Progression of coronary atherosclerosis from adolescents to mature adults.

Ten selected topographic sites of the coronary arteries were placed in sequence according to age, sex, branching anatomical pattern and smoking habit, in order to obtain an indirect sequencing of the pattern and rate of progression of early atherosclerotic lesions from adolescents to mature adults. The material came from 356 subjects aged 16-45 years who had died in violent accidents and included the light-microscopic examination of 3560 coronary artery samples. The dynamic reconstruction of thousands of static views revealed the existence of an age-related rate of progression of fibromuscular plaques, intimal necrotic areas, incorporated microthrombi and fatty streaks. All these early atherosclerotic lesions increased linearly and in parallel from one 5-year age group to the next and exhibited non-significant differences in their rate of progression over a period of 25 years. During this period the number of atherosclerotic plaques increased 4.7 times, of intimal necrotic areas 4.6 times, of incorporated microthrombi 4.3 times and of fatty streaks 3.9 times. Consequently, in the 10 selected topographic sites of the coronary arteries placed in sequence according to age, the pathological aspects became prevalent, microscopically, over the normal ones, starting from the fourth decade of life. This study also revealed that some endogenous and exogenous risk factors for coronary heart disease accelerated the age-related rate of progression of early atherosclerotic lesions. In addition, particular cycles of evolution towards advanced lesions appeared, leading to the onset of fibronecrotic and fibrohyaline plaques. Their obstructive character was related to both successive incorporation of microthrombi and the onset of large lipid deposits. Among the four types of early atherosclerotic lesions investigated, only the fatty streaks did not show this direct conversion to a lesion of possible clinical significance.