Platypnoea-orthodeoxia syndrome (POS) is characterized by dyspnoea and arterial desaturation in the sitting position. Although its pathophysiology is complex and still needed to be investigated, the disease is one of the clinical situations which should be immediately and adequately managed by health care workers from the initial presentation.
A 66-year-old woman with a history of systemic lupus erythematosus, deep vein thrombosis, and lumbar compression fracture was admitted for evaluation of the sudden onset of dyspnoea, while in the sitting position that was relieved on placing her in the supine position. Her transoesophageal echocardiogram did reveal a deformity in the patent foramen ovale (PFO) structure with a wide gap due to aortic compression, which was markedly different from that observed in the supine position, along with massive right-to-left shunting caused by redirected venous return due to a persistent Eustachian valve. With the computed tomography and angiograms, POS was diagnosed. Then, the patient received aortic replacement and patch closure of PFO, and her symptoms were completely resolved.
Platypnoea-orthodeoxia syndrome is a condition with quite unique features and needs multiple clinical measures for the diagnosis and medical management. For all health care workers, it is essential to have a high suspicion in order to detect POS in patients with unexplained dyspnoea. Echocardiography plays a major role in establishing the diagnosis and offering the choice of therapeutic options.

© The Author(s) 2020. Published by Oxford University Press on behalf of the European Society of Cardiology.