Summary

To evaluate the association between haemostatic parameters and increasedrisk of myocardial infarction (MI) at a young age, we measuredfibrinogen, factor VII, antithrombin III, protein C, protein S, tissue factor(TF), free form tissue factor pathway inhibitor (TFPI), plasminogen,α₂-antiplasmin, tissue plasminogen activator (tPA), plasminogen activatorinhibitor-I (PAI-I), and lipoprotein (a) in 140 young men withMI before age 45 and 150 age-matched healthy men. TF, TF/TFPI ratio,PAI-I, PAI-I/tPA ratio, plasminogen, and lipoprotein (a) in young MIpatients were all significantly higher than controls, while TFPI, antithrombinIII, and tPA were significantly lower (P <0.001 of each). Significantdeterminants of MI risk were PAI-I/tPA ratio (R² = 0.300,P <0.001), TF/TFPI ratio (R² = 0.049, P <0.001), antithrombin III (R² =0.034, P <0.001), hyperlipidaemia (R² = 0.019, P = 0.004), diabetes (R² =0.014, P = 0.015), lipoprotein (a) (R² = 0.012, P = 0.023), α₂-antiplasmin(R² = 0.014, P = 0.012), and protein C (R² = 0.012, P = 0.018). We concludethat the imbalances of PAI-I/tPA and TF/TFPI are significantly associatedwith MI at a young age, perhaps mediated via impaired fibrinolytic activity.