The invention relates to an implantable cardiac stimulus device (ICSD) comprising a canister housing operational circuitry and a lead electrode assembly including a plurality of electrodes disposed thereon, with the lead electrode assembly configured to couple to the canister to electrically couple the operational circuitry to the electrodes on the lead electrode assembly, the operational circuitry comprising event detection means for detecting a series of events characterized by the operational circuitry further comprising interval analysis means for analyzing a detection interval between consecutive detected events and comparing the detection interval to a wide-complex (WC) detection interval threshold, peak analysis means for observing whether at least one of the following is also true: a) the consecutive detected events differ in polarity, where polarity is determined by observing whether a maximum or a minimum amplitude occurs first in time in the shape of each of the consecutive detected events or b) an interval between the latter of the minimum or maximum amplitude point for the first-in-time of the consecutive detected events and the first of the minimum or maximum amplitude point for the second-in-time of the consecutive detected events is less than an event peak threshold and determining means for determining, if the detection interval is less than the WC detection interval threshold and either a) or b) is true that one of the consecutive detected events is due to overdetection.
