Interatrial conduction block–related atrioventricular dyssynchrony treated with dual-site atrial pacing

Abstract

Dual-site atrial pacing can overcome interatrial conduction block and achieve AV synchrony as well as reduce unnecessary ventricular pacing. Introduction Interatrial conduction block (IACB) has been well described and is mostly seen in patients at risk of atrial fibrosis from advanced age, cardiac structural abnormalities, prior cardiac surgery, and extensive atrial ablation. In advanced forms, IACB is associated with increased burden of tachyarrhythmia, interatrial dyssynchrony with shortened left atrioventricular intervals as well as poor left atrial contractility, and functional atrioventricular (AV) block owing to delayed or absent conduction of sinoatrial nodal impulses to the AV node. Even with a dual-chamber pacemaker, conduction block of the atrial paced impulse owing to the lead tip being positioned proximal to the region of block can result in unnecessary ventricular pacing. This can potentially cause pacemaker syndrome if ventricular-paced beats are able to conduct retrograde via the AV node to the atrial tissue on the distal aspect of the region of block. Dual-site atrial pacing has been performed temporarily for the prevention of atrial fibrillation in post–coronary artery bypass graft patients as well as permanently in those at high risk for recurrence of atrial fibrillation. We report a rare case where dual-site atrial pacemaker “upgrade” was performed in a patient with IACB and a pre-existent traditional dual-chamber pacemaker, leading to resolution of unnecessary ventricular pacing and systemic AV dyssynchrony.