Systems, devices, and methods for tachyarrhythmia discrimination or therapy decisions

1. A system comprising:

an atrial contraction detector circuit, including an atrial rate detector circuit to detect an atrial rate between atrial contractions of a heart;

a ventricular contraction detector circuit, including a ventricular rate detector circuit to detect a ventricular rate between ventricular contractions of the heart;

a tachyarrhythmia classification circuit, configured to classify a tachyarrhythmia using a rhythm discrimination parameter having a value; and

a processor, coupled to the atrial and ventricular contraction detector circuits and the tachyarrhythmia classification circuit, the processor configured to:

determine a relationship between the atrial rate and the ventricular rate including comparing a difference between the atrial rate and the ventricular rate to a threshold value to determine whether the atrial rate is substantially equal to the ventricular rate; and

when the difference between the atrial rate and the ventricular rate exceeds the threshold value thereby indicating that the atrial rate is not substantially equal to the ventricular rate, adjust the value of the rhythm discrimination parameter using the relationship between the atrial rate and the ventricular rate, including adjusting the value of the rhythm discrimination parameter using both of (1) information about whether the atrial rate exceeds the ventricular rate or vice-versa; and (2) a magnitude of the difference between the atrial rate and the ventricular rate.

2. The system of claim 1 , wherein the processor is configured to adjust the value of the rhythm discrimination parameter using at least one of the atrial rate or the ventricular rate in addition to using the relationship between the atrial rate and the ventricular rate.

3. The system of claim 2 , wherein the processor is configured to adjust the value of the rhythm discrimination parameter using information about the amount that the ventricular rate exceeds the atrial rate as a function of at least one of the atrial rate or the ventricular rate.

4. The system of claim 3 , wherein the processor is configured to adjust the value of the rhythm discrimination parameter using information about whether the ventricular rate exceeds the atrial rate by a threshold value, wherein the threshold value varies as a function of at least one of the atrial rate or the ventricular rate.

5. The system of claim 1 , wherein the atrial rate is represented by an atrial interval between atrial contractions and the ventricular rate is represented by a ventricular interval between ventricular contractions.

6. The system of claim 1 , wherein the tachyarrhythmia classification circuit includes a comparator configured to compare information from at least one of the atrial contraction detector circuit or the ventricular contraction detector circuit to the value of the rhythm discrimination parameter, and the tachyarrhythmia classification circuit is configured to classify the tachyarrhythmia using the results of the comparison.

7. The system of claim 1 , wherein the rhythm discrimination parameter includes at least one of stability, onset, or morphology correlation.

8. The system of claim 7 , wherein the rhythm discrimination parameter includes stability and the value of the rhythm discrimination parameter includes a variance threshold.

9. The system of claim 8 , wherein the ventricular contraction detector circuit is configured to detect a ventricular contraction and provide a ventricular contraction signal, and the rhythm discrimination parameter includes morphology correlation between the ventricular contraction signal and a template, and the value of the rhythm discrimination parameter includes a morphology correlation threshold value.

10. The system of claim 7 , wherein the rhythm discrimination parameter includes onset and the value of the rhythm discrimination parameter includes a rate progression threshold.

11. The system of claim 1 , wherein the ventricular contraction detector circuit is configured to detect a ventricular contraction and provide a ventricular contraction signal, and the rhythm discrimination parameter includes morphology correlation and the value of the rhythm discrimination parameter includes a morphology correlation threshold between the ventricular contraction signal and a template.

12. The system of claim 11 , wherein the template includes at least one of a normal sinus rhythm ventricular contraction template or a tachyarrhythmia ventricular contraction template.

13. The system of claim 1 , including a therapy delivery circuit, configured to deliver an anti-tachyarrhythmia therapy if the tachyarrhythmia classification circuit classifies the tachyarrhythmia as a ventricular tachyarrhythmia.

14. A system comprising:

means for detecting atrial contractions of a heart and an atrial rate between the detected atrial contractions;

means for detecting ventricular contractions of the heart and a ventricular rate between the detected ventricular contractions;

means for classifying a tachyarrhythmia using a rhythm discrimination parameter having a value;

means for determining a relationship between the atrial rate and the ventricular rate including comparing a difference between the atrial rate and the ventricular rate to a threshold value to determine whether the atrial rate is substantially equal to the ventricular rate; and

means for adjusting, when the difference between the atrial rate and the ventricular rate exceeds the threshold value thereby indicating that the atrial rate is not substantially equal to the ventricular rate, the value of the rhythm discrimination parameter using the relationship between the atrial rate and the ventricular rate, including adjusting the value of the rhythm discrimination parameter using both of (1) information about whether the atrial rate exceeds the ventricular rate or vice-versa; and (2) a magnitude of the difference between the atrial rate and the ventricular rate.

15. A method comprising:

detecting atrial contractions of a heart and an atrial rate between the detected atrial contractions;

detecting ventricular contractions of the heart and a ventricular rate between the detected ventricular contractions;

classifying a tachyarrhythmia using a rhythm discrimination parameter having a value;

determining a relationship between the atrial rate and the ventricular rate including comparing a difference between the atrial rate and the ventricular rate to a threshold value to determine whether the atrial rate is substantially equal to the ventricular rate; and

when the difference between the atrial rate and the ventricular rate exceeds the threshold value, adjusting the value of the rhythm discrimination parameter using the relationship between the atrial rate and the ventricular rate, including adjusting the value of the rhythm discrimination parameter using both of (1) information about whether the atrial rate exceeds the ventricular rate or vice-versa; and (2) a magnitude of the difference between the atrial rate and the ventricular rate.

16. The method of claim 15 , wherein the adjusting the value of the rhythm discrimination parameter includes using at least one of the atrial rate or the ventricular rate in addition to using the relationship between the atrial rate and the ventricular rate.

17. The method of claim 16 , wherein the adjusting the value of the rhythm discrimination parameter includes using information about the amount that the ventricular rate exceeds the atrial rate as a function of at least one of the atrial rate or the ventricular rate.

18. The method of claim 17 , wherein the adjusting the value of the rhythm discrimination parameter includes using information about whether the ventricular rate exceeds the atrial rate by a threshold value that varies as a function of at least one of the atrial rate or the ventricular rate.

19. The method of claim 15 , wherein the detecting the atrial rate includes detecting an atrial interval between atrial contractions and the detecting the ventricular rate includes detecting a ventricular interval between ventricular contractions.

20. The method of claim 15 , including:

comparing information from at least one of the detected atrial contractions or the detected ventricular contractions to the value of the rhythm discrimination parameter; and

wherein the classifying the tachyarrhythmia includes using the results of the comparison.

21. The method of claim 15 , wherein the classifying the tachyarrhythmia using the rhythm discrimination parameter includes classifying the tachyarrhythmia using at least one of stability, onset, or morphology correlation.

22. The method of claim 21 , wherein the classifying the tachyarrhythmia using the rhythm discrimination parameter having a value includes classifying the tachyarrhythmia using stability having a variance threshold.

23. The method of claim 21 , wherein the classifying the tachyarrhythmia using the rhythm discrimination parameter having a value includes classifying the tachyarrhythmia using onset having a rate progression threshold.

24. The method of claim 15 , including:

providing a ventricular contraction signal using at least one detected ventricular contraction; and

wherein the classifying the tachyarrhythmia using the rhythm discrimination parameter having the value includes using morphology correlation having a morphology correlation threshold.

25. The method of claim 24 , wherein the using morphology correlation having the morphology correlation threshold includes determining a morphology correlation value between the ventricular contraction signal and a template and comparing the determined morphology correlation value to the morphology correlation threshold.

26. The method of claim 25 , wherein the template includes at least one of a normal sinus rhythm ventricular contraction template or a tachyarrhythmia ventricular contraction template.

27. The method of claim 15 , including delivering an anti-tachyarrhythmia therapy if the tachyarrhythmia is classified as a ventricular tachyarrhythmia.