Myocardial infarction is one of the rarer events causing acute graft failure during the postoperative period after transplantation and is usually caused by preexisting coronary artery disease of the donor heart. We discuss the case of a 56-year-old man in whom cardiogenic shock developed after heart transplantation, which was refractory to all medical treatment. He was put on emergency code and underwent retransplantation 30 hours later. Pathologic examination of the explanted donor heart showed massive recent inferior and posterior wall infarction, with normal coronary arteries; the right coronary artery was dominant and completely occluded by an embolus of fatty material surrounded by fibrin, which we suggest could have originated from the suture line of the left atrium.