Patent ID: 7904142

Claim:
An apparatus comprising: an implantable cardiac signal sensing circuit configured to provide an electrical cardiac signal representative of sensed cardiac activity of a subject; a memory to store at least one template, wherein the template includes a morphology of normal atrial-ventricular (A-V) conduction; a controller, communicatively coupled to the cardiac signal sensing circuit and the memory, including: a tachyarrhythmia detection circuit configured to detect a rhythm with elevated ventricular rate using the electrical cardiac signal; a correlation circuit configured to: iteratively calculate a value of correlation between the electrical cardiac signal and the template; and compare the calculated correlation value to a device-variable correlation threshold to determine whether the detected rhythm with elevated ventricular rate correlates to the template; and a therapy circuit configured to inhibit ventricular tachycardia (VT) therapy when the detected rhythm correlates to the template according to a comparison of the calculated correlation value to the device-variable correlation threshold.