Abstract
A patient with a large tumour of the superior mediastinum, detected by routine chest X-ray examination, is presented. Compression of the heart and the superior mediastinum produced the clinical picture of cardiac tamponade and obstruction of the superior vena cava and trachea. The solid nature of the tumour was established by echocardiography which, in addition, showed: (1) posterior displacement of the heart; (2) diminished dimensions of the left atrium and left ventricle; (3) prominent respiratory variation in the position of the interventricular septum, the dimensions of both ventricles, and the duration of systolic separation of the aortic valve cusps; and (4) 'pseudo-prolapse' of the mitral valve. All abnormal clinical signs and echocardiographic findings disappeared promptly after surgical resection of the tumour which was found to be a thymoma.