Is there a hypercoagulable phase during initiation of antithrombotic therapy with oral anticoagulants in patients with atrial fibrillation?

INTRODUCTION: During commencement of oral anticoagulant therapy (OAT) a theoretical possibility of a transient hypercoagulable state emerges from the difference in plasma half-life between the vitamin K-dependent pro-coagulation factors II and X, and the vitamin K-dependent anticoagulant proteins C and S. In the present study, markers reflecting the activity in the haemostatic system (prothrombin fragment 1+2 [F1+2], D-dimer and soluble fibrin) was assessed during initiation of OAT compared to subcutaneously administered low-molecular weight heparin (LMWH) which does not cause any imbalance between the concentrations of the pro- and anticoagulation proteins.
METHODS: Thirty-three patients with atrial fibrillation were randomly treated either with OAT (warfarin 10, 7.5, and 5 mg for three consecutive days) or LMWH administered in a fixed dose of 200 anti-Xa IU/kg body weight in one subcutaneous injection daily. The biochemical markers were measured at baseline, and after 12, 36 and 60 h of treatment. RESULTS AND
CONCLUSIONS: After introducing antithrombotic therapy, none of the biochemical markers increased within the study period in the two treatment groups. The level of F1+2 had declined significantly at 60 h in both groups. The level of soluble fibrin showed a significant decrease within the first 60 h in the OAT group, and no significant changes were seen in the LMWH group. No significant change in the level of D-dimer was seen during the first 60 h of treatment in either group. Taken together, no transient hypercoagulable state could be identified within the first 60 h of commencing OAT in patients with atrial fibrillation.

RCT Entities:   Population Interventions Outcomes