Determining validity of heart sound signals from implantable medical devices

Abstract

An apparatus, system, and method for determining the validity of a recorded segment of heart sound are disclosed. A medical system may include a heart sound sensor, an electrical sensor / stimulus for sensing or providing a ventricular electrical event, and a processor. The processor records a segment comprising a plurality of heart sound segments, each triggered by an instance of the ventricular electrical event. For each heart sound segment, the processor determines a correlation between the heart sound segment and each other heart sound segment in the segment. Under the condition that the value related to the median value of each heart sound segment in the other heart sound segments in the segment is larger than a threshold value, the heart sound segments are considered to be effective samples. Where the segment of heart sound greater than a threshold number is characterized as a valid sample, the segment is considered to have meaningful physiological data.

Description

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 387,353, filed Dec. 14, 2022, the entire content of which is incorporated herein by reference. Technical Field

[0002] This disclosure relates generally to medical devices and, more particularly, to devices configured to sense heart sound signals. Background Art

[0003] Heart sounds provide important diagnostic information related to heart failure. For example, acoustic sensing of heart sounds using a stethoscope is a well - established technique for clinicians to detect cardiac output and diagnose heart problems. Some examples of implantable medical devices (IMDs) include implantable cardiac monitors (ICMs) that include sensors capable of sensing and recording heart sound data. An ICM is a small electronic device for monitoring a patient's heart. The ICM can be inserted under the patient's skin and can monitor and record cardiac data for several years. Other examples of IMDs include pacemakers and cardioverter - defibrillators. Summary of the Invention

[0004] An implantable medical device (IMD) that records heart sound data operates in a noisy environment. Sometimes it may be difficult to determine whether a given data set includes valid heart sound data or whether the data set includes noise. The validity of a heart sound data set is an important consideration before providing diagnostic information based on the heart sound data set. According to various aspects, this disclosure provides techniques for determining whether a heart sound signal is valid (i.e., whether the heart sound signal has meaningful physiological information). By using the techniques described herein, heart sound data can be reliably verified as valid and used for any suitable purpose, such as diagnosis and treatment. Heart sound data can be used to evaluate the systolic and diastolic functions of the heart. Diagnostic metrics for tracking the progression of heart failure can be derived from heart sounds. Additionally, the data can be used to optimize pacing therapy to resynchronize a failing heart. That is, ventricular electrical events can be synchronized based on heart sound data.

[0005] In some examples, an IMD having a heart sound sensor can be a pacemaker or other device that provides pacing therapy. A pacemaker can sense intrinsic ventricular electrical events and deliver pacing pulses when, for example, an intrinsic ventricular event does not occur. In other examples, an IMD having a heart sound sensor may not be configured to deliver pacing therapy (such as an implantable cardiac monitor (ICM)), but rather to sense ventricular electrical events. In either case, a trigger (such as an instance of a ventricular electrical event) can trigger the IMD to sense (and in some examples, store) heart sound data. Such recordings can have any suitable duration, and each recording can include data from any suitable number of cardiac beats. In one example, each recording can have a duration of about 10 seconds. The IMD can sense and record heart sound data recordings in this manner. Such recordings are referred to herein as segments of heart sound data. In the present disclosure, a heart sound segment includes a plurality of heart sound data segments. A heart sound data segment is a segment or duration of a window that begins with the occurrence of a ventricular electrical event and has any suitable duration, for example, in the range of 100 ms to 500 ms, and in one example, has a window of 200 ms. A 200 ms window should be sufficient to capture the S1 heart sound, which is typically one of the most prominent features of the cycle heart sound. Thus, the correlation between heart sound segments can largely be considered as the correlation between S1 segments across different cycles. In examples having a longer window (e.g., in the range of 500 ms), the window can include not only the S1 heart sound but also at least a portion of the S2 sound. In this example, the correlation between heart sound segments can be considered not only as the correlation between S1 segments but also as the correlation between portions of S2. In any case, when the window length is consistent across heart sound segments, each heart sound segment should be associated with the same heart sound phase across different cycles.

[0006] When a recording has been made, the processor can process the heart sound data to determine whether the recording includes valid heart sound data. While in some examples the processor can be within the IMD, in other examples the IMD can transmit the heart sound data to an external device for processing.

[0007] For each heart sound data segment in the recorded data, the processor can determine the correlation between the heart sound data segment and each other heart sound data segment in the segment. For example, if there are N heart sound data segments in the segment, the processor can compute a correlation coefficient ρ representing the correlation between each heart sound data segment and each other heart sound data segment. x,y . Here, the first subscript x represents the index of the heart sound data segment, where x ∈ {1…N}; and the second subscript y represents the other heart sound data segment for the correlation, where y ≠ x ∈ {1…N}. For example, if there are 5 heart sound segments in the segment, the processor computes 4 correlation coefficients ρ for each of the 5 heart sound segments, for a total of 20 correlation coefficients ρ:

[0008] ρ 1,2 、ρ 1,3 、ρ 1,4 、ρ 1,5

[0009] ρ 2,1 、ρ 2,3 、ρ 2,4 、ρ 2,5

[0010] ρ 3,1 、ρ 3,2 、ρ 3,4 、ρ 3,5

[0011] ρ 4,1 、ρ 4,2 、ρ 4,3 、ρ 2,5

[0012] ρ 5,1 、ρ 5,2 、ρ 5,3 、ρ 5,4

[0013] Once the relevant values are calculated, the processor can determine the average (e.g., mean, median, mode, etc.) relevant value μ for each heart sound data segment with respect to each heart sound data segment in other heart sound data segments. For example, continuing with the above example of having 5 heart sound segments in a fragment, the median relevant value μ x is as follows, where x ∈ {1…N}:

[0014] μ1 = median(ρ 1,2 , ρ 1,3 , ρ 1,4 , ρ 1,5 )

[0015] μ2 = median(ρ 2,1 , ρ 2,3 , ρ 2,4 , ρ 2,5 )

[0016] μ3 = median(ρ 3,1 , ρ 3,2 , ρ 3,4 , ρ 3,5 )

[0017] μ4 = median(ρ 4,1 , ρ 4,2 , ρ 4,3 , ρ 2,5 )

[0018] μ5 = median(ρ 5,1 , ρ 5,2 , ρ5,3 , ρ 5,4 )

[0019] When the corresponding median correlation value μ of a given heart sound data segment is greater than a suitable correlation threshold τ (where 0 ≤ τ ≤ 1), the given heart sound data segment can be considered a valid sample. Within the scope of the present disclosure, any suitable correlation threshold τ ∈ [0, 1] can be utilized. In some examples, the threshold can be any value from 0.7 to 0.9. By calculating the median, outliers (e.g., very high or very low correlation values) can be excluded.

[0020] When at least a threshold number T (where T ≤ N) of heart sound data segments are characterized as valid samples, a recording of a heart sound segment including all the heart sound data segments can be considered valid or verified, e.g., including meaningful physiological data. Thus, the processor can store or send the recording of the heart sound segment for diagnosis, treatment, or other purposes.

[0021] In some examples, a medical system is disclosed that includes a heart sound sensor, an electrical sensor / stimulation circuit, and a processor. The heart sound sensor is configured to sense heart sound data. The electrical sensor circuit is configured to sense ventricular electrical events, or the electrical stimulation circuit is configured to provide the ventricular electrical events. The processor is configured to record a segment of heart sound data including a plurality of heart sound segments, each heart sound segment being triggered by an instance of the ventricular electrical event. For each heart sound segment in the segment, the processor determines the correlation between the heart sound segment and each other heart sound segment in the segment. For each heart sound segment in the segment, the processor then determines the average (e.g., median) correlation value with each other heart sound segment in the other heart sound segments in the segment. For each heart sound segment in the segment, when the corresponding median correlation value is greater than a first threshold, the processor then characterizes the heart sound segment as a valid sample. When at least a second threshold number of the heart sound segments are characterized as valid samples, the processor then stores the segment.

[0022] The present invention content aims to provide an overview of the subject matter described in the present disclosure. It is not intended to provide an exclusive or exhaustive interpretation of the devices and methods described in the following drawings and description. Details of one or more aspects of the present disclosure are set forth in the following drawings and the specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Illustrates an example environment of an example medical system in combination with a patient in accordance with one or more examples of the present disclosure.

[0024] Figure 2 Is a diagram illustrating an implantable medical device (IMD) in accordance with one or more examples of the present disclosure.

[0025] Figure 3 An example environment of an example medical system in combination with a patient in accordance with one or more examples of the present disclosure is illustrated.

[0026] Figure 4 is a block diagram illustrating internal components of an IMD in accordance with one or more examples of the present disclosure.

[0027] Figure 5 is a flowchart illustrating an example process for generating and storing heart sound segments in accordance with one or more examples of the present disclosure.

[0028] Figure 6 is a flowchart illustrating an example process for determining whether a heart sound segment is valid (including meaningful physiological data) in accordance with one or more examples of the present disclosure. Detailed Description

[0029] Figure 1 An environment of an example medical system 2 in combination with a patient 4 in accordance with one or more techniques of the present disclosure is illustrated. Example techniques may be used with an implantable cardiac monitor (ICM) 10, which may communicate wirelessly with an external device 6 and at least one other device (not shown). In some examples, the ICM 10 is implanted outside the chest cavity of the patient 4 (e.g., subcutaneously implanted at the illustrated chest location). The ICM 10 may be positioned near or just below the level of the patient 4's heart, near the sternum, e.g., at least partially within the cardiac silhouette. The ICM 10 may be positioned at other locations, such as in the cranial region of the patient 4. The ICM 10 includes a heart sound sensor (not shown) and is configured to sense the heart sounds of the patient 4. In some examples, the ICM 10 is in the form of a Reveal LINQ Figure 1 or LINQ II TM TM Figure 1 ICM. In some examples, the ICM 10 includes additional sensors for sensing ventricular electrical activity, such as an ECG sensor (not shown). Figure 1 Figure 1

[0030] The external device 6 may be a computing device having a user-viewable display and an interface for receiving user input into the external device 6. In some examples, the external device 6 may be a laptop computer, a tablet computer, a workstation, one or more servers, a cellular phone, a personal digital assistant, or another computing device capable of running an application that enables the computing device to interact with the ICM 10. The external device 6 is configured to communicate wirelessly with the ICM 10 and optionally with another computing device ( Figure 1 ​​​​communicate (not shown). The external device 6 can communicate, for example, via near-field communication technologies (e.g., inductive coupling, NFC, or other communication technologies operable at ranges less than 10 cm to 20 cm) and far-field communication technologies (e.g., radio frequency (RF) telemetry according to 802.11 or other communication technologies operable at ranges greater than those of near-field communication technologies).

[0031] The external device 6 can be used to configure the operating parameters and / or device settings of the ICM 10. The external device 6 can be used to retrieve data from the ICM 10. The retrieved data can include values of physiological parameters measured by the ICM 10, indications of cardiac segments (e.g., arrhythmia segments) or other diseases detected by the ICM 10, and physiological signals recorded by the ICM 10. In some examples, the retrieved data can include heart sound data.

[0032] The processing circuitry of the medical system 2 (e.g., the processing circuitry of the ICM 10, the external device 6, and / or one or more other computing devices) can be configured to perform the example techniques for determining whether a heart sound segment is valid as set forth in this disclosure.

[0033] Figure 2 is a diagram illustrating an IMD, which can be an example configuration of an ICM 10 Figure 1 of the ICM. In Figure 2 the example shown, the ICM 10 can be embodied as a monitoring device having a housing 12 and a heart sound sensor 14. The housing 12 can also include a first major surface 16, a second major surface 18, a proximal end 20, and a distal end 22. The housing 12 encloses the electronic circuitry located inside the ICM 10 and protects the circuitry contained therein from body fluids. The housing 12 can be hermetically sealed and configured for subcutaneous implantation.

[0034] In Figure 2 the example shown, the ICM 10 includes a heart sound sensor 14. Although the heart sound sensor 14 is described herein as being located on the housing 12 of the ICM 10, in other examples, the heart sound sensor 14 can be located on the housing of another type of IMD within the patient 4, such as a transvenous, subcutaneous, or extravascular pacemaker or ICD, or connected to such a device via a lead. Additionally, although the heart sound sensor 14 is illustrated as being located on the first major surface 16 and the proximal end 20 of the ICM 10, the heart sound sensor 14 can be located at any suitable location such that the heart sound sensor can detect the patient's heart sounds.

[0035] In Figure 2In the example shown, the ICM 10 is defined by a length L, a width W, and a thickness or depth D, and is in the form of an elongated rectangular prism, where the length L is much greater than the width W, which in turn is greater than the depth D. In one example, the geometry of the ICM 10 (specifically, the width W greater than the depth D) is selected to allow the ICM 10 to be inserted under the patient's skin using a minimally invasive procedure and to remain in the desired orientation during insertion. For example, Figure 2 The device shown includes a radial asymmetry (specifically, a rectangular shape) along the longitudinal axis, which maintains the device in the correct orientation after insertion.

[0036] For example, the length L of the ICM 10 can range from 30 mm to about 70 mm. In other examples, the length L can range from 5 mm to 60 mm, 40 mm to 60 mm, 45 mm to 60 mm, and can be any length or range of lengths between about 30 mm and about 70 mm. Additionally, the width W of the main surface 16 can range from 3 mm to 15 mm, 3 mm to 10 mm, or 5 mm to 15 mm, and can be any single width or range of widths between 3 mm and 15 mm. The thickness or depth D of the ICM 10 can range from 2 mm to 15 mm, 2 mm to 9 mm, 2 mm to 5 mm, 5 mm to 15 mm, and can be any single depth or range of depths between 2 mm and 15 mm. Additionally, the ICM 10 according to examples of the present disclosure has a geometry and size designed for easy implantation and patient comfort. Examples of the ICM 10 described in the present disclosure can have a volume of 3 cubic centimeters (cm) or less, 1.5 cubic cm or less, or any volume between 3 cubic centimeters and 1.5 cubic centimeters.

[0037] In Figure 2 the example shown, once inserted into the patient, the first main surface 16 faces outward, toward the patient's skin, while the second main surface 18 is located in a position opposite the first main surface 16. Additionally, in Figure 2 the example shown, the proximal end 20 and the distal end 22 are rounded to reduce discomfort and irritation to the surrounding tissue once inserted under the patient's skin. The ICM 10 (including the instrument and method for inserting the ICM 10) is described, for example, in U.S. Patent Publication No. 2014 / 0276928, which is hereby incorporated by reference in its entirety.

[0038] Although described in the context of examples where an IMD that senses a patient's cardiac activity can include the ICM 10, example systems including any type of one or more implantable, wearable, or external devices configured to sense a patient's heart sounds can be configured to implement the techniques of the present disclosure.

[0039] Figure 3 Illustrates an environment of an example medical system 310 that incorporates a patient 314 in accordance with one or more techniques of the present disclosure. The example techniques may be used with a pacemaker 316 that may communicate wirelessly with an external device 324 and Figure 3 at least one other device not shown in Figure 3 In an example of, system 310 includes a pacemaker 316 that is coupled to leads 318, 320, and 322 and an external device 324. Pacemaker 316 may be, for example, an implantable pacemaker, cardioverter, and / or defibrillator that provides electrical signals to heart 312 via electrodes coupled to one or more of leads 318, 320, and 322.

[0040] In Figure 3 an example of, leads 318, 320, 322 extend into heart 312 of patient 314 to sense electrical activity of heart 312 (e.g., one or more electrocardiogram signals) and / or deliver electrical stimulation to heart 312. The illustrated number and location of leads 318, 320, and 322 are examples. In other examples, pacemaker 310 may be coupled to one, two, or more than three leads that extend to various locations. In some examples, system 310 may additionally or alternatively include one or more leads or lead segments that deploy one or more electrodes within the vena cava or other vein ( Figure 3 not shown in). Additionally, in some examples, system 310 may additionally or alternatively include an extravascular lead having electrodes implanted outside of heart 312 as an alternative or supplement to transvenous, intracardiac leads 318, 320, 322. Such leads may be used for one or more of cardiac sensing, pacing, or cardioversion / defibrillation. Additionally, in some examples, system 310 may include one or more leadless cardiac pacing devices, such as the Micra TM pacemaker commercially available from Medtronic, Inc., as an alternative or supplement to IMD 316.

[0041] Figure 4 is a block diagram that illustrates an example of an IMD 400 that may be an example configuration of an ICM 10 that is an ICM of Figure 1 and / or an example configuration of a pacemaker 316 of Figure 3 In Figure 4In the example shown, the IMD 400 includes a processor 402, a memory 404, an input / output (transceiver) 406, a heart sound sensor 408, a battery 410, and an electrical sensor / stimulation circuit 412. The processor 402 is operatively coupled to the memory 404, the transceiver 406, the heart sound sensor 408, and the electrical sensor / stimulation circuit 412. The battery 410 provides operating power for the processor 402, the memory 404, the transceiver 406, the heart sound sensor 408, and the electrical sensor / stimulation circuit 412.

[0042] The processor 402 may include fixed function circuitry and / or programmable processing circuitry. The processor 402 may include any one or more of the following: a microprocessor, a controller, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or equivalent discrete or analog logic circuitry. In some examples, the processor 402 may include multiple components (such as any combination of one or more microprocessors, one or more controllers, one or more DSPs, one or more ASICs, or one or more FPGAs) and other discrete or integrated logic circuitry. The functionality attributable to the processor 402 herein may be embodied as software, firmware, hardware, or any combination thereof. The processor 402 may include one or more processors configured to implement functional and / or process instructions for execution within the IMD 400. For example, the processor 402 may be capable of processing instructions stored in the memory 404.

[0043] The transceiver 406 may include any suitable hardware, firmware, software, or any combination thereof for communicating with another device (such as an external device 6, another networked computing device, or another IMD or sensor). Under the control of the processor 402, the transceiver 406 may receive downlink telemetry from the external device 6 or another device and transmit uplink telemetry to the external device or another device by means of an internal or external antenna. Additionally, the processor 402 may communicate with a networked computing device via an external device (e.g., external device 6) and a computer network (such as the Medtronic network). The transceiver 406 may be configured to send and / or receive signals via inductive coupling, electromagnetic coupling, near field communication (NFC), radio frequency (RF) communication, Bluetooth, WiFi, or other proprietary or non-proprietary wireless communication schemes.

[0044] In some examples, the memory 404 is a computer-readable medium that includes instructions that, when executed by the processor 402, cause the ICM 400 and the processor 402 to perform the various functions attributed to the ICM 400 and the processor 402 herein. The memory 404 can include any volatile, non-volatile, magnetic, optical, or electrical medium, such as random access memory (RAM), read-only memory (ROM), non-volatile RAM (NVRAM), electrically erasable programmable ROM (EEPROM), ferroelectric RAM (FRAM), dynamic random access memory (DRAM), flash memory, or any other digital medium.

[0045] In some examples, the electrical sensor / stimulation circuit 412 can be coupled to a set of one or more electrodes, such as electrodes 20 and 22 ( Figure 2 ) or electrodes 318, 320, and 322 ( Figure 3 ), and is configured to detect ventricular electrical activity via the electrodes. The electrical sensor / stimulation circuit 412 can include filters and amplifiers that, in some cases, can be configured to detect ventricular electrical events, such as R waves and / or P waves. The electrical sensor / stimulation circuit 412 can include analog-to-digital conversion circuitry and provide a digitized version of the cardiac electrical signal to the processor 402.

[0046] In some examples, the electrical sensor / stimulation circuit 412 can be configured to pace the patient's heart via the electrodes via active electrical pulse signaling, for example, in response to the non-detection of ventricular electrical events within a programmed interval. In such examples, the electrical sensor / stimulation circuit 412 can include pulse generation circuitry, such as a charge pump, capacitors, and switches. In some examples, the electrical sensor / stimulation circuit 412 can be configured for both electrical activity sensing and pacing.

[0047] The processor 402 may be configured to receive signals from the electrical sensor / stimulation circuit 412 and use them to interpret the received signals. For example, the processor 402 may be configured to detect P waves, R waves, or any other suitable characteristic of the sensed ventricular electrical signals (or receive signals from the sensor / stimulation circuit 412 indicating the detection of P waves, R waves, or any other suitable characteristic of the sensed ventricular electrical signals). In another example, the processor 402 may detect the delivery of pacing pulses by the electrical sensor / stimulation circuit 412. In yet another example, the processor 402 may receive from the electrical sensor / stimulation circuit 412 any suitable signal indicating an intrinsic or paced ventricular event, such as an explicit timing signal. The processor 402 may be further configured to use the signals from the electrical sensor / stimulator 412 (e.g., sensed ventricular electrical signals and / or ventricular pacing signals) as a trigger to start recording heart sound segments. That is, when the processor 402 detects a suitable signal from the electrical sensor / stimulator 412, the processor may be configured to use the heart sound sensor 408 to sense heart sound data and store the heart sound data in the memory 404.

[0048] The heart sound sensor 408 may include any suitable sensor for acoustic sensing. For example, the heart sound sensor 408 may include one or more piezoelectric probes, microphones, accelerometers, etc. capable of performing acoustic sensing.

[0049] Figure 5 and Figure 6 are flowcharts illustrating example processes for generating and validating heart sound clips that include multiple heart sound segments. In some examples, Figure 5 and Figure 6 The processes may be performed by an IMD (such as the IMD 400 described above). In some examples, Figure 5 and Figure 6 The processes may be shared between the IMD 400 and an external device 6. For example, the IMD 400 may be used to sense heart sounds, while the external device 6 may be used to determine whether the heart sound clip is valid.

[0050] A heart sound clip includes multiple heart sound segments. As Figure 5As shown, the IMD 400 can begin a process of recording heart sound segments by waiting for a trigger event (502). In some examples, the trigger event can correspond to an instance of a ventricular electrical event, such as a sensed ECG signal, a pacing signal, or other suitable signal from the electrical sensor / stimulator 412 to the processor 402. When the IMD 400 detects the trigger event, the IMD can record heart sound data. For example, the heart sound sensor 408 can be used to sense the heart sound data and the memory 404 can be used to store the heart sound data (504). In some examples, the IMD 400 can store the heart sound data and the timing of the electrical pacing / sensing events recorded by the IMD. Each recording can consist of a number of heart sound segments: the segments of interest can be identified by windowing the heart sound signal from the start of the ventricular sensing or pacing event to a fixed predetermined period (e.g., 200 ms). For example, a heart sound segment can include any suitable number of heart sound segments. Additionally, depending on the length of the window used, each heart sound segment can include any suitable heart sounds, such as the S1 sound, the S1 and S2 sounds, a portion of the S1 and S2 sounds, etc.

[0051] Figure 6 An exemplary procedure for detecting or determining whether a heart sound segment is valid (i.e., whether the heart sound segment includes meaningful physiological data) is illustrated. As indicated above, in some examples, Figure 6 the process can be performed by the IMD 400, while in other examples, Figure 6 the process can be performed by an external processor in the external device 6. For each heart sound segment stored in the memory in the heart sound segment, the processor can determine the correlation between that heart sound segment and each other heart sound segment in the segment (602). For example, the processor can calculate a correlation coefficient indicating the degree of similarity between each heart sound segment and each other heart sound segment in the segment. In some examples, the correlation coefficient can take a value between 0 (indicating no similarity) and 1 (indicating complete similarity). In some examples, the determined correlation coefficient can be stored in the memory.

[0052] For each heart sound segment, the processor can then determine the average (e.g., median) correlation value between that heart sound segment and each of the other recorded heart sound segments in the segment (604). Thus, if there are N heart sound segments in the segment, the processor can determine (N)(N - 1) median correlation values, as described above.

[0053] For each heart sound segment, in the case where the determined median correlation value is greater than a suitable threshold, the processor can characterize that heart sound segment as a valid sample (606). The threshold can be predetermined and can depend on the number of heart sound segments. In some examples, the threshold can be any value from 0.7 to 0.9.

[0054] In the case where more than a threshold number of heart sound segments in the segment are characterized as valid, the processor may characterize the heart sound segment as a valid segment (608). In the case where the heart sound segment is valid (the "yes" branch of 610), the processor may further analyze the data from the segments within the segment to determine relevant diagnostic metrics for storage for additional analysis and / or display. That is, the heart sound data of the segment can be used for diagnosis, testing, or any other suitable purpose because the heart sound data of the segment is characterized as representing meaningful physiological data. On the other hand, in the case where the heart sound segment is invalid (the "no" branch of 610: i.e., fewer than the threshold number of heart sound segments are valid), the processor may discard the data corresponding to the heart sound segment as noise.

[0055] Although example systems and techniques have been shown and described, it should be understood that all terms used herein are descriptive rather than restrictive, and many changes, modifications, and substitutions may be made by those skilled in the art without departing from the spirit and scope of the present invention. The following embodiments are embodiments of the systems, devices, and methods described herein.

[0056] Embodiment 1: In some embodiments, a medical system includes at least one of a heart sound sensor, an electrical sensor circuit, or an electrical stimulation circuit, and a processor. The heart sound sensor is configured to sense heart sound data; the electrical sensor / stimulator is configured to sense or provide ventricular electrical events, respectively. The processor is configured to record a segment of heart sound data including a plurality of heart sound segments, each heart sound segment being triggered by an instance of the ventricular electrical event. For each heart sound segment in the segment, the processor is further configured to determine the correlation between the heart sound segment and each other heart sound segment in the segment. For each heart sound segment in the segment, the processor is further configured to determine an average correlation value with each other heart sound segment in the segment. For each heart sound segment in the segment, the processor is further configured to characterize the heart sound segment as a valid sample in the case where the corresponding median correlation value is greater than a first threshold. The processor is further configured to store the segment in the case where at least a second threshold number of the heart sound segments are characterized as valid samples.

[0057] Embodiment 2: In some embodiments of the medical system according to Embodiment 1, the processor configured to determine the average correlation value is further configured to determine the median correlation value with each other heart sound segment in the segment.

[0058] Embodiment 3: In some embodiments of the medical system according to Embodiments 1 to 2, the system further includes a transmitter for sending data corresponding to the segment to an external device.

[0059] Example 4: In some embodiments of the medical system according to Embodiments 1 to 3, the system further includes a memory for storing data corresponding to the segment.

[0060] Example 5: In some embodiments of the medical system according to Embodiments 1 to 4, the first threshold is between 0.7 and 0.9.

[0061] Example 6: In some examples of the medical system according to Embodiments 1 to 5, the processor is further configured to evaluate the systolic or diastolic function of the heart based on the heart sound data.

[0062] Example 7: In some embodiments of the medical system according to Embodiments 1 to 6, the processor is further configured to generate a diagnostic metric related to heart failure based on the heart sound data.

[0063] Example 8: In some embodiments of the medical system according to Embodiments 1 to 7, the processor is further configured to synchronize the ventricular electrical events based on the heart sound data.

[0064] Example 9: In some embodiments of the medical system according to Embodiments 1 to 8, the system includes an implantable medical device (IMD), and the IMD includes at least one of the heart sound sensor and the electrical sensor circuit or the electrical stimulation circuit.

[0065] Example 10: In some embodiments of the medical system according to Embodiments 1 to 9, the IMD further includes the processor.

[0066] Example 11: In some embodiments of the medical system according to Embodiments 1 to 10, at least one of the electrical sensor circuit or the electrical stimulation circuit includes the electrical stimulation circuit, and the IMD is configured to deliver cardiac pacing via the electrical stimulation circuit.

[0067] Example 12: In some embodiments of the medical system according to Embodiments 1 to 11, the system includes an external device, and the external device includes the processor.

[0068] Example 13. A method includes: using a heart sound sensor to record a segment of heart sound data, the segment including a plurality of heart sound segments, each heart sound segment being triggered by an instance of a ventricular electrical event; recording ventricular electrical event data associated with the segment of heart sound data via at least one of a ventricular electrical sensor or a ventricular electrical stimulator; for each heart sound segment in the segment, determining a correlation between the heart sound segment and each other heart sound segment in the segment; for each heart sound segment in the segment, determining an average correlation value with each other heart sound segment in the segment; for each heart sound segment in the segment, characterizing the heart sound segment as a valid sample if a corresponding median correlation value is greater than a first threshold; and storing the segment if at least a second threshold number of the heart sound segments are characterized as valid samples.

[0069] Example 14. The method according to Example 13, wherein determining the average correlation value includes: determining the median correlation value with each other heart sound segment in the segment.

[0070] Example 15. The method according to Example 13, wherein the first threshold is between 0.7 and 0.9.

[0071] Example 16. The method according to Example 13, the method further includes evaluating a systolic or diastolic function of the heart based on the heart sound data.

[0072] Example 17. The method according to Example 13, the method further includes generating a diagnostic metric related to heart failure based on the heart sound data.

[0073] Example 18. The method according to Example 13, the method further includes synchronizing the ventricular electrical events based on the heart sound data.

[0074] Example 19. A non-transitory computer-readable medium storing computer-executable code, the computer-executable code including instructions for causing a device to perform the following operations: using a heart sound sensor to record a segment of heart sound data, the segment including a plurality of heart sound segments, each heart sound segment being triggered by an instance of a ventricular electrical event; recording ventricular electrical event data associated with the segment of heart sound data via at least one of a ventricular electrical sensor or a ventricular electrical stimulator; for each heart sound segment in the segment, determining a correlation between the heart sound segment and each other heart sound segment in the segment; for each heart sound segment in the segment, determining an average correlation value with each other heart sound segment in the segment; for each heart sound segment in the segment, characterizing the heart sound segment as a valid sample if a corresponding median correlation value is greater than a first threshold; and storing the segment if at least a second threshold number of the heart sound segments are characterized as valid samples.

[0075] The techniques described in this disclosure may be implemented, at least in part, in hardware, software, firmware, or any combination thereof. For example, aspects of the techniques may be implemented within one or more processors or processing circuits that include one or more microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or any other equivalent integrated or discrete logic circuitry, as well as any combination of such components. The term “processor” or “processing circuit” generally may refer to any of the foregoing logic circuitry or any other equivalent circuitry, either alone or in combination with other logic circuitry. A control unit including hardware may also perform one or more of the techniques of this disclosure.

[0076] Such hardware, software, and firmware may be implemented within the same device or within separate devices to support the various operations and functions described in this disclosure. Additionally, any of the described units, circuits, or components may be implemented together or separately as discrete but interoperable logic devices. Describing different features as circuits or units is intended to highlight different functional aspects and does not necessarily imply that such circuits or units must be implemented by separate hardware or software components. Rather, the functions associated with one or more circuits or units may be performed by separate hardware or software components, or integrated within common or separate hardware or software components.

[0077] The techniques described in this disclosure may also be embodied or encoded in a computer-readable medium, such as a computer-readable storage medium, that includes instructions. The computer-readable medium may be described as non-transitory. The instructions embedded or encoded in the computer-readable storage medium may cause a programmable processor or other processor to perform the method, for example, when the instructions are executed. The computer-readable storage medium may include random access memory (RAM), read only memory (ROM), programmable read only memory (PROM), erasable programmable read only memory (EPROM), electrically erasable programmable read only memory (EEPROM), flash memory, a hard disk, a CD-ROM, a floppy disk, a cassette tape, magnetic media, optical media, or other computer-readable media.

[0078] Various embodiments have been described. These and other embodiments are within the scope of the appended claims.

Claims

1. A medical system, the medical system comprising: A heart sound sensor configured to sense heart sound data; At least one of an electrical sensor circuit or an electrical stimulation circuit, the electrical sensor circuit being configured to sense ventricular electrical events and the electrical stimulation circuit being configured to provide the ventricular electrical events; A processor configured to: Record a segment of heart sound data including a plurality of heart sound segments, each heart sound segment being triggered by a corresponding instance of the ventricular electrical event; For each heart sound segment in the segment, determine the correlation between the heart sound segment and each other heart sound segment in the segment; For each heart sound segment in the segment, determine an average correlation value with each of the other heart sound segments in the segment; For each heart sound segment in the segment, characterize the heart sound segment as a valid sample if a corresponding median correlation value is greater than a first threshold; And Store the segment if at least a second threshold number of the heart sound segments are characterized as valid samples.

2. The system according to claim 1, wherein the processor configured to determine the average correlation value is further configured to determine a median correlation value with each of the other heart sound segments in the segment.

3. The system according to any one of the preceding claims, wherein the first threshold is between 0.7 and 0.

9.

4. The system according to any one of the preceding claims, wherein the processor is further configured to: Evaluate the systolic or diastolic function of the heart based on the heart sound data.

5. The system according to any one of the preceding claims, wherein the processor is further configured to: Generate a diagnostic metric related to heart failure based on the heart sound data.

6. The system according to any one of the preceding claims, wherein the processor is further configured to: Synchronize the ventricular electrical events based on the heart sound data.

7. The system according to any one of the preceding claims, wherein the system includes an implantable medical device (IMD) including the heart sound sensor and at least one of the electrical sensor circuit or the electrical stimulation circuit, wherein at least one of the electrical sensor circuit or the electrical stimulation circuit includes the electrical stimulation circuit, and wherein the IMD is configured to deliver cardiac pacing via the electrical stimulation circuit.

8. The system according to claim 7, wherein the system includes an external device including a processor, and wherein the IMD further includes a transmitter for sending data corresponding to the segment to the external device.

9. The system according to any one of the preceding claims, the system further including a memory for storing data corresponding to the segment.

10. A method, the method comprising: Recording a segment of heart sound data using a heart sound sensor, the segment including a plurality of heart sound segments, each heart sound segment being triggered by an instance of a ventricular electrical event; Recording ventricular electrical event data associated with the segment of heart sound data via at least one of a ventricular electrical sensor or a ventricular electrical stimulator; For each heart sound segment in the segment, determine the correlation between the heart sound segment and each other heart sound segment in the segment; For each heart sound segment in the segment, determine the average correlation value with each heart sound segment among the other heart sound segments in the segment; For each heart sound segment in the segment, if the corresponding median correlation value is greater than a first threshold, characterize the heart sound segment as a valid sample; And Store the segment if at least a second threshold number of the heart sound segments are characterized as valid samples.

11. The method according to claim 10, wherein determining the average correlation value comprises: Determine the median correlation value with each heart sound segment among the other heart sound segments in the segment.

12. The method according to claim 10 or 11, wherein the first threshold is between 0.7 and 0.

9.

13. The method according to any one of claims 10 to 12, the method further comprising: Evaluate the systolic or diastolic function of the heart based on the heart sound data.

14. The method according to any one of claims 10 to 13, the method further comprising: Generate a diagnostic metric related to heart failure based on the heart sound data.

15. A non-transitory computer-readable medium storing computer-executable code, the computer-executable code including instructions for causing a device to perform the following operations: Record a segment of heart sound data using a heart sound sensor, the segment including a plurality of heart sound segments, each heart sound segment being triggered by an instance of a ventricular electrical event; Record ventricular electrical event data associated with the segment of heart sound data via at least one of a ventricular electrical sensor or a ventricular electrical stimulator; For each heart sound segment in the segment, determine the correlation between the heart sound segment and each other heart sound segment in the segment; For each heart sound segment in the segment, determine the average correlation value with each heart sound segment among the other heart sound segments in the segment; For each heart sound segment in the segment, if the corresponding median correlation value is greater than a first threshold, characterize the heart sound segment as a valid sample; And Store the segment if at least a second threshold number of the heart sound segments are characterized as valid samples.

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