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

• US 6,449,503 B1
• Filed: 07/14/1999
• Issued: 09/10/2002
• Est. Priority Date: 07/14/1999
• Status: Expired due to Term

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Hsu, William
• Primary Examiner(s): EVANISKO, GEORGE ROBERT
• Application Number:
  US09/352,056
• Time in Patent Office: 1,154 Days
• Field of Search: 600/517, 600/510, 600/516, 600/515, 600/518, 607/4, 607/5, 607/14
• US Class Current: 600/518
• 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:

sensing a first cardiac signal and a second cardiac signal, wherein the first cardiac signal has a voltage;

detecting a first cardiac complex of a cardiac cycle in the first cardiac signal;

detecting a second cardiac complex of the cardiac cycle in the second cardiac signal, wherein the second cardiac complex includes a predetermined alignment feature;

defining a datum at a specified interval from the predetermined alignment feature of the second cardiac complex;

selecting two or more morphological features along the first cardiac complex;

obtaining two or more predefined measurement intervals from the datum, the two or more predefined measurement intervals being measured between the datum and the respective two or more morphological features; and

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

2. The method of claim 1, including:

detecting a first model cardiac complex in the first cardiac signal;

detecting a second model cardiac complex in the second cardiac signal;

locating a predetermined alignment feature relative the second model cardiac complex;

measuring the specified interval between the predetermined alignment feature and the datum;

storing the specified interval;

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

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

3. The method of claim 2, wherein detecting the first model cardiac complex includes detecting a first normal sinus rhythm (NSR) cardiac complex of a NSR cardiac cycle in the first cardiac signal;

wherein detecting the second model cardiac complex includes detecting a second NSR cardiac complex of the NSR cardiac cycle in the second cardiac signal; and

locating the predetermined alignment feature includes identifying the predetermined alignment feature in the second NSR cardiac complex.

4. The method of claim 3, including positioning the first NSR cardiac complex and the second NSR cardiac complex in an analysis window, wherein the analysis window includes the datum from which voltage values of the first cardiac signal are measured;

and

positioning the first cardiac complex and the second cardiac complex relative the first NSR cardiac complex and the second NSR cardiac complex in the analysis window to align the predetermined alignment feature of the second cardiac complex and the second NSR cardiac complex.

5. The method of claim 2, wherein detecting the first model cardiac complex in the first cardiac signal includes:

delivering electrical pulses to a supraventricular location;

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

6. The method of claim 5, 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 predetermined rate which is faster than the average intrinsic atrial rate.

7. The method of claim 2, including:

detecting a tachycardia episode;

sensing the first cardiac complex of the first cardiac signal and the second cardiac complex of the second cardiac signal during the tachycardia episode;

comparing the stored voltage values of the first model cardiac complex to the voltage values of the first cardiac complex measured during the tachycardia episode; and

determining whether the first cardiac complex is a ventricular tachycardia complex based on the comparison.

8. The method of claim 7, including calculating a correlation coefficient from the stored voltage values of the first model cardiac signal and the measured voltage values of the first cardiac signal;

classifying the first cardiac complex as a VT complex when the correlation coefficient is less than or equal to a predetermined threshold; and

classifying the first cardiac complex as an SVT complex when the correlation coefficient is greater than the predetermined threshold.

9. The method of claim 8, including detecting, over a plurality of cardiac cycles, first cardiac complexes in the first cardiac signal and second cardiac complexes in the second cardiac signal;

classifying a predetermined number of the first cardiac complexes;

declaring a ventricular tachycardia episode when a threshold number of the predetermined number of the first cardiac complexes are classified as ventricular tachycardia complexes; and

declaring a supraventricular tachycardia episode when the threshold number of the predetermined number of the first cardiac complexes are classified as supraventricular tachycardia complexes.

10. The method of claim 8, including detecting, over a plurality of cardiac cycles, first cardiac complexes in the first cardiac signal and second cardiac complexes in the second cardiac signal;

declaring a ventricular tachycardia episode when a threshold percentage of the first cardiac complexes from the plurality of cardiac cycles are classified as ventricular tachycardia complexes; and

declaring a supraventricular tachycardia episode when the threshold percentage of the first cardiac complexes from the plurality of cardiac cycles are classified as supraventricular tachycardia complexes.

11. The method of claim 7, including multiplying the specified interval by a scaling percentage to give a revised specified interval;

defining the datum at the revised specified interval from the predetermined alignment feature of the second cardiac complex;

multiplying each of the two or more measurement intervals by the scaling percentage to give revised measurement intervals; and

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

12. The method of claim 1, including positioning the first cardiac complex and the second cardiac complex in an analysis window, wherein the analysis window includes the datum from which voltage values of the first cardiac signal are measured.

13. The method of claim 1, wherein the predetermined alignment feature is a repeatably identifiable portion of the second cardiac complex.

14. The method of claim 13, wherein the predetermined alignment feature is a point of at least one of a maximum deflection and a maximum slew.

15. The method of claim 1, wherein each of the two or more the morphological features includes a repeatably identifiable portion of the first cardiac complex.

16. The method of claim 15, wherein each of the two or more of the morphological features includes at least one of a maximum deflection point, a minimum deflection point, a beginning of the first cardiac complex, and an ending of the first cardiac complex.