Third heart sound activity index for heart failure monitoring

• US 20050149136A1
• Filed: 12/24/2003
• Published: 07/07/2005
• 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., Green, Laura
• Granted Patent: US 7,115,096 B2
• Time in Patent Office: Days
• US Class Current: 607/17
• 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 heart sound processing system, comprising:

a cardiac signal input to receive a cardiac signal indicative of heart beats;

a beat counter, coupled to the cardiac signal input, to count the heart beats;

an acoustic signal input to receive an acoustic signal indicative of at least third heart sounds (S3);

a heart sound detector, coupled to the acoustic signal input, to detect S3;

a heart sound counter, coupled to the heart sound detector, to count S3 beats each being a heart beat during which one of S3 is detected; and

a heart sound analyzer coupled to the beat counter and the heart sound counter, the heart sound analyzer including a ratio calculator to calculate an S3 index being a ratio of a number of the S3 beats counted during a predetermined time period to the number of the heart beats counted during the predetermined time period.

2. The system of claim 1, further comprising a measurement timer to time predetermined measurement sessions and predetermined measurement periods each including a plurality of the predetermined measurement sessions.

3. The system of claim 2, wherein the measurement timer comprises a measurement session clock to time a predetermined time interval as each of the predetermined measurement sessions.

4. The system of claim 2, wherein the measurement timer comprises a measurement session counter to count a predetermined number of heart beats as each of the predetermined measurement sessions.

5. The system of claim 2, wherein the measurement timer comprises a measurement period clock to time predetermined time intervals as each of the predetermined measurement periods.

6. The system of claim 2, wherein the measurement timer comprises a measurement period counter to count a predetermined number of the predetermined measurement sessions as each of the predetermined measurement period.

7. The system of claim 2, wherein the ratio calculator calculates an S3 session ratio being a ratio of a number of the S3 beats counted during one of the predetermined measurement sessions to the number of the heart beats counted during that one of the predetermined measurement sessions, and the heart sound analyzer further comprises an averaging module calculating an average of the S3 session ratios for one of the predetermined measurement periods.

8. The system of claim 7, wherein the heart sound analyzer further comprises a trend generator to generate a trend of the S3 index as a moving average of the S3 session ratios over the predetermined measurement periods.

9. The system of claim 2, wherein the ratio calculator calculates an S3 periodic ratio being a ratio of a number of the S3 beats counted during one of the predetermined measurement period to the number of the heart beats counted during that one of the predetermined measurement period, and further comprising a trend generator to generate an trend of S3 index over the predetermined measurement periods.

10. The system of claim 2, further comprising an activity detector, coupled to the measurement timer, to detect a physical activity level and issue a permission signal allowing the measurement timer to start timing each of the predetermined measurement sessions when the physical activity level is below a predetermined activity level.

11. The system of claim 10, further comprising a measurement delay timer, coupled to the activity detector, to postpone the issuance of the permission signal if the physical activity level equals or exceeds the predetermined activity level.

12. The system of claim 1, further comprising an implantable acoustic sensor to sense the acoustic signal.

13. The system of claim 12, wherein the acoustic sensor comprises a microphone.

14. The system of claim 12, wherein the acoustic sensor comprises an accelerometer.

15. The system of claim 12, further comprising an implantable medical device, wherein the cardiac signal input, the beat counter, the acoustic signal input, the heart sound detector, the heart sound counter, and the heart sound analyzer are included in the implantable medical device.

16. The system of claim 15, wherein the implantable medical device further comprises:

a sensing circuit to sense at least one electrogram; and

an event detector, coupled to the sensing circuit, to produce the cardiac signal indicative of the cardiac events.

17. The system of claim 16, wherein the at least one electrogram comprises ventricular electrogram, and the event detector comprises a ventricular event detector.

18. A cardiac rhythm management system, comprising:

means for counting heart beats from a cardiac signal;

means for detecting third heart sounds (S3) from an acoustic signal;

means for counting S3 beats each being a heart beat during which one of the S3 is detected; and

means for calculating an S3 index being a ratio of a number of the S3 beats counted during a predetermined time period to a number of the heart sounds counted during the predetermined time period.

19. The system of claim 18, further comprising means for sensing the acoustic signal.

20. The system of claim 18, wherein means for detecting S3 comprises:

means for detecting second heart sounds (S2) from the acoustic signal;

means for generating S3 windows each temporally related to one of the detected S2;

means for comparing the acoustic signal to an S3 threshold; and

means for adjusting the S3 threshold dynamically.

21. The system of claim 18, wherein the predetermined time period comprises a predetermined measurement period including a plurality of predetermined measurement sessions, and further comprising means for timing the predetermined measurement period and means for timing the predetermined measurement sessions.

22. The system of claim 21, further comprising means for detecting a physical activity level and means for issuing a signal permitting the means for timing the predetermined measurement sessions to start timing.

23. The system of claim 21, further comprising means for producing a trend of the S3 index.

24. The system of claim 23, wherein the means for calculating the trend of the S3 index comprises means for calculating the S3 index for each of the plurality of predetermined measurement sessions.

25. The system of claim 24, wherein the means for producing the trend of the S3 index further comprises means for calculating an average of the S3 indexes calculated for the plurality of predetermined measurement sessions over the predetermined measurement period.

26. The system of claim 23, wherein the means for producing the trend of the S3 index comprises means for calculating the S3 index being a ratio of the total number of S3 beats to the total number of the heart beats for the predetermined measurement period.

27. A cardiac rhythm management system comprising:

an implantable system including;

an implantable acoustic sensor to sense an acoustic signal indicative of at least third heart sounds (S3);

an implant heart sound processor, coupled to the implantable acoustic sensor, to process the acoustic signal; and

an implant telemetry module, coupled to the implant heart sound processor, to transmit the processed acoustic signal; and

an external system communicatively coupled to the implantable medical device, the external system including;

an external telemetry module to receive the processed acoustic signal; and

an external heart sound module coupled to the external telemetry module, the external heart sound module including means for generating a trend of an S3 index, wherein the S3 index is a ratio of a number of heart beats with S3 detected during a predetermined time period to a total number of heart beats detected during the predetermine time period.

28. The system of claim 27, wherein the implantable system comprises an implantable device and at least one lead connected to the implantable device.

29. The system of claim 28, wherein the implantable acoustic sensor comprises an implantable accelerometer.

30. The system of claim 28, wherein the implantable acoustic sensor comprises an implantable microphone.

31. The system of claim 28, wherein the implantable device comprises a hermetically sealed can to house at least the implantable acoustic sensor and the implant heart sound processor.

32. The system of claim 28, wherein the implantable acoustic sensor is incorporated into the at least one lead.

33. The system of claim 28, wherein the implantable device further comprises a cardiac pacemaker.

34. The system of claim 33, wherein the implantable device further comprises a cardioverter/defibrillator.

35. The system of claim 33, wherein the implantable device further comprises a cardiac resynchronization device.

36. The system of claim 33, wherein the implantable device further comprises a cardiac remodeling control device.

37. The system of claim 28, wherein the external system comprises a medical device programmer communicatively coupled to the implantable device through a wireless telemetry link, the programmer including the external heart sound module.

38. The system of claim 28, wherein the external system comprises:

an external device communicatively coupled to the implantable device through a wireless telemetry link;

a network coupled to the external device; and

a remote device coupled to the network.

39. The system of claim 38, wherein the external device includes the external heart sound module.

40. The system of claim 38, wherein the remote device includes the external heart sound module.

41. A heart sound processing method, comprising:

receiving a cardiac signal indicative of cardiac events;

receiving an acoustic signal indicative of at least third heart sounds (S3);

detecting the cardiac events from the cardiac signal;

counting heart beats based on the cardiac events;

detecting S3 from the acoustic signal;

counting S3 beats each being a heart beat during which an occurrence of S3 is detected; and

producing a trend of an S3 index, wherein the S3 index is a ratio of a number of the S3 beats counted during a predetermined time period to a number of the heart beats counted during the predetermined time period.

42. The method of claim 41, further comprising timing predetermined measurement periods and timing predetermined measurement sessions, wherein the predetermined periods each include a plurality of the predetermined measurement sessions.

43. The method of claim 42, wherein timing the predetermined measurement sessions comprises timing a predetermined time interval.

44. The method of claim 42, wherein timing the predetermined measurement sessions comprising counting a predetermined number of heart beats.

45. The method of claim 42, wherein timing the predetermined measurement period comprises timing a predetermined time interval.

46. The method of claim 42, wherein timing the predetermined measurement period comprising counting a predetermined number of the predetermined measurement sessions.

47. The method of claim 42, wherein producing the trend of S3 index comprises calculating the S3 index for each of the predetermined measurement sessions.

48. The method of claim 47, wherein producing the trend of S3 index further comprises:

calculating an average of the S3 index calculated for each of the predetermined measurement sessions over each of the predetermined measurement periods; and

producing the trend of the S3 index as a moving average being the averages over a plurality of the predetermined measurement periods.

49. The method of claim 42, wherein producing the trend of S3 index comprises:

calculating an overall ratio of a total number of S3 beats to the total number of the heart beats, both counted during one of the predetermined measurement periods; and

producing the trend of the S3 index as a moving ratio being the overall ratios over a plurality of the predetermined measurement periods.

50. The method of claim 42, further comprising:

detecting a physical activity level; and

issuing a permission signal to allowing to start timing each of the predetermined measurement sessions if the physical activity level is below a predetermined threshold activity level.

51. The method of claim 50, further comprising postponing the issuance of the permission signal if the physical activity level equals or exceeds the predetermined activity level.

52. The method of claim 51, further comprising:

postponing the issuance of the permission signal for a predetermined delay period if the physical activity level equals or exceeds the predetermined threshold activity level;

issuing the permission signal if the physical activity level is below the predetermined threshold activity level when the predetermined delay expires; and

repeating the postponing the issuance of the permission signal for the predetermined delay period if the physical activity level equals or exceeds the predetermined threshold activity level when the predetermined delay expires.

53. The method of claim 41, further comprising sensing the acoustic signal.

54. The method of claim 53, wherein sensing the acoustic signal comprises sensing an audio signal using a microphone.

55. The method of claim 53, wherein sensing the acoustic signal comprises sensing an acceleration.

56. The method of claim 41, further including:

sensing at least one electrogram; and

producing the cardiac signal indicative of the cardiac events.

57. The method of claim 56, wherein sensing the at least one electrogram comprises sensing a ventricular electrogram, and producing the cardiac signal comprises detecting ventricular events and producing ventricular event markers.