Valve of inferior vena cava

The valve of the inferior vena cava (Eustachian valve) is a crescent-shaped fold of endocardium located at the junction where the inferior vena cava enters the right atrium. In adults, the Eustachian valve is typically rudimentary and has no significant hemodynamic function, but in fetal life, it helps direct oxygenated blood from the IVC toward the foramen ovale and into the left atrium, bypassing the pulmonary circulation.

The Eustachian valve is derived embryologically from the right valve of the sinus venosus. Remnants of this structure in adults may also contribute to the formation of the crista terminalis and, in some cases, the Thebesian valve at the coronary sinus orifice.

The valve is most often visualized as a thin, mobile structure on echocardiography or during anatomical dissection, and its prominence can vary widely among individuals.