Method for discriminating between ventricular and supraventricular arrhythmias

• US 20050192505A1
• Filed: 05/02/2005
• Published: 09/01/2005
• Est. Priority Date: 11/21/2001
• Status: Active Grant

• Current Assignee: Cameron Health Inc (Boston Scientific Corporation)
• Original Assignee: Cameron Health Inc (Boston Scientific Corporation)
• Inventors: Ostroff, Alan H., Bardy, Gust H., Warren, Jay A.
• Granted Patent: US 7,444,182 B2
• Time in Patent Office: Days
• US Class Current: 600/509
• CPC Class Codes: A61B 5/287 Holders for multiple electrodes, e.g. electrode catheters for electrophysiological study [EPS]
• CPC Class Codes: A61B 5/35 by template matching
• CPC Class Codes: A61B 5/363 Detecting tachycardia or bradycardia
• CPC Class Codes: A61B 5/686 Permanently implanted devices, e.g. pacemakers, other stimulators, biochips A61B5/6861 takes precedence
• CPC Class Codes: A61N 1/3925 Monitoring; Protecting
• CPC Class Codes: A61N 1/3956 Implantable devices for applying electric shocks to the heart, e.g. for cardioversion
• CPC Class Codes: A61N 1/3987 characterised by the timing or triggering of the shock

Abstract

The present invention is directed toward a detection architecture for use in implantable cardiac rhythm devices. The detection architecture of the present invention provides methods and devices for discriminating between arrhythmias. Moreover, by exploiting the enhanced specificity in the origin of the identified arrhythmia, the detection architecture can better discriminate between rhythms appropriate for device therapy and those that are not.

Claims

1. A method of observing and analyzing cardiac function, the method comprising:

capturing electrical cardiac signals using at least first and second electrodes implanted in a patient;

selecting portions of the cardiac signals for analysis including a set of samples each indicative of a cardiac event;

generating a number of scores related to the correlation of individual samples to a cardiac template;

calculating a set variance metric related to a variance in the correlation scores of the set of samples;

comparing the set variance metric to a threshold and

if the set variance metric does not exceed the threshold, determining that the patient is likely experiencing a malignant cardiac event.

2. A method of cardiac signal analysis comprising:

repeating the method of claim 1 for a number, Y, of temporally related sample sets; and

determining whether electrical cardiac stimulus is indicated by counting a number of sample sets, X, in which it is determined that the patient is likely experiencing a malignant cardiac event, and comparing X to Y.

3. A method as in claim 1, further comprising:

identifying a score related to the correlation of a most recent sample to the cardiac template;

comparing the identified score to a threshold; and

if the identified score does not exceed the threshold, determining that the patient is likely experiencing a malignant cardiac event.

4. A method of cardiac signal analysis comprising:

repeating the method of claim 3 for Y temporally related sample sets;

determining whether electrical cardiac stimulus is indicated by counting a number, X, of sample sets in which it is determined that the patient is likely experiencing a malignant cardiac event.

5. A method as in claim 1, further comprising observing a cardiac triggering event, the cardiac triggering event being the presence of a cardiac event rate in excess of a predetermined level, wherein the cardiac template is a cardiac template representative of non-malignant cardiac events occurring after a cardiac triggering event.

6. The method of claim 5, wherein the cardiac template is dynamically updated.

7. The method of claim 1, further comprising comparing an individual score threshold to one of the generated number of scores to determine whether an associated individual sample is indicative of a malignant cardiac condition.

8. A method of cardiac signal analysis comprising:

collecting a set of electrical signal samples of a patient'"'"'s cardiac function from implanted electrodes;

comparing a number of individual signal samples to a cardiac signal template to generate a comparison score related to a correlation between the signal sample and the cardiac signal template;

for a number of individual signal samples, marking the individual signal sample as indicative of a malignant cardiac condition if at least one of the following conditions is met;

(a) a subset of signal samples including the individual signal sample and a number of prior signal samples illustrates a variance of comparison scores in excess of a predetermined threshold; and

(b) a cardiac rate triggering event has been detected, the cardiac rate triggering event comprising the detection of a cardiac rate in excess of a predetermined level, and a correlation between the individual signal sample and a post-event template falls below a predetermined level;

and

observing whether at least a threshold number of signal samples are marked as indicative of a malignant cardiac condition within a predetermined number of signal samples.

9. A method of determining whether cardiac treatment is appropriate comprising:

capturing an electrical cardiac signal from implanted electrodes;

observing a first metric of the electrical cardiac signal;

determining whether the first metric;

(a) indicates malignant cardiac function;

(b) indicates non-malignant cardiac function;

or

(c) neither of the above;

if (a), determining that cardiac function appears malignant;

if (c), observing a second metric of the patient'"'"'s cardiac function to clarify whether cardiac stimulus is appropriate and determining whether the second metric;

(d) indicates malignant cardiac function;

(e) indicates non-malignant cardiac function;

or

(f) neither of the above;

if (b) and (d), determining that cardiac function appears malignant.

10. The method of claim 9, wherein the electrical cardiac signal includes a number of cardiac events of a patient.

11. The method of claim 10, wherein the first metric is related to the patient'"'"'s cardiac event rate.

12. The method of claim 11, wherein the second metric is related to morphology of one or more of the patient'"'"'s cardiac events.

13. The method of claim 9, wherein the first and second metrics are both related to the morphology of one or more of the patient'"'"'s cardiac events.

14. A method comprising repeating the steps of claim 9, a number of times, each time corresponding to a cardiac event, wherein if it is determined that cardiac function appears malignant for a threshold number of cardiac events, it is determined that stimulus is appropriate.

15. A method of observing cardiac function, the method comprising:

implanting first and second electrodes subcutaneously in a patient;

observing a number of cardiac events using the subcutaneously implanted electrodes to generate a cardiac event template; and

;

(a) observing an electrical signal between the first and second electrodes;

(b) determining that the electrical signal likely corresponds to a cardiac event;

(c) analyzing the electrical signal, including performing correlation waveform analysis (CWA) between the electrical signal and the cardiac event template;

(d) classifying the electrical signal as either malignant or non-malignant in light of results determined in step (c); and

repeating steps a-d to generate a count indicative of patient cardiac function.

16. The method of claim 15, wherein step (c) comprises generating a CWA score between a cardiac event and the template, and step (d) includes comparing the CWA score to a threshold.

17. The method of claim 15, wherein the CWA is a first metric capable of indicating whether the electrical signal is indicative of malignant or non-malignant cardiac function and the analyzing step further comprises generating a second metric with respect to the electrical signal, the second metric also capable indicating whether the electrical signal is indicative of malignant or non-malignant cardiac function.

18. The method of claim 17, wherein the classifying step comprises:

first, determining whether the first metric indicates a malignant cardiac condition; and

second, determining whether the second metric indicates a malignant cardiac condition.

19. The method of claim 15, wherein step (c) includes generating scores for CWA between a plurality of cardiac events and at least one template, the plurality of cardiac events being temporally related, and observing a variability of the scores for the plurality of cardiac events.

20. The method of claim 15, wherein step (c) includes recording a CWA score for a comparison of the electrical signal to a template, wherein step (d) includes comparing the CWA score for the electrical signal to CWA scores for other recent electrical signals to observe variability in the CWA scores for a set of electrical signals.