Introduction
Antidromic atrioventricular reentrant tachycardia (AVRT) usually requires an accessory pathway (AP) with good conduction to serve as the anterograde limb of the circuit[1-3]. Pathways demonstrating intermittent or unstable conduction properties are infrequently seen in antidromic tachycardia[1,3,4]. When mapping a pathway, presence of AP potential often suggests a highly effective target for ablation. Here we report a phenomenon of widely split AP potentials due to significantly slow conduction within an atrioventricular pathway in a patient with antidromic AVRT.