AN OPTIMIZED AV DELAY ALGORITHM FOR PATIENTS WITH INTERMITTENT ATRIOVENTRICULAR-CONDUCTION

Defection and promotion of an intermittent atrioventricular (AV) condu ction is the objective of an AV delay hysteresis algorithm in dual cha mber pacemaker (DDD) pacing. The AV delay following an atrial event is automatically extended by a programmable interval (A S' hysteresis in terval) if the previous cycle showed spontaneous AV conduction, i.e., a ventricular event was detected within the previous AV delay. An auto matic search mode scans for spontaneous ventricular events during the hysteresis interval: a single AV delay extension (equal to the program med AV delay hysteresis) will occur after a successive, programmable n umber of A Sr cycles with ventricular pacing. If a spontaneous AV cond uction is present, the AV delay will remain extended by the hysteresis interval. Our first results in 17 patients with intermittent AV block disclosed a satisfactorily working algorithm with effective reduction of ventricular stimuli. In relation to the underlying conduction dist urbance and pacemaker settings, the majority of our patients showed a reduction of ventricular pacing events up to 90% without any adverse h emodynamic or electrophysiological changes. Based on clinical (promoti on of a physiological activation and contraction sequence) and technic al (reduction of power consumption) advantages, the AV hysteresis prin ciple could be of increment al value for future dual chamber pacing in patients with intermittent complete heart block.