Differences in the pattern of atherosclerotic involvement between non-branched regions and adjacent branching points of human coronary arteries.

A light-microscopic study carried out on 816 coronary arterial trees revealed that the variety of atherosclerotic lesions detected in non-branched segments was 3-5 times greater than that recorded in branching points. The fibromuscular and fibronecrotic plaques, small fatty streaks, small intimal necrotic areas, incorporated microthrombi and intramural organized thrombi were recorded in both non-branched regions and branching points. The mucoid, foam cell-rich and necrotic plaques, large fatty streaks with abundant extracellular lipid and large intimal necrotic areas with lipid and fibrin deposition were recorded only in non-branched regions, whereas the fibrohyaline plaques were recorded only in the branching points. The complexity of atherosclerotic involvement of the branch areas increased with the branch mouth diameter: at a diameter of 1 mm only fibromuscular and fibrohyaline plaques were recorded; at a diameter between 1 and 2 mm the fibronecrotic plaques and at a diameter of more than 2 mm the small fatty streaks and small intimal necrotic areas were also detected. The results showed that along a distance of only 2-5 mm there are in the coronary arterial tree local hemodynamic and structural patterns which in non-branched regions favour and in adjacent branching sites restrict the onset and progression of atherosclerotic lesions; there are also local factors which in non-branched regions enlarge and in adjacent branching sites limit the types of atherosclerotic lesions which will develop. Any view on the etiopathogenesis of human coronary atherosclerosis needs to be considered in conjunction with the hemodynamic and structural patterns existing in the different parts of the coronary arterial tree, both closely related to the coronary branching anatomical pattern.