Patent ID: 8565878

Claim:
An implantable cardiac stimulus device (ICSD) comprising: a canister housing operational circuitry configured to perform cardiac signal analysis and configured to provide cardiac stimulus; and a lead electrode assembly coupled to the canister and operatively coupled to the operational circuitry; wherein a plurality of electrodes are provided on the lead electrode assembly and/or canister, the plurality of electrodes being coupled to the operational circuitry; wherein the operational circuitry is configured to perform a beat detection method comprising: capturing electrical signals from the electrodes; identifying events in the captured electrical signals using a detection profile, the detection profile providing a threshold having a threshold configuration for comparison to the captured signals such that, when the captured signals exceed the threshold, a detected event is declared; comparing a peak amplitude of a first detected event to a peak amplitude of a second detected event to determine whether the first and second events are similar or dissimilar; and if the first and second events are similar, using a first threshold configuration for detecting a subsequent event; or if the first and second events are dissimilar, using a second threshold configuration for detecting a subsequent event, wherein a sensitivity of the second threshold configuration is different than that of the first threshold configuration; and wherein the operational circuitry is further configured such that the first and second threshold configurations define at least the following time periods: a refractory period during which detected events are not declared; a constant threshold time period having a duration, CTD and an amplitude CTA; and a decay time period during which the threshold changes with time from a starting amplitude DTA; and further wherein the first threshold configuration has a longer CTD and higher CTA and DTA than the second threshold configuration.