The arrhythmogenicity of the vein of Marshall (VoM) in atrial fibrillation (AF) has been known for more than 20 years.1 A recent randomized trial showed a reduced odds ratio (0.63; 95% confidence interval 0.41–0.97; P = .04) for the primary outcome of AF or atrial tachycardia (AT) recurrence in patients with persistent AF by adding VoM ethanol infusion (VoM-Et) to the standard ablation approach.2 The VoM is involved in 30% of ATs after AF ablation, and VoM ablation significantly improves the freedom from recurrent arrhythmia.