Electrophysiological Study
As previously described2, an electrophysiological procedure was performed with standard catheter positions in the coronary sinus, His bundle region and high anterolateral right atrial wall after informed consent was obtained. Following a single transseptal puncture by use of the modified brockenbrough technique and an 8 Fr SL1 transseptal sheath (St. Jude Medical), systemic anticoagulation was made with intravenous heparin (50 u/kg) was administered, with additional 1000 u boluses every hour after the first infusion. An ablation catheter was positioned at the left atrium through a transseptal puncture. Then activation mapping with the Ensite Precision (St Jude Medical, Inc., Minnesota, USA) cardiac mapping system was performed at the left atrium.