Study procedure
Details of the procedure in each group are shown in Figure 2 and 3 . EI-VOM was taken as the first step of the “upgraded 2C3L” approach in group 1. An 8.5-French-long sheath (SL1; St.Jude Medical, Minnetonka, MN, USA) is inserted into the right atrium just below the CS ostium, and a steerable long sheath (Agilis NxT; Abbott) is used if necessary. Under the right anterior oblique view, a 6F guiding catheter (Judkins R4.0, Medtronic, MN) is inserted into the CS pointing posteriorly and superiorly near the Vieussens Valve in search of the VOM ostium, and then a selective VOM venogram was acquired. A BMW guiding wire (0.014 inch × 190 cm; Abbott, MN) supported by an over‐the‐wire balloon (1.5‐2.5 mm diameter and 8‐12 mm length, Boston Scientific) catheter is advanced into the VOM. An appropriately sized balloon was gradually inflated at a maximum of 6 to 8 atm in the VOM. A selective venogram of the VOM is obtained by injecting 1 mL of contrast medium to confirm complete balloon occlusion and VOM distribution. 2-4 mL of ethanol (95% ethanol) is slowly injected into the distal of VOM and selective venography of the VOM is repeated. After 5 minutes, in the same way, another injection is performed for the proximal and/or middle part of the VOM. The maximum ethanol volume allowed was 12 ml. The endpoint of EI-VOM is the contrast media staining colocalizing the course of VOM.
RF ablation using the ‘2C3L’ approach is performed in both group 1 and group 2, the details of which have been described previously [2]. In brief, single-catheter technique was adopted for the ablation procedure in LA. Bilateral circumferential pulmonary vein antrum (PVA) ablation was firstly performed, followed by the roofline joining two circumferential lesions, and then posterior MI ablation was performed extending from the annulus to the left inferior pulmonary vein ostium. The CS will also be ablated if necessary. CTI ablation starts from the 6’o clock of the tricuspid valve annulus to the inferior cava vein. If an organized AT occurred during the procedure, mapping guided ablation will be performed. Cardioversion was performed if AF persists. After the restoration of SR, LAA was mapped to observe whether significant LAA activation delay was present, which was defined as the local activation of the LAA delayed beyond the onset of QRS wave.
In both groups, the endpoint of the procedure is complete PVAI and bidirectional block along all ablation lines, which was confirmed under sinus rhythm[7, 8].