Third heart sound activity index for heart failure monitoring

• US 8,840,563 B2
• Filed: 07/02/2013
• Issued: 09/23/2014
• 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., Green, Laura, Carlson, Gerrard M.
• Primary Examiner(s): Layno, Carl H
• Assistant Examiner(s): ANTHONY, JESSICA LYNN
• Application Number:
  US13/933,937
• Publication Number:
  US 20130296728A1
• Time in Patent Office: 448 Days
• Field of Search: 600508-509, 600513-514, 600/528
• US Class Current: 600/528
• 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. An implantable medical system, comprising:

a sensing circuit configured to sense at least one electrogram;

a cardiac event detector coupled to the sensing circuit and configured to produce a cardiac signal using the at least one electrogram, the cardiac signal indicative of heart beats;

an acoustic sensor configured to sense an acoustic signal indicative of third heart sounds (S3); and

a heart sound analyzer circuit coupled to the acoustic sensor and the cardiac event detector, the heart sound analyzer including;

an S3 index calculator configured to calculate an S3 index including a ratio of a number of S3 beats detected during a predetermined time period to a number of the heart beats detected during the predetermined time period; and

an S3 trend generator configured to generate a trend of S3 index using a plurality of S3 indices calculated over a plurality of measurement periods; and

a heart failure event detector configured to detect heart failure using the trend of S3 index.

2. The system of claim 1, comprising a hermetically sealed can housing one or more of the sensing circuit, the cardiac event detector, the heart sound analyzer, or the heart failure event detector.

3. The system of claim 2, wherein the acoustic sensor is external to the hermetically sealed can.

4. The system of claim 2, wherein the acoustic sensor is incorporated into at least one lead configured to be coupled to the hermetically sealed can.

5. The system of claim 1, wherein the acoustic sensor comprises an implantable accelerometer.

6. The system of claim 1, wherein the acoustic sensor comprises an implantable microphone.

7. The system of claim 1, wherein the S3 trend generator is configured to generate a moving average of the plurality of S3 indices over the plurality of measurement periods.

8. The system of claim 7, wherein the S3 trend generator is configured to generate a plot of daily S3 indices over a specified number of days.

9. The system of claim 1, further comprising an activity detector configured to detect a physical activity level, wherein the measurement periods each includes a plurality of prescheduled measurement sessions each starting in response to the detected physical activity level falling below a specified threshold.

10. The system of claim 1, wherein the heart failure event detector is configured to detect an event indicative of worsening of heart failure in response to an increase in the trend of S3 index over a specified time period.

11. A method for operating an implantable medical system to detect a heart failure event, the method comprising, by the implantable medical system:

sensing at least one electrogram;

producing a cardiac signal indicative of heart beats using the at least one electrogram;

sensing an acoustic signal indicative of third heart sounds (S3) using an implantable acoustic sensor;

calculating an S3 index being a ratio of a number of S3 beats detected during a predetermined time period to a number of heart beats detected during the predetermined time period;

generating a trend of S3 index using a plurality of S3 indices calculated over a plurality of measurement periods; and

detecting heart failure using the trend of S3 index.

12. The method of claim 11, wherein sensing the acoustic signal includes sensing an audio signal using a microphone sensor.

13. The method of claim 11, wherein sensing the acoustic signal includes sensing a cardiac mechanical vibration using an accelerometer sensor.

14. The method of claim 11, wherein calculating the S3 index comprises detecting S3 in response to an amplitude of the acoustic signal exceeding an S3 threshold.

15. The method of claim 14, wherein detecting S3 comprises dynamically adjusting the S3 threshold based on at least a mean and a standard deviation of total acoustic energy during systole of a plurality of cardiac cycles.

16. The method of claim 11, wherein generating the trend of S3 index includes generating a moving average of the plurality of S3 indices over the plurality of measurement periods.

17. The method of claim 11, wherein generating the trend of S3 index includes generating a plot of daily S3 indices over a specified number of days.

18. The method of claim 11, further comprising detecting a physical activity level, wherein generating the trend of S3 index includes calculating the plurality of S3 indices over the plurality of measurement periods each including a plurality of prescheduled measurement sessions each starting in response to the detected physical activity level falling below a specified threshold.

19. The method of claim 11, wherein detecting the heart failure includes detecting the hemodynamic performance using the trend of S3 index.

20. The method of claim 11, wherein detecting the heart failure includes calculating an increase in the trend of S3 index over a specified time period.