Eustachian valve

Eustachian valve/Persisent sinus venosus valve is an embryologic remnant of the inferior vena caval valve in the right atrium. This forms a ridge along the posterior wall of the right atrium and runs from the right side of the inferior vena cava to the interatrial septum, where it joins the fossa ovalis. In the fetal circulation, the Eustachian valve directs the oxygenated blood from the inferior vena cava across the interatrial septum to the left side of the heart. This membrane usually regresses, but can be quite prominent and can occasionally be mistaken for other masses.