Patent ID: 8494618

Claim:
A system comprising: a medical device including: a cardiac cycle sensing circuit, the sensing circuit configured to provide a sensed cardiac cycle; an impedance measurement circuit configured to provide an intracardiac impedance signal; and a controller circuit coupled to the impedance measurement circuit, the controller circuit configured to detect tachyarrhythmia from the intracardiac impedance signal using at least two of: a cardiac-cycle-to-cardiac-cycle change in a value of a baseline intracardiac impedance value calculated, for a particular cardiac cycle, to represent the baseline intracardiac impedance for that particular cardiac cycle; a cardiac-cycle-to-cardiac-cycle change in a value of maximum intracardiac impedance value calculated, for a particular cardiac cycle, to represent the maximum intracardiac impedance for that particular cardiac cycle; and a cardiac-cycle-to-cardiac-cycle change in a slope value of the intracardiac impedance waveform signal, for a particular cardiac cycle, the slope value measured at a time corresponding to one-half of a time interval over which a maximum intracardiac impedance change occurs during that particular cardiac cycle.