Abstract

Platypnea-Orthodeoxia Syndrome (POS) is dyspnea and hypoxemia in the upright position that improves in the supine position. Cardiac POS is predominantly caused by congenital interatrial communications (CIC) paired with changes in the thoracic anatomy, allowing orthostatic right to left cardiac shunting. High suspicion, especially with hypoxemia without significant pulmonary disease, that does not easily correct with supplemental oxygen, should lead the clinician to obtain echocardiographic imaging, documenting right to left shunting, typically through a patent foramen ovale (PFO). Transcatheter closure of the CIC is highly successful in relieving symptoms of dyspnea and resolving hypoxemia in the majority of patients.