(A) Endocardial recordings showing the left superior pulmonary vein activity before ablation. Bipole 20A 13-14 shows the earliest activation. I: surface electrocardiogram  lead recording; 20A 1-20: bipolar endocardial recordings from circumferential mapping catheter; CARTO^® 3 system 1-2: bipolar endocardial recordings from distal bipole on the coronary sinus catheter; Map 1-2: bipolar endocardial recordings from distal bipole on the ablation catheter. (B) CARTO^® 3 system views showing a duodecapolar circular mapping catheter placed at the ostium of left superior pulmonary vein and an ablation catheter close to a specific dipole (yellow circles) of the mapping catheter, corresponding to 20A 13-14 bipole.