[Postoperative hemopericardium compressing the left atrium. Apropos of a case]

We report a case of tamponade due to an effusion of blood which had occurred two weeks after an aorto-coronary bypass and was unusually located behind the left atrium. The effusion, with severe clinical symptoms, was diagnosed by echocardiography and computerized tomography of the chest. These examinations provided an accurate anatomical diagnosis on which the approach route of the emergency operation was based.