Intermittent cyanosis due to prominent eustachian valve in a newborn infant.

A full-term neonate presented with cyanosis only when sleeping, which was considered due to a prominent eustachian valve, directing blood flow from the inferior vena cava to the left atrium through the foramen ovale resulting in interatrial right-to-left shunting. In addition to the anatomical features, hemodynamic features shortly after birth, such as patent foramen ovale and high pulmonary vascular resistance, were also probably involved in the mechanism responsible for the patient's cyanosis. This case may provide insight into differential diagnosis for cyanotic infants.