Left superior vena cava conduction to the left atrium unmasked by adenosine in a patient with paroxysmal atrial fibrillation during pulmonary vein isolation

The use of adenosine in unmasking potential 'trigger' activity in a patient with paroxysmal atrial fibrillation (AF) and persistent left superior vena cava (LSVC) has never been reported. In a 75-year-old woman with paroxysmal AF and LSVC anomaly, pulmonary vein isolation (PVI) procedure was performed. After successful PVI, repeated bolus adenosine infusions were given. Adenosine response originating from the LSVC was observed: it was reproducible, brief, and exhibited decremental atrial-to-LSVC conduction properties until cessation. Pacing from the LSVC resulted in atrial capture (confirming vein-to-atrium conduction). Disconnection of the LSVC from the coronary sinus (CS) was obtained by successfully ablating within the distal CS. Adenosine challenge may be important to identify AF triggers in non-PVI foci.