Unusual case of preoperative hypoxaemia

Colour flow doppler revealing shunt from right to left atria across a patent foramen ovale (white arrow); Left atrium= LA, Right atrium= RA and interatrial septum= IAS Chest radiograph was normal as was spirometry with a forced expiratory volume (FEV1) of 132% predicted, forced vital capacity (FVC) of 145% predicted with an FEV1/FVC ratio of 71%. Previously documented acquired anatomic causes, other than kyphosis,1 include lung resection,4 aortic dilatation5 and spinal cord injury.6 In lung resection, the problem can be due to an altered mediastinal anatomy displacing the interatrial septum in relation to a fixed inferior vena cava.4 Alternatively, postoperatively an elevated right hemidiaphragm can compress the right ventricle with resultant pressure increase in the right atrium and subsequent shunting through a PFO.4 In pathological interatrial shunting, the mainstay of treatment usually consists of closure of the septal defect. Incidence and size of patent foramen ovale during the first 10 decades of life: an autopsy study of 965 normal hearts.