Indigence of atherosclerosis in the left internal mammary artery selected for coronary artery bypass graft

ABSTRACT

In patients undergoing coronary artery bypass graft [CABG] surgery at Queen Alia Heart Institute, internal mammary grafts are the second most commonly used conduits for myocardial revascularization, i.e. saphenous vein grafts. This prospective study was designed to determine the incidence of atherosclerosis in the left internal mammary artery [LIMA]. Patients and Materials In 100 consecutive patients undergoing coronary artery bypass graft a biopsy was taken from the distal left internal mammary artery. There were 95 males and 5 females with a mean age of 56.1 years. The presence of risk factors for atherosclerosis [smoking, diabetes mellitus, hypertension, hyperlipidemia and family history of coronary artery disease] was documented as well as other concomitant diseases. The atherosclerotic involvement of LIMA was classified histologically into grade 0,1,2 and 3. Grade 0 corresponds to normal artery without atherosclerosis, Grade 1 minimal intimal hyperplasia, Grade 2 lumen obliteration of less than 50% and Grade 3 lumen obliteration of more than 50%. Of the 100 LIMA specimens examined, five were found to have evidence of atherosclerosis. Only one patient had grade 3 atherosclerosis and was suffering from connective tissue disease on steroid therapy. The five patients were all males with ages ranging between 45-55 years. The atherosclerotic involvement of LIMA has not correlated to a constant risk factor. The internal mammary artery [IMA] is not immune but definitely has a lower incidence of atherosclerosis compared to the coronary arteries or other conduits used for CABG. We conclude that the incidence of IMA atherosclerosis in patients with coronary artery disease is low. The presence of clinically significant atherosclerosis in LIMA is difficult to predict. However, a routine angiographic evaluation of the LIMA is not warranted as a preoperative investigation. Furthermore no constant predictive risk factor for its atherosclerotic involvement could be found