Journal of Interventional Cardiac Electrophysiology 4, 241±244(2000) #2000 Kluwer Academic Publishers. Manufactured in The Netherlands. Case Report Unique Interaction Between an Atrial Single-Chamber Pacemaker and a Ventricular De®brillator

Abstract. A well described interaction between an anti-bradycardia pacemaker and a ventricular de®brillator is sensing of pacemaker stimuli by the ventricular de®brillator. This report describes an interaction between an atrial demand pacemaker and a ventricu-lar de®brillator that resulted in ventricular asystole and polymorphic ventricular tachycardia. In this case, the ventricular de®brillator sensed atrial pacing stimuli when complete atrioventricular block with a slow ventricular escape rate developed. De®brillator-based ventricular demand pacing was inhibited, result-ing in prolonged periods of ventricular asystole, polymorphic ventricular tachycardia, and multiple de®brillator shocks. Ventricular de®brillator sensing of atrial pacemaker stimuli in the setting of complete atrioventricular block and ventricular asystole cannot be simulated during de®brillator implantation when atrioventricular conduction is intact. Therefore, a pacemaker programmed to atrial demand pacing in a patient with a ventricular de®brillator can result in inappropriate inhibition of ventricular pacing in the setting of complete heart block. Furthermore, this interaction can be avoided with a dual-chamber pacing ventricular de®brillator. Key Words. complete atrioventricular block, pacemaker±de®brillator interaction, ventricula