Platypnoea-orthodeoxia syndrome: more than just a PFO

Summary Platypnea-orthodeoxia syndrome (POS) is a rare condition characterised by episodes of dyspnoea and desaturation when changing from a recumbent to a sitting or standing position, due to a right-to-left shunt through the atrial septum (cardiac POS) or a pulmonary vascular shunt. A consistent finding among patients with cardiac POS is an interatrial communication (patent foramen ovale [PFO] or atrial septal defect [ASD]), but these often-congenital anatomies, alone, do not account for development of massive right-to-left shunt, which frequently occurs later in life leading to severe hypoxaemia. We present the case of an 84-year-old woman known for evolutive right breast carcinoma with successive loco-regional progressions, which over several years, despite local and systemic therapy, eventually invaded the right pectoral muscle, with skin infiltration of the right chest wall and right diaphragmatic paralysis. She subsequently developed rapidly progressive dyspnoea: a cardiac workup including contrast examinations (trans-cranial duplex and trans-thoracic echocardiography) showed a massive intra-cardiac right-to-left shunt, while transoesophageal echocardiography confirmed the presence of a large PFO. Based on these findings, the patient was diagnosed with POS and PFO closure was performed with immediate normalisation of oxygen saturation, and at 6–month follow-up no further episodes of desaturation were reported. The aim of this case discussion was to underline the mechanisms leading to significant right-to-left shunt among patients with PFO, especially when in an upright position, and to elucidate the therapeutic op