Patent ID: 8239022

Claim:
A method for discriminating between cardiac signal waveforms using an implantable medical device, said method comprising: sensing atrial waveforms of a heart and determining an atrial rate based on the atrial waveforms; sensing ventricular waveforms of the heart and determining a ventricular rate based on first candidate waveforms and second candidate waveforms within the ventricular waveforms; determining if the ventricular rate exceeds the atrial rate; if the ventricular rate exceeds the atrial rate, comparing each of the first candidate waveforms of the ventricular waveforms and the second candidate waveforms of the ventricular waveforms to a first predetermined waveform template to obtain a first morphology indicator and a second morphology indicator, wherein the first and second morphology indicators represent a degree to which the respective first and second candidate waveforms match the first predetermined waveform template; determining if the ventricular rate is correct, based on one or both of the first morphology indicator and the second morphology indicator; if the ventricular rate is correct, applying therapy; if the ventricular rate is incorrect, comparing the ventricular rate to the atrial rate to determine if the ventricular rate exceeds the atrial rate by a threshold amount; and if the ventricular rate exceeds the atrial rate by the threshold amount, inhibiting the application of therapy to the heart, otherwise applying therapy.