Early identification of acute myocardial infarction by activated protein C–protein C inhibitor complex

IntroductionIncreased coagulation activity due to coronary thrombosis in a ruptured plaque should result in activation of the protein C anticoagulant system with formation of complexes between activated protein C (APC) and the protein C inhibitor (PCI), which reflects coagulation activity. We hypothesized that elevated APC-PCI concentration might allow earlier detection of ongoing myocardial infarction than traditional biochemical markers. We have evaluated a newly devised immunofluorimetric assay for measuring plasma concentration of APC-PCI complexes among patients with suspected acute coronary syndrome.Materials and methodsBlood samples were taken from 340 patients (median 71 years, range 31–97) with suspected acute coronary syndrome at first presentation in the emergency department. Electrocardiogram was recorded and APC-PCI, Troponin I and Creatine kinase-MB concentrations were repeatedly measured 3 times at 6 h interval.ResultsThe 74 patients who were eventually diagnosed with myocardial infarction had a higher median level of APC-PCI complex than those without myocardial damage; 0.27 vs. 0.20 μg/L (p = 0.001). In a multivariate regression model, APC-PCI level in the fourth quartile (> 0.32 μg/L) independently predicted myocardial infarction with an odds ratio of 3.7 (95% CI 1.4–9.6, p < 0.01).ConclusionEarly APC-PCI elevation can be detected among patients with a normal first Troponin I and non-ST-elevation myocardial infarction and provides additional risk assessment in acute coronary syndrome.