Ablation of a symptomatic spontaneous automatic focus arising from an atriofascicular fiber

Atriofascicular accessory pathways (AP), often referred to as Mahaim pathways, are uncommon electrical connections that most often course along the lateral right atrium and insert within the distal right bundle branch (RBB). Pathognomomic electrophysiological characteristics are well described, including unidirectional anterograde conduction with AV node–like decremental properties. Reported targets for ablation include the site of the Mahaim potential along the atrial aspect of the tricuspid annulus or at the ventricular insertion site of the pathway. Spontaneous activity arising from an atriofascicular AP fiber has been described during ablation of its atrial insertion. Herein, we report the first case of ablation of symptomatic atriofascicular AP automaticity mimicking apicolateral right ventricular (RV) ectopy, which manifested years after AP ablation for antidromic atrioventricular reentrant tachycardia (AVRT).