System and method of classifying tachyarrhythmia episodes as associated or disassociated

• US 6,456,871 B1
• Filed: 12/01/1999
• Issued: 09/24/2002
• Est. Priority Date: 12/01/1999
• Status: Expired due to Fees

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Lovett, Eric G., Sweeney, Robert J., Hsu, William
• Primary Examiner(s): Schaetzle, Kennedy
• Application Number:
  US09/452,670
• Time in Patent Office: 1,028 Days
• Field of Search: 600/518, 600/519, 600/521, 600/515, 607/14
• US Class Current: 600/518
• CPC Class Codes: A61N 1/3622 comprising two or more electrodes co-operating with different heart regions
• CPC Class Codes: A61N 1/3702 Physiological parameters A61N1/365 takes precedence; evoked response A61N1/371

Abstract

A method and system for classifying tachyarrhythmia episodes as associated or disassociated. Primary and auxiliary depolarizations are detected from different cardiac regions during a tachycardia episode. A first time interval is positioned to surround each of one or more primary depolarizations, including auxiliary depolarizations that occur in the first time interval. The auxiliary depolarizations occurring in the first time interval are then counted. Based on the number and the location of the auxiliary depolarizations counted in the first time intervals, the one or more primary depolarizations and the auxiliary depolarizations of the tachycardia episode are classified as disassociated or associated.

Claims

1. A system, comprising:

control circuitry where the control circuitry receives a first cardiac signal and a second cardiac signal of a tachycardia episode, where the first cardiac signal includes indications of depolarizations in a first cardiac area and the second cardiac signal includes indications of depolarizations in a second cardiac area, the control circuitry including;

a first depolarization detector circuit to detect the occurrence of primary

depolarizations in the first cardiac signal;

a second depolarization detector circuit to detect the occurrence of auxiliary depolarizations in the second cardiac signal;

a cycle length interval circuit coupled to the first depolarization detector circuit

and the second depolarization detector circuit, where the cycle length interval circuit measures cardiac cycle lengths including one of intervals between consecutively detected primary depolarizations and intervals between consecutively detected auxiliary depolarizations;

a cardiac data analyzing circuit coupled to the first depolarization detector circuit, the second depolarization detector circuit, and the cycle length interval circuit, where the cardiac data analyzing circuit calculates a first time interval based on the cardiac cycle lengths;

a cardiac depolarization counting circuit coupled to the first depolarization detector circuit, the second depolarization detector circuit, and the cardiac data analyzing circuit, where the cardiac depolarization counting circuit counts the number of auxiliary depolarizations that occur during the first time interval positioned to surround each of one or more primary depolarizations of the primary depolarizations; and

a microprocessor coupled to the cardiac depolarization counting circuit, where the microprocessor classifies the one or more primary depolarizations and the auxiliary depolarizations of the tachycardia episode as either associated or disassociated based on the number of auxiliary depolarizations.

2. The system of claim 1, where the number of auxiliary depolarizations counted by the cardiac depolarization counting circuit is a first number (K) of auxiliary depolarizations counted during a first-half of the first time interval that precedes each of the one or more primary depolarizations;

and

the microprocessor classifies the one or more primary depolarizations and the auxiliary depolarizations of the tachycardia episode as either associated or disassociated based on K.

3. The system of claim 2, where the cardiac depolarization counting circuit counts a second number (J) of auxiliary depolarizations during a second-half of the first time interval subsequent to each of the one or more primary depolarizations, and the microprocessor classifies the one or more primary depolarizations and the auxiliary depolarizations as associated when K and J are statistically different at a predetermined confidence level.

4. The system of claim 3, where the microprocessor classifies the one or more primary depolarizations and the auxiliary depolarizations as disassociated when K and J are not statistically different at the predetermined confidence level.

5. The system of claim 2, where the cardiac depolarization counting circuit counts a total number (N) of auxiliary depolarizations during the first time interval for each of the one or more primary depolarizations, and the microprocessor calculates K/N and classifies the one or more primary depolarizations and the auxiliary depolarizations of the tachycardia episode as either associated or disassociated based on K/N.

6. The system of claim 5, where the microprocessor classifies the one or more primary depolarizations and the auxiliary depolarizations of the tachycardia episode as disassociated when K/N is equal to approximately one-half (0.5).

7. The system of claim 5, where the microprocessor classifies the one or more primary depolarizations and the auxiliary depolarizations of the tachycardia episode as associated when K/N is not equal to approximately one-half (0.5).

8. The system of claim 5, where the microprocessor classifies the one or more primary depolarizations and the auxiliary depolarizations of the tachycardia episode as associated when K/N is statistically different from one-half (0.5) at a predetermined confidence level and where the microprocessor classifies the one or more primary depolarizations and the auxiliary depolarizations of the tachycardia episode as disassociated when K/N is not statistically different from one-half (0.5) at the predetermined confidence level.

9. The system of claim 8, where the microprocessor classifies the one or more primary depolarizations and the auxiliary depolarizations of the tachycardia episode as disassociated when K is less than or equal to K_low or when K is greater than or equal to K_high, and classifies the one or more primary depolarizations and the auxiliary depolarizations of the tachycardia episode as associated when K is between Kl_ow and K_high.

10. The system of claim 1, where the first cardiac area includes at least one ventricular chamber and the primary depolarizations are ventricular depolarizations, and the second cardiac area includes at least one atrial chamber and the auxiliary depolarizations are atrial depolarizations.

11. The system of claim 1, where the first cardiac area includes at least one atrial chamber and the primary depolarizations are atrial depolarizations, and the second cardiac area includes at least one ventricular chamber and the auxiliary depolarizations are ventricular depolarizations.

12. The system of claim 1, where the first cardiac area includes a first atrial chamber and the primary depolarizations are first atrial chamber depolarizations, and the second cardiac area includes a second atrial chamber and the auxiliary depolarizations are second atrial chamber depolarizations.

13. The system of claim 1, where both the first cardiac area and the second cardiac area include an atrial chamber, where the primary depolarizations are atrial chamber first area depolarizations and the auxiliary depolarizations are atrial chamber second area depolarizations.

14. The system of claim 1, where the first cardiac area includes a first ventricular chamber and the primary depolarizations are first ventricular chamber depolarizations, and the second cardiac area includes a second ventricular chamber and the auxiliary depolarizations are second ventricular chamber depolarizations.

15. The system of claim 1, where both the first cardiac area and the second cardiac area include an ventricular chamber, where the primary depolarizations are ventricular chamber first area depolarizations and the auxiliary depolarizations are ventricular chamber second area depolarizations.

16. The system of claim 1, where the cardiac data analyzing circuit positions a first time interval to surround each of one or more primary depolarizations of the primary depolarizations.

17. The system of claim 16, where the cycle length interval circuit measures auxiliary cycle lengths between pairs of consecutively sensed auxiliary depolarizations in a measurement window interval, and calculates an average value (XX_avg) and a standard deviation value (XX_sd) of the auxiliary cycle lengths for the consecutively sensed auxiliary depolarizations in the measurement window interval, and where the cardiac data analyzing circuit calculates the first time interval, where the first time interval is equal to (XX_avg−

Y*XX_sd), where Y is a predetermined constant.

18. The system of claim 17, where the measurement window interval has a predetermined duration.

19. The system of claim 17, where the measurement window interval has a duration sufficient to detect a predetermined number of primary depolarizations.

20. The system of claim 17, where the microprocessor compares K to threshold values K_low and K_high to determine when primary and auxiliary depolarizations are classified with a predetermined confidence level and extends the measurement window interval when the relationship of K to threshold values K_low and K_high shows that primary and auxiliary depolarizations are not classified with the predetermined confidence level.

21. The system of claim 20, where the microprocessor repeats the measurement window interval when the relationship of K to threshold values K_low and K_high shows that primary and auxiliary depolarizations are not classified with the predetermined confidence level.

22. The system of claim 20, where the microprocessor stops the measurement window interval when the relationship of K to threshold values K_low and K_high shows that primary and auxiliary depolarizations are classified with the predetermined confidence level.

23. The system of claim 1, where the first time interval includes a midpoint location, and the cardiac data analyzing circuit positions the first time interval with the midpoint location of the first time interval at each primary depolarization of the one or more primary depolarizations.

24. The system of claim 1, where the cardiac data analyzing circuit positions a second time interval to surround each of one or more auxiliary depolarizations of the auxiliary depolarizations;

the cardiac depolarization counting circuit counts the number of primary depolarizations that occur during the second time interval; and

where the microprocessor classifies the one or more primary depolarizations and the one or more auxiliary depolarizations of the tachycardia episode as either associated or disassociated based on the number of primary depolarizations and the number of auxiliary depolarizations.

25. The system of claim 24, where the first time interval and the second time interval includes a midpoint location, and the cardiac data analyzing circuit positions the first time interval with the midpoint location of the first time interval at each primary depolarization of the one or more primary depolarizations and positions the second time interval with the midpoint location of the second timer interval at each auxiliary depolarization of the one or more auxiliary depolarizations.

26. The system of claim 24, where the cardiac depolarization counting circuit counts a first number (K) of auxiliary depolarizations which occur during a first-half of the first time interval that precedes each of the one or more primary depolarizations, counts a total number (N) of auxiliary depolarizations during the first time interval for each of the one or more primary depolarizations, counts a first number (L) of primary depolarizations which occur during a first-half of the second time interval that precedes each of the one or more auxiliary depolarizations, and counts a total number (M) of primary depolarizations during the second time interval for each of the one or more auxiliary depolarizations;

and

where the microprocessor makes a first classification of the one or more primary depolarizations and the one or more auxiliary depolarizations of the tachycardia episode as either associated or disassociated based on K and N, makes a second classification of the one or more primary depolarizations and the one or more auxiliary depolarizations of the tachycardia episode as either associated or disassociated based on L and M, and makes an overall classification of the tachycardia episode as either associated or disassociated based on the first classification and the second classification.

27. The system of claim 26, where the microprocessor classifies the tachycardia episode as associated when the first classification and the second classification are classified as associated.

28. The system of claim 26, where the microprocessor classifies the tachycardia episode as disassociated when the first classification and the second classification are classified as disassociated.

29. The system of claim 26, where the microprocessor classifies the tachycardia episode as associated when either the first classification or the second classification are classified as associated.

30. The system of claim 26, where the microprocessor classifies the tachycardia episode as disassociated when either the first classification or the second classification are classified as disassociated.

31. The system of claim 26, where the microprocessor calculates a statistical significance for each of the first classification and the second classification, and classifies the tachycardia episode as associated when the first classification and the second classification have different classifications and the associated classification has a higher statistical significance than the disassociated classification.

32. The system of claim 26, where the microprocessor calculates a statistical significance for each of the first classification and the second classification, and classifies the tachycardia episode as disassociated when the first classification and the second classification have different classifications and the disassociated classification has a higher statistical significance than the associated classification.

33. A method, comprising:

sensing at least one cardiac signal of a tachycardia episode, where the at least one cardiac signal includes auxiliary depolarizations and primary depolarizations;

measuring cardiac cycle lengths, where the cardiac cycle lengths include one of intervals between consecutive auxiliary depolarizations and intervals between consecutive primary depolarizations;

calculating a first time interval based on the cardiac cycle lengths;

positioning the first time interval to surround one or more primary depolarizations;

counting auxiliary depolarizations in the first time interval; and

classifying the one or more primary depolarizations and the auxiliary depolarizations of the tachycardia episode as disassociated or associated based on the auxiliary depolarizations counted in the first time interval.

34. The method of claim 33, where sensing at least one cardiac signal includes sensing a first cardiac signal and a second cardiac signal, where the first cardiac signal includes the primary depolarizations and the second cardiac signal includes the auxiliary depolarizations;

and

sensing the primary depolarizations in the first cardiac signal and the auxiliary depolarizations in the second cardiac signal.

35. The method of claim 33, including:

measuring auxiliary cycle lengths between pairs of consecutively sensed auxiliary depolarizations in a measurement window interval;

calculating an average value (XX_avg) and a standard deviation value (XX_sd) of the auxiliary cycle lengths for the consecutively sensed auxiliary depolarizations in the measurement window interval; and

calculating the first time interval, where the first time interval has a value equal to;

36. The method of claim 35, including programming a predetermined duration for the measurement window interval.

37. The method of claim 35 including programming a predetermined number of primary depolarizations that define the duration of the measurement window interval.

38. The method of claim 35, where the first time interval includes a first-half, and counting auxiliary depolarizations during the first time interval includes:

counting a first number (K) of auxiliary depolarizations during the first-half of the first time interval for each of the one or more primary depolarizations;

comparing K to threshold values K_low and K_high to classify the primary and auxiliary depolarizations at a predetermined confidence level; and

extending the measurement window interval when the relationship of K to threshold values K_low and K_high shows that primary and auxiliary depolarizations are not classified with the predetermined confidence level.

39. The method of claim 35, where the first time interval includes a first-half, and counting auxiliary depolarizations during the first time interval includes:

counting a first number (K) of auxiliary depolarizations during the first-half of the first time interval for each of the one or more primary depolarizations; and

classifying the primary and auxiliary depolarizations as associated when K is less than or equal to K_low or greater than or equal to K_high.

40. The method of claim 35, where the first time interval includes a first-half, and counting auxiliary depolarizations during the first time interval includes:

counting a first number (K) of auxiliary depolarizations during the first-half of the first time interval for each of the one or more primary depolarizations; and

classifying the primary and auxiliary depolarizations as disassociated when K is between K_low and K_high.

41. The method of claim 33, where the first time interval includes a first-half, and counting auxiliary depolarizations during the first time interval includes:

counting a total number (N) of auxiliary depolarizations during the first time interval for each of the one or more primary depolarizations;

counting a first number (K) of auxiliary depolarizations during the first-half of the first time interval for each of the one or more primary depolarizations;

calculating K/N; and

p1 where classifying the one or more primary depolarizations and the auxiliary depolarizations includes classifying the one or more primary depolarizations and the auxiliary depolarizations of the tachycardia episode as disassociated or associated based on K/N.

42. The method of claim 41, where classifying the one or more primary depolarizations and the auxiliary depolarizations includes classifying the one or more primary depolarizations and the auxiliary depolarizations of the tachycardia episode as disassociated when K/N is equal to approximately one-half (0.5).

43. The method of claim 41, where classifying the one or more primary depolarizations and the auxiliary depolarizations includes classifying the one or more primary depolarizations and the auxiliary depolarizations of the tachycardia episode as associated when K/N is not equal to approximately one-half (0.5).

44. The method of claim 33, where the first time interval includes a midpoint location, and includes positioning the midpoint of the first time interval at each of the one or more primary depolarizations.

45. The method of claim 44, where the first time interval includes a first-half which precedes the midpoint location and a second-half which is subsequent the midpoint location, where counting auxiliary depolarizations in the first time interval includes counting a first number of auxiliary depolarizations in the first-half of the first time interval for the one or more primary depolarizations, and a second number of auxiliary depolarizations in the second-half of the first time interval for the one or more primary depolarizations, and determining whether the first number and the second number are statistically different at a predetermined confidence level.

46. The method of claim 45, where classifying the one or more primary depolarizations and the auxiliary depolarizations of the tachycardia episode includes classifying the one or more primary depolarizations and the auxiliary depolarizations as associated when the number of auxiliary depolarizations in the first-half of the first time interval and the second-half of the first time interval for the one or more primary depolarizations are statistically different at the predetermined confidence level.

47. The method of claim 45, where classifying the one or more primary depolarizations and the auxiliary depolarizations of the tachycardia episode includes classifying the one or more primary depolarizations and the auxiliary depolarizations as disassociated when the number of auxiliary depolarizations in the first-half of the first time interval and the second-half of the first time interval for the one or more primary depolarizations are not statistically different at the predetermined confidence level.

48. The method of claim 45, including calculating the first-half and the second-half of the first time interval with the equation:

49. The method of claim 45, including

counting a first number of primary depolarizations during a first-half of a second time interval for the one or more auxiliary depolarizations;

counting a second number of primary depolarizations during a second-half of the second time interval for the one or more auxiliary depolarizations; and

classifying the one or more primary depolarization and auxiliary depolarizations and the one or more auxiliary depolarizations and primary depolarizations as either associated or disassociated based on the first number or primary depolarizations, the second number of primary depolarizations, the first number of auxiliary depolarizations and the second number of auxiliary depolarizations.

50. The method of claim 33, including

counting primary depolarizations in a second time interval surrounding the one or more auxiliary depolarizations;

and

classifying the one or more primary depolarizations and the one or more auxiliary depolarizations of the tachycardia episode as disassociated or associated based on the auxiliary depolarizations counted in the first time interval for the one or more primary depolarizations and the primary depolarizations counted in the second time interval.

51. The method of claim 50, counting a first number (K) of auxiliary depolarizations which occur during a first-half of the first time interval that precedes each of the one or more primary depolarizations;

counting a total number (N) of auxiliary depolarizations during the first time interval for each of the one or more primary depolarizations;

counting a first number (L) of primary depolarizations which occur during a first-half of the second time interval that precedes each of the one or more auxiliary depolarizations;

counting a total number (M) of primary depolarizations during the second time interval for each of the one or more auxiliary depolarizations; and

making a first classification of the one or more primary depolarizations and the one or more auxiliary depolarizations of the tachycardia episode as either associated or disassociated based on K and N;

making a second classification of the one or more primary depolarizations and the one or more auxiliary depolarizations of the tachycardia episode as either associated or disassociated based on L and M; and

classifying the tachycardia episode as either associated or disassociated based on the first classification and the second classification.

52. The method of claim 50, where classifying the tachycardia episode includes classifying the tachycardia episode as associated when the first classification and the second classification are classified as associated.

53. The method of claim 50, where classifying the tachycardia episode includes classifying the tachycardia episode as disassociated when the first classification and the second classification are classified as disassociated.

54. The method of claim 50, where classifying the tachycardia episode includes classifying the tachycardia episode as associated when either the first classification or the second classification are classified as associated.

55. The method of claim 50, where classifying the tachycardia episode includes classifying the tachycardia episode as disassociated when either the first classification and the second classification are classified as disassociated.

56. The method of claim 50, including calculating a statistical significance for each of the first classification and the second classification;

and classifying the tachycardia episode as associated when the first classification and the second classification have different classifications and the associated classification has a higher statistical significance than the disassociated classification.

57. The method of claim 50, including calculating a statistical significance for each of the first classification and the second classification;

and classifying the tachycardia episode as disassociated when the first classification and the second classification have different classifications and the disassociated classification has a higher statistical significance than the associated classification.