Platypnea - Orthodeoxia Syndrome Caused by a Patent Foramen Ovale Associated with Ascending Aortic Ectasia

Platypnea–orthodeoxia syndrome (POS) is a rare and often underdiagnosed condition characterized by dyspnea and arterial desaturation induced by the upright position, with improvement in the supine position. The most common mechanism involves a right-to-left shunt, frequently through a patent foramen ovale (PFO), facilitated by anatomical or functional alterations. We report the case of a 73-year-old woman admitted with recurrent episodes of exertional dyspnea and severe hypoxemia. Initial investigations, including chest imaging and laboratory tests, were unremarkable. Marked positional hypoxemia was documented by arterial blood gas analysis, with significant improvement in the supine position. Given the clinical suspicion of platypnea–orthodeoxia syndrome, transesophageal echocardiography was performed and revealed a patent foramen ovale with a right-to-left shunt triggered by upright posture and Valsalva maneuver, associated with an atrial septal aneurysm and a horizontally oriented, ectatic ascending aorta. Percutaneous closure of the PFO was successfully performed, resulting in complete resolution of symptoms and normalization of oxygen saturation. This case highlights the importance of considering platypnea–orthodeoxia syndrome in patients with otherwise unexplained positional hypoxemia. Careful clinical observation and targeted imaging performed in the appropriate posture are essential for diagnosis. Percutaneous closure of the intracardiac shunt can lead to rapid and complete symptom resolution.