Changes in levels of factor VII and protein S after acute myocardial infarction: Effects of low-dose warfarin

Persistent coagulation activity after an acute myocardial infarction may in crease the risk of reinfarction, We prospectively investigated the effects on plasma coagulation of a low, fixed dose of warfarin in combination with aspirin after myocardial infarction. We also evaluated the influence of coa gulation activity on clinical outcome. Plasma samples from 97 patients, ran domised to 1.25 mg of warfarin daily in combination with 75 mg of aspirin o r aspirin alone were drawn 4 days, 1 month, and 6 months after myocardial i nfarction. Patients receiving warfarin had a greater reduction in factor VI I coagulation activity (FVII:C) after 6 months: 0.18 vs. 0.06 U/mL,(95% CI, 0.02-0.22), whereas no differences were seen in levels of protein C, prote in S, or prothrombin fragment 1+2. In the acute phase, the level of free pr otein S was lower than after 6 months in both groups: 25.6 vs. 28.8% (95% C I, 4.19--2.35). Cardiovascular mortality, reinfarction, and stroke were eva luated after 4 years (median). In a survival analysis, every 0.1 U/mL incre ase in the level of FVII:C 1 month after myocardial infarction was associat ed with an 15% increase in risk of cardiovascular events (95% CI, 1.01-1.30 ). Warfarin at 1.25 mg daily reduces FVII:C but not systemic thrombin gener ation measured as prothrombin fragment 1+2, Low levels of the anticoagulant protein S may contribute to a procoagulant state. (C) 1999 Elsevier Scienc e Ltd. All rights reserved.