Patent foramen ovale and ascending aortic aneurysm causing the platypnea-orthodeoxia syndrome.

Patent foramen ovale (PFO) is present in about 25% of the population. Platypnea-orthodeoxia syndrome (POS), which is dyspnea and hypoxemia in the upright position that is relieved when supine, is a rare manifestation of PFO. We describe a case of a 74-year-old woman who presented with new-onset hypoxia. A PFO and a dilated aorta causing POS were found on workup. Symptoms were resolved after undergoing percutaneous PFO closure. This case highlights the mechanism by which an ascending aortic aneurysm can alter hemodynamics through an existing PFO, leading to symptoms of a previously clinically insignificant PFO, and emphasizes how early recognition of POS allows for appropriate intervention.