Classification of supraventricular and ventricular cardiac rhythms using cross channel timing algorithm

• US 8,315,697 B2
• Filed: 10/31/2011
• Issued: 11/20/2012
• Est. Priority Date: 07/14/1999
• Status: Expired due to Fees

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Hsu, William
• Primary Examiner(s): Evanisko, George
• Application Number:
  US13/285,483
• Publication Number:
  US 20120046566A1
• Time in Patent Office: 386 Days
• Field of Search: 600515-518, 607/4, 607/5, 607/14
• US Class Current: 600/515
• CPC Class Codes: A61B 5/363 Detecting tachycardia or bradycardia
• 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

A system and method for classifying cardiac complexes sensed during a tachycardia episode. A first cardiac signal and a second cardiac signal are sensed, where the first cardiac signal has a voltage. A first cardiac complex and a second cardiac complex of a cardiac cycle are detected in the first and second cardiac signal, respectively. A predetermined alignment feature is identified in the second cardiac complex. A datum is defined, or positioned, at a specified interval from the predetermined alignment feature of the second cardiac complex. Voltage values are then measured from the first cardiac complex at each of two or more measurement intervals from the datum. The voltage values are then compared voltage values measured from NSR cardiac complexes to classify the first cardiac complex is either a ventricular tachycardia complex or a supraventricular tachycardiac complex.

Claims

1. A method comprising:

detecting, at differing first and second locations, respective first and second cardiac complexes that are both associated with a first heart depolarization;

detecting a fiducial point in the first cardiac complex and noting a corresponding first cardiac complex fiducial point time;

establishing measurement intervals each between a feature of features in the second cardiac complex and a reference time spaced from the first cardiac complex fiducial point time;

detecting, at the first and second locations, respective third and fourth cardiac complexes that are both associated with a second heart depolarization instance;

detecting the fiducial point in the third cardiac complex and noting a corresponding third cardiac complex fiducial point time; and

measuring voltages of the fourth cardiac complex at times spaced from a further reference time by the measurement intervals, the further reference time spaced from the third cardiac complex fiducial point time.

2. The method of claim 1, further comprising:

measuring voltages of the second cardiac complex at the measurement intervals;

forming a first vector from the measured voltages of the second cardiac complex;

forming a second vector from the measured voltages of the fourth cardiac complex; and

comparing the first and second vectors.

3. The method of claim 2, further comprising detecting whether a tachyarrhythmia is present, and wherein detecting the first and second cardiac complexes is carried out in the absence of the tachyarrhythmia, and wherein detecting the third and fourth cardiac complexes is carried out in the presence of the tachyarrhythmia, and further comprising classifying the tachyarrhythmia as a supraventricular tachyarrhythmia (SVT) or a ventricular tachyarrhythmia (VT) using the comparing of the first and second vectors.

4. The method of claim 3, wherein comparing the first and second vectors comprises computing a correlation coefficient between the first and second vectors, and wherein classifying the tachyarrhythmia includes classifying the tachyarrhythmia as SVT if the correlation coefficient exceeds a predetermined threshold and classifying the tachyarrhythmia as VT if the correlation coefficient is less than or equal to the predetermined threshold.

5. The method of claim 4, wherein detecting the first and second cardiac complexes is carried out during normal sinus rhythm.

6. The method of claim 4, wherein detecting the first and second cardiac complexes is carried out during delivery of electrical pulses to a supraventricular location.

7. The method of claim 1, wherein establishing measurement intervals comprises:

defining the reference time at a specified interval from the first cardiac complex fiducial point time; and

defining the further reference time at the specified interval from the third cardiac complex fiducial point time.

8. The method of claim 1, wherein detecting the first and second cardiac complexes comprises detecting the first and second cardiac complexes during normal sinus rhythm.

9. The method of claim 8, further comprising:

measuring voltages of the second cardiac complex at the measurement intervals; and

creating a template feature vector using the measured voltages of the second cardiac complex.

10. The method of claim 9, further comprising:

detecting a tachyarrhythmia episode;

detecting the third and fourth cardiac complexes during the detected tachyarrhythmia episode; and

creating a complex feature vector using the measured voltages of the fourth cardiac complex.

11. The method of claim 10, further comprising:

computing a correlation coefficient between the template feature vector and the complex feature vector;

classifying the tachyarrhythmia episode as a supraventricular tachyarrhythmia (SVT) in response to the correlation coefficient exceeding a predetermined threshold; and

classifying the tachyarrhythmia episode as a ventricular tachyarrhythmia (VT) in response to the correlation coefficient not exceeding the predetermined threshold.

12. The method of claim 1, further comprising:

delivering electrical pulses to a supraventricular location; and

detecting the first and second cardiac complexes being cardiac complexes that are both associated with a heart depolarization induced by one of the electrical pulses.

13. The method of claim 12, further comprising:

measuring voltages of the second cardiac complex at the measurement intervals; and

creating a template feature vector using the measured voltages of the second cardiac complex.

14. The method of claim 13, further comprising:

detecting a tachyarrhythmia episode;

detecting the third and fourth cardiac complexes during the detected tachyarrhythmia episode; and

creating a complex feature vector using the measured voltages of the fourth cardiac complex.

15. The method of claim 14, further comprising:

computing a correlation coefficient between the template feature vector and the complex feature vector;

classifying the tachyarrhythmia episode as a supraventricular tachyarrhythmia (SVT) in response to the correlation coefficient exceeding a predetermined threshold; and

classifying the tachyarrhythmia episode as a ventricular tachyarrhythmia (VT) in response to the correlation coefficient not exceeding the predetermined threshold.

16. The method of claim 15, further comprising:

detecting an atrial signal from the supraventricular location;

calculating an average intrinsic atrial rate using the atrial signal; and

delivering the electrical pulses to the supraventricular location at a rate that is faster than the average intrinsic atrial rate.

17. The method of claim 1, wherein detecting the first, second, third, and fourth cardiac complexes each comprise detecting an R-wave.

18. The method of claim 1, further comprising:

measuring voltages of the second cardiac complex at the measurement intervals;

forming a first vector from the measured voltages of the second cardiac complex;

forming a second vector from the measured voltages of the fourth cardiac complex; and

classifying a tachyarrhythmia episode associated with the second heart depolarization instance using the first vector and the second vector.

19. The method of claim 18, wherein classifying the tachyarrhythmia episode comprises:

calculating a correlation coefficient between the first vector and the second vector; and

classifying the tachyarrhythmia episode using the correlation coefficient and a predetermined coefficient.

20. The method of claim 19, wherein classifying the tachyarrhythmia episode comprises:

classifying the tachyarrhythmia episode as a supraventricular tachyarrhythmia (SVT) or a ventricular tachyarrhythmia (VT) using the correlation coefficient and the predetermined coefficient.