Patent ID: 7376461

Claim:
In a multi-chamber cardiac rhythm management device capable of detecting tachyarrhythmia, a method of avoiding undersensing of ventricular tachycardia due to brady/tachy crossover, the method comprising the steps of: establishing an upper pacing rate limit interval in the device; establishing a lowest tachy zone interval in the device, wherein the upper pacing rate limit interval is greater than the lowest tachy rate zone interval; programming a scheduled first paced AV delay interval in the device between a scheduled atrial pace pulse and a scheduled ventricular pace pulse; progranmiing a specified fixed minimum paced AV delay interval between an atrial pace pulse and a ventricular pace pulse in the IMD, wherein the specified fixed minimum paced AV delay interval is shorter than the first paced AV delay; detecting an intrinsic ventricular tachyarrhythmia depolarization, thereby initiating timing of the lowest tachy rate zone interval, and also thereby initiating timing of a ventricular pace pulse interval; calculating an atrial pace pulse interval to follow the intrinsic ventricular depolarization using the ventricular pace pulse interval less the first paced AV delay interval; if the calculated atrial pace pulse interval is within the lowest tachy rate zone interval and the ventricular pace pulse interval less the lowest tachy rate zone interval equals or exceeds the specified fixed minimum paced AV delay, then delaying generation of the atrial pace pulse until after expiration of the lowest tachy zone interval by reducing the first paced AV delay, thereby preserving the ventricular pace pulse interval; and if the calculated atrial pace pulse interval is within the lowest tachy rate zone interval and the calculated ventricular pace pulse interval less the lowest tachy rate zone interval is less than the specified fixed minimum paced AV delay, then delaying the atrial pace pulse until after expiration of the lowest tachy rate zone interval and delaying generation of the ventricular pace pulse until after the minimum paced AV delay interval elapses following the delayed atrial pace pulse.