Paradoxical Platypnea-Orthodeoxia Syndrome Induced by Patent Foramen Ovale and Highly Tortuous Descending Thoracic Aorta: A Case Report.

Perioperative hypoxemia is common in patients with aortic dissection. Platypnea-orthodeoxia syndrome (POS), in which hypoxemia in the upright position improves with relocating to a recumbent position, can be a rare cause of hypoxemia. This syndrome is more likely to occur in patients with an intracardiac shunt and aortic malformation. Hypoxemic symptoms present in our patient were paradoxical to those of common POS due to the highly tortuous descending thoracic aorta (DTA) and Eustachian valve. Therefore, establishing the diagnosis was difficult. POS should be suspected when patients with high tortuosity and curvature of DTA show hypoxemia.