Patent ID: 8321016

Claim:
An implantable medical device comprising: a tachyarrhythmia detector that detects a ventricular tachyarrhythmia in a heart of a subject based on an electrocardiogram signal measured for said heart; an impedance determining unit that determines a cardiogenic impedance signal representative of volumetric dynamics of at least one ventricle of said heart; a state defining unit that defines a current subject state of said subject; and a tachyarrhythmia classifier that classifies said ventricular tachyarrhythmia as a stable ventricular tachyarrhythmia or an unstable ventricular tachyarrhythmia based on said cardiogenic impedance signal; wherein said tachyarrhythmia classifier comprises: a template selector that selects a defined signal template from a set of multiple defined signal templates based on said current subject state defined by said state defining unit, each defined signal template being associated with a given subject state; and a comparator that compares said cardiogenic impedance signal with said defined signal template selected by said template selector.