A system comprising: an implantable medical device comprising: an electrical stimulation circuit, configured to provide pacing electrical stimulation energy to an implantable ventricular electrode and an implantable atrial electrode; a ventricular sensing circuit, configured to detect an intrinsic ventricular tachyarrhythmia depolarization; a ventricular sensing circuit timer, configured to initiate timing of a lowest tachy rate zone interval and also a ventricular pace pulse interval; and an atrial pacing timer circuit configured to: calculate an atrial pace pulse interval to follow the intrinsic ventricular depolarization using the ventricular pace pulse interval less a paced atrioventricular delay interval; delay generation of the atrial pace pulse until after expiration of the LTR zone interval by decreasing the paced AV delay interval when the calculated atrial pace pulse interval is within the LTR zone interval, thereby preserving the ventricular pace pulse interval; and disable decreasing of the paced AV delay interval when an established lower rate limit interval less the paced AV delay interval at the LRL is less than the LTR zone interval. an implantable medical device comprising: an electrical stimulation circuit, configured to provide pacing electrical stimulation energy to an implantable ventricular electrode and an implantable atrial electrode; a ventricular sensing circuit, configured to detect an intrinsic ventricular tachyarrhythmia depolarization; a ventricular sensing circuit timer, configured to initiate timing of a lowest tachy rate zone interval and also a ventricular pace pulse interval; and an atrial pacing timer circuit configured to: calculate an atrial pace pulse interval to follow the intrinsic ventricular depolarization using the ventricular pace pulse interval less a paced atrioventricular delay interval; delay generation of the atrial pace pulse until after expiration of the LTR zone interval by decreasing the paced AV delay interval when the calculated atrial pace pulse interval is within the LTR zone interval, thereby preserving the ventricular pace pulse interval; and disable decreasing of the paced AV delay interval when an established lower rate limit interval less the paced AV delay interval at the LRL is less than the LTR zone interval. an electrical stimulation circuit, configured to provide pacing electrical stimulation energy to an implantable ventricular electrode and an implantable atrial electrode; a ventricular sensing circuit, configured to detect an intrinsic ventricular tachyarrhythmia depolarization; a ventricular sensing circuit timer, configured to initiate timing of a lowest tachy rate zone interval and also a ventricular pace pulse interval; and an atrial pacing timer circuit configured to: calculate an atrial pace pulse interval to follow the intrinsic ventricular depolarization using the ventricular pace pulse interval less a paced atrioventricular delay interval; delay generation of the atrial pace pulse until after expiration of the LTR zone interval by decreasing the paced AV delay interval when the calculated atrial pace pulse interval is within the LTR zone interval, thereby preserving the ventricular pace pulse interval; and disable decreasing of the paced AV delay interval when an established lower rate limit interval less the paced AV delay interval at the LRL is less than the LTR zone interval. calculate an atrial pace pulse interval to follow the intrinsic ventricular depolarization using the ventricular pace pulse interval less a paced atrioventricular delay interval; delay generation of the atrial pace pulse until after expiration of the LTR zone interval by decreasing the paced AV delay interval when the calculated atrial pace pulse interval is within the LTR zone interval, thereby preserving the ventricular pace pulse interval; and disable decreasing of the paced AV delay interval when an established lower rate limit interval less the paced AV delay interval at the LRL is less than the LTR zone interval.