Vein of Marshall Ethanol Infusion in Atrial Fibrillation.

The vein of Marshall (VOM) is a patent segment of the left cardinal vein that shrinks during embryologic development. The VOM runs along the lateral ridge of the left atrium, between the left pulmonary veins and the left atrial appendage, where it colocalizes with fat, intrinsic nerves, and a vestigial epicardial musculature named the Marshall bundle (MB). Ectopic beats can originate from the MB and trigger atrial fibrillation (AF) under sympathetic input. It has also been shown that high-frequency stimulation of the parasympathetic intrinsic nerves near the VOM induces AF. Because fat-insulating properties strongly protect the MB against electric energy, it frequently supports epicardial gaps during mitral line ablation. The VOM is a true atrial vein that can be safely used as a vascular route for retrograde chemical ablation of these structures implicated in the AF process and mitral isthmus gaps. Recent randomized studies show that VOM ethanol infusion improves sinus rhythm maintenance in patients with persistent AF, all the more if combined with mitral line block, which it greatly facilitates. Beyond pulmonary vein isolation, anatomical atrial transection conditioned by successful VOM ethanol infusion seems a promising strategy for persistent AF ablation.