Morphogenesis of aortic and coronary atherosclerosis in North India - a composite study

Abstract

This paper deals with a composite gross, microscopic, and biochemical study of aortal and coronary arteries obtained from unselected medicolegal autopsies on subjects from 3 to 105 years of age in the Delhi area. Twenty-nine coronary arteries were studied grossly and microscopically; of these, biochemical analysis for total lipids and lipid fractions was made on 42 samples of normal intima and different types of atherosclerotic lesions. Eighty-eight aortas were studied microscopically in a similar manner. The study confirms previous observations that both in the aorta and coronary arteries, progression of early fatty streaks to more established lesions is distinctly slow in the local Indian population and that the frequency of fibrous plaques and complicated lesions is less than in the white population in the West. A diffuse sudanophilic thickening of the intima, as reported in the aorta, was observed in the coronary arteries also, starting as early as the second decade and increasing in incidence thereafter. This lesion is interpreted as a variant of the atherosclerotic lesion, representing a mode of evolution of the atherosclerotic process. The morphologic and biochemical studies show a sequential evolution of changes observed in the normal intima at one end of the spectrum, through diffuse intimal thickening, fatty streaks, and fibrous plaques to complicated lesions at the other end. A considerable overlap and histogenetic kinship of the lesions was obvious. The lipid pattern of the coronary intima showed interesting differences from that of the aorta, but in both vessels, it was basically similar to that reported in the Western white population. The observed geographic differences in the extent and severity of atherosclerosis cannot, therefore, be ascribed to differences in the quality and quantity of lipid deposition. The studies suggest two main bases for the observed differences. First, for reasons not fully understood, the intimal reaction to atherogenic stimuli among Indians is frequently of a diffuse nature, which does not compromise the lumen in an eccentric manner as the atheroma does. Second, fibrin deposits are rare in the early lesions of Indians. It is possible that these factors may account for tardy progression of the lesions to the occlusive variety. An unusual lesion of aortic medial calcification was found with high frequency. Its pathogenesis is obscure.