An 80-year-old man was admitted with severe refractory hypoxaemia following right lung radiotherapy for pulmonary carcinoma. The hypoxia was enhanced by the upright position and was associated with cyanosis. Computed tomography and lung scintigraphy did not identify a pulmonary cause explaining the degree of hypoxaemia. Transthoracic echocardiography (TTE) showed mild aortic root dilatation (48 mm) and a highly mobile atrial septum. Contrast-enhanced TTE showed massive and spontaneous right-to-left shunting through a large patent foramen oval (PFO). Transoesophageal echocardiography during PFO closure identified a markedly thickened septum secundum due to lipomatous hypertrophy and a very thin and floppy septum primum ( Fig. 1 ). Right-sided pressures were within the normal range. A 20-mm sizing balloon (NMT Medical, Boston, MA) engaged inside the tunnel showed an initial waist due to the septum secundum, but with further advancement no additional waist was identified suggesting a large PFO up to 20 mm ( Fig. 2 ). A 35-mm Amplatzer ® Cribriform occluder was implanted with excellent shunt resolution and immediate and sustained improvement in gaseous exchange ( Fig. 3 ).
