Quantitative studies on the relationship of fibrinogen and “fibrin” in intima and atherosclerotic plaque

This study was undertaken to determine if there is a direct correlation between severity of a plaque and its fibrin and fibrinogen content. The amount of fragment D antigen per mg protein of the intima-media layer of the human aorta was determined by quantitative immunoelectrophoresis and was measured as the salt soluble fraction (fibrinogen) and, after extraction, as the plasmin solubilized fraction (“fibrin”). The subjects were apparently healthy but died as result of a traumatic incident. Paired controls consisted of samples of grossly healthy tissue adjacent to the plaque. The “fibrin” or fibrinogen of uninvolved intima did not increase with age. The fibrinogen content could not be correlated with severity of the plaque but there was a significant correlation with “fibrin”. “Fibrin” was significantly decreased in grade 1 lesions. The results are not consistent with the thrombotic theory of plaque formation.