Role of rhythmic structures of aortic intima in the development of atherosclerosis.

Abstract

517 thoracic and abdominal aortas from newborns and children aged up to 14 years and 606 from males aged 20-39 years were examined. Rhythmic structures (wave lines) were detected in 4.7% of stillborns, but their frequency was found to increase with age. After the first year of life they occurred in 60% and after 20 years in 70%. Their frequency was significantly higher in the abdominal than in the thoracic aorta. Fibrous plaques were found in 39.4% of subjects aged 20-29 years and in 83% of those aged 30-39 years, and in 84% in the area of rhythmic structures. There were all stages of transformation of rhythmic structures into fibrous plaques. The extent of fibrous plaques was significantly higher in aortas with rhythmic structures than in those without. Initial microscopic changes in rhythmic structures involved smooth muscle cell proliferation in the underlying media and disintegration of the internal elastic membrane as well as migration of smooth muscle cells into the intima. The latter cases exhibited formation of an abundant irregular net of elastic and collagenous fibers and stromal edema with fibrin deposition, followed by sclerosis. Fibrous plaques contained no lipids. The latter were occasionally detected in some smooth muscle cells, whereas in subjects over 35 years they were also found extracellularly on the site of destructured foam cells.