Notched P-wave related to a conduction disturbance in a thoracic vein as a potential arrhythmogenic substrate of atrial fibrillation

A 65-year-old male underwent a second ablation procedure for recurrent paroxysmal atrial fibrillation (AF). Twelve-lead ECG during sinus rhythm exhibited biphasic and split P-wave with a prolonged duration, which called notched P-wave (NPW). Radio-frequency applica-tion in the coronary sinus (CS) resulted AF termination and elimination of triggering ectopy with NPW disappearance. The CS musculature which played a principal role in triggering and maintaining AF formed the NPW. In patients with repetitive recurrent AF after the estab-lishment of the PV isolation who exhibit NPW during sinus rhythm, the CS might be one of the arrhythmogenic sources of AF.