Cardiac rhythm management systems and methods using multiple morphology templates for discriminating between rhythms

Abstract

This document describes systems, devices, and methods that use multiple morphology templates for discriminating between rhythms, such as supraventricular tachyarrhythmias (SVTs) and ventricular tachyarrhythmias (VTs), for delivering a countershock in response to a VT episode, but withholding delivery of such a countershock in response to an SVT episode. In certain examples, the particular morphology used for storing morphological features is selected at least in part using a sensor-indicated activity level of a subject, or a metabolic need of the subject.

1 . A system comprising:
 a memory configured to store a first morphological template and a second morphological template, the first morphological template representing a subject's heart rhythm in the absence of an arrhythmia and the second morphological template representing the subject's heart rhythm under a condition different from that of the first morphological template;   an electrogram sensing circuit configured to sense a heart rate and a cardiac complex, the cardiac complex having a morphology; and   a processor, coupled to the electrogram sensing circuit, configured to access the first and second morphological templates from the memory and to declare an indication of one of a first and a second rhythm state by determining a degree of correlation between the cardiac complex and at least one of the first and second morphological templates.   
   
   
       2 . The system of  claim 1 , comprising:
 a shock circuit configured to be coupled to an electrode for delivering a shock to a heart; and   a shock control module, coupled to the processor and the shock circuit, the shock control module configured to trigger a shock when the processor declares the indication of the second rhythm state, and the shock control module to inhibit a shock when the correlation module declares the indication of the first rhythm state.   
   
   
       3 . The system of  claim 1 , wherein the second morphological template represents the subject's heart rhythm under a condition where the subject manifests at least one activity indicator value that is higher than the at least one activity indicator value associated with the first morphological template. 
   
   
       4 . The system of  claim 1 , wherein the second morphological template represents the subject's heart rhythm under a condition where the subject manifests an arrhythmia. 
   
   
       5 . The system of  claim 4 , wherein the arrhythmia is an induced arrhythmia. 
   
   
       6 . The system of  claim 1 , wherein the second morphological template represents the subject's heart rhythm under a condition where the subject manifests a supraventricular tachyarrhythmia. 
   
   
       7 . The system of  claim 6 , wherein the episode of the supraventricular tachyarrhythmia is obtained from historical electrogram data. 
   
   
       8 . The system of  claim 1 , wherein the second morphological template represents the subject's heart rhythm during high-rate atrial pacing. 
   
   
       9 . The system of  claim 1 , wherein the second morphological template represents the subject's heart rhythm during controlled physical exertion. 
   
   
       10 . A method comprising:
 accessing a first morphological template, the first morphological template representing a subject's heart rhythm in the absence of an arrhythmia;   accessing a second morphological template, the second morphological template representing the subject's heart rhythm under a condition different from that of the first morphological template;   accessing at least one cardiac complex;   determining a degree of correlation between the at least one cardiac complex and at least one of the first and second morphological templates; and   declaring one of first and second rhythm states at least in part using the determined degree of correlation.   
   
   
       11 . The method of  claim 10 , further including determining whether to deliver or inhibit a shock to a heart at least in part using which of the first and second rhythm states was declared. 
   
   
       12 . The method of  claim 10 , wherein the second morphological template represents the subject's heart rhythm under a condition where the subject manifests at least one activity indicator value that is higher than the at least one activity indicator value associated with the first morphological template. 
   
   
       13 . The method of  claim 10 , wherein the second morphological template represents the subject's heart rhythm under a condition where the subject manifests an arrhythmia. 
   
   
       14 . The method of  claim 13 , wherein the arrhythmia is an induced arrhythmia. 
   
   
       15 . The method of  claim 10 , wherein the second morphological template represents the subject's heart rhythm under a condition where the subject manifests a supraventricular tachyarrhythmia. 
   
   
       16 . The method of  claim 15 , wherein the episode of the supraventricular tachyarrhythmia is obtained from historical electrogram data. 
   
   
       17 . The method of  claim 10 , wherein the second morphological template represents the subject's heart rhythm during high-rate atrial pacing. 
   
   
       18 . The method of  claim 10 , wherein the second morphological template represents the subject's heart rhythm during controlled physical exertion. 
   
   
       19 . A machine-readable medium including instructions that, when performed by a machine, cause the machine to:
 access a first morphological template, the first morphological template representing a subject's heart rhythm in the absence of an arrhythmia;   access a second morphological template, the second morphological template representing the subject's heart rhythm under a condition different from that of the first morphological template;   access at least one cardiac complex;   determine a degree of correlation between the at least one cardiac complex and at least one of the first and second morphological templates; and   declare one of first and second rhythm states at least in part using the determined degree of correlation.   
   
   
       20 . A system comprising:
 means for accessing a first morphological template, the first morphological template representing a subject's heart rhythm in the absence of an arrhythmia;   means for accessing a second morphological template, the second morphological template representing the subject's heart rhythm under a condition different from that of the first morphological template;   means for accessing at least one cardiac complex;   means for determining a degree of correlation between the at least one cardiac complex and at least one of the first and second morphological templates; and   means for declaring one of first and second rhythm states at least in part using the determined degree of correlation.