Platelet Factor 4 Plasma Levels at Rest and after Exercise in Patients with Recent Myocardial Infarction

Abstract
Plasma levels of platelet factor 4 (PF 4) were determined in 30 patients with recent acute myocardial infarction. Comparisons were made with the levels in 26 age-matched controls. In another 15 patients, also with recent myocardial infarction, PF 4 plasma levels were determined before and immediately after a standardized exercise stress test. At rest, none of the patients had elevated PF 4 levels. Only 1 patient demonstrated an increase after exercise. These findings are in conflict with some recent reports. The importance of age-matched controls, the hazard of in vitro platelet activation and the possible effect of .beta.-blocking and Ca-antagonistic drugs on PF 4 plasma levels is discussed.