Abstract: An implantable cardiac stimulation device discriminates and treats accelerated atrial arrhythmias of a patient's heart. The device includes a sensing circuit that senses cardiac activity of one of the patient's atria to provide an atrial activity signal, a detector that detects an accelerated atrial arrhythmia of the patient's heart, and a classifying circuit that measures relative correspondence between successive P waves of the atrial activity signal to classify the detected accelerated atrial arrhythmia as either atrial tachycardia or atrial fibrillation. A therapy circuit provides anti-tachycardia pacing therapy responsive to a classified atrial tachycardia and defibrillation therapy responsive to a classified atrial fibrillation.

Abstract: A method for storing digitized electrogram and diagnostic data in a read/write memory of an implantable cardiac therapy device which includes the steps of configuring the memory into first and second memory blocks, configuring the first memory block into a plurality of successive EGM data records for storage of the electrogram data, and the second memory block into a plurality of successive diagnostic data records for storage of the diagnostic data, storing successive electrogram data corresponding to successive EGM trigger events in respective, successive ones of the EGM data records, and, storing successive diagnostic data corresponding to successive diagnostic trigger events in respective, successive ones of the diagnostic data records. The electrogram data is preferably written into the EGM data records in a wraparound, FIFO manner.