Changes of human platelets studied by scanning electron microscopy in acute myocardial infarction.

The formation of platelet aggregates has been suggested to be the initial step in coronary occlusion and the subsequent myocardial infarction (AMI). By scanning electron microscopy we followed: the platelet morphology and aggregation, the macrophage (M) morphology and the lymphocyte (T, B) count and structure in 11 patients with AMI and in 18 patients with unstable angina (UA). Generally, in the patients with AMI, most of the platelets presented relatively frequent (42.5%) or very frequent pseudopodia (35.27%) and the network of surface extensions was associated with several huge platelet aggregates in 6 patients. The mean lymphocyte count was: T = 40.36 +/- 23.95%; B = 28.09 +/- 7.38%; M = 31.54 +/- 21.25%. In the patients with unstable angina the proportion of platelets with pseudopodia was more reduced, namely, that of platelets with relatively frequent pseudopodia was 33.8% and with very frequent pseudopodia was 27.8%. The mean lymphocyte count was: T = 40.30 +/- 20.24%; B = 34.6 +/- 14.39%; M = 25 +/- 10.50%. These data indicate that platelet changes and the formation of aggregates can be an important factor in the occurrence of AMI. The change of immunocompetent cell count in both groups of coronary patients suggests the association of an immunologic process in coronary atherosclerosis.