Patent ID: 8014851

Claim:
A method of determining whether a patient is undergoing a malignant cardiac condition in an implantable cardiac stimulus device (ICSD) comprising a canister coupled to a plurality of electrodes, the method comprising: the ICSD capturing a cardiac signal having a cardiac event from a patient using implanted the plurality of electrodes; the ICSD detecting a cardiac event in the cardiac signal by comparing the cardiac signal to a detection threshold; the ICSD sampling and windowing the cardiac signal such that it is comprised of a plurality of signal samples representing a time varying amplitude of the captured cardiac signal during a window of time corresponding to the detected cardiac event; and the ICSD comparing the sampled and windowed cardiac signal to a stored template by determining a difference between a sample value for each sample in the sampled and windowed cardiac signal and a corresponding template value for each sample in the stored template to create a series of difference values, multiplying the series of difference values by a weighting vector to create a series of difference products and summing the series of difference products to yield a score indicative of correlation between the cardiac signal and the stored template, wherein at least some of the signal samples are provided with greater weight and others of the signal samples are provided with a lesser weight by the weighting vector.