Patent Application
20130053913
Embodiments of the subject matter described herein generally relate to adjustment of parameters for implantable medical devices, and more particularly to adjusting pacing parameters based on heart sounds to improve hemodynamic performance.
An implantable medical device (IMD) is implanted in a patient to monitor, among other things, electrical activity of a heart and to deliver appropriate electrical therapy, as required. Implantable medical devices include pacemakers, cardioverters, defibrillators, implantable cardioverter defibrillators (ICD), and the like. The electrical therapy produced by an IMD may include pacing pulses, cardioverting pulses, and/or defibrillator pulses to reverse arrhythmias (e.g., tachycardias and bradycardias) or to stimulate the contraction of cardiac tissue (e.g., cardiac pacing) to return the heart to its normal sinus rhythm. These pulses are referred to as stimulus or stimulation pulses.
IMDs supply a pacing therapy to hearts to treat various arrhythmias. The pacing therapy may include supplying stimulus pulses to the left and/or right ventricles of the heart at a programmed stimulation rate when intrinsic events are not detected within certain time periods, often referred to as delays. Applying the stimulus pulses to the ventricles may restore mechanical synchrony to the heart. For example, the stimulus pulses may return the heart to a normal rate of ventricular contraction.
Pacing therapies of some known IMDs monitor cardiac events in certain chambers of the heart to determine when to supply stimulus pulses to other chambers of the heart. For example, after detecting a paced or intrinsic cardiac event in the right atrium (or right ventricle), the IMD monitors the ventricles (or left ventricle) for cardiac signals to determine if a subsequent intrinsic cardiac event occurs during a predetermined delay after the preceding cardiac event. Examples of the delays include a delay between an atrial event and the successive ventricular event (AV delay), a delay between a right ventricular event and a left ventricular event (W delay), and a delay between a ventricular event and the next atrial event (VA delay). The AV delay, VV delay and VA delay are examples of some of the pacing parameters that are programmable by a clinician, and in certain types of IMDs are automatically adjusted during operation. If no subsequent cardiac event is detected during the predetermined delay, then the IMD supplies a stimulus pulse. When responding to an atrial cardiac event, the IMD will supply pulses to one or both ventricles of the heart to induce contraction of the heart. When responding to a right ventricular cardiac event, the IMD will supply pulses to the left ventricle or right atrium.
The pacing parameters are adjusted in an effort to improve hemodynamic performance of an individual patient. For example, when the AV delay is too short, a patient may experience reduced cardiac output. However, when the AV delay is properly set, the patient experiences good cardiac output (relative to the patients overall health) and good overall hemodynamic performance that may be as good as possible.
Recently, it has been proposed to utilize heart sounds in connection with certain aspects of IMD operation. Heart sounds are the noises generated by the beating heart and the resultant flow of blood, and are typically referred to as S1, S2, S3 and S4. An S1 heart sound is caused by the sudden block of reverse blood flow due to closure of the atrioventricular valves (mitral and tricuspid) at the beginning of ventricular contraction. When the ventricles begin to contract, so do the papillary muscles in each ventricle. The papillary muscles are attached to the tricuspid and mitral valves via chorda tendinae, which bring the cusps of the valve closed (chorda tendinae also prevent the valves from blowing into the atria as ventricular pressure rises due to contraction). The closing of the inlet valves prevents regurgitation of blood from the ventricles back into the atria. The S1 sound results from reverberation within the blood associated with the sudden block of flow reversal by the valves.
An S2 heart sound is caused by the sudden block of reversing blood flow due to closure of the aortic valve and pulmonary valve at the end of ventricular systole, i.e beginning of ventricular diastole. As the left ventricle empties, its pressure falls below the pressure in the aorta, aortic blood flow quickly reverses back toward the left ventricle, catching the aortic valve leaflets and is stopped by aortic (outlet) valve closure. Similarly, as the pressure in the right ventricle falls below the pressure in the pulmonary artery, the pulmonary (outlet) valve closes. The S2 sound results from reverberation within the blood associated with the sudden block of flow reversal.
Heretofore, it has been proposed to control an AV interval or VV interval based on a pulse width of an “S1” heart sound. It also has been proposed to control the AV interval or VV interval based on a sum of the duration of the S1 heart sound and an “S2” heart sound.
However, a need remains to identify better techniques for monitoring hemodynamic performance and to control adjustment of various parameters.
In accordance with one embodiment, a method is provided to determine pacing parameters for an implantable medical device (IMD). The method comprises an implantable medical device (IMD) collecting heart sounds during the cardiac cycles. The heart sounds include sounds representative of a degree of blood flow turbulence wherein the heart sounds include S1, S2 and linking segments. The S1 segment is associated with initial systole activity, the S2 segment is associated with initial diastole activity and the linking segment is associated with heart activity occurring during a systolic interval between the initial systole and diastole activity.
The method further comprises changing a value for a pacing parameter between the cardiac cycles and analyzing a characteristic of interest from the heart sounds within at least a portion of the linking segment. The characteristic of interest is indicative of an amount of heart sounds over at least a portion of the systolic interval between the initial systole and diastole activity, the level of the characteristic of interest changing as the pacing parameter is changed. The method further provides setting a desired value for the pacing parameter based on the characteristic of interest from the heart sounds from the linking segment.
Optionally, the method provides an analyzing operation that includes identifying S1 and S2 peaks associated with the initial systole and diastole activity, respectively, and integrates the heart sounds over the time period between the S1 and S2 peaks. Additionally, the method further provides an analyzing operation that determines an energy content within the linking segment, the energy content within the linking segment excluding an energy content within the S1 and S2 segments and the setting operation reducing the energy content within the linking segment to below a predetermined level.
The analyzing operation further determines S1 energy content associated with the S1 segment, S2 energy content associated with the S2 segment, and linking energy content associated with the linking segment. The S1, S2 and linking energy contents may be mutually exclusive of one another. The setting operation limits a ratio of the S1, S2 and linking energy contents to a predetermined level.
Optionally, the method provides that the characteristic analyzed during the analyzing operation identifies at least one of intensity or energy content of the heart sounds as the amount over an entirety of the systolic interval following the S1 heart sound. The method further comprises determining a minimum level for the heart sounds from a collection of the heart sounds collected over multiple cardiac cycles, the setting operation setting the desired value to correspond to the minimum level for the heart sounds. Optionally, the collecting operation may be performed during implantation of the IMD wherein an external programmer controls the collecting, changing and analyzing operations.
The collecting operation may include deriving heart sounds from signals produced by an accelerometer within the IMD. The IMD may represent a rate-responsive IMD. The collecting, changing and identifying operations are repeated periodically by the rate-responsive IMD to provide real-time updates to the pacing parameter throughout operation.
Additionally, the pacing parameter may represent at least one of an AV delay, a VV delay and a VA delay. The changing operation changes at least one of the AV delay, the W delay and VA delay in order reduce systolic turbulence and regurgitation.
In accordance with an embodiment, a system is provided that comprises inputs configured to be coupled to at least one lead having electrodes to sense intrinsic events and to deliver pacing pulses over cardiac cycles. The system may include an IMD and/or a programmer. The system has a sensor for collecting heart sounds during cardiac cycles. The heart sounds include sounds representative of a degree of blood flow turbulence. The sensor collects the heart sounds that include S1, S2 and linking segments. The S1 segment is associated with initial systole activity, the S2 segment associated with initial diastole activity. The linking segment is associated with heart activity occurring during a systolic interval between the initial systole and diastole activity.
The system further provides a controller to control delivery of pacing pulses based on pacing parameters. The controller changes a value for at least one of the pacing parameters between the cardiac cycles. Additionally, the system comprises an analysis module to analyze a characteristic of interest from the heart sounds within at least a portion of the linking segment. The characteristic of interest is indicative of an amount of the heart sounds over at least a portion of the systolic interval between the initial systole and diastole activity. The level of the characteristic of interest changes as the pacing parameter is changed. A setting module sets a desired value for the pacing parameter based on the characteristic of interest from the heart sounds from the linking segment.
Optionally, the analysis module identifies S1 and S2 peaks associated with the initial systole and diastole activity, respectively, and integrates the heart sounds over the time period between the S1 and S2 peaks. The analysis module may determine an energy content within the linking segment. The energy content within the linking segment excludes an energy content within the S1 and S2 segments. The setting operation may reduce the energy content within the linking segment to below a predetermined level.
Optionally, the analysis module may determine S1, S2 and linking energy contents individually associated with the S1, S2 and linking segments, respectively, where the S1, S2 and linking energy contents are mutually exclusive of one another. The setting module may limit a ratio of the S1, S2 and linking energy contents to a predetermined level.
The analysis module may identify at least one of intensity or energy content as the amount of the heart sounds over an entirety of the systolic interval following the S1 heart sound.
In accordance with an embodiment, an IMD is provided that uses a device-based accelerometer to measure heart sound intensity to assess the degree of blood turbulence during systolic (ejection) as well as diastolic (filling) time for a set of cardiac device therapy parameters. A desired parameter value may be chosen based on minimal heart sound intensity between S1 and S2.
Further, embodiments can be implemented to apply in rate adaptive pacing where AV delay adaptation is desired. On-the-fly AV delay adaptation is possible to achieve relatively low systolic turbulence.
In accordance with an embodiment, a PSA/Programmer based system is provided with a wand having mean of acoustic sensing (microphone or accelerometer) and that will determine optimal parameters during CRT device follow-ups or at the time of implant.
The “coronary sinus” lead 16 is placed in the “coronary sinus region” via the coronary sinus for positioning a distal electrode adjacent to the left ventricle and/or additional electrode(s) adjacent to the left atrium. The coronary sinus lead 16 includes a left ventricular tip electrode 32, a left atrial ring electrode 34, and a left atrial coil electrode 36. Optionally, the lead 16 may also include multiple LV electrodes 31, 32, 33 and 35 to afford additional left ventricular sensing and pacing sites. It should also be understood that fewer or additional stimulation leads (with one or more pacing, sensing and/or shocking electrodes) may be used in order to efficiently and effectively provide pacing stimulation to the left side of the heart or atrial cardioversion and/or defibrillation.
One or more of the leads 12, 14 and 16 detect intracardiac electrogram (IEGM) signals that form an electrical activity indicator of myocardial function over multiple cardiac cycles. The IEGM signals represent analog signals that are subsequently digitized and analyzed to identify waveforms of interest. Examples of waveforms identified from the IEGM signals include the P-wave, T-wave, the R-wave, the QRS complex and the like. The lead 16 may include a sensor 40 for sensing left atrial activity.
The IMD 10 may be coupled to an acoustic sensor 19 through an insulated conductor 17. As shown in
The IMD 10 stores heart sound data sets over multiple cardiac cycles, continuously or periodically (e.g., every hour, every day, etc.). The heart sound data sets may be analyzed by the IMD 10, or transmitted externally for analysis, such as by a programmer, a hospital network, a workstation and the like. The systolic and diastolic intervals may be determined from several indicators, such as IEGM, ECG, heart sounds, myocardial pressure and the like.
An acoustic terminal 50 is adapted to be connected to the external acoustic sensor 19 or 23 or the internal acoustic sensor 21, depending upon which (if any) of sensors 19, 21 and 23 is used. Terminal 51 is adapted to be connected to sensor 25 to collect measurements associated with glucose levels, natriuretic peptide levels, or catecholamine levels.
The IMD 10 includes a programmable microcontroller 60, which controls operation. The microcontroller 60 (also referred to herein as a processor module or unit) typically includes a microprocessor, or equivalent control circuitry, designed specifically for controlling the delivery of stimulation therapy and may further include RAM or ROM memory, logic and timing circuitry, state machine circuitry, and I/O circuitry. Typically, the microcontroller 60 includes the ability to process or monitor input signals (data) as controlled by program code stored in memory. The details of the design and operation of the microcontroller 60 are not critical to the invention. Rather, any suitable microcontroller 60 may be used that carries out the functions described herein. Among other things, the microcontroller 60 receives, processes, and manages storage of digitized cardiac data sets from the various sensors and electrodes. For example, the cardiac data sets may include IEGM data, pressure data, heart sound data, and the like.
The IMD 10 includes an atrial pulse generator 70 and a ventricular/impedance pulse generator 72 to generate pacing stimulation pulses for delivery by the right atrial lead 12, the right ventricular lead 14, and/or the coronary sinus lead 16 via an electrode configuration switch 74. It is understood that in order to provide stimulation therapy in each of the four chambers of the heart, the atrial and ventricular pulse generators, 70 and 72, may include dedicated, independent pulse generators, multiplexed pulse generators or shared pulse generators. The pulse generators, 70 and 72, are controlled by the microcontroller 60 via appropriate control signals, 76 and 78, respectively, to trigger or inhibit the stimulation pulses.
The microcontroller 60 further includes timing control circuitry 79 used to control the timing of such stimulation pulses (e.g., pacing rate, atria-ventricular (AV) delay, atrial interconduction (A-A) delay, or ventricular interconduction (V-V) delay, etc.) as well as to keep track of the timing of refractory periods, blanking intervals, noise detection windows, evoked response windows, alert intervals, marker channel timing, and the like. Switch 74 includes a plurality of switches for connecting the desired electrodes to the appropriate I/O circuits, thereby providing complete electrode programmability. Accordingly, the switch 74, in response to a control signal 80 from the microcontroller 60, determines the polarity of the stimulation pulses (e.g., unipolar, bipolar, etc.) by selectively closing the appropriate combination of switches (not shown) as is known in the art.
Atrial sensing circuit 82 and ventricular sensing circuit 84 may also be selectively coupled to the right atrial lead 12, coronary sinus lead 16, and the right ventricular lead 14, through the switch 74 for detecting the presence of cardiac activity in each of the four chambers of the heart. Accordingly, the atrial (ATR SENSE) and ventricular (VTR SENSE) sensing circuits, 82 and 84, may include dedicated sense amplifiers, multiplexed amplifiers or shared amplifiers. The outputs of the atrial and ventricular sensing circuits, 82 and 84, are connected to the microcontroller 60 which, in turn, are able to trigger or inhibit the atrial and ventricular pulse generators, 70 and 72, respectively, in a demand fashion in response to the absence or presence of cardiac activity in the appropriate chambers of the heart.
Cardiac signals are also applied to the inputs of an analog-to-digital (A/D) data acquisition system 90. The data acquisition system 90 is configured to acquire IEGM signals, convert the raw analog data into a digital IEGM signal, and store the digital IEGM signals in memory 94 for later processing and/or telemetric transmission to an external device 102. The data acquisition system 90 is coupled to the right atrial lead 12, the coronary sinus lead 16, and the right ventricular lead 14 through the switch 74 to sample cardiac signals across any combination of desired electrodes. The data acquisition system 90 is also coupled, through switch 74, to one or more of the acoustic sensors 19, 21 and 23. The data acquisition system 90 acquires, performs ND conversion, produces and saves the digital pressure data, and/or acoustic data.
The controller 60 controls the acoustic sensor 19 and/or physiologic sensor 108 to collect heart sounds during one or more cardiac cycles. The heart sounds include sounds representative of a degree of blood flow turbulence. The sensor 19 or 108 collects the heart sounds that include S1, S2 and linking segments. The S1 segment is associated with initial systole activity. The S2 segment is associated with initial diastole activity. The linking segment is associated with at least a portion of heart activity occurring between the S1 and S2 segments during a systolic interval between the initial systole and diastole activity. The controller 60 changes a value for at least one of the pacing parameters between the cardiac cycles. The controller 60 implements one or more processes described herein to determine values for one or more pacing parameters that yield a desired level of hemodynamic performance.
The controller 60 includes an analysis module 71 and a setting module 73 that function in accordance with embodiments described herein. The analysis module 71 analyzes a characteristic of interest from the heart sounds within at least a portion of the linking segment. The characteristic of interest is indicative of an “amount” of the heart sounds over at least a portion of the systolic interval between the initial systole and diastole activity. The amount of the heart sounds may be derived in different manners, such as determining the energy content, intensity and the like, as well as relations therebetween. The level of the characteristic changes as the pacing parameter is changed. The setting module 73 sets a desired value for the pacing parameter based on the characteristic of interest from the heart sounds for at least the portion of the linking segment. The pacing parameter may represent at least one of an AV delay, a VV delay, a VA delay, intra-ventricular delays, electrode configurations and the like. The controller 60 changes at least one of the AV delay, the VV delay, the VA delay, the intra-ventricular delays, electrode configurations and like in order to reduce systolic turbulence and regurgitation.
By way of example, with reference to
The analysis module 71 may identify S1 and S2 peaks associated with the initial systole and diastole activity, respectively, and integrate the heart sounds over the time period between the S1 and S2 peaks to derive the amount of the heart sounds. Optionally, the analysis module 71 may determine an energy content within the linking segment to derive the amount of the heart sounds. The energy content within the linking segment excludes an energy content within the S1 and S2 segments. The setting module reduces the energy content within the linking segment to below a predetermined level. Optionally, the analysis module 71 may determine S1, S2 and linking energy contents individually associated with the S1, S2 and linking segments respectively. In this example, the S1, S2 and linking energy contents are mutually exclusive of one another, and the setting module 73 limits a ratio of the S1, S2 and linking energy contents to a predetermined level. The characteristic of interest analyzed by the analysis module 71 may identify at least one of intensity or energy content of the heart sounds over an entirety of the systolic interval following the S1 heart sound. The analysis module 71 may determine a minimum level for the heart sounds from a collection of the heart sounds collected over multiple cardiac cycles. The setting module 73 may set the desired value to correspond to the minimum level for the heart sounds.
The microcontroller 60 is coupled to memory 94 by a suitable data/address bus 96, wherein the programmable operating parameters used by the microcontroller 60 are stored and modified, as required, in order to customize the operation of IMD 10 to suit the needs of a particular patient. The memory 94 also stores data sets (raw data, summary data, histograms, etc.), such as the IEGM data, heart sound data, pressure data, Sv02 data and the like for a desired period of time (e.g., 1 hour, 24 hours, 1 month). The memory 94 may store instructions to direct the microcontroller 60 to analyze the cardiac signals and heart sounds identify characteristics of interest and derive values for predetermined statistical parameters. The IEGM, pressure, and heart sound data stored in memory 94 may be selectively stored at certain time intervals, such as 5 minutes to 1 hour periodically or surrounding a particular type of arrhythmia of other irregularity in the heart cycle. For example, the memory 94 may store data for multiple non-consecutive 10 minute intervals.
The pacing and other operating parameters of the IMD 10 may be non-invasively programmed into the memory 94 through a telemetry circuit 100 in telemetric communication with the external device 102, such as a programmer, trans-telephonic transceiver or a diagnostic system analyzer, or with a bedside monitor 18. The telemetry circuit 100 is activated by the microcontroller 60 by a control signal 106. The telemetry circuit 100 allows intra-cardiac electrograms, pressure data, acoustic data, Sv02 data, and status information relating to the operation of IMD 10 (as contained in the microcontroller 60 or memory 94) to be sent to the external device 102 through an established communication link 104.
The memory 94 may be programmed with multiple conditions that, when satisfied by the indicators, are representative of potential ischemic episodes. For example, the conditions may include one or more of i) amplitudes and/or durations for heart sounds S1, S2, S3 and/or S4, ii) timing, intervals between and/or deviation of events of interest (e.g., mitral valve closing, mitral valve opening, aortic valve closing, aortic valve opening), iii) amplitudes and durations of points in the IEGM signal, and iv) durations of systolic interval, diastolic interval, isovolumic relaxation interval, and/or isovolumic contraction interval. The conditions may be preprogrammed from an external device or automatically set by the IMD 10 based on prior operation and historic data collected from the patient.
The IMD 10 may include an accelerometer or other physiologic sensor 108, commonly referred to as a “rate-responsive” sensor because it is typically used to adjust pacing stimulation rate according to the exercise state of the patient. Optionally, the physiological sensor 108 may further be used to detect changes in cardiac output, changes in the physiological condition of the heart, or changes in activity (e.g., detecting sleep and wake states) and to detect arousal from sleep. While shown as being included within IMD 10, it is to be understood that the physiologic sensor 108 may also be external to IMD 10, yet still be implanted within or carried by the patient. A common type of rate responsive sensor is an activity sensor incorporating an accelerometer or a piezoelectric crystal, which is mounted within the housing 38 of IMD 10.
The physiologic sensor 108 may be used as the acoustic sensor 23 (
The IMD 10 additionally includes a battery 110, which provides operating power to all of the circuits shown. The IMD 10 is shown as having an impedance measuring circuit 112 which is enabled by the microcontroller 60 via a control signal 114. Herein, impedance is primarily detected for use in evaluating ventricular end diastolic volume (EDV) but is also used to track respiration cycles. Other uses for an impedance measuring circuit include, but are not limited to, lead impedance surveillance during the acute and chronic phases for proper lead positioning or dislodgement; detecting operable electrodes and automatically switching to an operable pair if dislodgement occurs; measuring respiration or minute ventilation; measuring thoracic impedance for determining shock thresholds; detecting when the device has been implanted; measuring stroke volume; and detecting the opening of heart valves, etc. The impedance measuring circuit 120 is advantageously coupled to the switch 74 so that impedance at any desired electrode may be obtained.
The heart sounds 302 (also referred to as a phonocardiogram) may be detected by the physiologic sensor 108 and/or the separate acoustic sensors 19 or 21. The sounds are produced by blood turbulence and vibration of cardiac structures due to the closing of the valves within the heart. Four sounds that may be identified are S1, S2, S3, and S4. S1 is usually the loudest heart sound and is the first heart sound during ventricular contraction. S1 occurs at the beginning of ventricular systole interval and represents the initial systole activity as it relates to the closure of the atrioventricular valves between the atria and the ventricles. S2 occurs at the beginning of the diastole interval and represents the initial diastole activity as it relates to the closing of the semilunar valves separating the aorta and pulmonary artery from the left and right ventricles, respectively. S3 occurs in the early diastolic period and is caused by the ventricular wall distending to the point it reaches its elastic limit. S4 occurs near the end of atrial contraction and is also caused by the ventricular wall distending until it reaches its elastic limit.
The CPU 402 typically includes a microprocessor, a micro-controller, or equivalent control circuitry, designed specifically to control interfacing with the external device 409 and with the IMD 10. The CPU 402 may include RAM or ROM memory 404, logic and timing circuitry, state machine circuitry, and I/O circuitry to interface with the IMD 10. The display 422 (e.g., may be connected to the video display 432) and the touch screen 424, display graphic information relating to the IMD 10. The touch screen 424 accepts a user's touch input 434 when selections are made. The keyboard 426 (e.g., a typewriter keyboard 436) allows the user to enter data to the displayed fields, as well as interface with the telemetry subsystem 430. Furthermore, custom keys 428 turn on/off 438 (e.g., EVVI) the external device 409. The printer 412 prints copies of reports 440 for a physician to review or to be placed in a patient file, and speaker 410 provides an audible warning (e.g., sounds and tones 442) to the user. The parallel I/O circuit 418 interfaces with a parallel port 444. The serial I/O circuit 420 interfaces with a serial port 446. The floppy drive 416 accepts diskettes 448. Optionally, the floppy drive 416 may include a USB port or other interface capable of communicating with a USB device such as a memory stick. The CD-ROM drive 4714 accepts CD ROMs 450.
The telemetry subsystem 430 includes a central processing unit (CPU) 452 in electrical communication with a telemetry circuit 454, which communicates with both an ECG circuit 456 and an analog out circuit 458. The ECG circuit 456 is connected to ECG leads 460. The telemetry circuit 454 is connected to a telemetry wand 462. The analog out circuit 458 includes communication circuits to communicate with analog outputs 464. The external device 108 may wirelessly communicate with the IMD 10 and utilize protocols, such as Bluetooth, GSM, infrared wireless LANs, HIPERLAN, 3G, satellite, as well as circuit and packet data protocols, and the like. Alternatively, a hard-wired connection may be used to connect the external device 108 to the IMD 10.
The server 502 is a computer system that provides services to other computing systems over a computer network. The server 502 controls the communication of information such as cardiogenic impedance parameters and electrophysiologic response parameters. The server 502 interfaces with the communication system 512 to transfer information between the programmer 506, the local RF transceiver 508, the user workstation 510 as well as a cell phone 514, and a personal data assistant (PDA) 516 to the database 504 for storage/retrieval of records of information. On the other hand, the server 502 may upload raw cardiac signals from a surface ECG unit 520 or the IMD 10 via the local RF transceiver 508 or the programmer 506.
The database 504 stores information such as the measurements for the cardiogenic impedance parameters, the electrophysiologic response parameters, and the like, for a single or multiple patients. The information is downloaded into the database 504 via the server 502 or, alternatively, the information is uploaded to the server from the database 504. The programmer 506 is similar to the external device 108 and may reside in a patient's home, a hospital, or a physician's office. Programmer 506 interfaces with the surface ECG unit 520 and the IMD 10. The programmer 506 may wirelessly communicate with the IMD 10 and utilize protocols, such as Bluetooth, GSM, infrared wireless LANs, HIPERLAN, 3G, satellite, as well as circuit and packet data protocols, and the like. Alternatively, a hard-wired connection may be used to connect the programmer 506 to the IMD 10. The programmer 506 is able to acquire cardiac signals from the surface of a person (e.g., ECGs), intra-cardiac electrogram (e.g., IEGM) signals from the IMD 10, and/or values of cardiogenic impedance parameters and electrophysiologic response parameters from the IMD 10. The programmer 506 interfaces with the communication system 512, either via the internet or via POTS, to upload the information acquired from the surface ECG unit 520 or the IMD 10 to the server 502.
The local RF transceiver 508 interfaces with the communication system 512, via a communication link 524, to upload values of physiologic indices acquired from the surface ECG unit 520 and/or cardiogenic impedance parameters and electrophysiologic response parameters acquired from the IMD 10 to the server 502. In one embodiment, the surface ECG unit 520 and the IMD 10 have a bi-directional connection with the local RF transceiver via a wireless connection. The local RF transceiver 508 is able to acquire cardiac signals from the surface of a person, intra-cardiac electrogram signals from the IMD 10, and/or the values of cardiogenic impedance parameters and electrophysiologic response parameters from the IMD 10. On the other hand, the local RF transceiver 508 may download stored cardiogenic impedance parameters, electrophysiologic response parameters, cardiac data, and the like, from the database 504 to the surface ECG unit 520 or the IMD 10.
The user workstation 510 may interface with the communication system 512 via the internet or POTS to download values of the cardiogenic impedance parameters and electrophysiologic response parameters via the server 502 from the database 504. Alternatively, the user workstation 510 may download raw data from the surface ECG unit 520 or IMD 10 via either the programmer 506 or the local RF transceiver 508. Once the user workstation 510 has downloaded the cardiogenic impedance parameters and electrophysiologic response parameters, the user workstation 510 may process the information in accordance with one or more of the operations described above in connection with the process 500 (shown in
In example 650, the heart sound intensities begin around 75 (corresponding to an AV delay of 20 msecs.) but then slightly increase, approaching 80 at data points 653 and 654 (corresponding to AV delays of 40 and 65). As the AV delay increases to exceed 65 msecs., in the example A50, the heart sound intensity falls off sharply at data point 655 (to approximately 64) and even further at data point 655 (approximately 51).
In example 610, the data points 612-616 show that the heart sounds intensity begin near a maximum value with a shorter AV delay. More specifically, at data point 612, the heart sound intensity is approximately 50, and is maintained near 50 at data point 613. However, as the AV delay is extended above 60 msecs., data points 614-616 show that the heart sound intensity falls off sharply to below 40, approaching 30 at data point 616.
The foregoing examples illustrate that the heart sound intensity, at least over certain portions of the cardiac cycle, drops to a notable lower level when the AV delay is extended. While not illustrated, as the AV delay is extended even further, at some point the heart sound intensity begins to increase again. Thus, the heart sound intensity exhibits a local minimum that corresponds to a limited duration of the range for AV delay.
As explained throughout, methods and systems are provided herein to determine pacing parameters, such as the AV delay that, if implemented, would potentially yield improved hemodynamic performance through an increased contractility surrogate (as measured in one way through the maximum LVdp/dt).
At 814, the process begins implementation of a search for desired pacing parameter values. For example, at 814, initial values for certain pacing parameters may be obtained from memory in the IMD memory in a programmer, or based on recently collected physiologic information, such as cardiac signals, pressure measurements within one or more chambers of the heart, impedance measurements, sound measurements and the like. At 816, the current pacing value(s) are changed. For example, the pacing parameter may correspond to the AV delay, the VV delay, the VA delay, atrial and ventricular electrode combinations for pacing, atrial and ventricular electrodes to use for sensing, timing delays between left ventricular electrodes, time delays between left atrial electrodes, timing delays between LA and LV electrodes, and the like. Optionally, the pacing parameter may designate the pacing mode, such as the chambers of the heart where sensing occurs, the chambers of the heart where pacing occurs, which LV electrodes to use and the like. As a further option, the pacing parameter may represent the combination of electrodes used to deliver pacing pulses. The pacing parameter(s) may include one or more combinations of the above listed examples, as well as other parameters.
At 816, the value for one or more of the pacing parameters is changed. It is recognized that, during a first iteration through
At 818, a new series of heart sounds are collected for one or more cardiac cycles, while the IMD 10 operates using the pacing parameter value set in 816. In the foregoing example, when the AV delay is increased to 25 msecs., at 818, heart sounds, may be collected over 1 to 10 or more cardiac cycles, while the IMD 10 operates with the AV delay of 25 msecs. When heart sounds for multiple cardiac cycles are collected, each cardiac cycle may be separated (e.g., based on a marker such as the R-wave). The heart sounds for each cardiac cycle may be processed separately at 820 and 822. Alternatively, the heart sounds for each cardiac cycle may be aligned with one another and summed to form a composite signal for heart sounds. For example, an ensemble of heart sounds for 3, 5 or 10 cardiac cycles may be temporally aligned based on a marker such as the peak of the R-wave and summed. Optionally, the ensemble of heart sounds may be aligned through auto correlation, cross-correlation, or other techniques and then summed.
At 820, the S1 and S2 heart sounds are identified from the collected heart sounds. To identify the S1 and S2 heart sounds, the process may first establish S1 and S2 detection windows that are overlaid upon the heart sounds. The S1 and S2 detection windows are positioned to start a predetermined offset time after a marker of interest. For example, the S1 and S2 detection windows may be offset to start 100 msec. and 250 msec., respectively, after the peak R-wave. For example, the identification at 820 may include an identification of the peak in the S1 heart sound and the peak in the S2 heart sound during corresponding detection windows. Optionally, the identification may determine i) the center of the S1 and S2 heart sounds, ii) the durations of the S1 and S2 heart sounds, and iii) the peak amplitude of the S1 and S2 heart sounds. When identifying the center of the S1 and S2 heart sounds, the center may represent the temporal center or the center of the energy content for the S1 heart sound and the temporal center or the center for the energy content for the S2 heart sound.
When heart sounds for multiple cardiac cycles are collected at 818, each cardiac cycle may be processed individually at 820 and 822. Alternatively, when heart sounds for an ensemble of cardiac signals are combined, the composite heart sounds may be processed at 820 to identify a single composite S1 heart sound and a single composite S2 heart sound. The composite heart sounds are then analyzed at 822.
Next, the operations at 818 and 820 will be described in connection with
As one example, the process may analyze cardiac signals to identify a marker, such as the peak of the R-wave (denoted at 942). The process may then set an S1 detection window 944 to begin a programmed period of time after the marker 942. This programmed delay time 946 may be a set number of milliseconds or a percentage of the cardiac cycle length and the like. The length of the S1 detection window 944 may also be programmed. The process may similarly set an S2 detection window 948, beginning a delay time 949 after the marker 942. The process only searches for S1 and S2 peaks during the corresponding S1 and S2 detection windows 944 and 948.
During the identification operation at 820 (
The heart sounds may be collected over multiple cardiac cycles and separately analyzed to identify multiple S1 and S2 heart sounds at 820, or combined and analyzed to identify composite S1 and S2 heart sounds.
Returning to
It may be physiologically normal to hear a slight “splitting” of the second heart tone. However, different types of split S2 can be associated with medical conditions. For example, while a split during inspiration may be normal, a split during expiration may indicate pathology (e.g., Aortic stenosis, hypertrophic cardiomyopathy, left bundle branch block). When splitting does not vary with inspiration, it may be termed a “fixed split S2” and may be due to a septal defect, such as an atrial septal defect (ASD) or ventricular septal defect (VSD). The ASD or VSD creates a left to right shunt that increases the blood flow to the right side of the heart, thereby causing the pulmonary valve to close later than the aortic valve independent of inspiration/expiration.
A bundle branch block either LBB or RBB, (although RBB is known to be associated only with S1 split), may produce continuous splitting but the degree of splitting will still vary with respiration. When the pulmonary valve closes before the aortic valve, this is known as a “paradoxically split S2”.
In accordance with certain embodiments herein, the heart sounds are analyzed to identify a split S2 heart sound and to identify pacing parameters that reduce or minimize the degree/amount of S2 split. At 830, by way of example, a split in the heart sound S2 may be determined by analyzing the S2 heart sound for more than one peak. For example, the S2 heart sound may be compared to an S2 threshold, and a split may be declared when the S2 heart sound exceeds the S2 threshold in two distinct regions separated by a time delay. The time delay between the S2 heart sound regions may be predetermined, programmed and/or dynamically updated based on real time physiologic measurements. Optionally, the S2 heart sound may be analyzed to determine whether two or more absolute peaks exist and then the process may determine the spacing between these absolute peaks. Alternatively, when a first S2 (S2A) heart sound peak is identified, a split detection window may be overlaid on the remaining portion of the S2 heart sound. If a 2nd peak (S2B) occurs within the split detection window, then a split S2 heart sound is declared. The split detection window may start a predetermined time after the first S2 heart sound and then end before another type of heart sound may occur.
Alternatively, the S2 heart sound may be passed through a low pass filter to form a smoothed, filtered heart sound. The smoothed, filtered heart sound signal is then analyzed to determine changes in the slope of the heart sound signal. The points in time at which the slope changes from positive to negative may be used to identify local peaks. These local peaks (S2A and S2B) are compared to determine a time spacing there between. When the S2 heart sound signal exhibits two peaks that are separated in time by sufficient time spacing, this signal is declared to be split into S2A and S2B heart sounds at 830 and flow moves to 832.
At 832, the process determines the area (e.g., the energy) under the heart sound signal between S1 and the first S2 heart sound (S1-S2A area or S1-S2A energy). At 832, the process also identifies the distance between the first and second S2 heart sounds (S2A-S2B distance). This distance may be between the peaks of S2A and S2B. Optionally, the S2A-S2B distance may be between the centers of the S2A and S2B heart sounds. When identifying the center of the S2A and S2B heart sounds, the center may represent the temporal center or the center of the energy content for the S2A heart sound and the temporal center or the center for the energy content for the S2B heart sound. Optionally, the area or energy between S1 and S2B may be determined.
At 834, the process saves one or more of the S1-S2A energy under the heart sound signal between S1 and S2A, the S1-S2B energy under the heart sound signal between S1 and S2B and the distance between S2A and S2B as potential characteristics of interest.
At 836, the process compares one or more of the S1-S2A energy with a predetermined area or energy threshold GA, the S1-S2B energy with a predetermined area or energy threshold GB, and compares the S2A-S2B distance with a predetermined distance threshold OD. If the S1-S2A energy, S1-S2B energy and/or the S2A-S2B distance exceed the corresponding threshold ΘA, ΘB and/or ΘD, then the S2 split heart sounds are declared to not be suitable to base changes in pacing parameters thereon. Hence, flow moves to 824 and the process continues.
When at 836, the S1-S2A energy, S1-S2B energy and/or the S2A-S2B distance are determined to fall within and not exceed the corresponding threshold ΘA, ΘB and/or ΘD, then the split S2 heart sounds are declared to be suitable for further analysis and to be used as the basis to change pacing parameters. Hence, flow continues to 822.
At 822, one or more predetermined characteristics of interest for the heart sounds are analyzed. The heart sounds of interest have S1, S2 and linking segments. The heart sounds of interest may also include a split S2 and thus have an S2A portion, an S2B portion and a split segment between S2A and S2B. The S1 segment is associated with initial systole activity. The S2 segment is associated with initial diastole activity. The linking segment is associated with at least a portion of heart activity occurring between the S1 and S2 segments during a systolic interval between the initial systole and diastole activity. At 822, the characteristic of interest is representative of a degree of blood turbulence during the systolic interval which corresponds to the ventricular ejection phase of the cardiac cycle. The characteristic of interest is not simply limited to the S1 heart sound and not simply limited to the S2 heart sound. Instead, the characteristic of interest may solely relate to a phase of the cardiac cycle beginning after S1 and ending before S2. Alternatively, the characteristic of interest may represent a relation between S1, S2 and the phase therebetween. The characteristic of interest for the heart sounds may represent the intensity of the heart sounds, the energy content of the heart sounds, ratios between the energy content within different segments of the heart sounds, and the like.
The characteristic of interest may relate to a phase of a split S2 heart sound beginning at S2A and ending at S2B. Alternatively, the characteristic of interest may represent a relation between the split sounds, S2A and S2B, and the phase therebetween. The characteristic of interest for the split S2A, S2B heart sounds may represent the intensity of the S2A, S2B heart sounds, the energy content of the S2A, S2B heart sounds, ratios between the energy content within different segments of the S2A, S2B heart sounds, and the like. The operations at 820 and 822 are discussed hereafter in more detail in connection with
At 1014 and 1018, one or more features of S1 and S2 may be identified. For example, peak and duration for S1 and S2 may be identified, including start and end times for each of the S1 and S2 segments.
At 1040, the process determines whether there is a split in the heart sounds. By way of example, a split in the heart sound S2 may be determined by analyzing the S2 heart sound for more than one peak or in various other manners described herein and apparent here from. When the S2 heart sound signal exhibits two peaks that are separated in time by sufficient time spacing, this signal is declared to be split into S2A and S2B heart sounds at 1040 and flow moves to 1042.
At 1042, the process determines the area under the heart sound signal between S1 and the first S2 heart sound (S1-S2A energy). At 1042, the process also identifies the distance between the first and second S2 heart sounds (S2A and S2B). This distance may be between the peaks of S2A and S2B. Optionally, the distance may be between the centers of the S2A and S2B heart sounds. When identifying the center of the S2A and S2B heart sounds, the center may represent the temporal center or the center of the energy content for the S2A heart sound and the temporal center or the center for the energy content for the S2B heart sound.
At 1044, the process saves one or more of the S1-S2A energy under the heart sound signal between S1 and S2A, the S1-S2B energy under the heart sound signal between S1 and S2B and the distance between S2A and S2B as characteristics of interest. Next flow moves to 1020. Optionally, 1040 to 1044 may be skipped or omitted if the same test and the same information is tested, calculated and saved at 830-834 in
At 1020, the heart sounds are rectified to form a positive signal within a normalized range of 0 to 1. Next, one or more of multiple processes may be followed to analyze one or more desired characteristics of the heart sounds. In
In the example of
Alternatively or in addition, the heart sounds may be analyzed along branch 1024 by looking at an alternative characteristic of interest. Along branch 1024, the process first calculates the S1 energy content, S2 energy content and linking segment energy content. The process may identify the S1, S2 and linking segment energy contents by separately integrating the heart sound signals (rectified) over the corresponding S1, S2 and linking segments of the heart sounds. For example, the S1 energy content may be derived by integrating the heart sound signals within the range corresponding to S1 segment 962 (
At 1036, one or more different types of relations may be calculated between the S1, S2 and linking segment energies. For example, a ratio (Elink/Es1+Es2) may be calculated between the amount of energy in the linking segment 963 relative to the sum of the amount of energy in the S1 and S2 segments 962 and 964. As the heart sound signal increases during the linking segment 963, the ratio increases. It may be desirable to adjust the pacing parameters until the energy obtained during the linking segment 963 approaches a relatively low level or reaches a minimum. Once the ratio is calculated 1036, this ratio is saved as a characteristic value at 1032 in a one to one relation with the current pacing parameter value(s).
When flow moves along the branch 1048, the split S2 heart sounds are integrated over the range spanning from the S1 peak to the S2A peak. This split S2 integration value, and the distance between S2A and S2B are then saved as characteristic values at 1032 in one to one relation with the current pacing parameter values. It may be desirable to adjust the pacing parameters until the energy obtained during the S1-S2A energy, the energy obtained during the S1-S2B energy and/or the duration of the S2A-S2B time delay approach relatively low levels or reaches a minimum. As the operations discussed herein are repeated, the process seeks to reduce the S2 split by selecting pacing parameters that are associated with i) a low or minimum area under the curve between S1 and S2A, ii) a low or minimum area under the curve between S1 and S2B, and/or iii) a short time delay between S2A and S2B.
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Optionally, the characteristics of interest determined along branches 1022, 1024 and 1048 may be combined, such as through a weighted sum, to utilize all three types of characteristic information when selecting the desired pacing parameters. Alternatively, the characteristics determined along branches 1022, 1024 and 1048 may be used to separately identify three candidate pacing parameters, which are then merged to form a desired pacing parameter.
At 1108, a set of histograms are created, with an S1 histogram for the S1 segment, an S2 histogram counting peaks that occurred during the S2 segment, and a linking histogram counting peaks that occurred during the linking segment. The histograms include contiguous non-overlapping bins for different ranges of heart sound amplitudes. The S1 histogram stores a count in each bin for the number of peaks that occurred during the S1 segment having an amplitude within the corresponding range. The S2 histogram stores a count in each bin for the number of peaks that occurred during the S2 segment having an amplitude within the corresponding range. The linking histogram stores a count in each bin for the number of peaks that occurred during the linking segment having an amplitude within the corresponding range.
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At 1112, the statistical indicators are compared to one another to obtain one or more relations between the S1, S2, and linking histograms. These relations represent a characteristic value that is saved in connection with the current pacing parameter values. For example, the moment for the linking histogram may be compared to the moment for the S1 and/or S2 histograms. Optionally, the centroid for the linking histogram may be compared to an average of the centroids for the S1 and S2 histograms. Alternatively, a difference between the average for the S1 histogram and the average for the linking histogram may be compared to a difference between the average for the S2 histogram and the average for the linking histogram. Once the desired relation is determined, it is saved as a current characteristic value with the corresponding pacing parameter value, and flow returns to 824 (
The foregoing process, of
At 828, for example, an AV delay of approximately 100 msec. may have been set if the patient exhibited the behavior shown in
In accordance with an embodiment, an IMD is provided that uses a device-based accelerometer to measure heart sound intensity to assess the degree of blood turbulence during systolic (ejection) as well as diastolic (filling) time for a set of cardiac device therapy parameters. A desired parameter value may be chosen based on minimal heart sound intensity between S1 and S2. When the IMD represents a rate-responsive IMD, the collecting, changing and identifying operations may be repeated periodically by the rate-responsive IMD to provide real-time updates to the pacing parameter throughout operation
Further, embodiments can be implemented to apply in rate adaptive pacing where AV delay adaptation is desired. On-the-fly AV delay adaptation is possible to achieve relatively low systolic turbulence.
In accordance with an embodiment, a PSA/Programmer based system is provided with a wand having mean of acoustic sensing (microphone or accelerometer) and that will determine optimal parameters during CRT device follow-ups or at the time of implant.
It is to be understood that the above description is intended to be illustrative, and not restrictive. For example, the above-described embodiments (and/or aspects thereof) may be used in combination with each other. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope. While the dimensions, types of materials and coatings described herein are intended to define the parameters of the invention, they are by no means limiting and are exemplary embodiments. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Moreover, in the following claims, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements on their objects. Further, the limitations of the following claims are not written in means—plus-function format and are not intended to be interpreted based on 35 U.S.C. §112, sixth paragraph, unless and until such claim limitations expressly use the phrase “means for” followed by a statement of function void of further structure.
