An unusual accessory pathway: anteroseptal to ventricular outflow region connection

Accessory pathways are typically located along the left or right atrioventricular junction. Distinct ventricular pre-excitation patterns determined by surface electrocardiography can provide reasonable pathway localization prior to invasive mapping and catheter ablation. We report an accessory pathway producing an unusual electrocardiographic appearance suggestive of ventricular outflow region pre-excitation. Pacing maneuvers and standard intracardiac recordings confirmed an atrial insertion immediately adjacent to the atrioventricular (AV) node and supported a ventricular insertion at the outflow tract region well away from the AV junction. The elimination of pathway conduction was achieved with radiofrequency (RF) energy at the atrial insertion after successful ice mapping excluded AV block at the target site. This is the second such pathway observed at our institution over a 20-year period.