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

• US 20050159781A1
• Filed: 03/11/2005
• Published: 07/21/2005
• Est. Priority Date: 07/14/1999
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Hsu, William
• Granted Patent: US 7,580,744 B2
• Time in Patent Office: Days
• US Class Current: 607/4
• 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 system for use with a supraventricular electrode and first and second defibrillation electrodes, the system comprising:

a sensing system, adapted for coupling to the first and second defibrillation electrodes to detect a first cardiac signal between the first and second defibrillation electrodes;

a pace output circuit, coupled to the control system, wherein the pace output circuit delivers electrical pulses to the supraventricular electrode;

a control system, coupled to the sensing system to extract first model cardiac complexes from the first cardiac signal as electrical pulses are delivered to the supraventricular electrode; and

a morphology analyzing circuit, coupled to the control system to receive the first model cardiac complexes for creating a template of one or more first model cardiac complexes obtained from the first cardiac signal as the electrical pulses are delivered to the supraventricular electrode.

2. The system of claim 1, in which:

the sensing system is adapted for coupling to a pacing electrode to detect a second cardiac signal;

the control system is coupled to the sensing system to extract second model cardiac complexes from the second cardiac signal as electrical pulses are delivered to the supraventricular pacing electrode;

an R-wave detector circuit, coupled to the sensing system, to detect an R-wave obtained from the second cardiac signal;

an alignment circuit, coupled to the R-wave detector circuit and the control system, the alignment circuit adapted to analyze the second model cardiac complexes to locate an alignment feature on each of the second model cardiac complexes, the alignment circuit adapted to position a datum at a specified interval from the alignment feature on each of the second model cardiac complexes; and

a morphology analyzing circuit, coupled to the sensing system, the morphology analyzing circuit adapted to measure a voltage value of the first cardiac signal at each of two or more measurement intervals from the datum for each of the first model cardiac complexes.

3. The system of claim 1, wherein:

the sensing system is coupled to the supraventricular electrode to monitor an atrial cardiac signal for atrial cardiac complexes and to extract an average intrinsic atrial rate from the detected atrial cardiac complexes; and

the pace output circuit is configured to deliver electrical pulses to the supraventricular electrode faster than the average intrinsic atrial rate.

4. A system, comprising:

means for delivering electrical pulses to a supraventricular location;

means for detecting a first cardiac signal as the electrical pulses are delivered to the supraventricular location;

means for detecting cardiac complexes in the first cardiac signal as the electrical pulses are delivered to the supraventricular location; and

means for creating a template from the cardiac complexes that were detected as the electrical pulses are delivered to the supraventricular location.

5. The system of claim 4, including

means for detecting an atrial cardiac signal;

means for detecting atrial cardiac complexes in the atrial cardiac signal;

means for calculating an average intrinsic atrial rate from the detected atrial cardiac complexes; and

wherein the means for delivering electrical pulses to the supraventricular location includes means for delivering electrical pulses to the supraventricular location at a pacing rate that is faster than the average intrinsic atrial rate.

6. A method, comprising:

delivering electrical pulses to a supraventricular location;

detecting a first cardiac signal as the electrical pulses are delivered to the supraventricular location;

detecting cardiac complexes in the first cardiac signal as the electrical pulses are delivered to the supraventricular location; and

creating a template from the cardiac complexes that were detected as the electrical pulses are delivered to the supraventricular location.

7. The method of claim 6, including

detecting an atrial cardiac signal;

detecting atrial cardiac complexes in the atrial cardiac signal;

calculating an average intrinsic atrial rate from the detected atrial cardiac complexes; and

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

8. The method of claim 7, including setting the pacing rate at a percentage above the average intrinsic atrial rate.

9. The method of claim 8, including setting the percentage in a range of five to fifty percent.

10. The method of claim 7, including setting the pacing rate at a target heart rate between 40 to 165 pulses per minute.

11. The method of claim 6, wherein creating the template includes:

locating a predetermined alignment feature relative the first cardiac signal when one of the electrical pulses is delivered to the supraventricular location;

identifying a cardiac complex of the first cardiac signal after the electrical pulse is delivered;

defining a datum at a specified interval from the predetermined alignment feature;

measuring a voltage value of the first cardiac signal for the cardiac complex at each of two or more measurement intervals from the datum; and

storing the voltage values of the first cardiac signal at each of the two or more measurement intervals from the datum.

12. The method of claim 6, wherein creating the template includes:

locating a predetermined alignment feature relative the first cardiac signal for each electrical pulse of the electrical pulses delivered to the supraventricular location;

identifying a cardiac complex of the first cardiac signal after each of the electrical pulses is delivered;

defining a datum at a specified interval from the predetermined alignment feature for each cardiac complex identified in the first cardiac signal; and

measuring a voltage value of the first cardiac signal for each cardiac complex at each of two or more measurement intervals from the datum.

13. The method of claim 12, including:

calculating an average value for each of the two or more measurements intervals; and

storing the average value for each of the two or more measurements intervals.

14. The method of claim 12, including:

calculating a median value for each of the two or more measurements intervals; and

storing the median value for each of the two or more measurements intervals.

15. The method of claim 6, in which the delivering electrical pulses includes delivering between one and thirty electrical pulses.

16. 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 using times corresponding to features in the second cardiac complex relative to 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 said 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 using said measurement intervals taken relative to the third cardiac complex fiducial point time.

17. The method of claim 16, 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.

18. The method of claim 17, 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.

19. The method of claim 18, 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.

20. The method of claim 16, wherein establishing measurement intervals comprises:

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

defining the measurement times relative to the reference time.