Abnormal inferior vena cava morphology Enlarged Eustachian valve 2017-10-15T12:51:38Z Giant Eustachian valve An abnormally large Eustachian valve (postnatally). The Eustachian valve is also known as the valve of the inferior vena cava, and is an embryologic remnant of the valve of the inferior vena cava. Enlarged inferior vena cava valve During fetal life, the eustachian valve directs oxygen-rich blood from the inferior vena cava (IVC) toward the foramen ovale and away from the tricuspid valve. After the closure of the foramen ovale, it does not have a specific function. In echocardiographic examinations, the eustachian valve may appear as a thin flap originating from the orifice of the IVC, or it may be totally absent. Sometimes it may appear as a rigid, elongated structure in the inferior portion of the right atrium or as a membranous, undulating, echogenic mass within the right atrial cavity.