Patent ID: 8548587

Claim:
A method for use with an implantable system, comprising: (a) obtaining one or more electrogram (EGM) signal(s) indicative of cardiac electrical activity; (b) analyzing at least one of the EGM signal(s) to determine whether the EGM signal is fractionated, wherein step (b) comprises: (b.1) analyzing only one EGM signal to determine whether the one EGM signal is fractionated; and (b.2) if the one EGM signal is determined to be fractionated, then also determining a complexity metric indicative of a complexity of the fractionated EGM signal; and (c) using results of the analyzing to characterize a tachycardia and/or to select treatment for a tachycardia, wherein step (c) comprises: (c.1) if the one EGM signal is determined to not be fractionated, then determining that ATP will be delivered to attempt to terminate the tachycardia; (c.2) if the one EGM signal is determined to be fractionated and the complexity metric does not exceed a complexity threshold, then determining that ATP will be delivered to attempt to terminate the tachycardia; and (c.3) if the one EGM signal is determined to be fractionated and the complexity metric exceeds the complexity threshold, then determining that a shock will be delivered to attempt to terminate the tachycardia, without first delivering ATP.