Subcutaneous defibrillation timing correlated with induced skeletal muscle contraction

• US 20040220628A1
• Filed: 04/05/2004
• Published: 11/04/2004
• Est. Priority Date: 04/11/2003
• Status: Abandoned Application

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Wagner, Darrell Orvin
• Application Number:
  US10/818,188
• Publication Number:
  US 20040220628A1
• Time in Patent Office: Days
• US Class Current: 607/5
• CPC Class Codes: A61N 1/05 for implantation or insertion into the body, e.g. heart electrode A61N1/06 takes precedence
• CPC Class Codes: A61N 1/36542 controlled by body motion, e.g. acceleration
• CPC Class Codes: A61N 1/36585 controlled by two or more physical parameters
• CPC Class Codes: A61N 1/3956 Implantable devices for applying electric shocks to the heart, e.g. for cardioversion
• CPC Class Codes: A61N 1/39622 Pacing therapy

Abstract

Methods and systems for defibrillation therapy involve delivering a pre-shock waveform to cause contraction of skeletal musculature in the patient'"'"'s thorax before delivering a defibrillation waveform. A shock is delivered to the patient'"'"'s heart during contraction of the skeletal musculature for a reduction in defibrillation threshold. The pre-shock waveform is sufficient in energy to cause one or both of deflation of the patient'"'"'s lungs and muscle fiber shortening of the skeletal musculature. A delay interval may be initiated relative to delivery of the pre-shock waveform, wherein the defibrillation waveform is delivered following expiration of the delay interval. Motion of the patient'"'"'s thorax and/or expiration of the patient'"'"'s lungs may be detected, responsive to the pre-shock waveform. The defibrillation waveform may be delivered in coordination with the detected parameter, such as in relation to detection of a peak in the thoracic motion or minimum in transthoracic impedance.

Claims

1. A method of delivering a subcutaneous defibrillation therapy, comprising:

delivering, from a subcutaneous non-intrathoracic location relative to a patient'"'"'s heart, a pre-shock waveform sufficient in energy such that contraction of skeletal musculature occurs in the patient'"'"'s thorax, but insufficient in energy for defibrillating the patient'"'"'s heart; and

delivering, from the subcutaneous non-intrathoracic location or other subcutaneous non-intrathoracic location, a defibrillation waveform to the patient'"'"'s heart during contraction of the skeletal musculature.

2. The method of claim 1, wherein the pre-shock waveform is sufficient in energy such that deflation of the patient'"'"'s lungs occurs.

3. The method of claim 1, wherein the pre-shock waveform is sufficient in energy such that muscle fiber shortening of the skeletal musculature occurs.

4. The method of claim 1, further comprising providing electrodes configured for subcutaneous non-intrathoracic placement in the patient, wherein the pre-shock waveform is sufficient in energy such that displacement of the patient'"'"'s heart relative to the electrodes occurs.

5. The method of claim 4, wherein displacement of the patient'"'"'s heart relative to the electrodes achieves an increased defibrillation current density in the patient'"'"'s heart relative to a defibrillation current density in the patient'"'"'s heart achievable in the absence of displacement of the patient'"'"'s heart.

6. The method of claim 1, wherein the pre-shock waveform is sufficient in energy such that contraction of the skeletal musculature occurs, and reduces a defibrillation threshold relative to a defibrillation threshold associated with delivery of the defibrillation waveform in the absence of the skeletal musculature contraction.

7. The method of claim 1, further comprising initiating a delay interval relative to delivery of the pre-shock waveform, wherein the defibrillation waveform is delivered following expiration of the delay interval.

8. The method of claim 7, wherein the delay interval has a pre-established duration.

9. The method of claim 7, wherein the delay interval has a duration equal to or less than about 2 seconds.

10. The method of claim 7, wherein the delay interval has a duration equal to or less than about 200 milliseconds.

11. The method of claim 7, wherein the delay interval has a duration equal to or less than about 100 milliseconds.

12. The method of claim 1, wherein the pre-shock waveform has a pulse width equal to or less than about 2 milliseconds.

13. The method of claim 1, wherein the pre-shock waveform has a pulse width equal to or less than about 20% of that of the defibrillation waveform.

14. The method of claim 1, wherein the pre-shock waveform has an initial amplitude greater than that of the defibrillation waveform.

15. The method of claim 1, wherein the pre-shock waveform has an initial amplitude less than that of the defibrillation waveform.

16. The method of claim 1, wherein the defibrillation waveform comprises a multiphasic defibrillation waveform.

17. The method of claim 1, wherein the defibrillation waveform comprises a biphasic, truncated exponential defibrillation waveform.

18. The method of claim 1, wherein the pre-shock waveform has an energy level, and the defibrillation waveform has a first phase and a second phase, an energy level of one or both of the first phase and the second phase of the defibrillation waveform reduced by an amount of energy corresponding to the energy level of the pre-shock waveform.

19. The method of claim 1, wherein the pre-shock waveform is delivered using a first vector, and the defibrillation waveform is delivered using the first vector.

20. The method of claim 1, wherein the pre-shock waveform is delivered using a first vector, and the defibrillation waveform is delivered using a second vector differing from the first vector.

21. The method of claim 1, further comprising detecting motion of the patient'"'"'s thorax responsive to the pre-shock waveform, wherein delivering the defibrillation waveform is coordinated in relation to the detected motion.

22. The method of claim 21, further comprising coordinating delivery of the defibrillation waveform in relation to detection of a peak in the thoracic motion.

23. The method of claim 22, wherein coordinating delivery of the defibrillation waveform in relation to detection of the peak in the thoracic motion comprises using a pre-determined delay interval between delivery of the defibrillation and pre-shock waveforms.

24. The method of claim 1, further comprising:

detecting expiration of the patient'"'"'s lungs responsive to the pre-shock waveform using transthoracic impedance; and

coordinating delivery of the defibrillation waveform in response to the detected expiration.

25. The method of claim 24, further comprising coordinating delivery of the defibrillation waveform in relation to detection of a minimum in the transthoracic impedance.

26. A system for delivering a subcutaneous defibrillation therapy, comprising:

a housing configured for subcutaneous non-intrathoracic placement relative to a patient'"'"'s heart;

detection circuitry provided in the housing;

energy delivery circuitry provided in the housing;

one or more electrodes configured for subcutaneous non-intrathoracic placement relative to the patient'"'"'s heart, the one or more electrodes coupled to the detection and energy delivery circuitry; and

a controller provided in the housing and coupled to the detection and energy delivery circuitry, the controller, in response to detection of a cardiac fibrillation event, coordinating delivery of a pre-shock waveform sufficient in energy such that contraction of skeletal musculature occurs in the patient'"'"'s thorax but insufficient in energy for defibrillating the patient'"'"'s heart, and delivery of a defibrillation waveform to the patient'"'"'s heart during contraction of the skeletal musculature.

27. The system of claim 26, wherein the one or more electrodes comprise a can electrode of the housing and at least one subcutaneous non-intrathoracic electrode coupled to the detection and energy delivery circuitry.

28. The system of claim 26, wherein the one or more electrodes comprise a can electrode of the housing and at least one subcutaneous non-intrathoracic electrode array coupled to the detection and energy delivery circuitry via a lead.

29. The system of claim 26, wherein the one or more electrodes comprise at least two subcutaneous non-intrathoracic electrodes coupled to the detection and energy delivery circuitry.

30. The system of claim 26, wherein the energy delivery circuitry comprises a capacitor module that stores energy for the subcutaneous defibrillation therapy, a total energy of the capacitor module dischargeable by the capacitor module divided between pre-shock waveform energy and defibrillation waveform energy.

31. The system of claim 30, wherein the pre-shock waveform energy represents less than about 10% of the total energy.

32. The system of claim 26, wherein the pre-shock waveform has a pulse width equal to or less than about 2 milliseconds.

33. The system of claim 26, wherein the pre-shock waveform has a pulse width equal to or less than about 20% of that of the defibrillation waveform.

34. The system of claim 26, wherein the pre-shock waveform has an initial amplitude greater than that of the defibrillation waveform.

35. The system of claim 26, wherein the pre-shock waveform has an initial amplitude less than that of the defibrillation waveform.

36. The system of claim 26, wherein the defibrillation waveform comprises a multiphasic defibrillation waveform.

37. The system of claim 26, wherein the defibrillation waveform comprises a biphasic, truncated exponential defibrillation waveform.

38. The system of claim 26, wherein the pre-shock waveform has an energy level, and the defibrillation waveform has a first phase and a second phase, an energy level of one or both of the first phase and the second phase of the defibrillation waveform reduced by an amount of energy corresponding to the energy level of the pre-shock waveform.

39. The system of claim 26, wherein the pre-shock waveform is sufficient in energy such that deflation of the patient'"'"'s lungs occurs.

40. The system of claim 26, wherein the pre-shock waveform is sufficient in energy such that muscle fiber shortening of the skeletal musculature occurs.

41. The system of claim 26, wherein the pre-shock waveform is sufficient in energy such that displacement of the patient'"'"'s heart relative to the one or more electrodes occurs.

42. The system of claim 41, wherein the patient'"'"'s heart is displaced relative to the one or more electrodes to achieve an increased defibrillation current density in the patient'"'"'s heart relative to a defibrillation current density in the patient'"'"'s heart achievable in the absence of displacement of the patient'"'"'s heart.

43. The system of claim 26, wherein the pre-shock waveform is sufficient in energy such that contraction of the skeletal musculature occurs and reduces a defibrillation threshold relative to a defibrillation threshold associated with delivery of the defibrillation waveform in the absence of the skeletal musculature contraction.

44. The system of claim 26, wherein the controller initiates a delay interval relative to delivery of the pre-shock waveform, wherein the defibrillation waveform is delivered following expiration of the delay interval.

45. The system of claim 44, wherein the delay interval has a pre-established duration.

46. The system of claim 44, wherein the delay interval has a duration equal to or less than about 2 seconds.

47. The system of claim 44, wherein the delay interval has a duration equal to or less than about 200 milliseconds.

48. The system of claim 44, wherein the delay interval has a duration equal to or less than about 100 milliseconds.

49. A system for delivering a subcutaneous defibrillation therapy, comprising:

means for delivering, from a subcutaneous non-intrathoracic location relative to a patient'"'"'s heart, a pre-shock waveform sufficient in energy such that contraction of skeletal musculature occurs in the patient'"'"'s thorax but insufficient in energy for defibrillating the patient'"'"'s heart; and

means for delivering, from the subcutaneous non-intrathoracic location or other subcutaneous non-intrathoracic location, a defibrillation waveform to the patient'"'"'s heart during contraction of the skeletal musculature.

50. The system of claim 49, further comprising means for initiating a delay interval relative to delivery of the pre-shock waveform, wherein the defibrillation waveform is delivered following expiration of the delay interval.

51. The system of claim 50, wherein the delay interval has a pre-established duration.

52. The system of claim 50, wherein the delay interval has a duration of equal to or less than 2 seconds.

53. The system of claim 50, wherein the delay interval has a duration equal to or less than about 200 milliseconds.

54. The system of claim 50, wherein the delay interval has a duration equal to or less than about 100 milliseconds.

55. The system of claim 49, further comprising means for delivering the pre-shock waveform using a first vector and means for delivering the defibrillation waveform using the first vector.

56. The system of claim 49, further comprising means for delivering the pre-shock waveform using a first vector and means for delivering the defibrillation waveform using a second vector differing from the first vector.

57. The system of claim 49, further comprising means for detecting motion of the patient'"'"'s thorax responsive to the pre-shock waveform, wherein the means for delivering the defibrillation waveform coordinates delivery of the defibrillation waveform in relation to the detected motion.