second window start point positioned a predetermined distance from the sensed pacing event, wherein the pre-ejection period is determined in response to a time period extending between the sensed pacing event and the maximum of the rectified derivative of the EM signal, and the left ventricular ejection time is determined in response to a time period extending between the second window start point and the maximum of the EM signal.
Embodiment 3
• The method of any ofembodiments 1 to 2, wherein the first window extends approximately 260 ms from the sensed pacing event, the second window start point is positioned approximately 200 ms from the sensed pacing event and the second window extends approximately 600 ms from the second window start point.
Embodiment 4
• The method of any of embodiments 1-3, further comprising:
• • determining trend data associated with the pre-ejection period, the left ventricular ejection time and a ratio of the pre-ejection period and the left ventricular ejection time for a plurality of the sensed cardiac events;
  • determining whether the pre-ejection period is increasing;
  • determining whether the ratio of the pre-ejection period and the left ventricular ejection time is increasing; and
  • adjusting delivery of the cardiac pacing therapy in response to one of determining the pre-ejection period is increasing and determining the ratio of the pre-ejection period and the left ventricular ejection time is increasing.
Embodiment 5
• The method of any of embodiments 1-4, wherein determining whether the pre-ejection period increases comprises one of determining whether the pre-ejection period increases by greater than a predetermined percentage over a predetermined number of days and determining whether the pre-ejection period increases above a predetermined numerical threshold, and wherein determining whether the ratio of the pre-ejection period increases comprises one of determining whether the ratio of the pre-ejection period and the left ventricular ejection time increases by greater than a predetermined percentage over a predetermined number of days and determining whether the ratio of the pre-ejection period and the left ventricular ejection time increases above a predetermined numerical threshold.
Embodiment 6
• The method of any of embodiments 1-5, further comprising:
• • determining trend data associated with the pre-ejection period, the left ventricular ejection time and a ratio of the pre-ejection period and the left ventricular ejection time for a plurality of the sensed cardiac events;
  • determining whether the pre-ejection period is increasing;
  • determining whether the left ventricular ejection time is decreasing;
  • determining whether the ratio of the pre-ejection period and the left ventricular ejection time is increasing;
  • determining whether heart failure is indicated in response to determining at least two of the pre-ejection period determined to be increasing, the left ventricular ejection time determined to be decreasing, and the ratio of the pre-ejection period and the left ventricular ejection time determined to be increasing; and
  • generating an alert in response to heart failure being indicated.
Embodiment 7
• The method of any of embodiments 1-6, wherein determining whether the pre-ejection period increases comprises one of determining whether the pre-ejection period increases by greater than a predetermined percentage over a predetermined number of days and determining whether the pre-ejection period increases above a predetermined numerical threshold, wherein determining whether the left ventricular ejection time decreases comprises one of determining whether the left ventricular ejection time decreases by greater than a predetermined percentage over a predetermined number of days and determining whether the left ventricular ejection time decreases above a predetermined numerical threshold, and wherein determining whether the ratio of the pre-ejection period increases comprises one of determining whether the ratio of the pre-ejection period and the left ventricular ejection time increases by greater than a predetermined percentage over a predetermined number of days and determining whether the ratio of the pre-ejection period and the left ventricular ejection time increases above a predetermined numerical threshold.
Embodiment 8
• The method of any of embodiments 1-7, further comprising:
• • determining trend data associated with the pre-ejection period, the left ventricular ejection time and a ratio of the pre-ejection period and the left ventricular ejection time for a plurality of the sensed cardiac events;
  • determining whether the pre-ejection period is increasing;
  • determining whether the left ventricular ejection time is decreasing;
  • determining whether the ratio of the pre-ejection period and the left ventricular ejection time is increasing;
  • determining whether heart failure is indicated in response to determining at least two of the pre-ejection period determined to be increasing, the left ventricular ejection time determined to be decreasing, and the ratio of the pre-ejection period and the left ventricular ejection time determined to be increasing;
  • adjusting delivery of the cardiac pacing therapy in response to one of determining the pre-ejection period is increasing and determining the ratio of the pre-ejection period and the left ventricular ejection time is increasing; and
  • generating an alert in response to heart failure being indicated.
Embodiment 9
• The method of any of embodiments 1-8, wherein determining whether the pre-ejection period increases comprises one of determining whether the pre-ejection period increases by greater than a predetermined percentage over a predetermined number of days and determining whether the pre-ejection period increases above a predetermined numerical threshold, wherein determining whether the left ventricular ejection time decreases comprises one of determining whether the left ventricular ejection time decreases by greater than a predetermined percentage over a predetermined number of days and determining whether the left ventricular ejection time decreases above a predetermined numerical threshold, and wherein determining whether the ratio of the pre-ejection period increases comprises one of determining whether the ratio of the pre-ejection period and the left ventricular ejection time increases by greater than a predetermined percentage over a predetermined number of days and determining whether the ratio of the pre-ejection period and the left ventricular ejection time increases above a predetermined numerical threshold.
Embodiment 10
• The method of any of embodiments 1-9, wherein the cardiac pacing device comprises a leadless pacemaker device and the sensed pacing event comprises a ventricular pacing event.
Embodiment 11
• A cardiac pacing device for delivering a cardiac pacing therapy, comprising:
• • one or more electrodes for sensing a cardiac event and delivering the pacing therapy;
  • a sensor for sensing an electromechanical signal; and
  • a processor configured to determine a pre-ejection period in response to the sensed electromechanical signal, determine a left ventricular ejection time in response to the sensed electromechanical signal, and perform one or both of adjusting a pacing parameter setting and generating an alert in response to the determined pre-ejection period and the determined left ventricular ejection time.
Embodiment 12
• The device of embodiment 11, wherein the processor is configured to determine a maximum of a rectified derivative of the EM signal within a first time window extending a predetermined time period from the sensed pacing event, and determine a maximum of the EM signal within a second time window extending from a second window start point positioned a predetermined distance from the sensed pacing event, wherein the pre-ejection period is determined in response to a time period extending between the sensed pacing event and the maximum of the rectified derivative of the EM signal, and the left ventricular ejection time is determined in response to a time period extending between the second window start point and the maximum of the EM signal.
Embodiment 13
• The device of any of embodiments 11-12, wherein the first window extends approximately 260 ms from the sensed pacing event, the second window start point is positioned approximately 200 ms from the sensed pacing event and the second window extends approximately 600 ms from the second window start point.
Embodiment 14
• The device of any of embodiments 11-13, wherein the processor is configured to determine trend data associated with the pre-ejection period, the left ventricular ejection time and a ratio of the pre-ejection period and the left ventricular ejection time for a plurality of the sensed cardiac events, determine whether the pre-ejection period is increasing, determine whether the ratio of the pre-ejection period and the left ventricular ejection time is increasing, and adjust delivery of the cardiac pacing therapy in response to one of determining the pre-ejection period is increasing and determining the ratio of the pre-ejection period and the left ventricular ejection time is increasing.
Embodiment 15
• The device of any of embodiments 11-14, wherein determining whether the pre-ejection period increases comprises one of determining whether the pre-ejection period increases by greater than a predetermined percentage over a predetermined number of days and determining whether the pre-ejection period increases above a predetermined numerical threshold, and wherein determining whether the ratio of the pre-ejection period increases comprises one of determining whether the ratio of the pre-ejection period and the left ventricular ejection time increases by greater than a predetermined percentage over a predetermined number of days and determining whether the ratio of the pre-ejection period and the left ventricular ejection time increases above a predetermined numerical threshold.
Embodiment 16
• The device of any of embodiments 11-15, wherein the processor is configured to determine trend data associated with the pre-ejection period, the left ventricular ejection time and a ratio of the pre-ejection period and the left ventricular ejection time for a plurality of the sensed cardiac events, determine whether the pre-ejection period is increasing, determine whether the left ventricular ejection time is decreasing, determine whether the ratio of the pre-ejection period and the left ventricular ejection time is increasing, determine whether heart failure is indicated in response to determining at least two of the pre-ejection period determined to be increasing, the left ventricular ejection time determined to be decreasing, and the ratio of the pre-ejection period and the left ventricular ejection time determined to be increasing, and generate an alert in response to heart failure being indicated.
Embodiment 17
• The device of any of embodiments 11-16, wherein determining whether the pre-ejection period increases comprises one of determining whether the pre-ejection period increases by greater than a predetermined percentage over a predetermined number of days and determining whether the pre-ejection period increases above a predetermined numerical threshold, wherein determining whether the left ventricular ejection time decreases comprises one of determining whether the left ventricular ejection time decreases by greater than a predetermined percentage over a predetermined number of days and determining whether the left ventricular ejection time decreases above a predetermined numerical threshold, and wherein determining whether the ratio of the pre-ejection period increases comprises one of determining whether the ratio of the pre-ejection period and the left ventricular ejection time increases by greater than a predetermined percentage over a predetermined number of days and determining whether the ratio of the pre-ejection period and the left ventricular ejection time increases above a predetermined numerical threshold.
Embodiment 18
• The device of any of embodiments 11-17, wherein the processor is configured to determine trend data associated with the pre-ejection period, the left ventricular ejection time and a ratio of the pre-ejection period and the left ventricular ejection time for a plurality of the sensed cardiac events, determine whether the pre-ejection period is increasing, determine whether the left ventricular ejection time is decreasing; determine whether the ratio of the pre-ejection period and the left ventricular ejection time is increasing, determine whether heart failure is indicated in response to determining at least two of the pre-ejection period determined to be increasing, the left ventricular ejection time determined to be decreasing, and the ratio of the pre-ejection period and the left ventricular ejection time determined to be increasing, adjust delivery of the cardiac pacing therapy in response to one of determining the pre-ejection period is increasing and determining the ratio of the pre-ejection period and the left ventricular ejection time is increasing, and generate an alert in response to heart failure being indicated.
Embodiment 19
• The device of any of embodiments 11-18, wherein determining whether the pre-ejection period increases comprises one of determining whether the pre-ejection period increases by greater than a predetermined percentage over a predetermined number of days and determining whether the pre-ejection period increases above a predetermined numerical threshold, wherein determining whether the left ventricular ejection time decreases comprises one of determining whether the left ventricular ejection time decreases by greater than a predetermined percentage over a predetermined number of days and determining whether the left ventricular ejection time decreases above a predetermined numerical threshold, and wherein determining whether the ratio of the pre-ejection period increases comprises one of determining whether the ratio of the pre-ejection period and the left ventricular ejection time increases by greater than a predetermined percentage over a predetermined number of days and determining whether the ratio of the pre-ejection period and the left ventricular ejection time increases above a predetermined numerical threshold.
Embodiment 20
• The device of any of embodiments 11-19, wherein the cardiac pacing device comprises a leadless pacemaker device and the sensed pacing event comprises a ventricular pacing event.
Embodiment 21
• A non-transitory computer readable medium storing instructions which cause a cardiac medical device to perform a method comprising:
• • delivering the cardiac pacing therapy from a cardiac pacing device;
  • sensing a pacing event from a plurality of electrodes of the pacing device;
  • sensing an electromechanical signal from an electromechanical sensor of the pacing device;
  • determining a pre-ejection period in response to the sensed electromechanical signal;
  • determining a left ventricular ejection time in response to the sensed electromechanical signal; and
  • performing one or both of adjusting a pacing parameter setting and generating an alert in response to the determined pre-ejection period and the determined left ventricular ejection time.
Embodiment 22
• A medical device system comprising means to perform the method of any one of claims1-10.
Embodiment 23
• A computer-readable storage medium comprising instructions that, when executed by processing circuitry of a medical device system, cause the processing circuitry to perform the method of any of claims1-10.

Claims (24)

What is claimed:

1. A method of delivering a cardiac pacing therapy, comprising:

delivering the cardiac pacing therapy from a cardiac pacing device;

sensing a pacing event from a plurality of electrodes of the pacing device;

sensing an electromechanical signal from an electromechanical sensor of the pacing device;

determining a pre-ejection period in response to the sensed electromechanical signal;

determining a left ventricular ejection time in response to the sensed electromechanical signal; and

performing one or both of adjusting a pacing parameter setting and generating an alert in response to the determined pre-ejection period and the determined left ventricular ejection time.

2. The method ofclaim 1, wherein the electromechanical sensor comprises an accelerometer.

3. The method ofclaim 1, further comprising:

determining a maximum of a rectified derivative of the EM signal within a first time window extending a predetermined time period from the sensed pacing event; and

determining a maximum of the EM signal within a second time window extending from a second window start point positioned a predetermined distance from the sensed pacing event, wherein the pre-ejection period is determined in response to a time period extending between the sensed pacing event and the maximum of the rectified derivative of the EM signal, and the left ventricular ejection time is determined in response to a time period extending between the second window start point and the maximum of the EM signal.

4. The method ofclaim 3, wherein the first window extends approximately 260 ms from the sensed pacing event, the second window start point is positioned approximately 200 ms from the sensed pacing event and the second window extends approximately 600 ms from the second window start point.

5. The method ofclaim 1, further comprising:

determining trend data associated with the pre-ejection period, the left ventricular ejection time and a ratio of the pre-ejection period and the left ventricular ejection time for a plurality of the sensed cardiac events;

determining whether the pre-ejection period is increasing;

determining whether the ratio of the pre-ejection period and the left ventricular ejection time is increasing; and

adjusting delivery of the cardiac pacing therapy in response to one of determining the pre-ejection period is increasing and determining the ratio of the pre-ejection period and the left ventricular ejection time is increasing.

6. The method ofclaim 5, wherein determining whether the pre-ejection period increases comprises one of determining whether the pre-ejection period increases by greater than a predetermined percentage over a predetermined number of days and determining whether the pre-ejection period increases above a predetermined numerical threshold, and wherein determining whether the ratio of the pre-ejection period increases comprises one of determining whether the ratio of the pre-ejection period and the left ventricular ejection time increases by greater than a predetermined percentage over a predetermined number of days and determining whether the ratio of the pre-ejection period and the left ventricular ejection time increases above a predetermined numerical threshold.

7. The method ofclaim 1, further comprising:

determining trend data associated with the pre-ejection period, the left ventricular ejection time and a ratio of the pre-ejection period and the left ventricular ejection time for a plurality of the sensed cardiac events;

determining whether the pre-ejection period is increasing;

determining whether the left ventricular ejection time is decreasing;

determining whether the ratio of the pre-ejection period and the left ventricular ejection time is increasing;

determining whether heart failure is indicated in response to determining at least two of the pre-ejection period determined to be increasing, the left ventricular ejection time determined to be decreasing, and the ratio of the pre-ejection period and the left ventricular ejection time determined to be increasing; and

generating an alert in response to heart failure being indicated.

8. The method ofclaim 7, wherein determining whether the pre-ejection period increases comprises one of determining whether the pre-ejection period increases by greater than a predetermined percentage over a predetermined number of days and determining whether the pre-ejection period increases above a predetermined numerical threshold, wherein determining whether the left ventricular ejection time decreases comprises one of determining whether the left ventricular ejection time decreases by greater than a predetermined percentage over a predetermined number of days and determining whether the left ventricular ejection time decreases above a predetermined numerical threshold, and wherein determining whether the ratio of the pre-ejection period increases comprises one of determining whether the ratio of the pre-ejection period and the left ventricular ejection time increases by greater than a predetermined percentage over a predetermined number of days and determining whether the ratio of the pre-ejection period and the left ventricular ejection time increases above a predetermined numerical threshold.

9. The method ofclaim 1, further comprising:

determining trend data associated with the pre-ejection period, the left ventricular ejection time and a ratio of the pre-ejection period and the left ventricular ejection time for a plurality of the sensed cardiac events;

determining whether the pre-ejection period is increasing;

determining whether the left ventricular ejection time is decreasing;

determining whether the ratio of the pre-ejection period and the left ventricular ejection time is increasing;

determining whether heart failure is indicated in response to determining at least two of the pre-ejection period determined to be increasing, the left ventricular ejection time determined to be decreasing, and the ratio of the pre-ejection period and the left ventricular ejection time determined to be increasing;

adjusting delivery of the cardiac pacing therapy in response to one of determining the pre-ejection period is increasing and determining the ratio of the pre-ejection period and the left ventricular ejection time is increasing; and

generating an alert in response to heart failure being indicated.

10. The method ofclaim 9, wherein determining whether the pre-ejection period increases comprises one of determining whether the pre-ejection period increases by greater than a predetermined percentage over a predetermined number of days and determining whether the pre-ejection period increases above a predetermined numerical threshold, wherein determining whether the left ventricular ejection time decreases comprises one of determining whether the left ventricular ejection time decreases by greater than a predetermined percentage over a predetermined number of days and determining whether the left ventricular ejection time decreases above a predetermined numerical threshold, and wherein determining whether the ratio of the pre-ejection period increases comprises one of determining whether the ratio of the pre-ejection period and the left ventricular ejection time increases by greater than a predetermined percentage over a predetermined number of days and determining whether the ratio of the pre-ejection period and the left ventricular ejection time increases above a predetermined numerical threshold.

11. The method ofclaim 1, wherein the cardiac pacing device comprises a leadless pacemaker device and the sensed pacing event comprises a ventricular pacing event.

12. A cardiac pacing device for delivering a cardiac pacing therapy, comprising:

one or more electrodes for sensing a cardiac event and delivering the pacing therapy;

a sensor for sensing an electromechanical signal; and

a processor configured to determine a pre-ejection period in response to the sensed electromechanical signal, determine a left ventricular ejection time in response to the sensed electromechanical signal, and perform one or both of adjusting a pacing parameter setting and generating an alert in response to the determined pre-ejection period and the determined left ventricular ejection time.

13. The device ofclaim 12, wherein the sensor comprises an accelerometer.

14. The device ofclaim 12, wherein the processor is configured to determine a maximum of a rectified derivative of the EM signal within a first time window extending a predetermined time period from the sensed pacing event, and determine a maximum of the EM signal within a second time window extending from a second window start point positioned a predetermined distance from the sensed pacing event, wherein the pre-ejection period is determined in response to a time period extending between the sensed pacing event and the maximum of the rectified derivative of the EM signal, and the left ventricular ejection time is determined in response to a time period extending between the second window start point and the maximum of the EM signal.

15. The device ofclaim 14, wherein the first window extends approximately 260 ms from the sensed pacing event, the second window start point is positioned approximately 200 ms from the sensed pacing event and the second window extends approximately 600 ms from the second window start point.

16. The device ofclaim 12, wherein the processor is configured to determine trend data associated with the pre-ejection period, the left ventricular ejection time and a ratio of the pre-ejection period and the left ventricular ejection time for a plurality of the sensed cardiac events, determine whether the pre-ejection period is increasing, determine whether the ratio of the pre-ejection period and the left ventricular ejection time is increasing, and adjust delivery of the cardiac pacing therapy in response to one of determining the pre-ejection period is increasing and determining the ratio of the pre-ejection period and the left ventricular ejection time is increasing.

17. The device ofclaim 16, wherein determining whether the pre-ejection period increases comprises one of determining whether the pre-ejection period increases by greater than a predetermined percentage over a predetermined number of days and determining whether the pre-ejection period increases above a predetermined numerical threshold, and wherein determining whether the ratio of the pre-ejection period increases comprises one of determining whether the ratio of the pre-ejection period and the left ventricular ejection time increases by greater than a predetermined percentage over a predetermined number of days and determining whether the ratio of the pre-ejection period and the left ventricular ejection time increases above a predetermined numerical threshold.

18. The device ofclaim 12, wherein the processor is configured to determine trend data associated with the pre-ejection period, the left ventricular ejection time and a ratio of the pre-ejection period and the left ventricular ejection time for a plurality of the sensed cardiac events, determine whether the pre-ejection period is increasing, determine whether the left ventricular ejection time is decreasing, determine whether the ratio of the pre-ejection period and the left ventricular ejection time is increasing, determine whether heart failure is indicated in response to determining at least two of the pre-ejection period determined to be increasing, the left ventricular ejection time determined to be decreasing, and the ratio of the pre-ejection period and the left ventricular ejection time determined to be increasing, and generate an alert in response to heart failure being indicated.

19. The device ofclaim 18, wherein determining whether the pre-ejection period increases comprises one of determining whether the pre-ejection period increases by greater than a predetermined percentage over a predetermined number of days and determining whether the pre-ejection period increases above a predetermined numerical threshold, wherein determining whether the left ventricular ejection time decreases comprises one of determining whether the left ventricular ejection time decreases by greater than a predetermined percentage over a predetermined number of days and determining whether the left ventricular ejection time decreases above a predetermined numerical threshold, and wherein determining whether the ratio of the pre-ejection period increases comprises one of determining whether the ratio of the pre-ejection period and the left ventricular ejection time increases by greater than a predetermined percentage over a predetermined number of days and determining whether the ratio of the pre-ejection period and the left ventricular ejection time increases above a predetermined numerical threshold.

20. The device ofclaim 12, wherein the processor is configured to determine trend data associated with the pre-ejection period, the left ventricular ejection time and a ratio of the pre-ejection period and the left ventricular ejection time for a plurality of the sensed cardiac events, determine whether the pre-ejection period is increasing, determine whether the left ventricular ejection time is decreasing; determine whether the ratio of the pre-ejection period and the left ventricular ejection time is increasing, determine whether heart failure is indicated in response to determining at least two of the pre-ejection period determined to be increasing, the left ventricular ejection time determined to be decreasing, and the ratio of the pre-ejection period and the left ventricular ejection time determined to be increasing, adjust delivery of the cardiac pacing therapy in response to one of determining the pre-ejection period is increasing and determining the ratio of the pre-ejection period and the left ventricular ejection time is increasing, and generate an alert in response to heart failure being indicated.

21. The device ofclaim 20, wherein determining whether the pre-ejection period increases comprises one of determining whether the pre-ejection period increases by greater than a predetermined percentage over a predetermined number of days and determining whether the pre-ejection period increases above a predetermined numerical threshold, wherein determining whether the left ventricular ejection time decreases comprises one of determining whether the left ventricular ejection time decreases by greater than a predetermined percentage over a predetermined number of days and determining whether the left ventricular ejection time decreases above a predetermined numerical threshold, and wherein determining whether the ratio of the pre-ejection period increases comprises one of determining whether the ratio of the pre-ejection period and the left ventricular ejection time increases by greater than a predetermined percentage over a predetermined number of days and determining whether the ratio of the pre-ejection period and the left ventricular ejection time increases above a predetermined numerical threshold.

22. The device ofclaim 12, wherein the cardiac pacing device comprises a leadless pacemaker device and the sensed pacing event comprises a ventricular pacing event.

23. A non-transitory computer readable medium storing instructions which cause a cardiac medical device to perform a method comprising:

delivering the cardiac pacing therapy from a cardiac pacing device;

sensing a pacing event from a plurality of electrodes of the pacing device;

sensing an electromechanical signal from an electromechanical sensor of the pacing device;

determining a pre-ejection period in response to the sensed electromechanical signal;

determining a left ventricular ejection time in response to the sensed electromechanical signal; and

performing one or both of adjusting a pacing parameter setting and generating an alert in response to the determined pre-ejection period and the determined left ventricular ejection time.

24. A medical device system comprising means to perform the method of any one ofclaims 1-10.

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