Atherosclerotic involvement of coronary branch vessels.

The atherosclerotic involvement of coronary branch vessels (first diagonal, first septal, posterior descending, left and right marginals, conus and the vessels supplying the conduction system) was investigated in 450 apparently healthy subjects aged 11-55 years who died of accidental causes. In subjects 35-55 years old, 1 out of every 3 persons with atherosclerotic plaques in the major coronary arteries also had atherosclerotic plaques in coronary branch vessels; the respective relation for fatty streaks was 1 out of every 12 subjects, for intimal necrotic areas 1 out of every 7 subjects and for incorporated microthrombi 1 out of every 9 subjects. One out of every 3 subjects 51-55 years old had more than 50% lumen reduction in the undistended major coronary arteries, compared to 1 out of every 6 subjects in undistended coronary branch vessels. A small subgroup (8.2%) showed more severe stenotic lesions in coronary branch vessels than in coronary major arteries. The atherosclerotic plaques of coronary branch vessels appeared as 'underdeveloped', lacking a thick fibrohyaline cap, a large detritus cavity, abundant lipid deposition, cholesterol crystals, basal vascularization, intraplaque hemorrhage, ulceration, calcification, occlusive thrombosis. On the other hand the stenotic character of these plaques was often severe (more than 75% lumen reduction). The questionable value of the estimation of the ischemic significance of a coronary stenosis in the absence of available data on the development of a compensatory collateral circulation is discussed.