Ablation procedure
Radiofrequency catheter ablation (RFCA) or cryoballoon ablation (CBA) was performed at the discretion of the operators. CA was performed under general anesthesia with 0.4 μg/kg/h of dexmedetomidine, 0.1 mg/kg/h of propofol, and 0.5–1.0 mg of injected fentanyl with non-invasive or invasive positive airway pressure for respiratory support. Esophageal temperature monitoring (Esophastar®, Japan Lifeline Co., Ltd., Tokyo, Japan) was performed. Vascular access was obtained and 2000–3000 U of heparin was intravenously injected, followed by continuous infusion with a target activated clotting time of 300–350 s. A single transseptal puncture was performed using intracardiac echocardiography (SOUNDSTAR®, Biosense Webster, Inc., Diamond Bar, CA, USA or ViewFlex Xtra®, Abbott, St. Paul, MN, USA). For RFCA, two long sheaths (Agilis and 8.0 Fr SL-0 sheath; Abbott, St Paul, MN, USA) were inserted into the left atrium (LA). For CBA, a FlexCath Advance Steerable Sheath® (Medtronic, Inc., Minneapolis, USA) was inserted into the LA. A detailed 3D model of the LA was created using a high-density mapping catheter (PENTARAY®, Biosense Webster Inc., Diamond Bar, CA, USA; HD Grid Mapping Catheter Sensor Enabled®, Abbott, St. Paul, MN, USA; or IntellaMap Orion®, Boston Scientific, Inc, Washington DC, USA) and 3D mapping system (CARTO3®, Biosense Webster, Inc., Diamond Bar, CA, USA; EnSite Velocity™, Abbott, St. Paul MN, USA; or Rhythmia HDx™, Boston Scientific, Inc, Washington DC, USA). Extensive circumferential ablation of the ipsilateral pulmonary veins (PVs) was performed with irrigated-tip ablation catheters (THERMOCOOL SMARTTOUCH® SF, Biosense Webster, Inc., Diamond Bar, CA, USA; TactiCath™, Abbott, St. Paul, MN, USA; or IntellaNav MiFi OI, Boston Scientific, Inc, Washington DC, USA) for RFCA. The radiofrequency energy was 30–35 W, and ablation was performed using ablation index, lesion size index, and local impedance drop as indicators of effective lesion formation. Additional procedures such as posterior wall or superior vena cava isolation were performed at the operators’ discretion. At least 15 min of observation was performed after pulmonary vein isolation (PVI), and spontaneous reconnection and dormant conduction were evaluated by administering 2–4 μg of isoproterenol followed by rapid injection of 20 mg adenosine triphosphate to find the electrical gaps. Additional RFCA was performed at gap areas adjacent to the first-pass ablation line. For CBA, right-sided phrenic nerve pacing was performed to detect phrenic nerve injury. A cryoballoon catheter with a 28-mm balloon (Arctic Front Advance II®, Medtronic, Inc., Minneapolis, USA) and a PV mapping catheter (Achieve Mapping Catheter®, Medtronic, Inc., Minneapolis, USA) were inserted, and freezing for 3 min was performed on each PV. Additional freezing was performed if the PV was not isolated. After PVI, exit blocks were confirmed based on the pacing from the circular mapping catheter in each PV.