Adherent platelets and surface microthrombi of the human aorta and left coronary artery: a scanning electron microscopy feasibility study. 
As part of a feasibility phase of an investigator-initiated multicenter NIH supported study on the Pathobiological Determinants of Atherosclerosis in Youth (PDAY), we report observations on microthrombi and adherent platelets on the intima of the aorta and left anterior descending coronary artery.  The long-term objective of this cooperative study is to define more precisely the pathogenesis of atherosclerosis during late childhood and early adulthood and to investigate the influence of selected risk factors known to be associated with clinically manifest disease in later life.  Scanning electron microscopy (SEM) was utilized to survey broad areas of arterial intima.  Of 109 specimens studied from 52 cases, microthrombi composed of a mixture of aggregated platelets and fibrin and measuring approximately 30-70 micron in size were observed in about 4% [corrected] of the specimens and in about 6% of the cases, while individually adherent platelets were observed in approximately 7% of the specimens and about 10% of the cases.  Microthrombi and adherent platelets may be important in atherogenesis by stimulating proliferation of intimal smooth muscle cells through the release of a growth factor from platelets.  This feasibility study has shown that SEM is a rapid and effective method for surveying large areas of arterial intima for the study of adherent platelets and microthrombi.