The early development of intimal thickening of human coronary arteries

Abstract

To investigate the initiation of intimal thickening in human coronary arteries, the anterior descending branches of the left coronary arteries of 53 infants less than 6 months of age were compared with those of 161 subjects between 6 months and 20 years of age, and with the internal thoracic arteries of subjects from the same age groups. In the first 6 months of life, the coronary arteries showed rapid increases in luminal diameter (35%), thickness of media (68%), and mean thickness of the intima relative to that of the media (850%). These showed a much slower increase in the following two decades. Discontinuities of the internal elastic lamina were present at birth, intimal thickening developing initially in regions where the internal elastic lamina appeared discontinuous. The percentage of discontinuity of the internal elastic lamina closely correlated with mean intimal thickness (correlation coefficient, 0.91). There were no discontinuities of the internal elastic lamina or intimal thickening in the internal thoracic arteries. These observations suggest the gaps in the internal elastic lamina allow smooth-muscle cells of the media to proliferate into the intima and that the rate of this growth reflects the early response of medial smooth-muscle cells to increasing tangential tension on the arterial wall.