REBOUND AFTER CESSATION OF ORAL ANTICOAGULANT-THERAPY - THE BIOCHEMICAL-EVIDENCE

The existence of a phenomenon of rebound hypercoagulability after cess ation of oral anticoagulant therapy is controversial. The sensitive pr ocoagulant markers for in vivo thrombin and fibrin formation are poten tial tools for the reassessment of the presence of such a phenomenon. We examined 19 patients anticoagulated for 6+/-2 months (SD, range 3-1 2) because of venous thromboembolism or myocardial infarction as follo ws: twice during stable, oral anticoagulation (INR 3.1-3.7) and then o n days 1, 2, 3, 4, 5, 7, 9, 11, 13, 15 and >30 after cessation of oral anticoagulation. Thrombin-antithrombin III complexes (TAT) and fibrin opeptide A (FPA) were measured in addition to the prothrombin times an d factors II, V, VII, and X. None of the 19 patients developed clinica lly manifest thromboembolism within the following 9-18 months. However , the patients' TAT levels increased transiently: rising from 1.5+/-0. 1 ng/ml (SEM) to 3.0+/-0.2 ng/ml on day 4 (P<0.001), and returned to 1 .7+/-0.1 ng/ml after day 30 (normals 1.8+/-0.33). 17/19 patients showe d TAT peak levels above the upper limit of normal between days 3 and 1 1 (average: day 4), which normalized again after 30d. 8/19 patients al so had transient FPA levels above the upper normal limits (<1.81). We conclude that our patients increased their thrombin and fibrin formati on transiently and that a subpopulation reached values consistent with a prethrombotic state.