Method and apparatus for monitoring of diastolic hemodynamics

• US 20040127792A1
• Filed: 12/30/2002
• Published: 07/01/2004
• Est. Priority Date: 12/30/2002
• 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., Zhu, Qingsheng
• Granted Patent: US 7,972,275 B2
• Time in Patent Office: Days
• US Class Current: 600/439
• 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 7/00 Instruments for auscultation
• 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 1/36528 the parameter being measured by means of ultrasound

Abstract

A cardiac rhythm management system provides for ambulatory monitoring of hemodynamic performance based on quantitative measurements of heart sound related parameters for diagnostic and therapeutic purposes. Monitoring of such heart sound related parameters allows the cardiac rhythm management system to determine a need for delivering a therapy and/or therapy parameter adjustments based on conditions of a heart. This monitoring also allows a physician to observe or assess the hemodynamic performance for diagnosing and making therapeutic decisions. Because the conditions of the heart may fluctuate and may deteriorate significantly between physician visits, the ambulatory monitoring, performed on a continuous or periodic basis, ensures a prompt response by the cardiac rhythm management system that may save a life, prevent hospitalization, or prevent further deterioration of the heart.

Claims

1. A system, comprising:

an acoustic sensor to sense an acoustic energy and produce an acoustic sensor signal indicative of heart sounds;

a cardiac sensing circuit to sense a cardiac signal indicative of cardiac electrical events;

a heart sound detector coupled to the acoustic sensor and the cardiac sensing circuit, the heart sound detector adapted to detect selected heart sounds based on the acoustic sensor signal and the cardiac signal;

a parameter generator coupled to the heart sound detector, the parameter generator adapted to generate values of at least one predetermined parameter related to the selected heart sounds;

a processor coupled to the parameter generator, the processor including a trending analyzer adapted to produce and analyze at least one trend related to one or more types of the selected heart sounds based on the values of the at least one predetermined parameter; and

a therapy circuit communicatively coupled to the processor, the therapy circuit adapted to deliver at least one cardiac therapy with at least one therapy parameter determined based on the at least one trend.

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

3. The system of claim 1, wherein the acoustic sensor comprises a microphone.

4. The system of claim 1, further comprising a sensor interface module coupled between the acoustic sensor and the parameter generator, the sensor interface module including:

a digitizer, coupled to the acoustic sensor, to digitize the acoustic senor signal; and

a band-pass filter having at least one programmable cutoff frequency, coupled to the digitizer, to enhance indications of the selected heart sounds in the digitized acoustic sensor signal.

5. The system of claim 4, wherein the band-pass filter includes an envelope-detector type filter having a low cutoff frequency in the range of 5 to 20 Hz and a high cutoff frequency in the range of 30 to 120 Hz.

6. The system of claim 1, wherein the cardiac sensing circuit comprises:

a cardiac events detector, coupled to the sensing amplifier, to detect the cardiac electrical events; and

an event marker generator, coupled to the cardiac events detector, to generate event markers representing selected events of the detected cardiac electrical events.

7. The system of claim 1, wherein the heart sound detector comprises a gating module coupled to the acoustic sensor and the cardiac sensing circuit, the gating module adapted to generate heart sound detection windows each timed for detection of one of the selected heart sounds based on a time of occurrence of one of selected cardiac electrical events.

8. The system of claim 7, wherein the parameter generator comprises a measurement module including at least one of:

a strength detector adapted to measure amplitudes each associated with a selected type of the selected heart sounds;

a relative strength detector adapted to determine differences each between amplitudes associated with two selected types of the selected heart sounds;

a duration timer adapted to measure durations each associated with a selected type of the selected heart sounds;

an electro-mechanical interval timer adapted to measure time intervals each between a selected type of the selected heart sounds and a selected type of the selected cardiac electrical events;

a mechanical interval timer adapted to measure time intervals each between two selected types of the selected type heart sounds; and

a frequency analyzer adapted to compute a fundamental frequency associated with a selected type of the selected heart sounds.

9. The system of claim 8, wherein the parameter generator further comprises a screening module coupled to the measurement module, the screening module adapted to exclude noisy values among the raw values of the at least one predetermined parameter, the noisy values including values of the at least one predetermined parameter measured when a background noise exceeds a predetermined level.

10. The system of claim 9, further comprising an activity monitoring module coupled to the screening module, the activity monitoring module including an activity sensor to sense physical activities related to the background noise.

11. The system of claim 9, further comprising an activity monitoring module coupled to the acoustic sensor, the activity monitoring module adapted to produce an activity level signal indicative of the background noise.

12. The system of claim 9, wherein the parameter generator further comprises a memory circuit, coupled to the screening module, to store screened values of the at least one predetermined parameter.

13. The system of claim 12, further comprising a data acquisition timer coupled to the parameter generator, the data acquisition timer adapted to enable one or more of the sensor interface module, the heart sound detector, the parameter generator, and the processor for a predetermined duration on a periodic basis.

14. The system of claim 1, further comprising an alert signal generator, coupled to the trending analyzer, the alert signal generator adapted to generate an alert signal indicative of a predetermined cardiac condition based an outcome of a trending analysis.

15. The system of claims 14, wherein the trending analyzer comprises a comparator including a first input representative of the at least one trend, a second input representative of a threshold level, and an output representative of the outcome of the trending analysis.

16. The system of claim 15, wherein the trending analyzer further comprises a threshold generator adapted to generate the threshold level based on the values of the at least one predetermined parameter measured during a second predetermined period of time.

17. A method, comprising:

sensing an acoustic energy to produce an acoustic sensor signal indicative heart sounds;

sensing at least one cardiac signal indicative of cardiac electrical events;

detecting selected heart sounds;

generating values of at least one predetermined parameter related to the selected heart sounds and selected cardiac electrical events;

analyzing selected values of the at least one predetermined parameter, the selected values associated with one or more types of the selected heart sounds detected during a first predetermined period of time;

producing at least one trend based on the selected values of the at least one predetermined parameter; and

delivering at least one therapy with at least one parameter determined based on the at least one trend.

18. The method of claim 17, wherein sensing an acoustic energy comprises sensing an acceleration indicative of the acoustic energy.

19. The method of claim 17, further comprising:

Determine at least one cutoff frequency facilitating detection of third heart sounds (S3) and fourth heart sounds (S4);

programming the at least one cutoff frequency to a filter; and

filtering the acoustic sensor signal to enhance indications of S3 and S4 in the acoustic sensor signal.

20. The method of claim 17, wherein sensing at least one cardiac signal comprises:

detecting the cardiac electrical events including atrial and ventricular contractions; and

generating event markers representative of selected events of the detected cardiac electrical events.

21. The method of claim 17, wherein detecting the selected heart sounds comprises generating heart sound detection windows each timed for detecting one of the selected heart sounds based on a time of occurrence of one of the selected cardiac electrical events.

22. The method of claim 21, wherein generating values of at least one predetermined parameter comprises generating at least one of:

amplitudes each associated with a selected type of the selected heart sounds;

relative strengths being differences each between amplitudes associated with two selected types of the selected heart sounds;

durations each associated with a selected type of the selected heart sounds;

electromechanical time intervals each between a selected type of the selected heart sounds and a selected type of the selected cardiac electrical events;

mechanical time intervals each between two selected types of the selected type heart sounds; and

fundamental frequencies each associated with a selected type of the selected heart sounds.

23. The method of claim 22, wherein generating values of at least one predetermined parameter comprises generating values of at least one of:

amplitude of third heart sound (S3);

amplitude of fourth heart sound (S4);

strength of S3 relative to S4;

duration of S3;

duration of S4;

time interval between S3 and an adjacently subsequent atrial contraction;

time interval between S4 an adjacently preceding atrial contraction;

time interval between onsets of S3 and second heart sound (S2);

fundamental frequency of S3; and

fundamental frequency of S4.

24. The method of claim 22, wherein generating the values of the at least one predetermined parameter further comprises screening out noisy values including values of the at least one predetermined parameter measured when a background noise exceeds a predetermined level.

25. The method of claim 24, wherein screening out the noisy values comprises sensing a physical activity level indicative of the background noise.

26. The method of claim 25, wherein generating the values of at least one predetermined parameter including generating the values of the at least one predetermined parameter for a predetermined data acquisition duration on a predetermined periodic basis.

27. The method of claim 17, further comprising generating an alert signal indicative of a predetermined cardiac condition based on the at least one trend.

28. The method of claim 27, wherein producing the at least one trend comprises producing at least one trend related to at least one of third heart sound (S3) and fourth heart sound (S4).

29. The method of claim 27, wherein generating the alert signal comprises comparing a quantity associated with the at least one trend to a predetermined threshold level.

30. The method of claim 29, wherein generating the alert signal comprises generating the threshold based on values of the at least one predetermined parameter measured during a second predetermined period of time;

31. The method of claim 29, wherein generating the alert signal comprises generating an alert signal indicative of a change in one of diastolic filling patterns.

32. A cardiac rhythm management system, comprising:

an implantable device including;

an acoustic sensor to sense an acoustic energy to produce an acoustic sensor signal indicative heart sounds;

a cardiac sensing circuit to sense at least one cardiac signal indicative of cardiac electrical events;

a gating module coupled to the acoustic sensor and the cardiac sensing circuit, the gating module adapted to generate heart sound detection windows each timed for detection of one of selected heart sounds based on a time of occurrence of one of selected cardiac electrical events;

a heart sound detector, coupled to the gating module, to detect the selected heart sounds;

a measurement module coupled to the heart sound detector, the measurement module adapted to generate values of at least one predetermined parameter related to the selected heart sounds; and

a therapy circuit coupled to the measurement module, to deliver a therapy based on the values of the at least one predetermined parameter.

33. The cardiac rhythm management system of claim 32, wherein the implanted device is housed in a hermetically sealed metal can, and the acoustic sensor resides within the metal can.

34. The cardiac rhythm management system of claim 32, further comprising a lead having a proximal end coupled to the implantable device and distal end disposed in or about a heart, wherein the acoustic sensor is connected to the lead at or near the distal end.

35. The cardiac rhythm management system of claim 32, wherein the measurement module comprises at least one of:

a strength detector adapted to measure amplitudes each associated with a selected type of the selected heart sounds;

a relative strength detector adapted to determine differences each between amplitudes associated with two selected types of the selected heart sounds;

a duration timer adapted to measure durations each associated with a selected type of the selected heart sounds;

an electromechanical interval timer adapted to measure time intervals each between a selected type of the selected heart sounds and a selected type of the selected cardiac electrical events;

a mechanical interval time adapted to measure time intervals each between two selected types of the selected type heart sounds; and

a frequency analyzer adapted to compute a fundamental frequency associated with a selected type of the selected heart sounds.

36. The cardiac rhythm management system of claim 35, wherein the measurement module further comprises a screening module adapted to exclude noisy values including values of the at least one predetermined parameter measured when a background noise exceeds a predetermined level.

37. The cardiac rhythm management system of claim 36, wherein the screening module comprises an activity sensor adapted to sense physical activities related to the background noise.

38. The cardiac rhythm management system of claim 36, wherein the implantable device further comprises an activity monitoring module coupled to the acoustic sensor, the activity monitoring module adapted to produce an activity level signal indicative of the background noise.

39. The cardiac rhythm management system of claim 32, wherein the implantable device further comprises a processor coupled to the measurement module, the processor including a trending analyzer adapted to produce and analyze at least one trend related to one or more types of the selected heart sounds based on selected values of the at least one predetermined parameter measured during a predetermined period of time.

40. The cardiac rhythm management system of claim 39, wherein the implantable device further comprises an alert signal generator coupled to the trending analyzer, the alert signal generator adapted to generate an alert signal indicative of a predetermined cardiac condition based on an outcome of a trending analysis.

41. The cardiac rhythm management system of claim 40, wherein the therapy circuit includes a therapy controller adapted to execute a predetermined therapy control algorithm to determine therapy parameters based on the values of the at least one predetermined parameter related to the selected heart sounds.

42. The cardiac rhythm management system of claim 32, further comprising an external system communicatively coupled to the implantable device via a telemetry link, the external system including a processor coupled to the measurement module, the processor including a trending analyzer adapted to produce and analyze at least one trend related to one or more types of the selected heart sounds based on selected values of the at least one predetermined parameter measured during a predetermined period of time

43. The cardiac rhythm management system of claim 42, wherein the external system further comprises an alert signal generator coupled to the trending analyzer, the alert signal generator adapted to generate an alert signal indicative of a cardiac condition based on an outcome of a trending analysis.

44. The cardiac rhythm management system of claim 43, wherein the external system comprises a controller adapted to execute a predetermined therapy control algorithm to determine therapy parameters based on at least one of:

one or more of the values of the at least one predetermined parameter;

the at least one trend; and

the alert signal.