Platypnea-Orthodeoxia Syndrome Revealing an Undiagnosed Patent Foramen Ovale: A Case Report

Platypnea-orthodeoxia syndrome (POS) is an uncommon clinical entity characterized by position-dependent hypoxemia that worsens when standing and improves when lying down. Patent foramen ovale (PFO) was the most commonly reported site of an intracardiac shunt. In addition to PFO, intracardiac shunt leading to POS has been reported from either an atrial septal defect (ASD) or an atrial septal aneurysm (ASA). In cases where POS occurs due to intracardiac shunting in the absence of pulmonary hypertension, closure of the defect can be curative. We report a rare case of POS caused by a PFO in a 76-year-old woman. Transesophageal echocardiography was essential for identifying the shunt, excluding the presence of pulmonary hypertension, enabling successful percutaneous closure and complete resolution of her symptoms. This case adds novelty beyond typical PFO-related POS due to delayed diagnosis despite prior thromboembolic events.