Normal cardiac rhythm template generation system and method

• US 20020183637A1
• Filed: 04/30/2001
• Published: 12/05/2002
• Est. Priority Date: 04/30/2001
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Bocek, Joseph, Kim, Jaeho, White, Harley, Hsu, William
• Granted Patent: US 6,708,058 B2
• Time in Patent Office: Days
• US Class Current: 600/510
• CPC Class Codes: A61B 5/35 by template matching

Abstract

A method and system provides for generating a snapshot representative of one beat of a patient'"'"'s normal cardiac rhythm. Cardiac rate channel signals and shock channel signals are sensed. A fiducial point is determined for a predefined number of the cardiac rate channel signals. A predefined number of the shock channel signals are aligned using the fiducial point. A template is generated using the aligned shock channel signals, whereby the template is representative of one of the patient'"'"'s normal supra-ventricular conducted cardiac beats. The template is updated on a periodic basis.

Claims

1. A method of generating a snapshot representative of one beat of a patient'"'"'s normal cardiac rhythm, comprising:

sensing rate channel signals;

sensing shock channel signals;

determining a fiducial point for the rate channel signals;

aligning the shock channel signals using the fiducial point; and

generating a template using the aligned shock channel signals, the template representative of one of the patient'"'"'s normal supra-ventricular conducted beats.

2. The method of claim 1, further comprising updating the template on a periodic basis.

3. The method of claim 1, further comprising confirming, using subsequently detected template beats, whether the generated template is or is not representative of one of the patient'"'"'s normal supra-ventricular conducted beats.

4. The method of claim 1, further comprising determining that no template is presently stored, and storing the generated template in response to confirming that subsequently detected template beats correlate with the generated template.

5. The method of claim 1, further comprising determining that no template is presently stored, and discarding the generated template in response to confirming that subsequently detected template beats fail to correlate with the generated template.

6. The method of claim 1, further comprising:

determining that the generated template is stored; and

retaining the stored template in response to determining that subsequently detected template beats correlate with the stored template.

7. The method of claim 1, further comprising:

determining that the generated template is stored;

generating a new template in response to confirming that subsequently detected template beats fail to correlate with the stored template; and

replacing the stored template with the new template in response to confirming that newly detected template beats correlate with the new template.

8. The method of claim 1, further comprising:

determining that the generated template is stored;

generating a new template in response to the confirming that subsequently detected template beats fail to correlate with the stored template; and

retaining the stored template and discarding the new template in response to confirming that newly detected template beats fail to correlate with the new template.

9. The method of claim 1, wherein generating the template comprises averaging the aligned shock channel signals.

10. The method of claim 9, wherein averaging the aligned shock channel signals comprises point-by-point averaging or median filtering n samples acquired from the same time location of aligned n template beats.

11. The method of claim 1, further comprises determining that the rate channel signals satisfy predefined normalcy criteria using a running average (RRavg) of a plurality of RR intervals.

12. The method of claim 1, further comprising:

initiating template updating;

comparing a running average (RRavg) of a plurality of RR intervals to a predetermined rate threshold; and

suspending template updating if RRavg is less than a predetermined interval.

13. The method of claim 1, further comprising:

computing a running average (RRavg) of a plurality of RR intervals; and

classifying a beat as a regular beat if an RR interval associated with the beat falls within a predetermined percentage range of RRavg.

14. The method of claim 13, further comprising classifying a heart rate as regular if a predetermined percentage of the beats are regular beats.

15. The method of claim 1, further comprising skipping processing of a subsequently sensed rate channel signal if the subsequently sensed rate channel signal is detected before processing of a current sensed rate channel signal is completed.

16. The method of claim 1, further comprising determining whether the rate channel is noisy, and classifying a beat as noisy in response to the rate channel being determined noisy.

17. The method of claim 1, further comprising:

computing an average peak amplitude of a plurality of beats; and

adjusting shock channel gain to an available gain that sets the average peak amplitude to a predetermined percentage of a maximum ADC value.

18. The method of claim 1, further comprising classifying sensed beats as NSR beats in response to satisfying a first set of criteria, and classifying the NSR beats as template beats in response to satisfying a second set of criteria.

19. The method of claim 18, wherein generating the template further comprises generating the template using the aligned template beats.

20. The method of claim 1, wherein the fiducial point is characterized by a fiducial point type, the fiducial point type being determined by determining the larger of a positive peak and a negative peak for each of a plurality of NSR beats.

21. The method of claim 20, wherein the fiducial point type for alignment is determined by determining if the majority of NSR beats have positive peaks or negative peaks.

22. The method of claim 1, wherein aligning the shock channel signals comprises aligning shock channel waveforms of template beats centered with respect to the fiducial point.

23. The method of claim 21, wherein generating the template further comprises generating a template waveform by averaging a predetermined number of template beats.

24. The method of claim 1, wherein generating the template further comprises determining a plurality of features of the template.

25. The method of claim 24, wherein the plurality of template features comprises an absolute maximum peak and at least one of a turning point and a flat slope point.

27. The system of claim 26, wherein the control system updates the template on a periodic basis.

28. The system of claim 26, wherein the control system confirms whether the generated template is or is not representative of one of the patient'"'"'s normal supra-ventricular conducted beats using subsequently detected template beats.

29. The system of claim 26, wherein the control system, in response to determining that no template is stored in memory, stores the generated template in memory in response to confirming that subsequently detected template beats correlate with the generated template.

30. The system of claim 26, wherein the control system, in response to determining that no template is stored in memory, discards the generated template in response to determining that subsequently detected template beats fail to correlate with the generated template.

31. The system of claim 26, wherein the generated template is stored in memory, the control system retaining the stored template in memory in response determining that subsequently detected template beats correlate with the template stored in memory.

32. The system of claim 26, wherein the generated template is stored in memory, the control system further generating a new template in response to confirming that subsequently detected template beats fail to correlate with the template stored in memory, the control system replacing the template stored in memory with the new template in response to confirming that newly detected template beats correlate with the new template.

33. The system of claim 26, wherein the control system stores the generated template in memory, the control system further generating a new template in response to confirming that subsequently detected template beats fail to correlate with the template stored in memory, the control system retaining the template stored in memory and discarding the new template in response to confirming that newly detected template beats fail to correlate with the new template.

34. The system of claim 26, wherein the control system performs an averaging computation on the aligned shock channel signals.

35. The system of claim 26, wherein the control system computes a running average (RRavg) of a plurality of RR intervals and determines that the rate channel signals satisfy predefined normalcy criteria using RRavg.

36. The system of claim 26, wherein the control system initiates template updating, compares a running average (RRavg) of a plurality of RR intervals to a predetermined rate threshold, and suspends template updating if RRavg is less than a predetermined interval.

37. The system of claim 26, wherein the control system computes a running average (RRavg) of a plurality of RR intervals, and classifies a beat as a regular beat if an RR interval associated with the beat falls within a predetermined percentage range of RRavg.

38. The system of claim 37, wherein the control system classifies a heart rate as regular if a predetermined percentage of the beats are regular beats.

39. The system of claim 26, wherein the control system skips processing of a subsequently sensed rate channel signal if the subsequently sensed rate channel signal is detected before processing of a current sensed rate channel signal is completed.

40. The system of claim 26, wherein the control system determines whether the rate channel is noisy, and classifies a beat as noisy in response to the rate channel being determined noisy.

41. The system of claim 26, wherein the control system computes an average peak amplitude of a plurality of beats, and adjusts shock channel gain to an available gain that sets the average peak amplitude to a predetermined percentage of a maximum ADC value.

42. The system of claim 26, wherein the control system classifies sensed beats as NSR beats in response to satisfying a first set of criteria, and classifies the NSR beats as template beats in response to satisfying a second set of criteria.

43. The system of claim 42, wherein the control system generates the template using the aligned template beats.

44. The system of claim 26, wherein the control system determines the fiducial point type by determining the larger of a positive peak and a negative peak for each of a plurality of NSR beats.

45. The system of claim 44, wherein the fiducial point type for alignment is determined by the control system by determining if the majority of NSR beats have positive peaks or negative peaks.

46. The system of claim 26, wherein the control system aligns shock channel waveforms of template beats centered with respect to the fiducial point.

47. The system of claim 46, wherein the control system generates a template waveform by averaging a predetermined number of template beats.

48. The system of claim 26, wherein the control system determines a plurality of features of the template.

49. The system of claim 26, wherein the control system determines a plurality of template features comprising an absolute maximum peak and at least one of a turning point and a flat slope point.

50. The system of claim 26, wherein the control system updates the template in response to detecting establishment of connectivity between the lead system and the detector system.

26. A body implantable system, disposed in a housing having a can electrode, for generating a snapshot representative of one beat of a patient'"'"'s normal cardiac rhythm, comprising:

a lead system comprising electrodes, the lead system extending from the housing into a heart;

a detector system, coupled to the lead system, that detects rate channel signals and shock channel signals sensed by one or both of the lead system electrodes and the can electrode; and

a control system coupled to the detector system, the control system determining a fiducial point for the rate channel signals, aligning the shock channel signals using the fiducial point, and generating a template using the aligned shock channel signals, the template representative of one of the patient'"'"'s normal supra-ventricular conducted beats.

51. A system for generating a snapshot representative of one beat of a patient'"'"'s normal cardiac rhythm, comprising:

means for sensing rate channel signals;

means for sensing shock channel signals;

means for determining a fiducial point for the rate channel signals;

means for aligning the shock channel signals using the fiducial point; and

means for generating a template using the aligned shock channel signals, the template representative of one of the patient'"'"'s normal supra-ventricular conducted beats.

52. The system of claim 51, further comprising means for updating the template on a periodic basis.

53. The system of claim 51, further comprising means for confirming, using subsequently detected template beats, whether the generated template is or is not representative of one of the patient'"'"'s normal supra-ventricular conducted beats.

54. The system of claim 51, further comprising means for determining that no template is presently stored, and means for storing the generated template in response to confirming that subsequently detected template beats correlate with the generated template.

55. The system of claim 51, further comprising means for determining that no template is presently stored, and means for discarding the generated template in response to confirming that subsequently detected template beats fail to correlate with the generated template.

56. The system of claim 51, further comprising:

means for determining that the generated template is stored; and

means for retaining the stored template in response to determining that subsequently detected template beats correlate with the stored template.

57. The system of claim 51, further comprising:

means for determining that the generated template is stored;

means for generating a new template in response to confirming that subsequently detected template beats fail to correlate with the stored template; and

means for replacing the stored template with the new template in response to confirming that newly detected template beats correlate with the new template.

58. The system of claim 51, further comprising:

means for determining that the generated template is stored;

means for generating a new template in response to the confirming that subsequently detected template beats fail to correlate with the stored template; and

means for retaining the stored template and discarding the new template in response to confirming that newly detected template beats fail to correlate with the new template.

59. The system of claim 51, further comprises means for determining that the rate channel signals satisfy predefined normalcy criteria using a running average (RRavg) of a plurality of RR intervals.

60. The system of claim 51, further comprising means for skipping processing of a subsequently sensed rate channel signal if the subsequently sensed rate channel signal is detected before processing of a current sensed rate channel signal is completed.

61. The system of claim 51, further comprising:

means for computing an average peak amplitude of a plurality of beats; and

means for adjusting shock channel gain to an available gain that sets the average peak amplitude to a predetermined percentage of a maximum ADC value.

62. The system of claim 51, wherein the fiducial point is characterized by a fiducial point type, the system further comprising means for determining the fiducial point type as the larger of a positive peak and a negative peak for each of a plurality of NSR beats.

63. The system of claim 61, wherein the determining means determines the fiducial point type for alignment by determining if the majority of NSR beats have positive peaks or negative peaks.

64. The system of claim 51, wherein the aligning means further comprises means for aligning shock channel waveforms of template beats centered with respect to the fiducial point.

65. The system of claim 51, wherein the generating means further comprises means for determining a plurality of features of the template.

66. The system of claim 51, wherein the generating means further comprises means for determining a plurality of template features comprising an absolute maximum peak and at least one of a turning point and a flat slope point.

67. The system of claim 51, further comprising means for updating the template in response to detecting establishment of connectivity between the respective sensing means and at least the template generating means.