Third heart sound activity index for heart failure monitoring

• US 9,668,713 B2
• Filed: 05/23/2014
• Issued: 06/06/2017
• 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: Green, Laura, Carlson, Gerrard M., Siejko, Krzysztof Z.
• Primary Examiner(s): KAHELIN, MICHAEL WILLIAM
• Application Number:
  US14/286,314
• Publication Number:
  US 20140350425A1
• Time in Patent Office: 1,110 Days
• CPC Class Codes: A61B 2562/0204 Acoustic sensors
• CPC Class Codes: A61B 2562/0219 Inertial sensors, e.g. accelerometers, gyroscopes, tilt switches
• CPC Class Codes: A61B 5/02028 Determining haemodynamic parameters not otherwise provided for, e.g. cardiac contractility or left ventricular ejection fraction
• CPC Class Codes: A61B 5/024 Detecting, measuring or recording pulse rate or heart rate A61B5/0205, A61B5/021 take precedence
• CPC Class Codes: A61B 5/02438 with portable devices, e.g. worn by the patient
• CPC Class Codes: A61B 5/4836 Diagnosis combined with treatment in closed-loop systems or methods A61B5/0036 takes precedence
• CPC Class Codes: A61B 5/6847 mounted on an invasive device
• CPC Class Codes: A61B 5/7275 Determining trends in physiological measurement data; Predicting development of a medical condition based on physiological measurements, e.g. determining a risk factor
• CPC Class Codes: A61B 7/00 Instruments for auscultation
• CPC Class Codes: A61B 7/006 Detecting skeletal, cartilage or muscle noise A61B7/003 and A61B7/008 take precedence
• CPC Class Codes: A61B 7/04 Electric stethoscopes microphones, acoustic transducers therefor H04R
• CPC Class Codes: A61N 1/36514 controlled by a physiological quantity other than heart potential, e.g. blood pressure controlled by two or more physical parameters A61N1/36585
• CPC Class Codes: A61N 1/37 Monitoring; Protecting
• CPC Class Codes: A61N 1/3987 characterised by the timing or triggering of the shock

Abstract

A cardiac rhythm management system provides for the trending of a third heart sound (S3) index. The S3 index is a ratio, or an estimate of the ratio, of the number of S3 beats to the number of all heart beats, where the S3 beats are each a heart beat during which an occurrence of S3 is detected. An implantable sensor such as an accelerometer or a microphone senses an acoustic signal indicative heart sounds including S3. An S3 detector detects occurrences of S3 from the acoustic signal. A heart sound processing system trends the S3 index on a periodic basis to allow continuous monitoring of the S3 activity level, which is indicative of conditions related to heart failure.

Claims

1. A medical system, comprising:

a heart sound sensor configured to sense a heart sound signal;

a heart sound detector configured to detect a second heart sound (S2) and a third heart sound (S3) from the heart sound signal, wherein, to detect the S3, the heart sound detector is configured to;

determine an S2 timing estimate dynamically adjusted based on a heart rate;

determine an S3 window that begins at a delay with respect to the determined S2 timing estimate; and

to detect the S3 using the sensed heart sound signal in the S3 window;

a heart sound analyzer circuit coupled to the heart sound detector, the heart sound analyzer configured to;

generate an S3 index from the heart sound signal over a specified measurement period that includes a plurality of heart beats; and

generate a trend of the S3 index over a plurality of the specified measurement periods, the trend of the S3 index indicative of a degree of change of the S3 index over time; and

a heart failure detector circuit configured to detect a condition indicative of worsening heart failure using the trend of the S3 index.

2. The system of claim 1, wherein the heart sound analyzer circuit is configured to generate the trend of the S3 index including a plurality of measurements of S3 index each generated over a respective measurement period.

3. The system of claim 2, wherein the heart sound analyzer circuit is configured to generate a moving average of the plurality of measurements of S3 index.

4. The system of claim 1, wherein the heart sound analyzer circuit is configured to generate an S3 index using a plurality of measurements of amplitude of the detected S3 heart sounds.

5. The system of claim 1, wherein the heart sound analyzer circuit is configured to generate an S3 index using a plurality of measurements of energy of the detected S3 heart sounds.

6. The system of claim 1, wherein the heart sound analyzer circuit is configured to generate an S3 index including a ratio of a number of detected S3 heart sounds counted during a predetermined time period to the number of the heart beats counted during the predetermined time period.

7. The system of claim 1, wherein the heart sound sensor comprises an accelerometer configured for sensing a cardiac mechanical vibration.

8. The system of claim 1, wherein the heart sound sensor comprises a microphone configured for sensing a cardiac audio signal.

9. The system of claim 1, wherein the heart sound detector is configured to detect the S3 heart sound in response to an amplitude or an energy of the heart sound signal during an S3 window exceeding a specified S3 threshold.

10. The system of claim 1, further comprising an activity detector configured to detect a physical activity level, wherein the heart sound analyzer circuit generates the S3 index in response to the detected physical activity level falling below a specified threshold.

11. The system of claim 1, further comprising a therapy control circuit configured to deliver a heart failure therapy based on the detected condition indicative of worsening heart failure.

12. The system of claim 1, wherein the heart sound detector is further configured to generate an S2 threshold using at least one of a first heart sound (S1) amplitude or an S2 amplitude, and to detect the S2 by comparing the sensed heart sound signal to the generated S2 threshold.

13. The system of claim 1, wherein the heart sound detector is further configured to generate an S3 threshold using at least one of a S1 amplitude, an S1 energy, an S2 amplitude, an S2 energy, an acoustic energy in at least a portion of a cardiac cycle, or an estimate of background sound level, and to detect the S3 by comparing the sensed heart sound signal to the generated S3 threshold.

14. A method for operating a medical system;

the method comprising;

sensing a heart sound signal using a heart sound sensor;

determining a second heart sound (S2) timing estimate dynamically adjusted based on a heart rate;

determining a third heart sound (S3) window that begins at a delay with respect to the determined S2 timing estimate;

detecting the S3 using the sensed heart sound signal in the S3 window;

generating an S3 index from the heart sound signal over a specified measurement period that includes a plurality of heart beats; and

generating a trend of the S3 index over a plurality of the specified measurement periods;

the trend of the S3 index indicative of a degree of change of S3 index over time; and

detecting a condition indicative of worsening heart failure using the trend of the S3 index.

15. The method of claim 14, wherein the generating an S3 index includes producing a plurality of measurements of amplitude of the detected S3 heart sounds.

16. The method of claim 14, wherein the generating an S3 index includes producing a plurality of measurements of energy of the detected S3 heart sounds.

17. The method of claim 14, wherein the generating an S3 index includes producing a ratio of a number of detected S3 heart sounds counted during a predetermined time period to the number of the heart beats counted during the predetermined time period.

18. The method of claim 14, wherein generate a trend of the S3 index includes producing a plurality of measurements of S3 index over respective measurement periods.

19. The method of claim 14, wherein detecting the S3 heart sound includes declaring an S3 detection in response to an amplitude or energy of the heart sound signal during an S3 window exceeds a specified S3 threshold.

20. The method of claim 14, wherein detecting the condition indicative of worsening heart failure includes calculating an increase in the trend of S3 index and generating an indication of a detection of a heart failure event in response to the increase in the trend of S3 index exceeding a specified threshold.