Ethanol infusion of the vein of Marshall reduces localized voltage but preserves mitral isthmus conduction velocity

Background: Ethanol infusion of the vein of Marshall (EIVOM) has emerged as a promising adjunct to pulmonary vein isolation (PVI) for atrial fibrillation (AF). Methods: Patients undergoing catheter ablation for persistent AF (>3 months) were enrolled in this study. After PVI, high-density mapping (HD-Grid, Abbott, St Paul, MN) was performed during coronary sinus pacing (100 bpm) to assess left atrial conduction velocity (CV) and voltage. EIVOM was then performed (1-3 mL ethanol × 3 doses), followed by repeat mapping. The CV and voltage were analyzed in the left lateral wall (mitral isthmus/appendage base), with ≥300 points collected per region. A post-EIVOM electrophysiological study with isoprenaline was conducted to induce arrhythmias. Results: = 0.15). Atrial flutter was induced in three patients (one mitral isthmus-dependent, one tricuspid isthmus-dependent, and one roof-dependent). All patients maintained sinus rhythm at discharge without complications. Conclusions: In the acute setting, EIVOM induces localized voltage reduction in the atrial ridge regions without markedly affecting conduction velocity in the mitral isthmus areas.