Method and apparatus for third heart sound detection

• US 20090018461A1
• Filed: 09/16/2008
• Published: 01/15/2009
• Est. Priority Date: 12/24/2003
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Carlson, Gerrard M., Siejko, Krzysztof Z.
• Granted Patent: US 8,317,717 B2
• Time in Patent Office: Days
• US Class Current: 600/528
• CPC Class Codes: A61B 7/04 Electric stethoscopes microphones, acoustic transducers therefor H04R

Abstract

A cardiac rhythm management system includes a heart sound detector providing for detection of the third heart sounds (S3). An implantable sensor such as an accelerometer or a microphone senses an acoustic signal indicative heart sounds including the second heart sounds (S2) and S3. The heart sound detector detects occurrences of S2 and starts S3 detection windows each after a predetermined delay after a detected occurrence of S2. The occurrences of S3 are then detected from the acoustic signal within the S3 detection windows.

Claims

1. A heart sound detection system, comprising:

an acoustic signal input adapted to receive an acoustic signal indicative of heart sounds; and

a heart sound detector coupled to the acoustic signal input, the heart sound detector including;

an S2 detector adapted to detect second heart sounds (S2) using the acoustic signal;

an S3 window generator adapted to generate an S3 window in response to each detection of S2;

an S3 detector adapted to detect third heart sounds (S3) using the acoustic signal and an S3 threshold during the S3 windows;

a measurement module adapted to detect an acoustic energy using the acoustic signal; and

an S3 threshold generator adapted to determine the S3 threshold using the acoustic energy.

2. The system of claim 1, wherein the S3 window generator is adapted to generate the S3 window after a programmed delay starting with each of the detected S2.

3. The system of claim 2, wherein the measurement module is adapted to detect a total acoustic energy during a cardiac cycle, and the S3 threshold generator is adapted to dynamically adjust the S3 threshold using the total acoustic energy detected during the cardiac cycle.

4. The system of claim 3, wherein the S3 threshold generator is adapted to dynamically adjust the S3 threshold using a mean and a standard deviation of the total acoustic energy during the cardiac cycle.

5. The system of claim 2, wherein the measurement module is adapted to detect a total acoustic energy during systole of a cardiac cycle, and the S3 threshold generator is adapted to dynamically adjust the S3 threshold using the total acoustic energy during systole of the cardiac cycle.

6. The system of claim 5, wherein the S3 threshold generator is adapted to dynamically adjust the S3 threshold using a mean and a standard deviation of the total acoustic energy during the systole of the cardiac cycle.

7. A heart sound detection method, comprising:

receiving an acoustic signal indicative of heart sounds;

detecting second heart sounds (S2) using the acoustic signal;

generating an S3 window following each of the detected S2;

detecting third heart sounds (S3) during the S3 windows by comparing the acoustic signal to an S3 threshold;

detecting an acoustic energy using the acoustic signal; and

dynamically adjusting the S3 threshold using the acoustic energy.

8. The method of claim 7, wherein generating the S3 window comprises generating the S3 window after a programmed delay starting with each of the detected S2.

9. The method of claim 8, comprising:

receiving a cardiac signal indicative of ventricular events;

detecting ventricular events from the cardiac signal; and

terminating the S3 window if one of the ventricular events occurs during the S3 window.

10. The method of claim 8, comprising determining the S3 threshold using at least a mean and a standard deviation of the acoustic energy.

11. The method of claim 8, wherein detecting the acoustic energy comprises detecting a total acoustic energy during a cardiac cycle as the acoustic energy.

12. The method of claim 8, wherein detecting the acoustic energy comprises detecting a total acoustic energy during systole of a cardiac cycle as the acoustic energy.

13. A heart sound detection system, comprising:

an acoustic signal input to receive an acoustic signal indicative of heart sounds; and

a heart sound detector coupled to the acoustic signal input, the heart sound detector including;

an S2 detector adapted to detect second heart sounds (S2) using the acoustic signal;

an S3 window generator adapted to generate an S3 window in response to each detection of S2;

an S3 detector adapted to detect third heart sounds (S3) during the S3 windows using the acoustic signal and an S3 threshold; and

an S3 threshold generator adapted to determine the S3 threshold using an estimated background sound level (μ

_B) measured during a period between an occurrence of first heart sounds (S1) and an adjacent occurrence of S2.

14. The system of claim 13, wherein the S3 threshold generator is adapted to dynamically adjust the S3 threshold using μ

_B.

15. The system of claim 14, wherein the S3 threshold generator is adapted to calculate the S3 threshold as μ

_B*K, where K is an adjustable multiplier.

16. The system of claim 15, wherein the S3 threshold generator is adapted to scale the period between the occurrence of S1 and the adjacent occurrence of S2 for a heart rate.

17. The system of claim 16, comprising:

a cardiac signal input adapted to receive a cardiac signal indicative of ventricular events; and

an S2 window generator adapted to generate an S2 window in response to the detection of each of the ventricular events, and wherein the S2 detector is adapted to detect S2 during the S2 windows.

18. The system of claim 17, wherein the S3 window generator is adapted to generate the S3 window after a second programmed delay starting with each of the detected S2.

19. A heart sound detection method, comprising:

receiving an acoustic signal indicative of heart sounds;

detecting second heart sounds (S2) using the acoustic signal;

generating an S3 window following each of the detected S2;

detecting third heart sounds (S3) during the S3 windows by comparing the acoustic signal to a dynamically adjustable S3 threshold; and

dynamically adjusting the S3 threshold using an estimated background sound level (μ

_B) measured during a period between an occurrence of first heart sounds (S1) and an adjacent occurrence of S2.

20. The method of claim 19, wherein dynamically adjusting the S3 threshold comprises calculating the S3 threshold as μ

_B*K, where K is an adjustable multiplier.

21. The method of claim 20, comprising:

receiving a cardiac signal indicative of ventricular events;

detecting a heart rate using the cardiac signal; and

scaling the period between the occurrence of S1 and the adjacent occurrence of S2 for the heart rate.

22. The method of claim 21, comprising:

detecting ventricular events from the cardiac signal; and

terminating the S3 window if one of the ventricular event occurs during the S3 window.

23. The method of claim 19, comprising:

receiving a cardiac signal indicative of ventricular events; and

generating an S2 window in response to the detection of each of the ventricular events,

and wherein detecting S2 comprises detecting S2 during the S2 windows.

24. The method of claim 23, wherein generating the S3 window comprises generating the S3 window after a programmed delay starting with each of the detected S2.