severe persistant cyanosis in a newborn due to prominent eustachian valve

The valves of right horn of systemic venous sinus are prominent structures within the right atrium during early embryonic period. involution of these structures may not be complete, resulting in a spectrum of anatomical presentations such as cyanosis. a fullterm male neonate referred to our hospital for precise evaluation of severe cyanosis on the first day of life. echocardiographic examination revealed righttoleft interatrial shunting through patent foramen ovale due to prominent eustachian valve with normal estimated right heart pressures from peak tricuspid regurgitation velocity. he was maintained with supplemental oxygen and a pde5 inhibitor (sildenafil) and subsequently improvement in oxygen saturation was achieved. the patient was discharged after 2 weeks of treatment. in conclusion; the embryologic remmants of the sinus venosus rarely may lead to righttoleft shunting resulting in severe cyanosis. pulmonary vasodilators such as sildenafil may improve oxygen saturation in these patients even in case of normal right heart pressures.