Determining a patient's posture from mechanical vibrations of the heart

• US 20060025699A1
• Filed: 07/28/2004
• Published: 02/02/2006
• Est. Priority Date: 07/28/2004
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Siejko, Krzysztof Z., Maile, Keith R.
• Granted Patent: US 7,559,901 B2
• Time in Patent Office: Days
• US Class Current: 600/528
• CPC Class Codes: A61B 7/00 Instruments for auscultation
• CPC Class Codes: A61B 7/04 Electric stethoscopes microphones, acoustic transducers therefor H04R
• CPC Class Codes: A61N 1/36535 controlled by body position or posture
• CPC Class Codes: A61N 1/36542 controlled by body motion, e.g. acceleration
• CPC Class Codes: A61N 1/36578 controlled by mechanical motion of the heart wall, e.g. measured by an accelerometer or microphone

Abstract

A system for determining a patient'"'"'s posture by monitoring heart sounds. The system comprises an implantable medical device that includes a sensor operable to produce an electrical signal representative of heart sounds, a sensor interface circuit coupled to the sensor to produce a heart sound signal, and a controller circuit coupled to the sensor interface circuit. The heart sounds are associated with mechanical activity of a patient'"'"'s heart and the controller circuit is operable to detect a posture of the patient from a heart sound signal.

Claims

1. A system comprising:

an implantable medical device comprising;

a sensor operable to produce an electrical signal representative of heart sounds, the heart sounds associated with mechanical activity of a patient'"'"'s heart;

a sensor interface circuit coupled to the sensor to produce a heart sound signal; and

a controller circuit, coupled to the sensor interface circuit, wherein the controller circuit is operable to detect a posture of the patient from the heart sound signal.

2. The system of claim 1, wherein the controller circuit is operable to detect a posture of the patient from change in a frequency spectrum of the heart sound signal.

3. The system of claim 2, wherein the controller circuit is operable to perform a spectral analysis of energy of the heart sound signals to detect the change in the frequency spectrum.

4. The system of claim 3, wherein the spectral analysis includes a fast Fourier transform.

5. The system of claim 1, wherein the controller circuit is operable to detect a posture of the patient from an amplitude of the heart sound signal.

6. The system of claim 5, wherein the sensor interface circuit includes a peak detector circuit, and wherein the controller circuit detects a posture of the patient by detecting a change in amplitude of the heart sound signals using an output of the peak detector circuit.

7. The system of claim 5, wherein the sensor interface circuit includes an analog-to-digital converter to convert the heart sound signal into digital values, and wherein the controller detects a posture of the patient from a change in amplitude of the heart sound signal, and wherein the change in amplitude is determined using the digital values.

8. The system of claim 7, wherein the implantable medical device further includes a memory and the digital values are stored in the memory.

9. The system of claim 1, wherein the implantable medical device further includes a tilt sensor coupled to the controller, the tilt sensor operable to produce an electrical signal related to a patient posture, and wherein the controller circuit is operable to detect the posture of the patient from both the heart sound signal and the tilt sensor signal.

10. The system of claim 1, wherein the sensor is operable to produce electrical signals representative of both heart sounds and patient activity.

11. The system of claim 1, wherein the system further includes a pressure sensor coupled to the implantable medical device, wherein the pressure sensor is operable to produce electrical signals related to thoracic pressure of a patient, and wherein the controller circuit is operable to use both posture information and pressure information to provide a congestive heart failure status indicator.

12. The system of claim 1, wherein the system further includes a transthoracic impedance measurement circuit coupled to the implantable medical device, wherein the transthoracic impedance measurement circuit is operable to measure impedance across a thorax of the patient, and wherein the controller circuit uses posture information and transthoracic impedance information to provide a congestive heart failure status indicator.

13. The system of claim 1, wherein the implantable medical device includes a cardiac rhythm management device.

14. The system of claim 1, wherein the system further includes an external device operable to communicate with the implantable device, wherein the external device includes a display, and wherein the external device is further operable to display patient posture information obtained from the heart sound signal.

15. The system of claim 14, wherein the patient posture information includes a histogram of patient posture.

16. The system of claim 14, wherein the patient posture information includes trending information of patient posture.

17. The system of claim 14, wherein the external device is operable to communicate with a computer network.

18. A method comprising:

sensing heart sounds associated with activity of a patient'"'"'s heart using an implantable medical device; and

determining posture information of the patient from the heart sounds.

19. The method of claim 18, wherein determining posture information of the patient from the heart sounds includes determining posture information from a frequency spectrum of the heart sounds.

20. The method of claim 18, wherein determining posture information of the patient from the heart sounds includes determining posture information from a magnitude of the heart sounds.

21. The method of claim 18, wherein determining posture information of the patient from the heart sounds includes:

determining a baseline for the heart sounds; and

detecting a change from the baseline.

22. The method of claim 18, wherein the method further includes detecting a change in posture.

23. The method of claim 18, wherein sensing heart sounds includes sensing one or a combination of S1 and S2 heart sounds.

24. The method of claim 23, wherein sensing heart sounds includes sensing heart sounds during a timing window, wherein a beginning of the timing window is determined in relation to a sensed cardiac event.

25. The method of claim 24, wherein sensing heart sounds during a timing window includes determining a patient specific timing window.

26. The method of claim 24, wherein sensing heart sounds during a timing window includes determining a timing window from data taken from a patient population.

27. The method of claim 18, wherein the method further includes:

determining patient physical activity information; and

determining a patient rest posture from the posture information and the activity information.

28. The method of claim 27, wherein determining patient physical activity information includes determining activity information using a heart rate of the patient.

29. The method of claim 27, wherein determining patient physical activity information includes sensing patient physical activity using an accelerometer.

30. The method of claim 27, determining patient physical activity information includes determining patient physical activity information from a same sensor used to sense heart sounds.

31. The method of claim 18, wherein the method further includes:

determining patient thoracic pressure information using the implantable medical device; and

using both the posture information and the thoracic pressure information to provide a congestive heart failure status indicator.

32. The method of claim 18, wherein the method further includes:

determining transthoracic impedance information using the implantable medical device; and

using both the posture information and the transthoracic impedance information to provide a congestive heart failure status indicator.

33. The method of claim 18, wherein sensing heart sounds includes sampling an electrical signal representative of the heart sounds and storing samples of the signal as heart sound data, and wherein determining posture information of the patient from the heart sounds includes transmitting the heart sound data from the implantable medical device to an external device and deriving posture information using the external device.

34. The method of claim 18, wherein sensing heart sounds includes sampling electrical signal representative of the heart sounds and storing samples of the signal as heart sound data, and wherein determining posture information of the patient from the heart sounds includes creating a histogram from the heart sound data.

35. The method of claim 18, wherein sensing heart sounds includes sampling an electrical signal representative of the heart sounds and storing samples of the signal as heart sound data, and wherein determining posture information of the patient from the heart sounds includes trending the heart sound data.

36. A system comprising:

a sensor operable to produce an electrical heart sound signal representative of heart sounds associated with mechanical activity of a patient'"'"'s heart;

means for determining a change from a baseline for the heart sound signal; and

a controller circuit operable to determine a posture of the patient from the change from the baseline of the heart sound signal.

37. The system of claim 36, wherein the change from the baseline is a change in amplitude of the heart sound signal.

38. The system of claim 36, wherein the change from the baseline is a change in a frequency spectrum of the heart sound signal.