A 63 year old man underwent coronary artery bypass grafting in 1995 from which he made an excellent recovery. In early 2000 he was admitted to hospital with a lower respiratory tract infection. A chest x ray taken at the time suggested a large anterior mediastinal mass. Subsequent computed tomographic scanning demonstrated a 10 × 10 cm mass in the anterior mediastinum, with calcification in the walls. This mass was not present in 1995.

Transthoracic and transoesophageal echocardiograms showed an anterior mediastinal mass compressing the right ventricular outflow tract, and colour flow Doppler demonstrated blood communicating with the mass from the aortic wall, but the exact details of the mass were not clear.

Cardiovascular magnetic resonance imaging demonstrated a vascular mass(*) in the anterior mediastinum (below left). The mass measured 10.6 × 9 cm in size (aneurysm starred, proximal graft arrowed) with signal intensity consistent with a mixture of thrombus and slow moving blood. There was significant compression of the aorta and pulmonary artery (below centre: Ao, aorta; pa, main pulmonary artery; lv, left ventricle). Maximum intensity projection reformatting of the magnetic resonance angiogram (below right) suggested the left internal mammary artery-left anterior descending artery (LIMA-LAD) (long arrow) and saphenous vein graft-obtuse marginal (SVG-OM) (short arrow) grafts were patent, but displaced by the aneurysm. The signal intensity suggested flow in the proximal aneurysm, but no flow distal to the aneurysm. The left ventricular function was normal. There was septal flattening in diastole, suggestive of raised ventricular pressures.

The patient has remained stable and is currently being conservatively managed.