Method and apparatus for inducing defibrillation in a patient using a T-shock waveform

• US 20030088286A1
• Filed: 11/05/2001
• Published: 05/08/2003
• Est. Priority Date: 11/05/2001
• Status: Active Grant

• Current Assignee: Cameron Incorporated (Schlumberger NV)
• Original Assignee: Cameron Incorporated (Schlumberger NV)
• Inventors: Ostroff, Alan H., Rissmann, William J., Bardy, Gust H.
• Granted Patent: US 6,834,204 B2
• Time in Patent Office: Days
• US Class Current: 607/9
• CPC Class Codes: A61N 1/385 Devices for inducing an abnormal cardiac function, e.g. fibrillation
• CPC Class Codes: Y10S 977/932 for electronic or optoelectronic application

Abstract

A shock is delivered on the T-wave of a patient'"'"'s cardiac waveform by first detecting the occurrence of a QRS complex in the waveform and using that detection to set up for detection of the following T-wave. Narrowband filtering is used to first select the QRS complex and thereafter the T-wave, while peak detection is employed to define the actual occurrence of the respective waveforms. The capability is also provided to deliver the shock at a manually selected interval after QRS detection or after a coupling interval in a pacing application.

Claims

1. A method of delivering a T-shock comprising the steps of:

automatically detecting the occurrence of a QRS complex;

automatically detecting the occurrence of a T-wave following said QRS complex; and

responding to the automatic detection of said T-wave to deliver a shock.

2. The method of claim 1 wherein said step of automatically detecting the occurrence of the QRS complex employs a peak detection technique.

3. The method of claim 2 wherein said peak detection technique employs a manually set threshold.

4. The method of claim 3 wherein said peak detection technique employs a threshold set by an automatic gain control technique.

5. The method of claim 1 further including the step of employing a training algorithm to set expected parameters for the QRS complex and T-wave.

6. The method of claim 1 wherein the step of automatically detecting the occurrence of the T-wave employs narrow band filtering to select the T-wave component.

7. The method of claim 1 wherein the step of automatically detecting the QRS complex employs narrow band filtering to select the QRS component.

8. The method of claim 7 wherein the step of automatically detecting the occurrence of the T-wave employs a peak detection technique.

9. The method of claim 8 wherein said peak detection technique employs a manually set threshold.

10. The method of claim 8 wherein said peak detection technique employs a threshold set by an automatic gain control technique.

11. The method of claim 1 wherein said shock is delivered automatically in response to detection of said T-wave.

12. The method of claim 1 wherein said shock is delivered manually in response to detection of said T-wave.

13. An apparatus comprising:

a programmed digital processor; and

programmed process steps executable by said digital processor to detect occurrence of a QRS complex and to detect occurrence of a T-wave following said QRS complex.

14. The apparatus of claim 13 wherein said programmed process steps are further executable to implement narrowband filtering to select the QRS complex.

15. The apparatus of claim 14 wherein said programmed process steps are further executable to implement narrowband filtering to select the T-wave.

16. The apparatus of claim 15 wherein said programmed process steps are further executable to control delivery of a shock in response to detection of said T-wave.

17. The apparatus of claim 16 wherein said programmed process steps are further executable to detect a peak in said QRS complex.

18. The apparatus of claim 17 wherein programmed process steps are further executable to detect a peak in said T-wave.

19. The apparatus of claim 17 wherein said programmed process steps are further executable to implement automatic gain control in connection with detecting a peak in said QRS complex.

20. The apparatus of claim 17 wherein said programmed process steps are further executable to implement automatic gain control in connection with detecting a peak in said QRS complex in said T-wave.

21. The apparatus of claim 13 wherein said programmed process steps are further operable to implement an algorithm for determining an expected parameter of said QRS complex.

22. The apparatus of claim 13 wherein said programmed process steps are further operable to implement an algorithm for determining an expected parameter of said QRS complex in said T-wave.

23. An apparatus comprising:

means for detecting a QRS complex in a cardiac waveform; and

means responsive to detection of the QRS complex for detecting a T-wave following said QRS complex.

24. The apparatus of claim 23 further including means responsive to detection of the T-wave form to deliver a shock.

25. The apparatus of claim 23 wherein said means for detecting a QRS complex employs a peak detection technique.

26. The apparatus of claim 25 wherein said peak detection technique employs a manually set threshold.

27. The apparatus of claim 26 wherein said peak detection technique employs a threshold set by an automatic gain control technique.

28. The apparatus of claim 23 further including means for employing a training interval for deriving expected parameters for the QRS complex and T-wave.

29. The apparatus of claim 23 wherein said means for detecting the T-wave employs narrow band filtering to select a T-wave component.

30. The apparatus of claim 23 wherein said means for detecting the QRS complex employs narrow band filtering to select a QRS component.

31. The apparatus of claim 30 wherein said means for detecting the occurrence of the T-wave employs a peak detection technique.

32. The apparatus of claim 31 wherein said peak detection technique employs a manually set threshold.

33. The apparatus of claim 31 wherein said peak detection technique employs a threshold set by an automatic gain control technique.

34. The apparatus of claim 24 wherein said shock is delivered automatically in response to detection of said T-wave.

35. The apparatus of claim 24 wherein said shock is delivered manually in response to detection of said T-wave.

40. The apparatus of claim 23 wherein said means for detecting and said means responsive for detecting are implemented as either (1) entirely analog circuitry or (2) a combination of digital and analog circuitry without a programmed processor or (3) a combination of digital and analog circuitry including a programmed processor.

36. Apparatus comprising:

a filter for selecting a QRS complex from a cardiac waveform;

a first detector for detecting the occurrence of said QRS complex;

a filter for selecting a T-wave following said QRS complex; and

a second detector for detecting a T-wave following said QRS complex.

37. The apparatus of claim 36 wherein said detector is gated to be operable in response to detection of said QRS complex.

38. The apparatus of claim 36 wherein said first detector comprises a peak detector.

39. The apparatus of claim 38 wherein said second detector comprises a peak detector.

41. In a subcutaneous implantable cardioverter-defibrillator, the method comprising the steps of:

automatically detecting the occurrence of a QRS complex; and

responding to detection of the QRS complex by delivering a fibrillating shock to a patient.

42. The method of claim 41 wherein said defibrillator applies a pacing waveform to a patient and wherein said step of responding comprises delivering said shock at a selected point in time on or after expiration of the coupling interval.

43. The method of claim 41 wherein said step of responding comprises automatically delivering said shock at a point in time separated from the point of automatic detection by a manually selected time interval.

44. The method of claim 41 wherein said step of responding comprises the steps of:

automatically detecting the occurrence of a T-wave following the QRS complex; and

automatically delivering said shock in response to the automatic detection of the T-wave.