Atherosclerosis of the internal mammary artery. Histopathological analysis and implications on its results in coronary artery bypass graft surgery.

To evaluate internal mammary artery (IMA) atherosclerosis in our population, 38 segments of IMA obtained at the time of coronary surgery and 20 segments of IMA obtained at postmortem studies were histologically studied. Hematoxilin-eosin, Masson trichromic, elastic fibers and reticulin fibers were the stain methods used. A total of 236 sections were studied. Atherosclerosis was graded from 0 to 4 according to Kay and co-workers. Severe disease, with more than 50% luminal narrowing was found in one necropsy case (5%) and in no surgical case. In the surgical group, only one case (2.36%) showed a degree 3 luminal narrowing (between 25% and 50% luminal reduction). The remaining sections were normal or minimally affected. It is concluded that the IMA shows minimal atherosclerotic changes, being considered a protected vessel.