PV isolation
The procedures were performed by 3 independent operators under conscious sedation with midazolam and with fentanyl or morphine for analgesia. Intracardiac EGMs were recorded (filtered 30–500Hz for bipolar signals) using LabSystem Pro electrophysiology system (Boston Scientific) or Lead electrophysiology system (Jinjiang Electronic). Mapping and ablation was performed in all patients by using 3-dimensional (3D) mapping system (CARTO3, Biosense Webster). A steerable 6-French decapolar catheter (SinusFlex, APT Medical) was introduced into the coronary sinus. Two 8.5-French long sheaths (SL1, St. Jude Medical or NaviEase L1, Synaptic Medical) were advanced into the left atrium after double transseptal puncture guided by fluoroscopy, or by intracardiac echocardiography (CARTOSOUND catheter, Biosense Webster). 3D map of the left atrium was constructed using a duodecapolar mapping catheter (PentaRay with 2–6–2mm electrode spacing, Biosense Webster).
The circumferential ablation line was designed for antral PV isolation approximately 5–15mm away from the PV ostium based on the 3D shell. Radiofrequency ablation was performed with an 8-French 3.5mm irrigated-tip catheter (SmartTouch SF, Biosense Webster) using the approach based on the initial impedance change and ablation index (AI): Radiofrequency energy was delivered with power of 25-40 watts and contact force ranged from 5-20 grams, for a target impedance drop of at least 5 to 10 ohms within the first 10 seconds[12]. Each application was continued until an operator-tailored target AI was reached, or an impedance drop more than 20 ohms, or an abrupt impedance rise was present. AI was usually decreased at posterior wall when energy was delivered near esophagus localized by intracardiac echocardiography or computed tomography.