System and method for a classifying cardiac complexes

• US 6,438,410 B2
• Filed: 05/03/2001
• Issued: 08/20/2002
• Est. Priority Date: 02/12/1999
• Status: Expired due to Fees

• 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
• Application Number:
  US09/848,605
• Publication Number:
  US 20020019593A1
• Time in Patent Office: 474 Days
• Field of Search: 600/515, 600/516, 600/517, 600/518
• US Class Current: 600/516
• 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 method classify 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 cardiac signal and a second cardiac signal;

detecting a first cardiac complex in the first cardiac signal and a second cardiac complex in the second cardiac signal, the first and second cardiac complexes associated with the same heart contraction;

creating at least one first template cardiac complex for the first cardiac signal and at least one second template cardiac complex for the second cardiac signal, wherein each of the first and second template cardiac complexes represents a predetermined cardiac rhythm state;

comparing the first cardiac complex to the first template cardiac complex and the second cardiac complex to the second template cardiac complex to determine whether the heart contraction is representative of the predetermined cardiac rhythm state; and

classifying the heart contraction as being representative of the predetermined cardiac rhythm state based on the comparison of the first cardiac complex to the first template cardiac complex and the second cardiac complex to the second template cardiac complex.

2. The method of claim 1, further comprising determining a therapy at least in part in response to the classification of the heart contraction.

3. The method of claim 2, furthering comprising delivering, at least in part in response to the classification of the heart contraction, at least one of:

a cardiac pacing therapy;

a cardioversion therapy; and

a defibrillation therapy.

4. The method of claim 1, wherein the predetermined cardiac rhythm state includes at least one of:

a normal sinus rhythm (NSR);

a ventricular tachycardia (VT);

a supraventricular tachycardia (SVT);

a premature ventricular contraction (PVC); and

an ischemic event.

5. The method of claim 1, wherein the first and second template cardiac complexes are template morphologies and comparing the first and second cardiac complexes to the corresponding first and second template cardiac complexes comprises comparing morphologies of the first and second cardiac complexes to the respective first and second template morphologies.

6. The method of claim 5, further comprising deriving the first and second template morphologies from cardiac complexes detected in the first and second cardiac signals, respectively.

7. The method of claim 6, wherein the first and second template morphologies are each derived from at least one repeatably identifiable feature of cardiac complexes sensed from a patient manifesting at least one of the predetermined cardiac rhythm states.

8. The method of claim 6, wherein the first and second template morphologies are each derived from at least one repeatably identifiable feature of cardiac complexes sensed from a population of patients manifesting at least one of the predetermined cardiac rhythm states.

9. The method of claim 5, wherein comparing the morphologies comprises comparing at least one predetermined feature in the first and second cardiac complexes to a corresponding at least one predetermined feature in the corresponding one of the first and second template morphologies.

10. The method of claim 9, wherein the predetermined feature includes at least one of:

a maximum signal deflection;

a predetermined signal deviation from a baseline; and

a signal return to the baseline for a predetermined time period.

11. The method of claim 10, further comprising aligning the predetermined feature in the first and second cardiac complexes and the respective first and second morphologies.

12. The method of claim 11, furthering comprising utilizing a correlation waveform analysis algorithm for comparing the first and second cardiac complexes to the respective first and second morphologies.

13. A method, comprising:

monitoring a first cardiac signal and a second cardiac signal;

detecting a first cardiac complex in the first cardiac signal and a second cardiac complex in the second cardiac signal, the first and second cardiac complexes associated with the same heart contraction;

locating at least one first predetermined feature in the first cardiac complex and at least one second predetermined feature in the second cardiac complex;

generating at least one characteristic quantity as a function of a position of at least one of the first and second predetermined features; and

classifying the heart contraction as being representative of a predetermined cardiac rhythm state based at least in part on the characteristic quantity.

14. The method of claim 13, further comprising determining a therapy at least in part in response to the classification of the heart contraction.

15. The method of claim 14, furthering comprising delivering, at least in part in response to the classification of the heart contraction, at least one of:

a cardiac pacing therapy;

a cardioversion therapy; and

a defibrillation therapy.

16. The method of claim 13, wherein the cardiac signals are monitored to provide a substantially simultaneous view of a cardiac complex from at least two different cardiac locations.

17. The method of claim 13, wherein the predetermined cardiac rhythm state includes at least one of:

a normal sinus rhythm (NSR);

a ventricular tachycardia (VT);

a supraventricular tachycardia (SVT);

a premature ventricular contraction (PVC); and

an ischemic event.

18. The method of claim 13, wherein at least one of the first and second predetermined features is at least one of:

a maximum signal deflection;

a predetermined signal deviation from a baseline; and

a signal return to the baseline for a predetermined time period.

19. The method of claim 13, further comprising:

creating at least one classification quantity, wherein the classification quantity represents a predetermined cardiac rhythm state; and

comparing the characteristic quantity to the classification quantity to determine whether the characteristic quantity is representative of the predetermined cardiac rhythm state;

wherein the classifying the heart contraction is based at least in part on the outcome of the comparing the characteristic quantity to the classification quantity.

20. The method of claim 19, wherein the characteristic quantity comprises a characteristic scalar value, the classification quantity comprises a classification scalar value, and the comparing the characteristic quantity to the classification quantity comprises comparing the characteristic scalar value to the classification scalar value.

21. The method of claim 20, further comprising deriving the classification scalar value from cardiac complexes detected in the first and second cardiac signals.

22. The system of claim 19, wherein the characteristic scalar value is representative, at least in part, of at least one of:

a time associated with at least one of the first and second predetermined features;

a time difference between the first and second predetermined features;

an amplitude value of at least one of the first and second predetermined features; and

a time difference between two predetermined features in one cardiac signal.

23. The method of claim 19, wherein the classification scalar value is population-based.

24. The method of claim 19, wherein the classification scalar value is individual-based.

25. The method of claim 19, wherein:

the characteristic quantity is a characteristic vector comprising two or more scalar values;

the classification quantity is a classification vector; and

comparing the characteristic quantity to the classification quantity comprises comparing the characteristic vector to the classification vector.

26. The method of claim 25, wherein classifying the heart contraction comprises:

determining a correlation between the characteristic vector and the classification vector; and

classifying the cardiac complex as being representative of the predetermined cardiac rhythm state if the correlation exceeds a predetermined threshold.

27. The method of claim 26, wherein determining the correlation comprises determining a mean square error value between the characteristic vector and the classification vector.

28. A system, comprising

an amplifier to sense first and second cardiac signals;

a detector, coupled to the amplifier, to detect first and second cardiac complexes in the respective first and second cardiac signals, the first and second cardiac complexes associated with the same heart contraction;

a morphology analyzer, coupled to the detector, to locate at least one predetermined feature in a morphology of each of the first and second cardiac complexes;

a comparator, coupled to the morphology analyzer, to compare the first and second cardiac complexes with respective first and second template cardiac complexes; and

a processor, coupled to the comparator, to classify the heart contraction.

29. The system of claim 28, wherein the predetermined feature includes at least one of:

a maximum signal deflection;

a predetermined signal deviation from a baseline; and

a signal return to the baseline for a predetermined time period.

30. The system of claim 29, wherein the morphology analyzer further comprises at least one scalar value that is representative, at least in part, of at least one of:

a time associated with at least one of the first and second predetermined features;

a time difference between the first and second predetermined features;

an amplitude value of at least one of the first and second predetermined features; and

a time difference between two predetermined features in one cardiac signal.

31. The system of claim 29, further comprising a template generator, coupled to the comparator, to generate at least one template morphology for each of the first and second cardiac signals, wherein the template morphology represents a predetermined cardiac rhythm state that includes at least one of:

a normal sinus rhythm (NSR);

a ventricular tachycardia (VT);

a supraventricular tachycardia (SVT);

a premature ventricular contraction (PVC); and

an ischemic event.

32. The system of claim 31, wherein the template generator comprises a characterization vector comprising at least two scalar values.

33. The system of claim 28, further comprising a cardiac rhythm analyzer, coupled to the amplifier, to analyze at least one of the first and second cardiac signals to detect a predetermined cardiac condition.

34. The system of claim 33, wherein the cardiac rhythm analyzer comprises a heart rate detector.

35. The system of claim 28, wherein the comparator includes a correlation waveform analysis algorithm to compare the morphologies of the first and second cardiac complexes with respective first and second template morphologies.

36. The system of claim 28, wherein the comparator comprises comparing a characteristic quantity to a classification quantity.

37. The system of claim 36, wherein the comparator comprises comparing a characteristic scalar value to a classification scalar value.

38. The system of claim 36, wherein the comparator comprises comparing a characteristic vector to a classification vector, wherein the characteristic vector comprises at least two scalar values and the classification vector comprises at least two scalar values.

39. The system of claim 28, further comprising a therapy delivery circuit, wherein the therapy delivery circuit comprises at least one of:

a pace output circuit; and

a cardioversion and defibrillation output circuit.