A 2-year-old male with right isomerism was referred for supraventricular tachycardias. Atrial pacing study revealed that anterograde conduction was only through the posterior atrioventricular node. During the mapping of ventriculoatrial conduction, we identified a sharp potential resembling a His-bundle electrogram with a decremental property at the anterior wall of the common atrium. Catheter ablation for the potential eliminated the anterior ventriculoatrial conduction, thereby indicating retrograde activation of the possible anterior atrioventricular node.
