Method and apparatus for third heart sound detection

• US 8,827,919 B2
• Filed: 11/26/2012
• Issued: 09/09/2014
• 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: Siejko, Krzysztof Z., Carlson, Gerrard M.
• Primary Examiner(s): Schaetzle, Kennedy
• Application Number:
  US13/685,170
• Publication Number:
  US 20130085407A1
• Time in Patent Office: 652 Days
• Field of Search: None
• 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 system for detecting heart sounds from an acoustic signal indicative of heart sounds including first heart sounds (S1), second heart sounds (S2), and third heart sounds (S3), the system comprising:

an S3 detector configured to receive the acoustic signal, an S3 threshold, and S3 windows and detect S3 using the acoustic signal and the S3 threshold during the S3 windows;

a measurement module configured to receive the acoustic signal and detect an acoustic energy using the acoustic signal, the acoustic energy being a total acoustic energy of the acoustic signal over a specified time interval; and

an S3 threshold generator configured to normalize the S3 threshold using the detected acoustic energy.

2. The system of claim 1, wherein the measurement module is configured to detect a total acoustic energy during a cardiac cycle, and the S3 threshold generator is configured to dynamically normalize the S3 threshold using the total acoustic energy during the cardiac cycle.

3. The system of claim 1, wherein the measurement module is configured to detect a total acoustic energy during systole of a cardiac cycle, and the S3 threshold generator is configured to dynamically normalize the S3 threshold using the total acoustic energy during the systole of the cardiac cycle.

4. The system of claim 1, further comprising:

an S2 detector configured to detect S2 using the acoustic signal; and

an S3 window generator configured to generate the S3 windows each in response to a detection of S2.

5. The system of claim 4, further comprising an S1 detector configured to detect S1.

6. The system of claim 5, wherein the measurement module is configured to detect an amplitude of S1 and an amplitude of S2, the S2 detector is configured to detect S2 using the acoustic signal and an S2 threshold, and the S2 detector comprises an S2 threshold generator configured to determine the S2 threshold using the detected amplitude of S1 and the detected amplitude of S2.

7. The system of claim 1, comprising an implantable medical device including the S3 detector, the measurement module, and the S3 threshold generator.

8. A system for detecting heart sounds from an acoustic signal indicative of heart sounds including first heart sounds (S1), second heart sounds (S2), and third heart sounds (S3), the system comprising:

an S3 detector configured to receive the acoustic signal, an S3 threshold, and S3 windows and detect S3 using the acoustic signal and the S3 threshold during the S3 windows;

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

an S3 threshold generator configured to normalize the S3 threshold using the detected acoustic energy; and

an averaging circuit configured to improve a signal-to-noise ratio of the acoustic signal by ensemble averaging.

9. The system of claim 8, further comprising a cardiac signal input to receive a cardiac signal indicative of ventricular events, and wherein the averaging circuit is configured to align segments of the acoustic signal using the ventricular events.

10. The system of claim 8, wherein the averaging circuit is configured to align segments of the acoustic signal using the detected S2.

11. A method for detecting heart sounds from an acoustic signal indicative of heart sounds including first heart sounds (S1), second heart sounds (S2), and third heart sounds (S3), the method comprising:

receiving the acoustic signal;

detecting an acoustic energy by integrating the acoustic signal over a specified time interval;

receiving an S3 threshold;

dynamically normalizing the S3 threshold using the detected acoustic energy;

receiving S3 windows; and

detecting S3 using the acoustic signal and the S3 threshold during the S3 windows.

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

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

14. The method of claim 11, further comprising performing ensemble averaging of the acoustic signal, and detecting the S3 using the ensemble-averaged acoustic signal and the S3 threshold during the S3 windows.

15. The method of claim 11, further comprising:

detecting S2 using the acoustic signal; and

generating the S3 windows each in response to a detection of S2.

16. The method of claim 15, wherein generating the S3 windows comprises generating the S3 windows each after a predetermined delay starting with the detection of S2.

17. The method of claim 16, further comprising detecting S1 using the acoustic signal.

18. The method of claim 17, wherein detecting S2 comprises:

detecting an amplitude of S1;

detecting an amplitude of S2;

determining an S2 threshold using the detected amplitude of S1 and the detected amplitude of S2; and

detecting S2 using the acoustic signal and the S2 threshold.

19. The method of claim 18, wherein detecting S2 comprises detecting S2 using the acoustic signal and the S2 threshold during S2 windows, and further comprising:

detecting ventricular events from a cardiac signal; and

generating the S2 windows each after a predetermined delay starting with a detection of the ventricular events.

20. The method of claim 11, comprising sensing the acoustic signal using an implantable sensor.