Anatomic Variants Mimicking Pathology on Echocardiography: Differential Diagnosis

Anatomic variants are particularly common in the right atrium (RA). During cardiac development, embryonic sinus venosus fuses with trabecular RA appendage.1) The right sinus valve of embryonic sinus venosus normally regresses forming the crista terminalis and the Eustachian valve. Such regression process is highly variable. Incomplete regression results a spectrum of vestiges, such as Chiari network, Eustachian valve of inferior vena cava (IVC), the Thebesian valve of the coro-nary sinus, and a prominent crista terminalis.2) The Eustachian valve is a remnant of embryonic valve of IVC, which directs oxygen-rich vena caval return toward in-teratrial septum and left atrium (LA) in fetal heart. Eustachian valve appears as crescent-like fold of variable size at posterior margin of IVC (Fig. 1). In echocardiography, leaf-like linear structure is shown at the junction of IVC and RA. Right ven-pISSN 1975-4612 / eISSN 2005-965