Distribution of intimal and medial thickening in the human right coronary artery: a study of 17 RCAs

Objective: To quantify the distribution of intimal and medial thickening in human right coronary arteries (RCAs) obtained at autopsy. Background: The shear and tensile stresses created by arterial bifurcation are believed to result in eccentric fibromuscular intimal thickening that leads to atherosc lerosis. Vascular curvature has been cited as a cause of atherosclerosis; h owever, details of the location and extent of intimal and medial thickness in the largely curved human RCA are not adequately documented. Methods: The right coronary arteries were obtained from 40 postmortem hearts and cut in to 20-30 segments, each being 3-4 nim. in length. Microscopic sections from the proximal, acute margin, and distal regions of the RCA were digitized a round the circumference of the vessel. Seventeen arteries showed insignific ant stenosis ( < 50%) and were selected for detailed examination. Results: Seventy-one percent (12/17) of proximal sections displayed eccentric intima l thickening. Normalized ensemble averaging revealed a preferential thicken ing on the myocardial side of the artery. At the acute margin region where curvature is most pronounced and at the distal region, 51% (8/17) of the sa mples showed eccentric thickening, but the ensemble average thickening in t hese regions showed no preferential location. In these mildly diseased arte ries, the thickened intima comprised of mainly smooth muscle cells with an extracellular matrix of collagen and some elastin. A relatively uniform med ial smooth muscle layer was seen at all three locations. Conclusions: The p roximal region of the RCA appears to be a site of intrinsic eccentric intim al thickening with maximum thickness on the myocardial side of the artery. Eccentric thickening does occur in the acute margin and distal regions; how ever, no distinct pattern or location was evident. (C) 2001 Elsevier Scienc e Ireland Ltd. All rights reserved.