Method for correction of posture dependence on heart sounds

• US 20060161070A1
• Filed: 01/18/2005
• Published: 07/20/2006
• Est. Priority Date: 01/18/2005
• 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 7,662,104 B2
• Time in Patent Office: Days
• US Class Current: 600/528
• CPC Class Codes: A61B 5/1107 Measuring contraction of parts of the body, e.g. organ, muscle apparatus for measuring work or force in general G01L
• CPC Class Codes: A61B 5/1116 Determining posture transitions
• 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: A61B 8/0883 for diagnosis of the heart
• CPC Class Codes: A61N 1/3627 for treating a mechanical deficiency of the heart, e.g. congestive heart failure or cardiomyopathy
• CPC Class Codes: A61N 1/36535 controlled by body position or posture
• CPC Class Codes: A61N 1/36578 controlled by mechanical motion of the heart wall, e.g. measured by an accelerometer or microphone
• CPC Class Codes: A61N 1/36585 controlled by two or more physical parameters

Abstract

A system to monitor heart sounds. The system comprises an implantable heart sound sensor operable to produce an electrical signal representative of at least one heart sound, a heart sound sensor interface circuit coupled to the heart sound sensor to produce a heart sound signal, an implantable posture sensor operable to produce an electrical signal representative of a patient'"'"'s posture, and a controller circuit, coupled to the heart sound sensor interface circuit and the posture circuit. The controller circuit is operable to measure at least one heart sound in correspondence with at least one sensed patient posture.

Claims

1. A system comprising:

a device comprising;

an implantable heart sound sensor operable to produce an electrical signal representative of at least one heart sound, the heart sound associated with mechanical activity of a patient'"'"'s heart;

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

an implantable posture sensor operable to produce an electrical signal representative of a patient'"'"'s posture; and

a controller circuit, coupled to the heart sound sensor interface circuit and the posture circuit, wherein the controller circuit is operable to measure the at least one heart sound in correspondence with at least one sensed patient posture.

2. The system of claim 1, wherein the controller is operable to measure the heart sound in an upright posture.

3. The system of claim 1, wherein the controller is operable to measure the heart sound in a plurality of postures.

4. The system of claim 3, wherein the device further includes a storage circuit coupled to the controller, and wherein the controller is operable to store at least one heart sound measurement in correspondence with patient posture.

5. The system of claim 3, wherein the controller is operable to apply a scaling factor to at least one heart sound measurement, wherein the scaling factor is a function of a patient posture.

6. The system of claim 1, wherein the device further includes a clock circuit and the controller circuit is operable to measure heart sounds at a time of day when a patient is in a recumbent posture.

7. The system of claim 1, wherein the controller circuit is operable to use the electrical signal provided by the implantable heart sound sensor to determine that the interference is below a threshold level before a heart sound measurement is executed.

8. The system of claim 1, wherein the device further includes at least one implantable cardiac signal sensing circuit operable to detect at least one intrinsic cardiac signal, and wherein the controller is operable to measure the at least one heart sound in correspondence with at least one sensed patient posture when a patient heart rate is below a specified heart rate threshold value.

9. The system of claim 1, wherein the device further includes an implantable activity sensor and the controller is operable to measure the at least one heart sound in correspondence with at least one sensed patient posture when a patient activity level is below a specified activity threshold value.

10. The system of claim 1, wherein the device further includes an implantable trans-thoracic impedance measurement circuit to provide a trans-thoracic impedance signal of a subject, wherein the controller is operable to provide the trans-thoracic impedance measurement in correspondence with at least one sensed patient posture and the measured heart sound.

11. The system of claim 10, wherein the trans-thoracic impedance measurement circuit provides a measurement of near-DC trans-thoracic impedance and the controller is operable to provide the near-DC trans-thoracic impedance measurement in correspondence with at least one sensed patient posture and the measured heart sound.

12. The system of claim 1, wherein the device is an implantable device and 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 heart sound information in relation to sensed patient posture.

13. The system of claim 12, wherein the heart sound information includes at least one trend of heart sound information in relation to patient posture.

14. The system of claim 1, wherein the device is an implantable device and the system further includes an external device operable to communicate with the implantable device, and wherein the external device is in communication with a computer network.

15. The system of claim 14, wherein the external device is operable to communicate an alarm based on trends of information that include the heart sound signal and the patient posture.

16. A method comprising:

sensing at least one heart sound using an implantable medical device;

determining posture information of a patient using the implantable medical device; and

measuring the heart sound in correspondence with the posture information.

17. The method of claim 16, wherein measuring the at least one heart sound in correspondence with the posture information includes measuring heart sounds in correspondence with respective postures and relating a heart sound measurement to a posture.

18. The method of claim 17, wherein measuring the at least one heart sound in correspondence with respective postures includes applying at least one scaling factor to at least one heart sound measurement, wherein the scaling factor is a function of posture.

19. The method of claim 16, wherein measuring at least one heart sound is performed when a heart rate is below a specified heart rate threshold value.

20. The method of claim 16, wherein measuring at least one heart sound in correspondence with the patient'"'"'s posture includes measuring the heart sound contingent on the patient being in a specified posture.

21. The method of claim 20, wherein the specified posture is an upright posture.

22. The method of claim 16, wherein the measuring at least one heart sound in correspondence with the patient'"'"'s posture includes measuring the at least one heart sound when a patient activity level is below a specified activity threshold value.

23. The method of claim 16, wherein the measuring at least one heart sound in correspondence with the patient'"'"'s posture includes measuring the at least one heart sound when a mechanical interference level is below a threshold value.

24. The method of claim 16, wherein the measuring at least one heart sound in correspondence with the patient'"'"'s posture includes measuring a trend of heart sounds in relation to posture.

25. The method of claim 16, further including storing trending information of measurements of the at least one heart sound in correspondence with the patient'"'"'s posture.

26. The method of claim 25, further including communicating the trending information to an external device for display.

27. A system comprising:

an implantable medical device, the implantable medical device comprising;

a communication circuit;

a heart sound sensor operable to produce an electrical signal representative of a heart sound;

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

a posture sensor operable to produce an electrical signal representative of a patient'"'"'s posture; and

a controller circuit, coupled to the heart sound sensor interface circuit and the posture circuit, wherein the controller circuit is operable to measure heart sounds in correspondence with patient posture and to categorize the heart sound according to posture.

28. The system of claim 27, wherein the controller circuit is operable to apply a scaling factor to the heart sound measurement, wherein the scaling factor is a function of patient posture.

29. The system of claim 28, 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 heart sound information provided by the implantable medical device.

30. The system of claim 27, wherein the controller circuit is operable to initiate a heart sound measurement contingent on a specified patient posture.

31. The system of claim 30, wherein the specified patient posture includes an upright patient posture.

32. The system of claim 31, wherein the implantable medical device further includes an activity sensor, wherein the controller circuit is operable to initiate a heart sound measurement contingent on an upright patient posture and a patient activity being less than a specified activity threshold value.