An anomalous muscle bundle inside the right atrium possibly related to the right venous valve.

The right and left venous valves of the sinoatrial orifice regulate the flow of blood from the sinus venosus to the atrium in pisces, amphibians, and reptiles. In aves, mammals and humans, the venous valve loses its hemodynamic function and hence has become the 'Cinderella' among heart valves, receiving attention only when congenital anomalies occur that are related to it. The right venous valve persists in humans as the crista terminalis, Eustachian and Thebesian valves. An intraluminal muscle band is described located inside the right atrium, and coursing in the line of the crista terminalis between the septum spurium and inferior vena cava. This abnormal band is possibly derived from the right venous valve.