Histological study of the internal mammary artery with emphasis on its suitability as a coronary artery bypass graft.

The internal mammary, musculophrenic, and superior epigastric arteries were unilaterally harvested from 11 individuals (aged 49 to 83 years; mean age, 67 years) and were examined histologically at 1-cm intervals. In 2 individuals the media of the entire internal mammary artery was elastic, whereas in the other 9 individuals we observed an alternating histological pattern in the media of the internal mammary artery, that of the proximal and distal segments being elastomuscular and that of the mid segment being elastic. In 4 of the latter 9 individuals the distal 10% to 20% of the media of the internal mammary artery was muscular with rare elastic lamellae. The media of the first 1 to 2 cm of the musculophrenic and superior epigastric arteries was elastomuscular or muscular with rare elastic lamellae, whereas more distally the media was purely muscular. The degree of intimal hyperplasia was significantly greater in arterial segments with a purely muscular media (25.6%) than in those with elastic (16.7%), elastomuscular (15.3%), and muscular (with rare elastic lamellae) (17.5%) types of media (p < 0.01). The mean cross-sectional luminal area of the elastic segment (1.9 mm2) and proximal and distal elastomuscular segments (1.9 and 1.2 mm2, respectively) of the internal mammary artery was significantly greater than that of the muscular segments of the musculophrenic artery (0.9 mm2) and the superior epigastric artery (0.7 mm2) (p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)