The intima of human coronary arteries.

Intimal thickness relative to that of the media (r) was measured in coronary and internal mammary arteries from 300 human subjects. Whereas this ratio remained low (less than 0.17) in the mammary arteries, coronary arteries showed progressive intimal thickening (r = 4.10 by 60 years). The intimal surfaces of 70 pairs of arteries were compared by light, transmission, and scanning electron microscopy. The mammary arteries had a continuous endothelial lining, but the coronary arteries showed incomplete coverage of the thickened intima. In affected vessels the endothelial cells showed loss of attachment to adjacent cells and to the underlying tissue. It was concluded that the progressive intimal thickening of the human coronary artery, which develops early in life and is associated with defects in the internal elastic lamina, is also associated with endothelial cell separation and detachment, with the formation of denuded areas on the intimal surface.