A 58 year old man underwent mitral valve repair for prolapse of the anterior valve leaflet and consecutive severe mitral regurgitation. After weaning from cardiopulmonary bypass, transoesophageal echocardiography showed a successfully reconstructed mitral valve, but a large mass within or behind the left atrium that had not been present before surgery.

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Hiatal hernia or haematoma formation from oesophageal perforation were excluded by gastroscopy using a paediatric gastroscope while the echocardiography probe was still in place. Suspicion of left atrial thrombus formation could neither be excluded nor confirmed by additional epicardial echocardiography, cardiopulmonary bypass was therefore restarted. Opening the left atrium revealed a bulging posterior left atrial wall and near obliteration of the atrial lumen due to dissection and haematoma formation within the dissected cavity. The entry into the false lumen could not be identified, and the false lumen was therefore marsupialised transseptally to the right atrium (large arrow); the small arrow . . . [Full text of this article]