Method and apparatus for generating a template for arrhythmia detection and electrogram morphology classification

• US 20050137485A1
• Filed: 12/02/2004
• Published: 06/23/2005
• Est. Priority Date: 12/03/2003
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Gillberg, Jeffrey M., Cao, Jian, Gennaro, Chris J.
• Granted Patent: US 7,242,978 B2
• Time in Patent Office: Days
• US Class Current: 600/510
• CPC Class Codes: A61B 5/35 by template matching
• CPC Class Codes: A61B 5/363 Detecting tachycardia or bradycardia
• CPC Class Codes: A61B 5/726 using Wavelet transforms
• 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: A61N 1/3622 comprising two or more electrodes co-operating with different heart regions
• CPC Class Codes: A61N 1/3956 Implantable devices for applying electric shocks to the heart, e.g. for cardioversion
• CPC Class Codes: G16H 50/20 for computer-aided diagnosis, e.g. based on medical expert systems

Abstract

An implantable medical device and associated method for automatically generating morphology templates during fast cardiac rhythms, confirming a provisional template as a confirmed template, and using the confirmed template to classify subsequent detected arrhythmias. A provisional SVT template may be created during a fast ventricular rate and activated as a confirmed SVT template upon verification that the fast rate was due to an SVT. The confirmed SVT template may be used to discriminate SVT from VT/VF.

Claims

1. A method of discriminating cardiac depolarizations, comprising:

detecting a fast cardiac rate wherein a plurality of cardiac depolarizations are occurring at a rate corresponding to an arrhythmia detection interval;

storing digitized electrogram segments including signals indicative of depolarization of a chamber or chambers of a patient'"'"'s heart during the fast cardiac rate;

determining morphology match metrics corresponding to the stored electrogram segments;

summing the morphology match metrics;

identifying electrogram segments having higher morphology match metric sums; and

generating a provisional template from the identified electrogram segments.

2. The method of claim 1, wherein determining morphology match metrics comprises:

transforming the stored electrogram segments into signal wavelet coefficients;

identifying higher amplitude ones of the signal wavelet coefficients;

generating a match metric corresponding to the higher amplitude ones of the signal wavelet coefficients.

3. The method of claim 2, wherein transforming the stored electrogram segments comprises transforming the stored electrogram segments using a wavelet transform to obtain the signal wavelet coefficients.

4. The method of claim 1, further comprising:

verifying that the fast cardiac rate is a supraventricular tachycardia;

confirming the provisional template as a supraventricular tachycardia template in response to the fast cardiac rate being a supraventricular tachycardia.

5. A method for monitoring heart rhythms, comprising:

detecting a fast cardiac rate in response to cardiac depolarizations occurring at a rate corresponding to an arrhythmia detection interval;

storing first digitized electrogram segments including signals indicative of depolarization of a chamber of a patient'"'"'s heart during the fast cardiac rate;

determining a morphology match metric for each stored electrogram segment corresponding to other stored first electrogram segments;

summing the morphology match metrics determined for each stored first electrogram segment;

identifying first electrogram segments having higher morphology match metric sums;

generating a provisional template from the identified first electrogram segments;

verifying that the detected fast cardiac rate is a supraventricular tachycardia;

confirming the provisional template as a supraventricular tachycardia template in response to the fast cardiac rate being a supraventricular tachycardia;

storing second digitized electrogram segments including signals indicative of depolarizations of a chamber of a patient'"'"'s heart during an unknown rhythm;

transforming the second digitized signals into signal wavelet coefficients;

identifying higher amplitude ones of the signal wavelet coefficients;

generating a match metric corresponding to the higher amplitude ones of the signal wavelet coefficients; and

identifying the heart rhythm in response to the match metric.

6. A method of discriminating cardiac depolarizations, comprising:

detecting and storing cardiac depolarizations, including first cardiac depolarizations occurring at a rate corresponding to an arrhythmia detection interval and second cardiac depolarizations occurring at a rate not corresponding to the arrhythmia detection interval;

generating a first template in response to the detected first cardiac depolarizations;

generating a second template in response to the detected second cardiac depolarizations; and

classifying subsequent depolarizations as corresponding to one of SVT and VTNF in response to one or both of the first template and the second template.

7. A method of discriminating cardiac depolarizations, comprising:

detecting indications of a plurality of indications associated with determining the presence of a first event;

storing, prior to detecting all of the plurality of indications, a plurality of segments corresponding to signals associated with the detected indications;

comparing the plurality of segments; and

generating, in response to the comparing, a template for distinguishing the first event from a second event different from the first event.

8. The method of claim 7, wherein generating a template comprises determining whether a segment of the plurality of segments matches a predetermined number of the plurality of segments.

9. The method of claim 7, further comprising:

comparing the generated template with a segment corresponding to a previously classified arrhythmia episode;

updating the generated template in response to the comparing of the generated template.

10. The method of claim 9, further comprising displaying information corresponding to the generating.

11. The method of claim 10, wherein displaying comprises:

displaying the plurality of segments; and

displaying a match metric corresponding to each of the displayed plurality of segments in response to a comparative analysis between the plurality of segments and one or more reference templates.

12. The method of claim 7, further comprising:

setting a second index associated with a first generated template;

comparing a second generated template generated subsequent to the first generated template to the first generated template;

setting a second index associated with the second generated template in response to the comparing of the second generated template.

13. The method of claim 12, further comprising displaying the first index and the second index.

14. The method of claim 13, further comprising:

displaying the plurality of segments; and

displaying a match metric corresponding to each of the displayed plurality of segments in response to a comparative analysis between the plurality of segments and one or more reference templates.

15. The method of claim 7, further comprising:

determining the presence of the first event;

comparing a second plurality of segments corresponding to first depolarizations occurring subsequent to determining the presence of the first event to the generated template; and

classifying the first depolarizations as one of the first event and the second event in response to comparing the second plurality of segments.

16. The method of claim 7, wherein the first event is one of ventricular tachycardia and ventricular fibrillation and the second event is a surpraventricular event.