QRST subtraction using an adaptive template for analysis of TU wave obscured atrial activity

• US 6,615,075 B2
• Filed: 03/14/2001
• Issued: 09/02/2003
• Est. Priority Date: 03/15/2000
• Status: Expired due to Term

• Current Assignee: Regents of the University of California (University of California)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Mlynash, Michael D., Lesh, Michael D., Groenewegen, Arne Sippens
• Primary Examiner(s): WOLFE JR, WILLIS RAY
• Application Number:
  US09/809,719
• Publication Number:
  US 20010056245A1
• Time in Patent Office: 902 Days
• Field of Search: 600/508, 600/509, 600/513, 600/515, 600/516, 600/517, 600/518, 600/519, 705/2, 705/3
• US Class Current: 600/513
• CPC Class Codes: A61B 5/061 Determining position of a probe within the body employing means separate from the probe, e.g. sensing internal probe position employing impedance electrodes on the surface of the body A61B1/00158 takes precedence
• CPC Class Codes: A61B 5/282 Holders for multiple electrodes for introduction into the body A61B5/287
• CPC Class Codes: A61B 5/35 by template matching
• CPC Class Codes: A61B 5/6831 Straps, bands or harnesses
• CPC Class Codes: A61B 5/7232 involving compression of the physiological signal, e.g. to extend the signal recording period
• 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: G16H 50/20 for computer-aided diagnosis, e.g. based on medical expert systems

Abstract

The present invention provides a noninvasive localization, characterization and classification apparatus and method for cardiac arrhythmias. The invention enables discrete isolation of the intricate spatial and temporal detail in morphology of the atrial activity of interest from superimposed ventricular activity of a preceding heartbeat in a particular arrhythmia. An adaptive QRST subtraction template is used that is modulated for discrepancies in voltage and rate between the QRST template and arrhythmia signal. The QRST template modulation is accomplished by using one or more fiducial points and windows that are annotated in both the QRST template and the arrhythmia signal. The invention includes, but is not limited to, the isolation of atrial activity that are commonly known as: (1) P waves in case of focal atrial fibrillation, atrial tachycardia, and orthodromic AV reentrant tachycardia; (2) fibrillation waves in case of chronic atrial fibrillation; and (3) flutter waves in case of atrial flutter.

Claims

1. A noninvasive arrhythmia localization and classification apparatus, comprising a signal processor which is adapted to receive electrical heart signals indicative of a heart'"'"'s atrial and ventricular activity wherein said signal analyzer is further adapted to:

(a) receive an arrhythmia signal that contains said electrical heart signals obtained during an arrhythmia and said atrial activity is obscured by said ventricular activity;

(b) receive at least two template signals to construct a QRST template;

(c) identify and annotate one or more fiducial points and windows of said arrhythmia signal to create an annotated arrhythmia signal;

(d) identify and annotate one or more fiducial points and windows of said QRST template to create an annotated QRST template;

(e) align said annotated QRST template with said annotated arrhythmia signal using said one or more fiducial points and windows and thereby creating an aligned QRST template;

(f) resample and modulate said aligned QRST template to compensate for on one or more discrepancies between said aligned QRST template and said annotated arrhythmia signal using said one or more fiducial points and windows and thereby creating a resampled and modulated QRST template; and

(g) isolate said atrial activity from said arrhythmia signal obtained by a subtraction of said resampled and modulated QRST template from said arrhythmia signal.

2. The apparatus as set forth in claim 1, wherein said at least two template signals are obtained during a sinus rhythm.

3. The apparatus as set forth in claim 1, wherein said at least two template signals are obtained during an atrial overdrive pacing.

4. The apparatus as set forth in claim 1, wherein said at least two template signals are obtained during said arrhythmia and said arrhythmia signal is obtained during atrial fibrillation.

5. The apparatus as set forth in claim 1, further comprising at least one sensor which is adapted to detect said electrical heart signals and to transmit said electrical heart signals to said signal processor.

6. The apparatus as set forth in claim 1, wherein said at least one sensor is adapted to be placed on a suitable body surface of a subject.

7. The apparatus as set forth in claim 1, further comprising an analog-to-digital converter which is adapted to convert said electrical heart signals into digital signals.

8. The apparatus as set forth in claim 1, wherein said signal processor is adapted to annotate one or more fiducial points and windows of a QRS complex of said QRST template.

9. The apparatus as set forth in claim 1, wherein said signal processor is adapted to annotate one or more fiducial points and windows for a T wave of said QRST template.

10. The apparatus as set forth in claim 1, wherein said signal processor is adapted to annotate one or more fiducial points and windows of a QRS complex of said arrhythmia signal.

11. The apparatus as set forth in claim 1, wherein said signal processor is adapted to annotate one or more fiducial points and windows for a T wave of said arrhythmia signal.

12. The apparatus as set forth in claim 1, wherein said signal processor is adapted to apply filtering to eliminate possible QRS leakage after said subtraction.

13. The apparatus as set forth in claim 1, wherein said signal processor is adapted to apply filtering of said electrical heart signals.

14. The apparatus as set forth in claim 13, wherein said signal processor is adapted to apply a high-pass frequency filter to remove baseline drift.

15. The apparatus as set forth in claim 13, wherein said signal processor is adapted to apply a low-pass frequency filter to remove high frequency artifacts.

16. The apparatus as set forth in claim 13, wherein said signal processor is adapted to apply a notch filter to remove line frequency interference.

17. The apparatus as set forth in claim 1, wherein said signal processor is adapted to resample and modulate said QRST template for a TU complex discrepancy in a rate and at least one amplitude compared to said arrhythmia signal to create said resampled and modulated QRST template.

18. The apparatus as set forth in claim 17, wherein said signal processor is adapted to adjust said fiducial points and windows using signal sliding means to resample and modulate said QRST template.

19. The apparatus as set forth in claim 17, wherein said signal processor is adapted to adjust said fiducial points and windows using signal stretching or compressing means to resample and modulate said QRST template.

20. The apparatus as set forth in claim 17, wherein said signal processor is adapted to adjust said fiducial points and windows using variable signal adjusting means to resample and modulate said QRST template.

21. The apparatus as set forth in claim 1, wherein said signal processor is adapted to compute at least one analysis parameter of said atrial activity from said isolated atrial activity of said arrhythmia signal.

22. The apparatus as set forth in claim 21, wherein said signal processor is adapted to determine a localization or classification of said arrhythmia by a comparison of said at least one analysis parameter of said isolated atrial activity with a database containing said analysis parameters of said isolated atrial activity.

23. The apparatus as set forth in claim 21, wherein said arrhythmia signal is selected from the group focal atrial fibrillation, atrial tachycardia and orthodromic atrioventricular reentrant tachycardia and said isolated atrial activity is a P wave.

24. The apparatus as set forth in claim 23, wherein said signal processor is adapted to determine a localization of said arrhythmia by a comparison of said at least one analysis parameter of said isolated P wave with a database containing said analysis parameters of said P wave.

25. The apparatus as set forth in claim 21, wherein said arrhythmia is an atrial fibrillation and said isolated atrial activity is at least one fibrillation wave.

26. The apparatus as set forth in claim 25, wherein said signal processor is adapted to determine a classification of said arrhythmia by a comparison of said analysis parameter of said at least one isolated fibrillation wave with a database containing said analysis parameters of said fibrillation wave.

27. The apparatus as set forth in claim 21, wherein said arrhythmia is atrial flutter and said isolated atrial activity is a flutter wave.

28. The apparatus as set forth in claim 27, wherein said signal processor is adapted to determine a classification of said arrhythmia by a comparison of said analysis parameter of said isolated flutter wave with a database containing said analysis parameters of said flutter wave.

29. The apparatus as set forth in claim 1, wherein said signal processor is adapted to select at least two QRST complexes from said at least two template signals to create said QRST template.

30. The apparatus as set forth in claim 29, wherein said signal processor is adapted to compute an average of said selected QRST complexes by averaging their QRST intervals to create said QRST template.

31. The apparatus as set forth in claim 29, wherein said signal processor is adapted to detect a QRS complex in each said QRST complex.

32. The apparatus as set forth in claim 31, wherein said signal processor is adapted to select at least one dominant QRS morphology.

33. The apparatus as set forth in claim 32, wherein said signal processor is adapted to add at least one said QRST complex to said QRST complex with said at least one dominant QRS morphology based on at least one criteria.

34. The apparatus as set forth in claim 33, wherein said criteria is a QRS pattern.

35. The apparatus as set forth in claim 33, wherein said criteria is a RR interval length.

36. The apparatus as set forth in claim 35, wherein said signal processor is adapted to mark one or more fiducial points and windows to determine said RR interval length of selected said QRST complexes to create said QRST template.

37. The apparatus as set forth in claim 35, wherein said signal processor is adapted to compute an average of said RR interval length of said selected QRST complexes to create said QRST template.

38. A method for noninvasive arrhythmia localization and classification, comprising the steps of:

(a) providing a signal processor for receiving electrical heart signals indicating a heart'"'"'s atrial and ventricular activity;

(b) receiving at least two template signals for constructing a QRST template;

(c) receiving an arrhythmia signal containing said electrical heart signals obtained during an arrhythmia and said atrial activity is obscured by said ventricular activity;

(d) identifying and annotating one or more fiducial points and windows of said QRST template and creating an annotated QRST template;

(e) identifying and annotating one or more fiducial points and windows of said arrhythmia signal and creating an annotated arrhythmia signal;

(f) aligning said annotated QRST template to said annotated arrhythmia signal using said one or more fiducial points and windows and thereby creating an aligned QRST template;

(g) resampling and modulating said aligned QRST template to compensate for on one or more discrepancies between said aligned QRST template and said annotated arrhythmia signal using said one or more fiducial points and windows and thereby creating a resampled and modulated QRST template; and

(h) isolating said atrial activity from said arrhythmia signal obtained by subtracting said resampled and modulated QRST template from said arrhythmia signal.

39. The method as set forth in claim 38, wherein said at least two template signals for constructing a QRST template are obtained during a sinus rhythm.

40. The method as set forth in claim 38, wherein said at least two template signals for constructing a QRST template are obtained during an atrial overdrive pacing.

41. The method as set forth in claim 38, wherein said at least two template signals for constructing a QRST template are obtained during said arrhythmia and said arrhythmia signal is obtained during an atrial fibrillation.

42. The method as set forth in claim 38, further comprising the step of providing at least one sensor for detecting said electrical heart signals and transmitting said electrical heart signals to said signal processor.

43. The method as set forth in claim 38, wherein said step of providing at least one sensor further comprises the step of placing said at least one sensor on a suitable body surface of a subject.

44. The method as set forth in claim 38, further comprising the step of providing an analog-to-digital converter for converting said electrical heart signals into digital signals.

45. The method as set forth in claim 38, wherein said step of identifying and annotating one or more fiducial points and windows of said QRST template further comprises the step of identifying one or more fiducial points and windows of a QRS complex of said QRST template.

46. The method as set forth in claim 38, wherein said step of identifying and annotating one or more fiducial points and windows of said QRST template further comprises the step of identifying one or more fiducial points and windows of a T wave of said QRST template.

47. The method as set forth in claim 38, wherein said step of identifying and annotating one or more fiducial points and windows of said arrhythmia signal further comprises the step of identifying one or more fiducial points and windows of a QRS complex of said arrhythmia signal.

48. The method as set forth in claim 38, wherein said step of identifying and annotating one or more fiducial points and windows of said arrhythmia signal further comprises the step of identifying one or more fiducial points and windows of a T wave of said arrhythmia signal.

49. The method as set forth in claim 38, further comprises the step of applying filtering to eliminate possible QRS leakage after said step of subtracting.

50. The method as set forth in claim 38, further comprising the step of applying filtering to said electrical heart signals.

51. The method as set forth in claim 50, wherein said step of applying filtering further comprises the step of applying high-pass frequency filtering to remove baseline drift.

52. The method as set forth in claim 50, wherein said step of applying filtering further comprises the step of applying low-pass frequency filtering to remove high frequency artifacts.

53. The method as set forth in claim 50, wherein said step of applying filtering further comprises the step of applying notch filtering to remove line frequency interference.

54. The method as set forth in claim 38, wherein said step of resampling and modulating said annotated QRST template further comprises the step of resampling and modulating said QRST template for a TU complex discrepancy in a rate and at least one amplitude compared to said arrhythmia thereby creating said resampled and modulated QRST template.

55. The method as set forth in claim 54, wherein signal processor is adapted to adjust said fiducial points and windows using signal sliding means to resample and modulate said QRST template.

56. The method as set forth in claim 54, wherein signal processor is adapted to adjust said fiducial points and windows using signal stretching means to resample and modulate said QRST template.

57. The method as set forth in claim 54, wherein signal processor is adapted to adjust said fiducial points and windows using variable signal adjusting means to resample and modulate said QRST template.

58. The method as set forth in claim 38, further comprises the step of computing at least one analysis parameter of said atrial activity from said isolated atrial activity of said arrhythmia signal.

59. The method as set forth in claim 58, further comprises the step of determining a localization or classification of said arrhythmia by comparing of said at least one analysis parameter of said isolated atrial activity with a database containing said analysis parameters of said isolated atrial activity.

60. The method as set forth in claim 58, wherein said arrhythmia signal is selected from the group focal atrial fibrillation, atrial tachycardia, and orthodromic atrioventricular reentrant tachycardia and said isolated atrial activity is a P wave.

61. The method as set forth in claim 60, further comprises the step of determining a localization of said arrhythmia by comparing of said at least one analysis parameter of said isolated P wave with a database containing said analysis parameters of said P wave.

62. The method as set forth in claim 58, wherein said arrhythmia signal is an atrial fibrillation and said isolated atrial activity is at least one fibrillation wave.

63. The method as set forth in claim 62, further comprises the step of determining a classification of said arrhythmia by comparing of said at least one analysis parameter of said at least one isolated fibrillation wave with a database containing said analysis parameters of said fibrillation wave.

64. The method as set forth in claim 58, wherein said arrhythmia signal is an atrial flutter and said isolated atrial activity is a flutter wave.

65. The method as set forth in claim 64, further comprises the step of determining a classification of said arrhythmia by comparing of said at least one analysis parameter of said isolated flutter wave with a database containing said analysis parameters of said flutter wave.

66. The method as set forth in claim 38, wherein said step of constructing a QRST template further comprises the step of selecting at least two QRST complexes for creating said QRST template.

67. The method as set forth in claim 66, wherein said step of selecting at least two QRST complexes further comprises the step of detecting a QRS complex in each said QRST complex.

68. The method as set forth in claim 67, wherein said step of constructing a QRST template further comprises the step of computing an average of said selected QRST complexes by averaging their QRST intervals for creating said QRST template.

69. The method as set forth in claim 67, wherein said step of detecting a QRS complex further comprises the step of selecting at least one dominant QRS morphology.

70. The method as set forth in claim 69, wherein said step of constructing a QRST template further comprises the step of adding said at least one QRST complex to said QRST complex with said at least one dominant QRS morphology based on at least one criteria.

71. The method as set forth in claim 70, wherein said step of adding said at least one QRST complex based on at least one criteria further comprises the step of comparing a QRS pattern and said QRS pattern is said at least one criteria.

72. The method as set forth in claim 70, wherein said step of selecting said at least one QRST complex using at least one criteria further comprises the step of comparing a RR interval length and said RR interval length is said at least one criteria.

73. The method as set forth in claim 72, wherein said step of determining a RR interval length further comprises the step of marking R wave fiducial points for determining said RR interval length of each said selected QRST complex for creating said QRST template.

74. The method as set forth in claim 73, wherein said step of using a RR interval length further comprises the step of computing an average of said RR interval length of each said selected QRST complex for creating said QRST template.