System and method for classifying cardiac complexes

• US 6,266,554 B1
• Filed: 02/12/1999
• Issued: 07/24/2001
• Est. Priority Date: 02/12/1999
• Status: Expired due to Term

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Hsu, William, Smith, Joseph Martin
• Primary Examiner(s): Layno, Carl H.
• Application Number:
  US09/249,128
• Time in Patent Office: 893 Days
• Field of Search: 600/515-518
• US Class Current: 600/515
• CPC Class Codes: A61B 5/35 by template matching
• CPC Class Codes: A61B 5/7264 Classification of physiological signals or data, e.g. using neural networks, statistical classifiers, expert systems or fuzzy systems neural networks per se G06N3/00; expert systems per se G06N5/00
• CPC Class Codes: A61N 1/3622 comprising two or more electrodes co-operating with different heart regions
• CPC Class Codes: A61N 1/3704 Circuits specially adapted therefor, e.g. for sensitivity control
• CPC Class Codes: G16H 50/20 for computer-aided diagnosis, e.g. based on medical expert systems

Abstract

A system and a method for classifying cardiac complexes based on cardiac information derived from two or more cardiac signals. Two or more cardiac signals containing cardiac complexes are monitored. A cardiac complex in the two or more cardiac signals is isolated in an analysis window. The morphology of the cardiac complex in each of the two or more cardiac signals is then compared to the morphology of a template cardiac complex representing a predetermined cardiac condition. Based on this comparison, the cardiac complex is classified as either belonging or not belonging to the predetermined cardiac condition.

Claims

1. A method, comprising:

monitoring a first signal and a second signal representative of electrical cardiac activity;

detecting a cardiac complex in each of the first signal and the second signal;

analyzing at least the first signal to detect a tachycardia episode;

when the tachycardia episode is detected, detecting the cardiac complex in the first signal and the second signal;

locating a predetermined feature in the cardiac complex detected in the first signal and a first NSR representative complex, wherein the predetermined feature includes a repeatably identifiable complex section common to the cardiac complex detected in the first signal and the first NSR representative complex;

aligning the predetermined feature in the cardiac complex detected in the first signal and the first NSR representative complex;

comparing the cardiac complex detected in the second signal to a second NSR representative complex; and

classifying the cardiac complex as an arrhythmic cardiac complex based on the comparison of the morphology of the cardiac complex in the second cardiac signal to the second NSR representative complex.

2. The method of claim 1, including detecting a plurality of normal sinus rhythm (NSR) cardiac complexes in the first signal and the second signal;

determining the first NSR representative complex from the plurality of NSR cardiac complexes detected in the first signal; and

determining the second NSR representative complex from the plurality of NSR cardiac complexes detected in the second signal.

3. The method of claim 1, where the repeatably identifiable complex section common to the cardiac complex detected in the first signal and the first NSR representative complex is a maximum deflection of the first signal.

4. The method of claim 3, where the maximum deflection is along an R-wave sensed in the cardiac complex detected in the first signal and in the first NSR representative complex.

5. The method of claim 1, where the repeatably identifiable complex section common to the cardiac complex detected in the first signal and the first NSR representative complex is a predetermined deviation of the first signal from a baseline signal indicating a beginning of the cardiac complex and the first NSR representative complex.

6. The method of claim 1, where the repeatably identifiable complex section common to the cardiac complex detected in the first signal and the first NSR representative complex is a return of the first signal to a baseline signal for each of the cardiac complex and the first NSR representative complex for a predetermined time period indicating an ending of the cardiac complex and the first NSR representative complex.

7. The method of claim 1, where the second NSR representative complex has a second NSR morphology and the cardiac complex detected in the second signal has a second signal morphology, and comparing the cardiac complex detected in the second signal to the second NSR representative complex includes comparing the second NSR morphology to the second signal morphology to determine whether the cardia complex is an arrhythmic complex.

8. The method of claim 7, where comparing the second NSR morphology to the second signal morphology includes utilizing a correlation waveform analysis algorithm.

9. The method of claim 1, where monitoring the first signal includes sensing electrical cardiac activity through a far-field sensing channel, and sensing the second signal includes sensing electrical cardiac activity through a near-field sensing channel.

10. The method of claim 1, where monitoring the first signal includes sensing electrical cardiac activity through a near-field sensing channel, and sensing the second signal includes sensing electrical cardiac activity through a far-field sensing channel.

11. The method of claim 2, including detecting at least a portion of a QRS-complex in each of the plurality of NSR cardiac complexes;

determining the first NSR representative complex from the at least a portion of the QRS-complex in each of the plurality of NSR cardiac complexes detected in the first signal;

determining the second NSR representative complex from the at least a portion of the QRS-complex in each of the plurality of NSR cardiac complexes detected in the second signal;

detecting a QRS-complex in the cardiac complex,

comparing the second NSR morphology to the second signal morphology to determine whether the cardia complex is a ventricular tachycardia complex;

determining a percentage of the ventricular tachycardia complex in a plurality of cardiac complexes sensed during the tachycardia episode; and

applying therapy for treating a ventricular tachycardia when the percentage of the ventricular tachycardia complex exceeds a predetermined percentage threshold.

12. The method of claim 11, where the predetermined percentage threshold is 50 percent.

13. A method, comprising:

monitoring two or more cardiac signals representative of electrical cardiac activity;

detecting a cardiac complex in each of the two or more cardiac signals;

locating at least one predetermined feature in the cardiac complex for each of the two or more cardiac signals, wherein the at least one predetermined feature includes a repeatably identifiable complex portion;

generating a scalar value as a function of a position of the at least one predetermined feature for each of the two or more cardiac signals;

using the scalar values to create a cardiac vector, where the cardiac vector represents the cardiac complex comparing the cardiac vector to one or more classification vectors, where each of the one or more classification vectors represents a predetermined cardiac condition;

determining a similarity coefficient from each comparison of the cardiac vector and the one or more classification vectors; and

classifying the cardiac complex as the predetermined cardiac condition when the cardiac complex similarity coefficient exceed a predetermined threshold.

14. The method of claim 13, where detecting the cardiac complex includes isolating the cardiac complex in an analysis window.

15. The method of claim 13, where the at least one predetermined feature in the cardiac complex is a maximum deflection of the two or more cardiac signals.

16. The method of claim 13, where the at least one predetermined feature in the cardiac complex is a predetermined deviation of the two or more cardiac signals from a baseline signal indicating a beginning of the cardiac complex.

17. The method of claim 13, where the at least one predetermined feature in the cardiac complex is a return of the two or more cardiac signal to a baseline signal for a predetermined time period indicating an ending of the cardiac complex.

18. The method of claim 13, where the scalar value is a time the at least one predetermined feature of the cardiac complex occurred.

19. The method of claim 13, where the scalar value is a difference in time between the occurrence of two of the at least one predetermined feature.

20. The method of claim 13, where the scalar value is a magnitude of the position of the at least one predetermined feature for each of the two or more cardiac signals.

21. The method of claim 13, where determining a similarity coefficient comprises determining a mean square error value from each comparison of the cardiac vector and the one or more classification vectors.

22. The method of claim 13, including aligning the cardiac vector with each of the one or more classification vectors prior to comparing the cardiac vector, where the cardiac vector includes element positions occupied by the scalar values, and each of the one or more classification vectors includes an equal number of element positions as the element positions of the cardiac vector, wherein the element positions of the one or more classification vectors are occupied by scalar values representing the predetermined cardiac condition, and wherein the cardiac vector is aligned with a classification vector of the one or more classification vectors by adjusting each scalar value of the cardiac vector so one of the element positions of the cardiac vector equals a scalar value in a corresponding element position in a classification vector.

23. A method, comprising:

monitoring a first cardiac signal and a second cardiac signal;

detecting a cardiac complex in each of the first cardiac signal and the second cardiac signal;

comparing the morphology of the cardiac complex in the first cardiac signal to a first template morphology and comparing the morphology of the cardiac complex in the second cardiac signal to a second template morphology; and

classifying the cardiac complex as one of a predetermined arrhythmic complex based on the comparison of the morphology of the cardiac complex in the first cardiac signal and the second cardiac signal to the first template morphology and the second template morphology.

24. The method of claim 23, where monitoring the first cardiac signal and the second cardiac signal comprises monitoring the first cardiac signal from a first cardiac region and the second cardiac signal from a second cardiac region.

25. The method of claim 23, including deriving the first template morphology from cardiac complexes sensed from approximately the first cardiac region.

26. The method of claim 23, including deriving the second template morphology from cardiac complexes sensed from approximately the second cardiac region.

27. The method of claim 23, including:

monitoring a third cardiac signal;

detecting the cardiac complex in the third cardiac signal;

comparing the morphology of the cardiac complex in the third cardiac signal to a third template morphology; and

classifying the cardiac complex as one of the predetermined arrhythmic complex based on the comparison of the morphology of the cardiac complex in the first cardiac signal, the second cardiac signal and the third cardiac signal to the first template morphology, the second template morphology and the third template morphology.

28. The method of claim 27, where monitoring the third cardiac signal comprises monitoring the third cardiac signal from a third cardiac region.

29. The method of claim 28, including deriving the third template morphology from cardiac complexes sensed from approximately the third cardiac region.

30. A system, comprising:

at least one catheter having at least a first cardiac electrode and a second cardiac electrode;

a sensing system attached to the first cardiac electrode and the second cardiac electrode, wherein the sensing system senses a first signal and a second signal representative of electrical cardiac activity;

a morphology analyzer circuit coupled to the sensing system, wherein the morphology analyzer circuit locates a position of at least one predetermined feature in the morphology of the cardiac complex in the first signal and the second signal and generates two or more scalar values as a function of the position of the at least one predetermined feature for each of the first signal and the second signal;

a template generator coupled to the morphology analyzer, wherein the template generator circuit creates a cardiac complex vector from the two or more scalar values generated by morphology analyzer circuit; and

a signal feature comparison circuit coupled to the morphology analyzer circuit and the template generator circuit, wherein the signal feature comparison circuit compares the cardiac complex vector to one or more classification vectors to classify the cardiac complex.

31. The system of claim 30, wherein the at least one predetermined feature is a maximum deflection of the first signal and the second signal.

32. The system of claim 30, wherein the at least one predetermined feature is a predetermined deviation of the of the first signal and the second signal from a baseline signal indicating a beginning of the cardiac complex.

33. The system of claim 30, wherein the at least one predetermined feature is a return of the first signal and the second signal to a baseline signal for a predetermined time period indicating an ending of the cardiac complex.

34. The system of claim 30, wherein the scalar value is a time the at least one predetermined feature in the morphology of the cardiac complex occurred.

35. The system of claim 30, wherein the scalar value is a difference in time between the occurrence of a first predetermined feature and a second predetermined feature.

36. The system of claim 30, wherein the scalar value is a magnitude of the position of the at least one predetermined feature of the first signal and the second signal.

37. The system of claim 30, wherein the signal feature comparison circuit determines a similarity coefficient for each comparison of the cardiac vector to the one or more classification vectors, and classifies the cardiac complex as a predetermined cardiac condition when the similarity coefficient exceed a predetermined threshold.

38. The system of claim 30, wherein the signal feature comparison circuit aligns the cardiac vector with each of the one or more classification vectors prior to comparing the vectors, where the cardiac vector includes element positions occupied by the scalar values, and each of the one or more classification vectors includes an equal number of element positions as the element positions of the cardiac vector, wherein the element positions of the one or more classification vectors are occupied by scalar values representing the predetermined cardiac condition, and wherein the cardiac vector is aligned with a classification vector of the one or more classification vectors by adjusting each scalar value of the cardiac vector so one of the element positions of the cardiac vector equals a scalar value in a corresponding element position in a classification vector.

39. A system, comprising:

at least one catheter having at least a first cardiac electrode and a second cardiac electrode;

a sensing system attached to the first cardiac electrode and the second cardiac electrode, wherein the sensing system senses a first signal and a second signal representative of electrical cardiac activity;

a template generator circuit coupled to the sensing system, wherein the template generator circuit determines a first NSR representative complex and a second NSR representative complex from a plurality cardiac complexes sensed during normal sinus rhythm;

a morphology analyzer circuit coupled to the sensing system, where the morphology analyzer circuit locates a predetermined feature in a cardiac complex detected in the first signal and in the first NSR representative complex, wherein the predetermined feature includes a repeatably identifiable complex section common to the cardiac complex detected in the first signal and the first NSR representative complex; and

a signal feature comparison circuit coupled to the morphology analyzer circuit and the template generator circuit, where the signal feature comparison circuit aligns the predetermined feature in the cardiac complex monitored in the first signal with the predetermined feature on the first NSR representative complex and compares the cardiac complex monitored in the second signal to the second NSR representative complex to determine whether the cardiac complex is an arrhythmic complex.

40. The system of claim 39, where the morphology analyzer circuit locates the predetermined feature at a maximum deflection of the cardiac complex detected in the first signal and in the first NSR representative complex.

41. The method of claim 40, where the maximum deflection is along an R-wave sensed in the cardiac complex detected in the first signal and in the first NSR representative complex.

42. The system of claim 39, where the morphology analyzer circuit locates the predetermined feature at a beginning of the cardiac complex detected in the first signal and the first NSR representative complex as indicated by a predetermined deviation of the first signal from a baseline signal.

43. The system of claim 39, where the morphology analyzer circuit locates the predetermined feature at an ending of the cardiac complex detected in the first signal and the first NSR representative complex as indicated by a return of the first signal to a baseline signal for a predetermined time period.

44. The system of claim 39, where the sensing system includes a far-field sensing channel over which the first signal is monitored and a near-field sensing channel over which the second signal is monitored.

45. The system of claim 39, where the sensing system includes a near-field sensing channel over which the first signal is monitored and a far-field sensing channel over which the second signal is monitored.

46. The system of claim 39, where the second NSR representative complex has a second NSR morphology and the cardiac complex detected in the second signal has a second signal morphology, and the signal feature comparison circuit compares the second NSR morphology to the second signal morphology to determine whether the cardiac complex is an arrhythmic complex.

47. The system of claim 46, where the signal feature comparison circuit uses a correlation waveform analysis algorithm to compare the second NSR morphology to the second signal morphology.

48. The system of claim 39, where the sensing system senses at least a portion of a QRS-complex in the first signal and the second signal, the template generator circuit determines the first NSR representative complex and the second NSR representative complex from the at least a portion of the QRS-complexes sensed during normal sinus rhythm, and the signal feature comparison circuit compares the QRS-complex monitored in the second signal to the QRS-complex in the second NSR representative complex to determine whether the cardiac complex a ventricular tachycardia complex.

49. The system of claim 48, where the signal feature comparison circuit determines a percentage of ventricular tachycardia complexes for a plurality of cardiac complexes, and the control system applies therapy for treating a ventricular tachycardia when the percentage of ventricular tachycardia complexes exceeds a predetermined percentage threshold.

50. The system of claim 49, where the predetermined percentage threshold is 50 percent.