Patent ID: 7076289

Claim:
In an implantable medical device that provisionally detects a polymorphic tachyarrhythmia of the heart of a patient as a function of measured time intervals between sensed events in a cardiac signal, a method of improving the specificity of discriminating between a monomorphic tachyarrhythmia and a polymorphic tachyarrhythmia comprising the steps of: a) provisionally declaring a polymorphic tachyarrhythmia when at least a first number of the measured time intervals satisfy the polymorphic tachyarrhythmia detection criteria; b) successively sampling, processing, and temporarily storing the cardiac signal to provide sampled signal amplitudes; c) determining a baseline window between sensed events and a sensed event window encompassing the sensed event; d) determining a set of signal slopes of the baseline window; e) determining a cumulative distribution of baseline window slopes CDS B ; f) determining a set of signal slopes of the event window; g) determining a cumulative distribution of event window slopes CDS E ; h) calculating a maximum absolute difference KS event between the CDS E and a sigmoid reference function; i) calculating a maximum absolute difference KS baseline between the CDS E and a CDS B ; j) calculating a slope distribution metric SD M value by SD metric =KS baseline âˆ’(0.5 âˆ’KS event ) k) comparing SD M to a slope distribution match threshold; l) accumulating a count x of SD M values that meet the slope distribution match threshold over y repetitions of steps b) through j) as long as a polymorphic tachyarrhythmia is provisionally declared in step a); m) withholding the final declaration of a polymorphic tachyarrhythmia if the count x indicates that the corresponding cardiac signals exhibit frequency content suggestive of a monomorphic tachyarrhythmia; and n) making the final declaration of a polymorphic tachyarrhythmia if the count x indicates that the corresponding cardiac signals exhibit frequency content suggestive of a polymorphic tachyarrhythmia and the polymorphic tachyarrhythmia is provisionally declared in step a).