1. An implantable cardiac stimulus (ICS) system comprising a canister housing operational circuitry for the ICS system, the canister having a canister electrode disposed thereon, and a lead having at least a first lead electrode disposed thereon, the canister electrode and the first lead electrode electrically coupled to the operational circuitry; wherein the operational circuitry is configured to perform a method comprising: detecting electrical events occurring within a patient; constructing event representations for the detected electrical events, the event representations each comprising a series of samples; comparing a first event representation to a template having a template fiducial point by identifying an event fiducial point in the first event representation and aligning the template fiducial point and the event fiducial point to one another and calculating a first correlation between the first event representation and the template when so aligned; again comparing the first event representation to the template, this time by selecting a different alignment of the template and event fiducial points; selecting from at least the first correlation or the second correlation whichever indicates greater correlation as the correlation result for the first event representation; using a series of correlation results to determine whether accurate event detection is occurring and, if not, correcting data in response to inaccurate event detection; determining whether a likely cardiac arrhythmia is occurring and, if so, determining whether stimulus is needed; and if stimulus is needed, delivering electrical stimulus to the patient from the ICS system.