A method and system for classifying tachyarrhythmia episodes as associated or disassociated. Primary and auxiliary depolarizations are detected from different cardiac regions during a tachycardia episode. A first time interval is positioned to surround each of one or more primary depolarizations, including auxiliary depolarizations that occur in the first time interval. The auxiliary depolarizations occurring in the first time interval are then counted. Based on the number and the location of the auxiliary depolarizations counted in the first time intervals, the one or more primary depolarizations and the auxiliary depolarizations of the tachycardia episode are classified as disassociated or associated.