Patent ID: 8260409

Claim:
A method comprising: sensing a first intrinsic cardiac signal during a normal sinus rhythm (NSR) using at least one heart rate sensing electrode and sensing a second intrinsic cardiac signal during the NSR using at least a second sensing electrode; generating a template using the first and second sensed cardiac signals, the template including a fiducial point on the first cardiac signal and correlation features on the second cardiac signal; sensing a third intrinsic cardiac signal during a detected rhythm with elevated ventricular rate using the rate sensing electrode and sensing a fourth intrinsic cardiac signal during the detected rhythm using the second sensing electrode; identifying a first fiducial position in the third cardiac signal and aligning the template correlation features and the correlation features of the fourth cardiac signal using the first fiducial position; calculating a correlation using the correlation features of the template and the correlation features of the fourth cardiac signal; iteratively searching for a replacement to the first fiducial position in the third cardiac signal according to the calculated correlation; and detecting tachyarrhythmia using the calculated correlation.