severe persistant cyanosis in a newborn due to prominent eustachian valve

abstractthe 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 full-term male neonate referred to our hospital for precise evaluation of severe cyanosis on the first day of life. echocardiographic examination revealed right-to-left 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 pde-5 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 right-to-left 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.