1. A method of cardiac signal analysis in an implantable cardiac stimulus device comprising: implanting, into the patient, a cardiac stimulus system comprising a canister and a lead assembly, the lead assembly including a plurality of electrodes thereon and the canister including at least one electrode thereon for use in cardiac activity sensing; selecting for default use a first electrode pair defining a first sensing vector by observing a cardiac signal metric for a plurality of available sensing vectors and using the first electrode pair as a default electrode pair when observing cardiac activity of the patient; attempting to form a template representative of normal sinus rhythm for the patient using the first sensing vector after the first electrode pair has been selected for default use; failing to form the template representative of normal sinus rhythm using the first sensing vector and, in response thereto, changing the default electrode pair to a different pair of electrodes defining a sensing vector other than the first sensing vector; wherein the first electrode pair is selected for default use on the basis of having a better cardiac signal metric when compared to other available sense vectors.