Implantable cardiac stimulation device that defibrillates the atria while avoiding the ventricular vulnerable period and method

1. An implantable cardiac stimulation device that applies defibrillating electrical energy to at least one atrium of a heart at a time which avoids inducing ventricular fibrillation of the heart, the device comprising:

an atrial fibrillation detector that detects atrial fibrillation of the heart;

a pacing pulse generator that applies a pacing pulse to at least one of the ventricles responsive to the atrial fibrillation detector detecting atrial fibrillation of the heart;

a timer that times a time period through an evoked response end a T-wave caused by the pacing pulse, the time period completing a predetermined time period after the T-wave ends; and

a defibrillation pulse generator that applies the defibrillating eletrical energy to the at least one atrium of the heart responsive to the timer completing the timing of the time period.

2. The device of claim 1 wherein the timer commences timing of the time period beginning with the application of the pacing pulse.

3. The device of claim 2 wherein the time period is between about 350 milliseconds and 450 milliseconds.

4. The device of claim 1 wherein the pacing pulse generator applies the pacing pulse to the right ventricle of the heart.

5. The device of claim 1 wherein the pacing pulse generator applies the pacing pulse to the left ventricle of the heart.

6. The device of claim 1 wherein the pacing pulse generator applies the pacing pulse to both the right ventricle and the left ventricle of the heart.

7. The device of claim 1 further comprising a cardiac interval timer that times cardiac intervals of the heart responsive to the atrial fibrillation detector detecting atriel fibrillation of the heart and wherein the pacing pulse generator applies the pacing pulse after the interval timer times a cardiac interval longer than a minimum cardiac interval.

8. The device of claim 1 further comprising an evoked response detector that detects the evoked response and wherein the defibrillation pulse generator inhibits the application of the defibrillating energy responsive to the evoked response detector failing to detect the evoked response.

9. The device of claim 1 wherein the pacing pulse generator applies a plurality of pacing pulses to at least one of the ventricles responsive to the atrial fibrillation detector detecting atrial fibrillation of the heart, and wherein the timer times the time period following a last one of the plurality of pacing pulses through the evoked response and T-wave caused by the last one of the plurality of pacing pulses.

10. The device of claim 9 wherein the pacing pulse generator applies the plurality of pacing pulses on demand and wherein the timer times the time period after the pacing pulse generator applies the plurality of pacing pulses during consecutive cardiac cycles.

11. The device of claim 9 wherein the timer commences timing of the time period beginning with the application of the last one of the pacing pulses.

12. The device of claim 11 wherein the time period is between about 350 milliseconds and 450 milliseconds.

13. The device of claim 9 wherein the pacing pulse generator applies the pacing pulses to the right ventricle of the heart.

14. The device of claim 9 wherein the pacing pulse generator applies the pacing pulses to the left ventricle of the heart.

15. The device of claim 9 wherein the pacing pulse generator applies the pacing pulses to both the right ventricle and the left ventricle of the heart.

16. The device of claim 9 further comprising an evoked response detector that detects the evoked response and wherein the defibrillation pulse generator inhibits the application of the defibrillating energy responsive to the evoked response detector failing to detect the evoked response.

17. The device of claim 9 further comprising an atrial pacing pulse generator that applies an atrial pacing pulse to at least one of the atria after the timer completes the timing of the time period and before the defibrillation pulse generator applies the defibrillating electrical energy to the atria.

18. The device of claim 9 further comprising an atrial sensing circuit that senses P-waves of the heart and wherein the defibrillation pulse generator applies the defibrillating electrical energy to the atria in timed relation to a sensed P-wave.

19. An implantable cardiac stimulation device that applies defibrillating electrical energy to at least one atrium of a heart at a time which avoids inducing ventricular fibrillation of the heart, the device comprising:

an atrial fibrillation detector that detects atrial fibrillation of the heart;

a pacing pulse generator that applies a pacing pulse to at least one of the ventricles responsive to the atrial fibrillation detector detecting atrial fibrillation of the heart;

a timer that times a time period through an evoked response and a T-wave caused by the pacing pulse, the time period completing after the T-wave;

a defibrillation pulse generator that applies the defibrillating electrical energy to the at least one atrium of the heart responsive to the timer completing the timing of the time period; and

an atrial pacing pulse generator that applies an atrial pacing pulse to at least one of the atria after the timer completes the timing of the time period and before the defibrillation pulse generator applies the defibrillating electrical energy to the atria.

20. An implantable cardiac stimulation device that applies defibrillating electrical energy to at least one atrium of a heart at a time which avoids inducing ventricular fibrillation of the heart, the device comprising:

an atrial fibrillation detector that detects atrial fibrillation of the heart;

a pacing pulse generator that applies a pacing pulse to at least one of the ventricles responsive to the atrial fibrillation detector detecting atrial fibrillation of the heart;

a timer that times a time period through an evoked resoonse and a T-wave caused by the pacing pulse, the time period completing after the T-wave;

a defibrillation pulse generator that applies the defibrillating electrical energy to the at least one atrium of the heart responsive to the timer completing the timing of the time period; and

an atrial sensing circuit that senses P-waves of the heart and wherein the defibrillation pulse generator applies the defibrillating electrical energy to the atria in timed relation to a sensed P-wave.

21. An implantable cardiac stimulation device for applying defibrillating electrical energy to at least one atrium of a heart at a time which avoids inducing ventricular fibrillation of the heart, the device comprising:

atrial fibrillation detecting means for detecting atrial fibrillation of the heart;

ventricular pacing pulse generating means for applying a pacing pulse to at least one of the ventricles responsive to the detection of atrial fibrillation;

timing means for timing a time period through an evoked response and T-wave caused by the ventricular pacing pulse and ending a predetermined time period after the T-wave ends; and

defibrillation pulse generating means for applying defibrillating electrical energy to the atria after the timing means times the time period.

22. The device of claim 21 wherein the timing means commences timing of the time period beginning with the application of the pacing pulse.

23. The device of claim 22 wherein the time period is between about 350 milliseconds and 450 milliseconds.

24. The device of claim 21 wherein the pacing pulse generating means applies the pacing pulse to the right ventricle of the heart.

25. The device of claim 21 wherein the pacing pulse generating means applies the pacing pulse to the left ventricle of the heart.

26. The device of claim 21 wherein the pacing pulse generating means applies the pacing pulse to both the right ventricle and the left ventricle of the heart.

27. The device of claim 21 further comprising cardiac interval timing means for timing cardiac intervals of the heart responsive to the atrial fibrillation detector means detecting atrial fibrillation of the heart and wherein the pacing pulse generating means applies the pacing pulse after the interval timing means times a cardiac interval longer than a minimum cardiac interval.

28. The device of claim 21 further comprising evoked response detecting means for detecting the evoked response and wherein the defibrlliation pulse generating means wtthholds the application of the defibrillating energy responsive to the evoked response detecting means failing to detect the evoked response.

29. The device of claim 21 wherein the ventricular pacing pulse generating means applies a plurality of pacing pulses to at least one of the ventricles responsive to the detection of atrial fibrillation, and wherein the timing means times the time period following a last one of the plurality of pacing pulses through the evoked response and T-wave caused by the last one of the plurality of pacing pulses.

30. The device of claim 29 wherein the ventricular pacing pulse generating means applies the plurality of pacing pulses on demand and wherein the timing means times the time period after the ventricular pacing pulse generating means applies the plurality of pacing pulses during consecutive cardiac cycles.

31. The device of claim 29 wherein the timing means commences timing of the time period beginning with the application of the last one of the pacing pulses.

32. The device of claim 31 wherein the time period is between about 350 milliseconds and 450 milliseconds.

33. The device of claim 29 wherein the pacing pulse generating means applies the pacing pulses to the right ventricle of the heart.

34. The device of claim 29 wherein the pacing pulse generating means applies the pacing pulses to the left ventricle of the heart.

35. The device of claim 29 wherein the pacing pulse generating means applies the pacing pulses to both the right ventricle and the left ventricle of the heart.

36. The device of claim 29 further comprising evoked response detecting means for detecting the evoked response and wherein the defibrillation pulse generating means withholds the application of the defibriliating energy responsive to the evoked response detecting means failing to detect the evoked response.

37. The device of claim 29 further comprising atrial pacing pulse generating means for applying an atrial pacing pulse to at least one of the atrial after the timing means times the time period and before the defibrillation pulse generating means applies the defibrillating electrical energy to the atria.

38. The device of claim 29 further comprising atrial sensing means for sensing P-waves of the heart and wherein the defibrillation pulse generating means applies the defibrillating electrical energy to the atria in timed relation to a sensed P-wave.

39. An implantable cardiac stimulation device for applying defibrillating electrical energy to at least one atrium of a heart at a time which avoids inducing ventricular fibrillation of the heart, the device comprising:

atrial fibrillation detecting means for detecting atrial fibrillation of the heart;

ventricular pacing pulse generating means for applying a first pacing pulse to at least one of the ventricles responsive to the detection of atrial fibrillation;

timing means for timing a time period through an evoked response and T-wave caused by the ventricular pacing pulse;

defibrillation pulse generating means for applying defibrillating electrical energy to the atria after the timing means times the time period; and

atrial pacing pulse generating means for applying an atrial pacing pulse to at least one of the atria after the timing means times the time period and before the defibrillation pulse generating means applies the defibrillating eletrical energy to the atria.

40. An implantable cardiac stimulation device for applying defibriliating electrical energy to at least one atrium of a heart at a time which avoids inducing ventricular fibrillation of the heart, the device comprising:

atrial fibrillation detecting means for detecting atrial fibrillation of the heart;

ventricular pacing pulse generating means for applying a first pacing pulse to at least one of the ventricles responsive to the detection of atrial fibrillation;

timing means for timing a time period through an evoked response and T-wave caused by the ventricular pacing pulse;

defibrillation pulse generating means for applying defibrillating electrical energy to the atria after the timing means times the time period; and

atrial sensing means for sensing P-waves of the heart and wherein the defibrillation pulse generating means applies the defibrillating electrical energy to the atria in timed relation to a sensed P-wave.

41. In an implantable cardiac stimulation device, a method of applying defibrillating electrical energy to at least one atrium of a heart, the method comprising:

stimulating at least one of the ventricles with a ventricular pacing pulse to cause an evoked response and T-wave;

waiting until the T-wave ends; and

applying defibrillating electrical energy to the at least one atrium a predetermined period after the T-wave ends.

42. The method of claim 41 wherein waiting comprises commencing timing of a predetermined time period beginning with the application of the pacing pulse.

43. The method of claim 42 wherein the time period is between about 350 milliseconds and 450 milliseconds.

44. The method of claim 41 wherein stimulating comprises applying the pacing pulse to the right ventricle of the heart.

45. The device of claim 41 further comprising detecting the evoked response including the T-wave and wherein applying is performed after the detected T-wave ends.

46. The method of claim 41 wherein stimulating comprises applying the pacing pulse to both the right ventricle and the left ventricle of the heart.

47. The method of claim 41 further comprising timing cardiac intervals of the heart responsive to detecting atrial fibrillation of the heart and wherein stimulating is performed after the timing of a cardiac interval longer than a minimum cardiac interval.

48. The method of claim 41 further comprising detecting the evoked response and wherein applying is performed only when the evoked response is detected.

49. The method of claim 41 wherein stimulating comprises applying a plurality of pacing pulses to at least one of the ventricles responsive to the detection of atrial fibrillation, and wherein timing comprises timing the time period following a last one of the plurality of pacing pulses through the evoked response end T-wave caused by the last one of the plurality of pacing pulses.

50. The method of claim 49 wherein stimulating comprises applying the plurality of pacing pulses on demand and wherein timing is commenced after the plurality of pacing pulses are applied during consecutive cardiac cycles.

51. The method of claim 49 wherein timing comprises commencing the timing of the time period beginning with the application of the last one of the pacing pulses.

52. The method of claim 51 wherein the time period is between about 350 milliseconds and 450 milliseconds.

53. The method of claim 49 wherein stimulating comprises applying the pacing pulse to the right ventricle of the heart.

54. The device of claim 49 wherein stimulating comprises applying the pacing pulses to the left ventricle of the heart.

55. The method of claim 49 wherein stimulating comprises applying the pacing pulses to both the right ventricle and the left ventricle of the heart.

56. The method of claim 49 further comprising detecting the evoked response and wherein applying is performed only when the evoked response is detected.

57. The method of claim 49 further comprising pacing at least one of the atria after the timing of the time period and before the applying of the defibrillating electrical energy to the atria.

58. The method of claim 49 further comprising sensing P-waves of the heart and wherein applying comprises applying the defibrillating electrical energy to the atria in timed relation to a sensed P-wave.

59. In an implantable cardiac stimulation device, a method of applying defibrillating electrical energy to at least one atrium of a heart, the method comprising:

stimulating at least one of the ventricles with a ventricular pacing pulse to cause an evoked response and T-wave;

waiting until the T-wave ends;

applying defibrillating electrical energy to the at least one atrium after the T-wave ends; and

pacing at least one of the atria after the timing of the time period and before the applying of the defibrillating electrical energy to the atria.

60. In an implantable cardiac stimulation device, a method of applying defibrillating electrical energy to at least one atrium of a heart, the method comprising:

stimulating at least one of the ventricles with a ventricular pacing pulse to cause an evoked response and T-wave;

waiting until the T-wave ends;

applying defibrillating electrical energy to the at least one atrium after the T-wave ends; and

sensing P-waves of the heart and wherein applying comprises applying the defibrillating electrical energy to the atria in timed relation to a sensed P-wave.

61. An implantable cardiac stimulation device comprising:

a lead assembly that is in electrical communication with a heart to sense physiologic activity of the heart and generate corresponding signals, and to deliver stimulation energy to the heart;

a pulse generator connected to the lead assembly and that generates stimulation pulses to be delivered to the heart via the lead assembly; and

control circuitry connected to the lead assembly and pulse generator, the control circuitry being operative to process the signals from the lead assembly to determine whether atrial fibrillation exists, the control circuitry being operative in response to detection of atrial fibrillation to control the pulse generator to generate at least one pacing pulse for delivery to at least one ventricle to cause an evoked response and T-wave in the at least one ventricle, the control circuitry further being operative to control the pulse generator to generate a defibrillation pulse for delivery to at least one atrium a predetermined period after the T-wave ends.