Persistent Eustachian valve and transient arterial hypoxemia in a newborn: a clinical observation

The Eustachian valve (EV) is located in the orifice of inferior vena cava and belongs to structures of the normal heart. It plays an important role in the fetal blood flow by directing the flow of blood from inferior vena cava through an open foramen ovale to the left atrium, thereby ensuring the systemic flow in a fetus and bypassing the pulmonary circulation. After birth and upon closure of the foramen ovale, the valve ceases to function and tends to regress. Usually, a prominent EV is a clinically non-significant ultrasound finding. In isolated cases, however, it can cause significant hemodynamic abnormalities and subsequent rhythm disorders, delayed fetal development and transient hypoxemia in newborns. It can extremely rare be a cause of blood right-toleft shunting through the foramen ovale leading to desaturation. Clinically it can manifest by central cyanosis in newborns and infants. The differential diagnosis is made in neonatal intensive care units. We present a  case of transient arterial hypoxemia in a  newborn with prominent EV and inter-atrial shunt. A  one-month old infant was transferred from the Department of Pediatric Cardiology with a  history of transient hypoxemic spells related to right-to-left shunting via atrial septal defect caused by obstruction of the tricuspid valve by the prominent EV. The instrumental findings including contrast-enhanced tomography supported this hypothesis. The patient was stable for subsequent 10 days of the follow-up, which allowed for further conservative managements until the conventional time point for children with an atrial septal defect. Potential regress of the prominent EV, as well as natural growth of an infant and his/hers intracardiac structures, provide mostly favorable outcome without a surgical intervention. This was clearly illustrated in the clinical case.