Late thrombotic occlusion of a left internal mammary artery graft causing ST-elevation myocardial infarction

Late occlusion of the left internal mammary artery (LIMA) is rare, and its pathological basis is unknown. We present a case of acute occlusion of the LIMA in a 77-year-old woman, 7 years after graft surgery, causing fatal myocardial infarction. Diagnostic angiography of the LIMA revealed a proximal occlusion just beyond the LIMA origin which re-canalised after repeated injection of contrast with near complete restoration of LIMA patency and flow with smooth angiographic appearance. Despite initial diminution of pain and electrocardiographic changes with recanalisation, pain and ST changes returned and the patient died. Restoration of near normal vessel patency with angiography suggests that the basis of this occlusion is not atherosclerotic plaque rupture, but is more likely to represent in situ thrombosis or, less likely, localized spasm. Early recognition of the possibility of LIMA occlusion may direct initial angiography to the LIMA rather than the native circulation, and reduce the time to reperfusion.