Atrial arrhythmia episode detection in a cardiac medical device

A medical device for detecting an atrial tachyarrhythmia episode, comprising:

• sensing circuitry configured to receive a cardiac signal from a plurality of electrodes coupled to the medical device;
• and
• a processor configured to:
• identify R-waves in the cardiac signal attendant ventricular depolarizations;
• determine classification factors from the R-waves identified over a first predetermined time period;
• classify the first predetermined time period as atrial tachyarrhythmia based on comparing the determined classification factors to classification criteria;
• adjust a classification criterion of the classification criteria from a first classification criterion to a second classification criterion after the first time period being classified as atrial tachyarrhythmia;
• classify at least one subsequent time period as atrial tachyarrhythmia by comparing classification factors determined over the subsequent time period to the adjusted classification criterion;
• and
• detect an atrial tachyarrhythmia episode in response to at least one subsequent time period being classified as atrial tachyarrhythmia based on the adjusted classification criterion.

A non-transitory, computer-readable storage medium storing instructions for causing a processor included in a medical device to perform a method for detecting an atrial tachyarrhythmia episode, the method comprising:

• sensing a cardiac signal;
• identifying R-waves in the cardiac signal attendant ventricular depolarizations;
• determining classification factors from the R-waves identified over a first predetermined time period;
• classifying the first predetermined time period as atrial tachyarrhythmia based on comparing the determined classification factors to classification criteria;
• adjusting a classification criterion of the classification criteria from a first classification criterion to a second classification criterion after classifying at least the first time period as atrial tachyarrhythmia;
• classifying at least one subsequent time period as one of unclassified, atrial tachyarrhythmia and non-atrial tachyarrhythmia by comparing classification factors determined over the subsequent time period to the adjusted classification criterion;
• and
• detecting an atrial tachyarrhythmia episode in response to at least one subsequent time period being classified as atrial tachyarrhythmia based on the adjusted classification criterion.