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 Twenty patients with AF (mean age, 64.30 [SD, 7.97] years, five women [25.0%]) with 24 (interquartile range: 6–60) months of AF duration underwent EIVOM (7.8 ± 2.1 mL). Voltage dropped from 1.92 (1.12–2.61) to 1.24 (0.91–2.05) mV postprocedure ( p < 0.05), particularly in the atrial ridge regions. CV remained unchanged (1.00 [0.92–1.10] vs. 1.02 [0.95–1.14] m/s, p = 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.