Intermittent fasciculoventricular pathway: ECG and electrophysiologic findings, clinical implications.

Although fasciculoventricular (FV) pathways never participate into tachycardia circuits, they give rise to ventricular pre-excitation of variable magnitude which can be source of ECG misinterpretation when associated to other supraventricular rhythm disorders. We report an intermittent FV pathway coincidentally unmasked during an electrophysiologic study performed for a symptomatic supraventricular tachycardia (atrial tachycardia). The clinical context, ECG and EP findings, and therapeutic options are described. Fasciculoventricular pathways need no medical or ablative treatment, thus their positive and differential diagnosis must be clearly assessed.