Age and fibroplasia as preconditions for atheronecrosis in the human thoracic aorta.

The atheronecrotic core of an aortic plaque is an easily recognized structural feature when present in histologic sections. This feature tends to be associated with other characteristics of the aorta, chief among these being old age, marked intimal fibroplasia, and diminished numbers of intimal smooth-muscle cells. The statistical relationships among these aortic characteristics were examined in a series of 356 autopsies. Intimal fibroplasia tended to be directly proportional to age. The density of smooth-muscle cells tended to be inversely proportional to intimal fibroplasia. The total cellularity of the intima was almost constant without regard to age or intimal thickness. The probability of finding atheronecrosis in a randomly chosen sample from the lateral thoracic aorta was directly proportional to age and to intimal thickness after appropriate mathematical transformations. Against this background of what is usual, two atypical kinds of lesion were identified.