Method and apparatus for rate-dependent morphology-based cardiac arrhythmia classification

A method for classifying cardiac arrhythmias using an implantable medical device, the method comprising:

• detecting an arrhythmia episode;
• producing a heart rate parameter representative of an arrhythmic heart rate associated with the detected arrhythmic episode;
• dynamically determining morphological feature locations each as a function of at least the heart rate parameter in response to the detected arrhythmia episode, the morphological feature locations including template feature locations each representative of timing of a plurality of template morphological features on a template waveform associated with a template heart beat and arrhythmic feature locations each representative of timing of a plurality of corresponding arrhythmic morphological features on an arrhythmic waveform associated with an arrhythmic heart beat, the template waveform sensed by the implantable medical device during a normal sinus rhythm and stored in the implantable medical device, the arrhythmic waveform sensed by the implantable medical device during the detected arrhythmia episode;
• extracting the plurality of template morphological features from the template waveform at the dynamically determined morphological feature locations;
• and
• extracting the plurality of corresponding arrhythmic morphological features from the arrhythmic waveform at the dynamically determined morphological feature locations.

A system for classifying cardiac arrhythmias, the system comprising:

• a tachyarrhythmia detector adapted to detect an arrhythmia episode;
• a template feature input to receive a plurality of template morphological features of a template waveform associated with a template heart beat of a known cardiac rhythm;
• an arrhythmic feature input to receive a plurality of arrhythmic morphological features of an arrhythmic waveform associated with an arrhythmic heart beat of the detected arrhythmia episode, the arrhythmic morphological features each corresponding to one of the template morphological features;
• an arrhythmic heart rate input to receive an arrhythmic heart rate parameter representative of an arrhythmic heart rate associated with the arrhythmic waveform;
• a rate-dependent weighting module coupled to the template feature input, the arrhythmic feature input, and the arrhythmic heart rate input and including a weighting factor generator adapted to produce weighting factors each as a function of at least the arrhythmic heart rate parameter, the rate-dependent weighting module adapted to produce weighted template morphological features and weighted arrhythmic morphological features by applying one of the weighting factors to each template morphological feature of the plurality of template morphological features and each arrhythmic morphological feature of the plurality of arrhythmic morphological features in response to the detected arrhythmia episode;
• and
• a correlation coefficient calculator, coupled to the rate-dependent weighting module, to calculate at least one correlation coefficient representative of a correlation between the weighted arrhythmic morphological features and the weighted template morphological features.

A method for classifying cardiac arrhythmias using an implantable medical device, the method comprising:

• detecting an arrhythmia episode;
• receiving a plurality of template morphological features of a template waveform associated with a template heart beat of a known cardiac rhythm, the template waveform sensed by the implantable medical device during the known cardiac rhythm and stored in the implantable medical device;
• receiving a plurality of arrhythmic morphological features of an arrhythmic waveform associated with an arrhythmic heart beat of the detected arrhythmia episode, the arrhythmic morphological features each corresponding to one of the template morphological features, the arrhythmic waveform sensed by the implantable medical device during the detected arrhythmia episode;
• receiving an arrhythmic heart rate parameter representative of an arrhythmic heart rate associated with the arrhythmic waveform;
• producing a plurality of weighting factors each as a function of at least the arrhythmic heart rate parameter;
• producing weighted template morphological features and weighted arrhythmic morphological features by applying a weighting factor of the plurality of weighting factors to each of the template morphological features and each of the arrhythmic morphological features in response to the detected arrhythmia episode;
• analyzing a correlation between the weighted template morphological features and the weighted arrhythmic morphological features;
• and
• classifying the detected arrhythmia episode based on the correlation.