We report the case of a patient with a past history of coronary atherosclerosis treated with primary angioplasty 5 hours following an inferior myocardial infarction. Echocardiography performed during the procedure revealed a mediastinal tumour invading the tricuspid, responsible for the occlusion of the right coronary. Infarction due to tumour compression is a rare presentation of mediastinal tumour. Diagnosis relies on echocardiographic, CT or magnetic resonance imaging. The prognosis is linked to the tumour pathology.