CLASSIFICATION OF SUPRAVENTRICULAR AND VENTRICULAR CARDIAC RHYTHMS USING CROSS CHANNEL TIMING ALGORITHM

• US 20090312811A1
• Filed: 08/24/2009
• Published: 12/17/2009
• Est. Priority Date: 07/14/1999
• Status: Active Grant

• Current Assignee: William Hsu
• Original Assignee: William Hsu
• Inventors: Hsu, William
• Granted Patent: US 8,050,757 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. An implantable cardiac defibrillator configured to be coupled to a first defibrillation electrode, a second defibrillation electrode, a supraventricular pacing electrode, and a further pacing electrode, the defibrillator comprising:

a sensing system configured to be coupled to the first defibrillation electrode and the second defibrillation electrode and detect a first cardiac signal between the first defibrillation electrode and the second defibrillation electrode;

a control system coupled to the sensing system and configured to monitor the first cardiac signal for first cardiac complexes including first model cardiac complexes and first sensed cardiac complexes;

a pace output circuit coupled to the control system and the supraventricular electrode and configured to deliver electrical pulses to the supraventricular pacing electrode under control of the control system, wherein the control system is configured to monitor the first cardiac signal for the first model cardiac complexes as the electrical pulses are delivered to the supraventricular pacing electrode; and

a morphology analyzing circuit coupled to the control system and configured to receive the first model cardiac complexes for creation of a template feature vector for classification of the first sensed cardiac complexes.

2. The defibrillator of claim 1, wherein the sensing system is configured to be coupled to the further pacing electrode and detect a second cardiac signal through the further pacing electrode, and the control system is configured to monitor the second cardiac signal for second model cardiac complexes as the electrical pulses are delivered to the supraventricular pacing electrode, and comprising:

an R-wave detector circuit coupled to the control system and configured to detect the second model cardiac complexes in the second cardiac signal; and

an alignment circuit coupled to the R-wave detector and configured to analyze each of the second model cardiac complexes to locate a predetermined alignment feature on each of the second model cardiac complexes and positions a datum at a specified interval from the alignment feature on the each of the second model cardiac complexes,

and wherein the morphology analyzing circuit is configured 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 from which the template feature vector is created from the 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 defibrillator of claim 2, wherein the sensing system is configured to be coupled to the supraventricular pacing electrode and detect an atrial cardiac signal from the supraventricular pacing electrode, the control system is configured to monitor the atrial cardiac signal for atrial cardiac complexes and calculate an average intrinsic atrial rate from the detected atrial cardiac complexes, and the pace output circuit is configured to deliver the electrical pulses to the supraventricular pacing electrode at a predetermined rate which is faster than the average intrinsic atrial rate.

4. The defibrillator of claim 2, wherein the control system comprises a memory circuit to store the template feature vector, and the morphology analyzing circuit is configured to measure a voltage value of the first cardiac signal at each of two or more measurement intervals from the datum for each first sensed cardiac complex of the first sensed cardiac complexes from which a complex feature vector is created from the voltage value of the first cardiac signal at each of two or more measurement intervals from the datum for each of the first sensed cardiac complexes, and comprising a vector comparison circuit coupled to the control system and configured to receive the voltage values measured at the measurement intervals, create the complex feature vector, compare the complex feature vector to the template feature vector, and classify the each first sensed cardiac complex using the comparison of the complex feature vector and the template feature vector.

5. The defibrillator of claim 4, wherein the vector comparison circuit is configured to calculate a correlation coefficient from the template feature vector and the complex feature vector and classify the each first sensed cardiac complex using the correlation coefficient and a threshold.

6. The system of claim 5, wherein the vector comparison circuit is configured to classify the each first sensed cardiac complex as a ventricular tachycardia complex when the correlation coefficient is less than or equal to the threshold, and classify the each first cardiac complex as a supraventricular tachycardia complex when the correlation coefficient is greater than the threshold.

7. The system of claim 6, wherein the vector comparison circuit is configured to classify a specified number of the first sensed cardiac complexes, and the control system is configured to declare a ventricular tachycardia episode when at least a threshold number of the specified number of the first sensed cardiac complexes are classified as ventricular tachycardia complexes.

8. A system, comprising:

a supraventricular pacing electrode;

at least a first defibrillation electrode and a second defibrillation electrode;

a sensing system coupled to the supraventricular pacing electrode and the first defibrillation electrode and the second defibrillation electrode, the sensing system configured to detect a first cardiac signal between the first defibrillation electrode and the second defibrillation electrode;

a control system coupled to the sensing system and configured to monitor the first cardiac signal for first cardiac complexes including first model cardiac complexes and first sensed cardiac complexes;

a pace output circuit coupled to the control system and configured to deliver electrical pulses to the supraventricular pacing electrode under control of the control system, wherein the control system is configured to monitor the first cardiac signal for the first model cardiac complexes as the electrical pulses are delivered to the supraventricular pacing electrode; and

a morphology analyzing circuit coupled to the control system and configured to receive the first model cardiac complexes for creation of a template feature vector for classification of the first sensed cardiac complexes.

9. The system of claim 8, comprising:

a further pacing electrode coupled to the sensing system, wherein the sensing system is configured to detect a second cardiac signal through the further pacing electrode, and the control system is configured to monitor the second cardiac signal for second model cardiac complexes as the electrical pulses are delivered to the supraventricular pacing electrode;

an R-wave detector circuit coupled to the control system and configured to detect the second model cardiac complexes in the second cardiac signal; and

an alignment circuit coupled to the R-wave detector and configured to analyze each of the second model cardiac complexes to locate a predetermined alignment feature on each of the second model cardiac complexes and positions a datum at a specified interval from the alignment feature on each of the second model cardiac complexes,

and wherein the morphology analyzing circuit is configured 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 from which the template feature vector is created from the 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.

10. The system of claim 9, wherein the sensing system is configured to detect an atrial cardiac signal from the supraventricular pacing electrode, the control system is configured to monitor the atrial cardiac signal for atrial cardiac complexes and calculate an average intrinsic atrial rate from the detected atrial cardiac complexes, and the pace output circuit is configured to deliver the electrical pulses to the supraventricular pacing electrode at a predetermined rate which is faster than the average intrinsic atrial rate.

11. The system of claim 9, wherein the control system comprises a memory circuit to store the template feature vector, and the morphology analyzing circuit is configured to measure a voltage value of the first cardiac signal at each of two or more measurement intervals from the datum for each first sensed cardiac complex of the first sensed cardiac complexes from which a complex feature vector is created from the voltage value of the first cardiac signal at each of two or more measurement intervals from the datum for each of the first sensed cardiac complexes, and comprising a vector comparison circuit coupled to the control system and configured to receive the voltage values measured at the measurement intervals, create the complex feature vector, compare the complex feature vector to the template feature vector, and classify the each first sensed cardiac complex using the comparison of the complex feature vector and the template feature vector.

12. The system of claim 11, wherein the vector comparison circuit is configured to calculate a correlation coefficient from the template feature vector and the complex feature vector and classify the each first sensed cardiac complex by comparing the correlation coefficient to a threshold.

13. The system of claim 12, wherein the vector comparison circuit is configured to classify a specified number of the first sensed cardiac complexes, and the control system is configured to declare a ventricular tachycardia episode when at least a threshold number of the specified number of the first sensed cardiac complexes are classified as ventricular tachycardia complexes.

14. The system of claim 9, comprising:

a first intracardiac catheter including the first defibrillation electrode, the second defibrillation electrode, and the further pacing electrode; and

a second intracardiac catheter including the supraventricular pacing electrode.

15. The system of claim 14, comprising:

a medical device programmer; and

a cardiac defibrillator coupled to the first and second intracardiac catheters and including an implantable housing encasing the control system and a transmitter/receiver coupled to the control system and configured to transmit signals to and receive signals from the medical device programmer,

wherein the medical device programmer is configured to transmit a first signal to control the alignment circuit to locate the predetermined alignment feature on the second model cardiac complex and to position the datum at the specified interval from the alignment feature on the second model cardiac complex, and transmit a second signal to supply the two or more measurement intervals to the morphology analyzing circuit.

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.