Adaptive sensing threshold for cross-chamber refractory period

• US 6,928,323 B2
• Filed: 12/30/2002
• Issued: 08/09/2005
• 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: Kim, Jaeho, Bocek, Joseph M., White, Harley, Harrington, Anthony
• Primary Examiner(s): Getzow, Scott M.
• Application Number:
  US10/334,217
• Publication Number:
  US 20040127947A1
• Time in Patent Office: 953 Days
• Field of Search: 607 9- 31
• US Class Current: 607/9
• CPC Class Codes: A61N 1/3704 Circuits specially adapted therefor, e.g. for sensitivity control

Abstract

A cross-chamber refractory period with an adaptively adjusted sensing threshold for use by a cardiac pacemaker is disclosed. In response to a cross-chamber event, the sensing threshold of a sensing channel is raised to an adaptively adjusted cross-chamber maximum refractory value. The cross-chamber maximum refractory value is derived from a peak amplitude measurement of the far-field signal resulting from the cross-chamber event.

Claims

1. A cardiac rhythm management device, comprising:

first and second sensing channels for sensing electrical activity in a first heart chamber and a second heart chamber, respectively;

circuitry for detecting a first chamber sense when the sensed electrical activity in the first sensing channel exceeds a first channel sensing threshold which has a minimum level equal to a specified first channel steady-state value;

circuitry for detecting a second chamber sense when the sensed electrical activity in the second sensing channel exceeds a second channel sensing threshold which has a minimum level equal to a specified second channel steady-state value;

circuitry for measuring a peak amplitude of a post-sense far-field signal generated in the first sensing channel after a second chamber sense is detected; and

,

circuitry for rendering the first sensing channel refractory for a post-sense cross-chamber refractory period after detection of a second chamber sense by raising the first channel sensing threshold above the first channel steady-state value, wherein the first channel sensing threshold is raised during the post-sense cross-chamber refractory period to a post-sense cross-chamber maximum refractory value derived from the measured peak amplitude of the post-sense far-field signal.

2. The device of claim 1 wherein the circuitry for rendering the first sensing channel refractory for a post-sense cross-chamber refractory period raises the first channel sensing threshold abruptly to the post-sense cross-chamber maximum refractory value after detection of a second chamber sense and subsequently decreases the first channel sensing threshold from the post-sense cross-chamber maximum refractory value toward the first steady-state value during the post-sense cross-chamber refractory period.

3. The device of claim 1 wherein the circuitry for rendering the first sensing channel refractory for a post-sense cross-chamber refractory period sets the first channel sensing threshold equal to a time-varying function after detection of a second chamber sense which rises to the post-sense cross-chamber maximum refractory value and subsequently decreases toward the first steady-state value during the post-sense cross-chamber refractory period.

4. The device of claim 3 wherein the time-varying function first rises to an initial post-sense cross-chamber refractory value derived from the measured peak amplitude of the post-sense far-field signal and subsequently increases to the post-sense cross-chamber maximum refractory value.

5. The device of claim 3 wherein the circuitry for rendering the first sensing channel refractory for a post-sense cross-chamber refractory period sets the first channel sensing threshold equal to first time-varying function after detection of a second chamber sense during a first cardiac cycle and sets the first channel sensing threshold equal to second time-varying function after detection of a second chamber sense during a subsequent cardiac cycle.

6. The device of claim 1 wherein the circuitry for rendering the first sensing channel refractory for a post-sense cross-chamber refractory period decreases the first channel sensing threshold from the post-sense cross-chamber maximum refractory value to the first channel steady-state value at the end of the post-sense cross-chamber refractory period.

7. The device of claim 1 wherein the circuitry for rendering the first sensing channel refractory for a post-sense cross-chamber refractory period decreases the first channel sensing threshold from the post-sense cross-chamber maximum refractory value to the first channel steady-state value at a decay rate derived from the measured peak amplitude of the post-sense far-field signal.

8. The device of claim 1 wherein the circuitry for rendering the first sensing channel refractory for a post-sense cross-chamber refractory period starts to decrease the first channel sensing threshold from the post-sense cross-chamber maximum refractory value toward the first channel steady-state value after a delay interval derived from the measured peak amplitude of the post-sense far-field signal.

9. The device of claim 1 wherein the circuitry for measuring the peak amplitude of the post-sense far-field signal measures the peak amplitude by computing a statistical function of the measured peak amplitudes of the post-sense far-field signal generated in the first sensing channel after a second chamber sense during a specified number of cardiac cycles.

10. The device of claim 1 wherein the post-sense cross-chamber maximum refractory value is approximately 125% of the measured peak amplitude of the post-sense far-field signal.

11. The device of claim 1 further comprising:

circuitry for rendering the first sensing channel refractory for a same-chamber refractory period upon detection of a first chamber sense or delivery of a first chamber pace by raising the first channel sensing threshold above the first channel steady-state value during the same-chamber refractory period; and

,

wherein the circuitry for rendering the first sensing channel refractory for a post-sense cross-chamber refractory period raises the first channel sensing threshold to a value dictated by either the post-sense cross-chamber refractory period or the same-chamber refractory period, whichever is greater, when the post-sense cross-chamber refractory period and the same-chamber refractory period overlap.

12. The device of claim 1 further comprising:

circuitry for delivering paces to the second chamber;

circuitry for measuring a peak amplitude of a post-pace far-field signal generated in the first sensing channel when a second chamber pace is delivered; and

circuitry for rendering the first sensing channel refractory for a post-pace cross-chamber refractory period upon delivery of a second chamber pace by raising the first channel sensing threshold to a post-pace cross-chamber refractory value which is proportional to the measured post-pace far-field signal peak amplitude; and

,

circuitry for rendering the first sensing channel refractory for a post-pace cross-chamber refractory period after delivery of a second chamber pace by raising the first channel sensing threshold above the first channel steady-state value, wherein the first channel sensing threshold is raised during the post-pace cross-chamber refractory period to a post-pace cross-chamber maximum refractory value derived from the measured peak amplitude of the post-pace far-field signal.

13. The device of claim 12 wherein the circuitry for rendering the first sensing channel refractory for post-sense cross-chamber and post-pace refractory periods raises the first sensing channel sensing threshold to an alternative maximum value during those periods if peak amplitudes of post-sense and post-pace far-field signals have not yet been measured.

14. The device of claim 1 wherein the circuitry for measuring a peak amplitude of a post-sense far-field signal generated in the first sensing channel after a second chamber sense is detected is configured to measure the peak amplitude only when a normal sinus rhythm is detected.

15. The device of claim 1 wherein the circuitry for measuring a peak amplitude of a post-sense far-field signal generated in the first sensing channel after a second chamber sense is detected is configured to measure the peak amplitude by computing a statistical function of the measured peak amplitudes of the post-sense far-field signal during a training period consisting of a specified number of cardiac cycles, and further wherein the circuitry for rendering the first sensing channel refractory does not derive the post-sense cross-chamber maximum refractory value from the measured peak amplitude until after completion of the training period.

16. A cardiac rhythm management device, comprising:

first and second sensing channels for sensing electrical activity in a first heart chamber and a second heart chamber, respectively;

circuitry for detecting a first chamber sense when the sensed electrical activity in the first sensing channel exceeds a -first channel sensing threshold which has a minimum level equal to a specified first channel steady-state value;

circuitry for detecting a second chamber sense when the sensed electrical activity in the second sensing channel exceeds a second channel sensing threshold which has a minimum level equal to a specified second channel steady-state value;

circuitry for delivering paces to the second chamber;

circuitry for measuring the peak amplitude of a post-pace far-field signal generated in the first sensing channel upon delivery of a second chamber pace; and

circuitry for rendering the first sensing channel refractory for a post-pace cross-chamber refractory period after delivery of a second chamber pace by raising the first channel sensing threshold above the first channel steady-state value, wherein the first channel sensing threshold is raised during the post-pace cross-chamber refractory period to a post-pace cross-chamber maximum refractory value derived from the measured peak amplitude of the post-pace far-field signal.

17. The device of claim 16 wherein the circuitry for rendering the first sensing channel refractory for a post-pace cross-chamber refractory period raises the first channel sensing threshold abruptly to the post-pace cross-chamber maximum refractory value after delivery of a second chamber pace and subsequently decreases the first channel sensing threshold from the post-pace cross-chamber maximum refractory value toward the first steady-state value during the post-pace cross-chamber refractory period.

18. The device of claim 16 wherein the circuitry for rendering the first sensing channel refractory for a post-pace cross-chamber refractory period sets the first channel sensing threshold equal to a time-varying function after delivery of a second chamber pace which rises to the post-pace cross-chamber maximum refractory value and subsequently decreases toward the first steady-state value during the post-pace cross-chamber refractory period.

19. The device of claim 18 wherein the time-varying function first rises to an initial post-pace cross-chamber refractory value derived from the measured peak amplitude of the post-pace far-field signal and subsequently increases to the post-pace cross-chamber maximum refractory value.

20. The device of claim 18 wherein the circuitry for rendering the first sensing channel refractory for a post-pace cross-chamber refractory period sets the first channel sensing threshold equal to first time-varying function after delivery of a second chamber pace during a first cardiac cycle and sets the first channel sensing threshold equal to second time-varying function after delivery of a second chamber pace during a subsequent cardiac cycle.

21. The device of claim 16 wherein the circuitry for rendering the first sensing channel refractory for a post-pace cross-chamber refractory period decreases the first channel sensing threshold from the post-pace cross-chamber maximum refractory value to the first steady-state value at the end of the post-pace cross-chamber refractory period.

22. The device of claim 16 wherein the circuitry for rendering the first sensing channel refractory for a post-pace cross-chamber refractory period decreases the first channel sensing threshold from the post-pace cross-chamber maximum refractory value to the first steady-state value at a decay rate derived from the measured peak amplitude of the post-pace far-field signal.

23. The device of claim 16 wherein the circuitry for rendering the first sensing channel refractory for a post-pace cross-chamber refractory period starts to decrease the first channel sensing threshold from the post-pace cross-chamber maximum refractory value to the first steady-state value after a delay interval derived from the measured peak amplitude of the post-pace far-field signal.

24. The device of claim 16 wherein the circuitry for measuring the peak amplitude of the post-pace far-field signal measures the peak amplitude by computing a statistical function of the measured peak amplitudes of the post-pace far-field signal generated in the first sensing channel after a second chamber pace during a specified number of cardiac cycles.

25. The device of claim 16 wherein the post-pace cross-chamber maximum refractory value is approximately 125% of the measured peak amplitude of the post-pace far-field signal.

26. The device of claim 16 further comprising:

circuitry for rendering the first sensing channel refractory for a same-chamber refractory period upon detection of a first chamber sense or delivery of a first chamber pace by raising the first channel sensing threshold above the first channel steady-state value during the same-chamber refractory period; and

,

wherein the circuitry for rendering the first sensing channel refractory for a post-pace cross-chamber refractory period raises the first channel sensing threshold to a value dictated by either the post-pace cross-chamber refractory period or the same-chamber refractory period, whichever is greater, when the post-pace cross-chamber refractory period and the same-chamber refractory period overlap.

27. The device of claim 16 wherein the circuitry for rendering the first sensing channel refractory for post-pace cross-chamber refractory period raises the first sensing channel sensing threshold to an alternative maximum value during that period if the peak amplitude of the post-pace far-field signal has not yet been measured.

28. The device of claim 16 wherein the circuitry for measuring a peak amplitude of a post-pace far-field signal generated in the first sensing channel after a second chamber pace is delivered is configured to measure the peak amplitude only when a normal sinus rhythm is detected.

29. The device of claim 16 wherein the circuitry for measuring a peak amplitude of a post-pace far-field signal generated in the first sensing channel after a second chamber pace is delivered is configured to measure the peak amplitude by computing a statistical function of the measured peak amplitudes of the post-pace far-field signal during a training period consisting of a specified number of cardiac cycles, and further wherein the circuitry for rendering the first sensing channel refractory does not derive the post-pace cross-chamber maximum refractory value from the measured peak amplitude until after completion of the training period.

30. A method for operating a cardiac rhythm management device, comprising:

sensing electrical activity in a first heart chamber through a first sensing channel and generating a first chamber sense when the sensed electrical activity exceeds a first channel sensing threshold which has a minimum level equal to a specified first channel steady-state value;

sensing electrical activity in a second heart chamber through a second sensing channel and generating a second chamber sense when the sensed electrical activity exceeds a second channel sensing threshold which has a minimum level equal to a specified second channel steady-state value;

measuring a peak amplitude of a post-event far-field signal generated in the first sensing channel after a specified second chamber event occurs; and

,

rendering the first sensing channel refractory for a cross-chamber post-event refractory period after occurrence of the second chamber event by raising the first channel sensing threshold above the first channel steady-state value, wherein the first channel sensing threshold is raised during the cross-chamber post-event refractory period to a maximum cross-chamber post-event refractory value derived from the measured peak amplitude of the post-event far-field signal.

31. The method of claim 30 wherein the specified second chamber event is a second chamber sense.

32. The method of claim 31 wherein the specified second chamber event is a second chamber pace.

33. The method of claim 30 wherein either of the first and second heart chambers may be a ventricle or an atrium.

34. The method of claim 30 wherein the first and second heart chambers are a ventricle and the contralateral ventricle.

35. The method of claim 30 wherein the peak amplitude of a post-event far-field signal generated in the first sensing channel after occurrence of a second chamber event is measured only when a normal sinus rhythm is detected.

36. The method of claim 30 wherein the peak amplitude of a post-event far-field signal generated in the first sensing channel after occurrence of a second chamber event is measured by computing a statistical function of the measured peak amplitudes of the post-event far-field signal during a training period consisting of a specified number of cardiac cycles, and further wherein the post-event cross-chamber maximum refractory value is not derived from the measured peak amplitude until after completion of the training period.