Cardiac rhythm management system with time-dependent frequency response

• US 7,983,749 B2
• Filed: 07/10/2003
• Issued: 07/19/2011
• Est. Priority Date: 03/12/1999
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Warren, Jay A.
• Primary Examiner(s): Patel; Niketa I
• Assistant Examiner(s): ALTER, ALYSSA MARGO
• Application Number:
  US10/615,636
• Publication Number:
  US 20040167578A1
• Time in Patent Office: 2,931 Days
• Field of Search: 607/9
• US Class Current: 607/9
• CPC Class Codes: A61N 1/362 Heart stimulators heart defibrillators A61N1/39
• CPC Class Codes: A61N 1/365 controlled by a physiological parameter, e.g. heart potential evoked response A61N1/371
• CPC Class Codes: A61N 1/3702 Physiological parameters A61N1/365 takes precedence; evoked response A61N1/371
• CPC Class Codes: A61N 1/3704 Circuits specially adapted therefor, e.g. for sensitivity control

Abstract

A cardiac rhythm management system includes a time-dependent frequency response for sensed heart signals. A change in the frequency response of a sensing circuit is triggered by a sensed or evoked event to make it less sensitive to the detection of a subsequent event for a period of time. For example, a passband bandwidth is reduced, then increased during the time period triggered by the event. For even more event-triggered selectivity, a gain is reduced, then increased during the time period triggered by the event. This provides better discrimination between particular events included in a heart signal so that appropriate therapy can be delivered to the patient based such events.

Claims

1. A cardiac rhythm monitoring or management system, including:

a sensing circuit configured for sensing an intrinsic electrical heart signal, the sensing circuit having a frequency response that is time-dependent during a first time period initiated by at least one of a detected pacing therapy event or a detected evoked or detected intrinsic heart chamber contraction event of the heart signal, the sensing circuit configured to trigger a frequency response that is temporarily less sensitive to detecting evoked and intrinsic events of the heart signal followed by gradual adjustment of a frequency bandwidth of the frequency response as a function of an elapsed time relative to the event such that the frequency response gradually becomes more sensitive to detecting evoked and intrinsic heart chamber contraction events of the heart signal, the elapsed time measured or received by the sensing circuit during the same cardiac cycle as the event, to restore the frequency response within a time period of less than or equal to 500 milliseconds such that the frequency response is restored during the same cardiac cycle as the event.

2. The system of claim 1, in which the sensing circuit is configured to trigger the adjustment in response to the detected evoked heart chamber contraction event and also in response to the detected intrinsic heart chamber contraction event.

3. The system of claim 1, in which the sensing circuit is configured such that the frequency response includes a bandwidth that is time-dependent for the first time period, and the first time period is initiated by at least one of the detected pacing therapy event, a detected evoked QRS complex of the heart chamber contraction of the heart signal, or a detected intrinsic QRS complex of the heart chamber contraction of the heart signal.

4. The system of claim 3, in which the sensing circuit is configured such that the bandwidth decreases to a second bandwidth value, from a first bandwidth value, upon occurrence of the event.

5. The system of claim 4, in which the sensing circuit is configured such that the bandwidth increases from the second bandwidth value toward the first bandwidth value during the first time period.

6. The system of claim 5, in which the sensing circuit is configured such that the bandwidth includes a passband.

7. The system of claim 6, in which the sensing circuit is configured such that an attenuation of a T-wave of the heart signal by the frequency response of the first sensing circuit during the first time period is greater than or equal to the attenuation of the T-wave immediately after expiration of the first time period.

8. The system of claim 7, in which the sensing circuit is configured such that the first time period is greater than or equal to 250 milliseconds.

9. The system of claim 8, in which the sensing circuit is configured such that the first time period is approximately between 250 milliseconds and 500 milliseconds.

10. The system of claim 8, in which the sensing circuit is configured such that the first time period is approximately 500 milliseconds.

11. The system of claim 10, in which the sensing circuit includes an automatic gain control (AGC) circuit.

12. The system of claim 1, in which the sensing circuit is configured such that a highpass pole frequency of the frequency response is time-dependent for the first time period, and the first time period is initiated by at least one of the detected pacing therapy event and detected evoked and detected intrinsic heart chamber contraction events of the heart signal.

13. The system of claim 12, in which the sensing circuit is configured such that the first time period is initiated by at least one of the detected pacing therapy event and detected evoked and detected intrinsic QRS complexes of the heart chamber contraction, and the highpass pole frequency increases to a second frequency value, from a steady-state first frequency value, in response to detection of the detected pacing therapy event or a QRS complex of the heart chamber contraction.

14. The system of claim 13, in which the sensing circuit is configured such that the highpass pole frequency gradually decreases from the second frequency value toward the first frequency value during the first time period.

15. The system of claim 1, in which the sensing circuit is configured such that a lowpass pole frequency is time-dependent for the first time period, and the first time period is initiated by at least one of the detected pacing therapy event and detected evoked and detected intrinsic heart chamber contraction events of the heart signal.

16. The system of claim 15, in which the sensing circuit is configured such that the first time period is initiated by at least one of the detected pacing therapy event and detected evoked and detected intrinsic QRS complexes of the heart chamber contraction, and the lowpass pole frequency decreases to a second frequency value, from a first frequency value during the first time period.

17. The system of claim 16, in which the sensing circuit is configured such that the first time period is initiated by at least one of the detected pacing therapy event and detected evoked and detected intrinsic QRS complexes of the heart chamber contraction, and the lowpass pole frequency gradually increases from the second frequency value toward the first frequency value during the first time period.

18. The system of claim 1, in which the sensing circuit includes a gain that is time-dependent during a second time period initiated by at least one of the pacing therapy event or the evoked or intrinsic event of the heart signal.

19. The system of claim 18, in which the sensing circuit is configured such that the second time period is initiated by at least one of the detected pacing therapy event and the detected evoked and detected intrinsic heart chamber contraction event of the heart signal.

20. The system of claim 19, in which the sensing circuit is configured such that the gain decreases to a second gain value, from a first gain value, during the second time period.

21. The system of claim 20, in which the sensing circuit is configured such that the gain gradually increases, from the second gain value toward the first gain value during the second time period.

22. The system of claim 1, wherein the gradual adjustment of the frequency bandwidth comprises a substantially continuous function of the elapsed time.

23. The system of claim 1, wherein the first time period is initiated by the detected pacing therapy event.

24. The system of claim 1, wherein the first time period is initiated by the detected evoked heart chamber contraction event of the heart signal.

25. The system of claim 1, wherein the first time period is initiated by the detected intrinsic heart chamber contraction event of the heart signal.

26. A cardiac rhythm management system, including:

an electronics unit including;

a therapy circuit;

a sensing circuit configured for sensing an intrinsic heart signal of a heart; and

a bandpass filter, included in the sensing circuit, the filter having a frequency response that is time-dependent during a first time period initiated by one of a detected pacing therapy event or a detected evoked or detected intrinsic heart chamber contraction event of the heart signal and the sensing circuit configured to trigger a frequency response that is temporarily less sensitive to detecting evoked and intrinsic events of the heart signal followed by gradual adjustment of a frequency bandwidth of the frequency response as a function of an elapsed time relative to the event such that the frequency response gradually becomes more sensitive to detecting evoked and intrinsic heart chamber contraction events of the heart signal, the elapsed time measured or received by the sensing circuit during the same cardiac cycle as the event, to restore the frequency response within a time period of less than or equal to 500 milliseconds such that the frequency response is restored during the same cardiac cycle as the event; and

a leadwire, coupled to the electronics unit and configured to be coupled to a portion of the heart; and

a programmer, remote from and communicatively coupled to the electronics unit, the programmer including a parameter controlling one of;

(a) the frequency response of the bandpass filter, and (b) the duration of the first time period.

27. The system of claim 26, in which the sensing circuit further includes a gain that decreases from a first gain value to a second gain value during a second time period initiated by one of the detected pacing therapy event or the detected evoked or detected intrinsic event of the heart signal.

28. The system of claim 26, wherein the gradual adjustment of a frequency bandwidth comprises a substantially continuous function of the elapsed time.

29. The system of claim 26, wherein the first time period is initiated by the pacing therapy event.

30. The system of claim 26, wherein the first time period is initiated by the detected evoked heart chamber contraction event of the heart signal.

31. The system of claim 26, wherein the first time period is initiated by the detected intrinsic heart chamber contraction event of the heart signal.