Patent ID: 8369938

Claim:
An apparatus comprising: an implantable cardiac signal sensing circuit, configured to provide a sensed depolarization signal from a ventricle and a sensed depolarization signal from an atrium; and a controller circuit communicatively coupled to the implantable cardiac signal sensing circuit, wherein the controller circuit includes: an onset detection circuit configured to: determine ventricular depolarization intervals (V-V intervals) and atrial depolarization intervals (A-A intervals); detect an onset episode that includes fast cardiac depolarizations; and identify an initiating onset depolarization in the onset episode; and a classification circuit configured to: classify the onset episode, when the V-V intervals differ from the A-A intervals by less than a specified interval threshold during the onset episode, as: supra-ventricular tachycardia (SVT) when the initiating onset depolarization is identified in the atrium and the number of atrial depolarizations is greater than or equal to the number of ventricular depolarizations during the onset episode; and ventricular tachycardia (VT) when the initiating onset depolarization is identified in the ventricle, the number of ventricular depolarizations is greater than the number of atrial depolarizations during the onset episode; and provide the classification to a user or process.