Monitoring of heart sounds

• US 8,597,197 B2
• Filed: 06/08/2012
• Issued: 12/03/2013
• Est. Priority Date: 11/20/2006
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Patangay, Abhilash, Stahmann, Jeffrey E., Sweeney, Robert J.
• Primary Examiner(s): Layno, Carl H
• Assistant Examiner(s): Stice, Paula J
• Application Number:
  US13/491,848
• Publication Number:
  US 20120310099A1
• Time in Patent Office: 543 Days
• Field of Search: None
• US Class Current: 600/528
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/0205 Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition
• CPC Class Codes: A61B 5/025 within occluders, e.g. responsive to Korotkoff sounds electric stethoscopes A61B7/04
• CPC Class Codes: A61B 5/029 Measuring or recording blood output from the heart, e.g. minute volume A61B8/065 takes precedence
• CPC Class Codes: A61B 5/0295 using plethysmography, i.e. measuring the variations in the volume of a body part as modified by the circulation of blood therethrough, e.g. impedance plethysmography
• CPC Class Codes: A61B 5/053 Measuring electrical impedance or conductance of a portion of the body
• CPC Class Codes: A61B 5/0816 Measuring devices for examining respiratory frequency measuring frequency of electric signals G01R23/00
• CPC Class Codes: A61B 5/103 Detecting, measuring or recording devices for testing the shape, pattern, colour, size or movement of the body or parts thereof, for diagnostic purposes A61B5/08 takes precedence; measuring aids for tailors A41H1/00; measuring instruments specially adapted for dentistry A61C19/04
• CPC Class Codes: A61B 5/318 Heart-related electrical modalities, e.g. electrocardiography [ECG]
• CPC Class Codes: A61B 7/00 Instruments for auscultation
• CPC Class Codes: A61B 7/04 Electric stethoscopes microphones, acoustic transducers therefor H04R
• CPC Class Codes: A61N 1/36521 the parameter being derived from measurement of an electrical impedance
• CPC Class Codes: A61N 1/36542 controlled by body motion, e.g. acceleration
• CPC Class Codes: A61N 1/36578 controlled by mechanical motion of the heart wall, e.g. measured by an accelerometer or microphone
• CPC Class Codes: G16H 40/63 for local operation

Abstract

A system comprises an implantable medical device (IMD) including an implantable heart sound sensor circuit configured to produce an electrical heart sound signal representative of a heart sound of a subject and a processor circuit. The processor circuit is coupled to the heart sound sensor circuit and includes a detection circuit, a heart sound feature circuit and a trending circuit. The detection circuit configured to detect a physiologic perturbation and the heart sound feature circuit is configured to identify a heart sound feature in the electrical signal. The processor circuit is configured to trigger the heart sound feature circuit in relation to a detected physiologic perturbation. The trending circuit is configured to trend the heart sound feature in relation to a recurrence of the physiologic perturbation. The processor circuit is configured to declare a change in a physiologic condition of the patient according to the trending.

Claims

1. A system comprising:

an implantable heart sound sensor circuit configured to produce an electrical heart sound signal representative of a heart sound of a subject;

a second sensor circuit that includes a respiration sensor configured to produce a respiration signal representative of respiration of the subject;

a processor circuit coupled to the heart sound sensor circuit and the second sensor circuit, wherein the processor circuit includes;

a detection circuit configured to detect a phase of a respiration cycle using the respiration signal;

a heart sound feature circuit configured to identify a heart sound feature in the electrical heart sound signal according to sensitivity of the identified feature to a change in the respiratory cycle, determine a metric for the identified heart sound feature, and select the identified heart sound signal feature for trending according to the determined metric; and

a trending circuit configured to trend a difference between the identified heart sound feature during the detected phase of the respiration cycle and outside the detected phase of the respiration cycle, and

wherein the processor circuit is configured to generate an indication of a change in a physiologic condition of the patient according to the trend and provide the indication to a user or process.

2. The system of claim 1, wherein the processor circuit is configured to trigger identification of the heart sound feature upon detection of the phase of the respiration cycle.

3. The system of claim 1, wherein the heart sound feature circuit is configured to identify a heart sound feature in relation to at least one of inspiration, exhalation, end-inspiration, a transition from inspiration to expiration, and a transition from expiration to inspiration.

4. The system of claim 1, wherein the heart sound feature circuit is configured to identify a duration of a heart sound, an interval between heart sounds, an amplitude of a peak of the heart sound signal, a magnitude of a heart sound a total energy of a heart sound, and a power spectrum of a heart sound.

5. The system of claim 1, wherein the heart sound feature circuit is configured to measure a first heart sound feature normalized by a second heart feature, and wherein the trending circuit is configured to trend a change in a difference in the first normalized heart sound feature.

6. The system of claim 1, including a cardiac signal sensing circuit configured to produce an electrical cardiac signal representative of an intrinsic cardiac signal of the subject, wherein the heart sound feature circuit is configured to identify a heart sound feature that includes an interval between a cardiac signal feature and a heart sound feature.

7. The system of claim 1, wherein the processor circuit is configured to enable the heart sound sensor circuit during at least a portion of the detected phase of the respiration cycle.

8. The system of claim 1, wherein the processor circuit is configured to store the metric of the heart sound feature in association with an index to identify a phase of the respiration cycle.

9. The system of claim 1, wherein the second sensor circuit further includes a blood volume sensor configured to produce an electrical blood volume signal representative of blood volume of the subject, and wherein the processor circuit is configured to declare a change in the physiologic condition of the patient according to the trend and sensed blood volume.

10. The system of claim 9, wherein trending circuit is configured to trend an amplitude of the S1 heart sound, and wherein the processor circuit is configured to detect a change in status of heart failure of the subject according to the trend and sensed blood volume.

11. A method comprising:

sensing a respiration signal representative of respiration of a subject;

detecting a phase of a respiration cycle using the respiration signal;

sensing an electrical heart sound signal representative of a heart sound of the subject;

identifying a heart sound feature in the electrical heart sound signal according to sensitivity of the identified feature to a change in the respiratory cycle and determining a metric for the identified heart sound feature;

selecting the identified heart sound signal feature for trending according to the determined metric;

trending a difference between the identified heart sound feature during the detected phase of the respiration cycle and outside the detected phase of the respiration cycle; and

generating an indication of a change in a physiologic condition of the subject according to the trend and providing the indication to a user or process.

12. The method of claim 11, including triggering identification of the heart sound feature upon detection of the phase of the respiration cycle.

13. The method of claim 11, wherein identifying a heart sound feature includes identifying the heart sound feature in relation to at least one of inspiration, exhalation, end-inspiration, a transition from inspiration to expiration, and a transition from expiration to inspiration.

14. The method of claim 11, wherein identifying a heart sound feature includes identifying a duration of a heart sound, an interval between heart sounds, an amplitude of a peak of the heart sound signal, a magnitude of a heart sound a total energy of a heart sound, and a power spectrum of a heart sound.

15. The method of claim 11, including:

measuring a first heart sound feature normalized by a second heart feature; and

trending a change in a difference between the normalized heart sound feature during the detected phase of the respiration cycle and the normalized heart sound feature outside of the detected phase of the respiration cycle.

16. The method of claim 11, including:

sensing an electrical cardiac signal representative of an intrinsic cardiac signal of the subject; and

identifying a heart sound feature that includes an interval between a cardiac signal feature and a heart sound feature.

17. The method of claim 11, including enabling the heart sound sensor circuit during at least a portion of the detected phase of the respiration cycle.

18. The method of claim 11, storing the metric of the heart sound feature in association with an index to identify a phase of the respiration cycle.

19. The method of claim 11, including:

sensing an electrical blood volume signal representative of blood volume of the subject; and

generating the indication of a change in the physiologic condition of the patient according to the trend and sensed blood volume.

20. The method of claim 19, including:

trending an amplitude of the S1 heart sound; and

detecting a change in status of heart failure of the subject according to the trend and sensed blood volume.