Comparison of the effect of ethanol infusion into the vein of Marshall between with and without collateral veins

Background Despite the potential benefits of ethanol infusion into the vein of Marshall (EIVOM) for atrial fibrillation (AF) ablation, concerns about its reversible and unpredictable effects persist. Objective To assess the effectiveness of EIVOM in the vein of Marshall (VOM) with collateral veins (CVs) during mitral isthmus and AF ablation. Methods We included 142 AF patients. EIVOM was performed before radiofrequency ablation, and low‐voltage areas (<0.5 mV) were measured before, immediately after, and 1 h after EIVOM. Results Among the 142 patients, 93 (65%) underwent EIVOM, and among these, 35 (37%) were found to have CVs. In the VOM with CVs group, areas with low voltage measured 0 (0–1.85) cm 2 before EIVOM, 6.9 (4.1–11.2) cm 2 immediately after EIVOM, and 5.7 (3.5–10.6) cm 2 1 h after EIVOM. Conversely, in the group designated as VOM without CVs—from which the nine leakage cases were excluded—the areas measured 0 (0–1.35) cm 2 , 5.5 (2.6–11.8) cm 2 , and 4.7 (1.8–13.5) cm 2 at the respective time points. MI line block was fully achieved in 89% (31/35) of cases in the VOM with CVs group and 88% (44/49) in the VOM without CVs groups ( p = .94). There was no significant difference in the outcome of AF ablation between these groups (log‐rank p = .73). Additionally, no significant difference was observed between EIVOM (+) and EIVOM (−) groups (log‐rank p = .59). Conclusion EIVOM effectively creates MI line block, and its beneficial effects are sustained for at least 1 h after the procedure despite the low‐voltage areas showing a slight reduction in size.