Eustachian valve

The eustachian valve (also known as the "valve of the inferior vena cava") is a ridge of variable thickness in the inferior right atrium. It is a remnant of a fetal structure that directed incoming oxygenated blood to the foramen ovale and away from the right atrium.

Incomplete regression of this structure results in a thickened ridge at the IVC/RA junction, which can occasionally be thick enough to mimic thrombus or a right atrial mass on echocardiography, cardiac CT, or cardiac MRI.

A thickened eustachian valve may also interfere with placement of an atrial septal defect or patent foramen ovale closure device.