Method and system for characterizing a representative cardiac beat using multiple templates

• US 20030181818A1
• Filed: 03/25/2002
• Published: 09/25/2003
• Est. Priority Date: 03/25/2002
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Bocek, Joseph, Kim, Jaeho
• Granted Patent: US 7,184,818 B2
• Time in Patent Office: Days
• US Class Current: 600/509
• CPC Class Codes: A61B 5/35 by template matching
• CPC Class Codes: A61N 1/3622 comprising two or more electrodes co-operating with different heart regions

Abstract

The present invention provides a method and system for characterizing one beat of a patient'"'"'s supraventricular rhythm. A plurality of templates is provided and updated using a plurality of qualified beats. Updating occurs by temporally aligning the shock channel waveforms of the template beats using rate channel fiducial points. The template beats are combined by point-by-point addition of the shock channel waveforms. The resultant updated template characterizes one of the patient'"'"'s supraventricular conducted cardiac beats.

Claims

1. A method of characterizing a patient'"'"'s supraventricular rhythm, comprising:

providing a plurality of templates;

selectively updating the plurality of templates using a plurality of qualified beats; and

characterizing the patient'"'"'s supraventricular rhythm using a particular template of the plurality of updated templates.

2. The method of claim 1, wherein providing a plurality of templates further comprises retrieving at least a first template from memory and forming one or more other templates using the qualified beats.

3. The method of claim 1, further comprising detecting the plurality of qualified beats by:

sensing rate channel signals;

sensing shock channel signals; and

determining if the rate channel signals and the shock channel signals meet predetermined criteria.

4. The method of claim 1, wherein updating the plurality of templates further comprises:

determining if a qualified beat is correlated to a selected template of the plurality of templates; and

updating the selected template with the qualified beat if the qualified beat is correlated to the selected template.

5. The method of claim 4, wherein updating the selected template further comprises combining the qualified beat to the selected template by any method selected from point-by-point addition of the qualified beat to the selected template, performing a running average of the qualified beat and the selected template, performing a weighted running average of the qualified beat and the selected template, and using a median filtering technique to combine the qualified beat and the selected template.

6. The method of claim 4, further comprising incrementing a counter associated with the selected template each time the selected template is updated.

7. The method of claim 1, wherein characterizing the patient'"'"'s supraventricular rhythm using the particular template of the plurality of updated templates further comprises storing the particular template.

8. The method of claim 4, wherein determining if the qualified beat is correlated to the selected template further comprises:

determining the fiducial points of the qualified beat and the selected template, respectively;

aligning shock channel signals of the qualified beat and the selected template;

identifying a plurality of features of shock channel signals of the qualified beat and the selected template; and

using the plurality of identified features to determine if the qualified beat is correlated to the selected template.

9. The method of claim 1, further comprising:

providing a plurality of counters associated with the plurality of templates;

incrementing one of the plurality of counters when the template associated with the counter is updated; and

using the template which has an associated counter with the highest count as a characterization of the patient'"'"'s supraventricular rhythm.

10. The method of claim 1, wherein updating the plurality of templates further comprises replacing one of the plurality of templates with a qualified beat when the qualified beat does not correlate to any of the plurality of templates and only one previous qualified beat has been used to form the template being replaced.

11. A method of characterizing a patient'"'"'s supraventricular rhythm, comprising:

providing a first template and a second template;

detecting qualified beats;

updating the first template using qualified beats correlated to the first template;

updating the second template using qualified beats correlated to the second template;

counting a first number of correlated beats associated with the first updated template;

counting a second number of correlated beats associated with the second updated template;

storing the first updated template as a current template if the first number of correlated beats reaches a predetermined count prior to the second number of correlated beats reaching the predetermined count; and

storing the second updated template as a current template if the second number of correlated beats reaches the predetermined count prior to the first number of correlated beats reaching the predetermined count, the current template representing one beat of the patient'"'"'s supraventricular conducted beats.

12. The method of claim 11, wherein the predetermined count is six.

13. The method of claim 11, further comprising updating the second template using qualified beats uncorrelated to the first template.

14. The method of claim 11, wherein:

providing the first template comprises retrieving a stored template and using the retrieved template as the first template; and

providing the second template comprises forming the second template using a qualified beat which is uncorrelated to the first template.

15. The method of claim 11, wherein:

providing the first template comprises forming the first template using a first qualified beat; and

providing the second template comprises forming the second template using a qualified beat uncorrelated to the first template.

16. The method of claim 11, wherein:

detecting qualified beats comprises sensing rate channel signals, sensing shock channel signals, and determining if the rate channel signals and the shock channel signals meet predetermined criteria.

17. The method of claim 11, wherein updating the first template using beats correlated to the first template further comprises:

identifying a plurality of features of the first template;

temporally aligning a qualified beat and the first template;

identifying a plurality of features of the qualified beat;

determining if the qualified beat is correlated to the first template using the plurality of features of the qualified beat and the plurality of features of the first template; and

updating the first template using the qualified beat correlated to the first template.

18. The method of claim 17, wherein the plurality of features of the first template comprise values of the first template at a plurality of times t_i, where i=1 to N, and the plurality of features of the qualified beat comprise values of the qualified beat at the plurality of times t_i, where i=1 to N.

19. The method of claim 17, wherein updating the first template using qualified beats correlated to the first template further comprises:

updating the first template by adding a value of the qualified beat at each of the times t_j to a value of the first template at each of the times t_j, where j=1 to M; and

counting a first number of correlated beats used to update the first template.

20. The method of claim 11, wherein storing the first updated template as a current template further comprises normalizing the first updated template.

21. The method of claim 11, wherein updating the second template using beats correlated to the second template further comprises:

identifying a plurality of features of the second template;

temporally aligning a qualified beat and the second template;

identifying a plurality of features of the qualified beat;

determining if the qualified beat is correlated to the second template using the plurality of features of the qualified beat and the plurality of features of the second template; and

updating the second template using the qualified beat correlated to the second template.

22. The method of claim 21, wherein the plurality of features of the second template comprise values of the second template at a plurality of times t_i, where i=1 to N, and the plurality of features of the qualified beat comprise values of the qualified beat at the plurality of times t_i, where i=1 to N.

23. The method of claim 21, wherein updating the second template using qualified beats correlated to the second template further comprises:

updating the second template by adding a value of the qualified beat at each of the times t_j to a value of the second template at each of the times t_j, where j=1 to M; and

counting a second number of correlated beats used to update the second template.

24. The method of claim 23, wherein storing the second updated template as a current template further comprises normalizing the second template.

25. The method of claim 11, further comprising replacing the second template with a qualified beat if the qualified beat does not correlate to the first or second templates and no beats are correlated to the second template.

26. The method of claim 11, further comprising replacing the first template with a qualified beat if one or more qualified beats are correlated with the second template and no beats are correlated with the first template and the first template was formed by retrieving a stored template.

27. A body implantable system for characterizing a patient'"'"'s supraventricular rhythm, comprising:

a lead system, the lead system comprising electrodes and extending into a heart;

a detector system, coupled to the lead system, that detects rate channel signals and shock channel signals sensed by the lead system electrodes; and

a control system coupled to the detector system, wherein the control system provides a plurality of templates, selectively updates the plurality of templates using a plurality of qualified beats, and characterizes a patient'"'"'s supraventricular rhythm using a particular template of the plurality of updated templates.

28. The system of claim 27, wherein the control system performs an automatic gain control adjustment for the shock channel signals prior to characterizing a patient'"'"'s supraventricular rhythm.

29. The system of claim 28, wherein the automatic gain control adjustment is performed by measuring a peak value in a predetermined number of regular beats and adjusting the shock channel gain such that an average peak value is a predetermined percentage of a maximum A/D converter value.

30. The system of claim 29, wherein the predetermined number of regular beats is four and the predetermined percentage of the maximum A/D converter value is 50%.

31. The system of claim 27, wherein the control system retrieves at least a first template from memory and forms one or more other templates using the qualified beats.

32. The system of claim 27, wherein the control system determines if the rate channel signals and the shock channel signals meet predetermined criteria.

33. The system of claim 27, wherein the control system

determines if a qualified beat is correlated to a selected template of the plurality of templates;

and

updates the selected template with the qualified beat if the qualified beat is correlated to the selected template.

34. The system of claim 33, wherein the control system updates the selected template by combining the qualified beat with the selected template by any method selected from point by point addition of the qualified beat to the selected template, performing a running average of the qualified beat and the selected template, performing a weighted running average of the qualified beat and the selected template and using a median filtering technique to combine the qualified beat and the selected template.

35. The system of claim 33, wherein the control system increments a counter associated with the selected template each time the selected template is updated.

36. The system of claim 33, wherein the control system:

aligns shock channel signals of the qualified beat and the selected template;

identifies the plurality of features of shock channel signals of the qualified beat and the selected template; and

uses the plurality of identified features to determine if the qualified beat is correlated to the selected template.

37. The system of claim 27, wherein the control system

provides a plurality of counters associated with the plurality of templates;

increments one of the plurality of counters when the template associated with the counter is updated; and

uses the template that has an associated counter with the highest count as a characterization of the patient'"'"'s supraventricular rhythm.

38. The system of claim 27, wherein the control system replaces one of the plurality of templates with a qualified beat when the qualified beat does not correlate to any of the plurality of templates and no qualified beats are correlated to the template being replaced.

39. A body implantable system for characterizing a patient'"'"'s supraventricular rhythm, comprising:

a lead system, the lead system comprising electrodes and extending into a heart;

a detector system, coupled to the lead system, that detects rate channel signals and shock channel signals;

a control system coupled to the detector system, wherein the control system

provides a first template and a second template,

updates the first template using qualified beats correlated to the first template;

updates the second template using qualified beats correlated to the second template;

counts a first number of correlated beats associated with the first updated template;

counts a second number of correlated beats associated with the second updated template;

stores the first updated template as a current template if the first number of correlated beats reaches a predetermined count prior to the second number of correlated beats reaching the predetermined count; and

stores the second updated template as a current template if the second number of correlated beats reaches the predetermined count prior to the first number of correlated beats reaching the predetermined count, the current template representing one beat of the patient'"'"'s supraventricular conducted beats.

40. The system of claim 39, wherein the predetermined count is six.

41. The system of claim 39, wherein the control system updates the second template using qualified beats uncorrelated to the first template.

42. The system of claim 39, wherein the control system provides the first template by retrieving a stored template and using the retrieved template as the first template and provides the second template by forming the second template using a qualified beat which is uncorrelated to the first template.

43. The system of claim 39, wherein the control system provides the first template using a qualified beat and provides the second template using a qualified beat uncorrelated to the first template.

44. The system of claim 39, wherein the control system determines if the rate channel signals and the shock channel signals meet predetermined criteria for qualified beats.

45. The system of claim 44, wherein the control system performs an automatic gain control adjustment for the shock channel signals.

46. The system of claim 45, wherein the automatic gain control adjustment is performed by measuring a peak value in a predetermined number of regular beats and adjusts the shock channel gain such that an average peak value is a predetermined percentage of a maximum A/D converter value.

47. The system of claim 46, wherein the predetermined number of regular beats is four and the predetermined percentage of the maximum A/D converter value is 50%.

48. The system of claim 39, wherein the control system

identifies a plurality of features of the first template,

temporally aligns a qualified beat and the first template,

identifies a plurality of features of the qualified beat,

determines if the qualified beat is correlated to the first template using the plurality of features of the qualified beat and the plurality of features of the first template, and

updates the first template using the qualified beat correlated to the first template.

49. The system of claim 48, wherein the plurality of features of the first template comprise values of the first template at a plurality of times t_i, where i=1 to N, and the plurality of features of the qualified beat comprise values of the qualified beat at the plurality of times t_i, where i=1 to N.

50. The system of claim 48, wherein the control system updates the first template using qualified beats correlated to the first template further by:

updating the first template by adding a value of the qualified beat at each of the times t_j to a value of the first template at each of the times t_j, where j=1 to M; and

counting a first number of correlated beats used to update the first template.

51. The system of claim 39, wherein the control system normalizes the first updated template before storing the first updated template as the current template.

52. The system of claim 39, wherein the control system:

identifies a plurality of features of the second template,

temporally aligns a qualified beat and the second template,

identifies a plurality of features of the qualified beat,

determines if the qualified beat is correlated to the second template using the plurality of features of the qualified beat and the plurality of features of the second template, and

updates the second template using the qualified beat correlated to the second template.

53. The system of claim 52, wherein the plurality of features of the second template comprise values of the second template at a plurality of times t_i, where i=1 to N, and the plurality of features of the qualified beat comprise values of the qualified beat at the plurality of times t_i, where i=1 to N.

54. The method of claim 52, wherein the control system updates the second template using qualified beats correlated to the second template by adding a value of the qualified beat at each of the times t_j to a value of the second template at each of the times t_j, where j=1 to M, and

counting a second number of correlated beats used to update the second template.

55. The system of claim 54, wherein the control system normalizes the second updated template before storing the second updated template as the current template.

56. The method of claim 39, wherein the control system replaces the second template with a qualified beat if the qualified beat does not correlate to the first or the second templates and no beats are correlated to the second template.

57. The method of claim 39, wherein the control system replaces the first template with a qualified beat if one or more qualified beats are correlated with the second template and no beats are correlated with the first template and the first template was formed by retrieving a stored template.

58. A system for characterizing a patient'"'"'s supraventricular rhythm, comprising:

means for providing a plurality of templates;

means for selectively updating the plurality of templates using a plurality of qualified beats; and

means for characterizing the patient'"'"'s supraventricular rhythm using a particular template of the plurality of updated templates.

59. A system of characterizing a patient'"'"'s supraventricular rhythm, comprising:

means for providing a first template and a second template;

means for detecting qualified beats;

means for updating the first template using qualified beats correlated to the first template;

means for updating the second template using qualified beats correlated to the second template;

means for counting a first number of correlated beats associated with the first updated template;

means for counting a second number of correlated beats associated with the second updated template;

means for storing the first updated template as a current template if the first number of correlated beats reaches a predetermined count prior to the second number of correlated beats reaching the predetermined count; and

means for storing the second updated template as a current template if the second number of correlated beats reaches the predetermined count prior to the first number of correlated beats reaching the predetermined count, the current template representing one beat of the patient'"'"'s supraventricular conducted beats.