Platelet number and volume during myocardial infarction in relation to infarct size.

Platelet number and mean platelet volume (MPV) were measured in 100 patients with acute chest pain, 41 with acute myocardial infarction (AMI), 33 with angina pectoris (AP) and 26 with non-coronary event (NCE), and compared with 21 controls. We found no significant difference in platelet count on admission in the patient groups, but it was lower compared with controls. There were no significant differences in MPV between the patient groups nor between patients and controls. Thirty patients with AMI were followed for 10 days and showed an initial 12% fall in platelet count followed by a 36% increase. Initially there was an increase in MPV (2%) followed by a fall (8%). The fall in platelet count and increase in MPV correlated with infarct size (maximum activity of lactate dehydrogenase (LDH)) and might reflect consumption of platelets. The precise role of platelets in the process of infarction is still unknown.