Electrophysiological study and ablation
All patients underwent ectopic ablation procedures under conscious sedation, with cessation of all anti-arrhythmic drugs at least five half-lives prior to the procedure. In each case a decapolar catheter was placed in the coronary sinus and 3D electroanatomical mapping was performed using a saline irrigated ablation catheter and one of two mapping systems: CARTO (Biosense Webster Inc., CA, USA) or NavX/Precision (Abbott Labs, IL, USA). Activation mapping was predominantly used to determine the SOO, with supplementary information provided by pace-mapping. Ablation was performed using a force sensing catheter with RF energy at 25-35W with a 17 ml/min flow rate. 30-60 second lesions were created with a target impedance drop of 10 Ohms and a temperature cut-off of 43 degrees Celsius.