Platypnea-Orthodeoxia Syndrome Secondary to Patent Foramen Ovale and Pulmonary Thromboembolism.

Platypnea-orthodeoxia syndrome (POS) is a rare condition characterized by dyspnea (platypnea) and hypoxemia (orthodeoxia) in the upright position, with symptom relief in the supine position. It is often linked to right-to-left shunts, such as a patent foramen ovale (PFO), and other factors like pulmonary embolism (PE) and aortic dilation. We present an 86-year-old woman with hypertension and dementia who developed POS following multiple events. She previously experienced platypnea after a vaginal hysterectomy 4 years before the present event, which resolved with hemoglobin normalization. On admission for ischemic stroke, she developed hypoxemia upon standing, which improved in the left lateral decubitus position. Pulmonary CT angiography revealed PE, and transthoracic echocardiography identified a left-to-right intracardiac shunt. Transesophageal echocardiography confirmed a PFO with bidirectional flow. Despite the diagnosis, surgical closure was not pursued due to her comorbidities, and she was treated with anticoagulation and oxygen therapy. This case highlights the diagnostic challenges of POS, which can result from a combination of intracardiac (PFO), pulmonary (PE), and aortic causes. The patient's symptoms were initially misattributed, in the first event of platynea that occurred 4 years before, delaying diagnosis. Paradoxical embolism from PFO may have contributed to her ischemic stroke. Early recognition of POS could improve outcomes, preventing complications like stroke and respiratory failure. POS is often underrecognized, especially in patients with unexplained positional dyspnea and stroke. Timely diagnosis and management can reduce the risk of severe complications, including paradoxical embolism, but a high degree of suspicion is necessary.