The [valve of the inferior vena cava] is probably better known by its eponym, the [Eustachian valve]. This is an incomplete valve found at the most distal end of the inferior vena cava, at the point where it opens into the right atrium of the heart. The valve is muscular at its base and composed mostly by membranous endocardium, and is normally the only valve present in the inferior vena cava.
It appears as a membranous semilunar fold extending posteriorly from the limbus fossa ovalis, anterior to the inferior caval orifice where it disappears. Its free border is usually membranous, concave, and directed anterosuperiorly. Its base is a transverse muscular ridge continuous with the anterior margin of the caval orifice.
It has no function in the adult, but in the fetus it helps to divert the flow of blood coming from the inferior vena cava towards the foramen ovale [fossa ovalis], as part of fetal circulation.
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|It has great anatomical variation in size, shape and thickness. On its medial aspect it joins with the Thebesian valve at the orifice of the coronary sinus.
First described by Bartolomeo Eustachius (c1500 - 1574) in 1653, the existence of the valve of the inferior vena cava was disputed by many until Winslow in 1717 confirmed its presence and suggested its function in fetal circulation.
1. "The Valve of the Inferior Vena Cava" Hickie, JB Br Heart J. 1956 Jul; 18(3): 320–326
2. "Bartolommeo Eustachio; a great medical genius whose masterpiece remained hidden for 150 years" Wells, WA Arch Otolaring (1925) 48: 58