Right-to-left atrial shunting associated with aortic root aneurysm: a case report of a rare cause of platypnea-orthodeoxia syndrome.

Platypnea-orthodeoxia is a rare syndrome characterised by dyspnoea and hypoxaemia worsened on upright posture. We report the case of a 76 year-old man treated for lung adenocarcinoma who had developed severe hypoxaemia due to right-to-left shunt through a patent foramen ovale (PFO). Diagnosis was suspected by systemic uptake of isotope during lung scintigraphy performed to exclude pulmonary embolism. Arterial blood gas analysis in supine and upright positions demonstrated orthodeoxia. Contrast-enhanced transoesophageal echocardiography revealed a slightly redundant atrial septum and large right-to-left shunt through a PFO despite normal pulmonary pressure. Chest computed tomography and echocardiography showed a 59-mm aneurysm of the thoracic aorta. The opening of the PFO seemed to be the result of mechanical deformation of the atrial septum by aortic root dilatation. Transcatheter closure of the atrial defect has provided excellent results, including a rapid increase in systemic saturation and improvement of symptoms without any complications.