Determination of markers of coagulation activation and reactive fibrinolysis in patients with mechanical heart valve prosthesis at different intensities of oral anticoagulation.

In a group of 60 patients with mechanical heart valve prosthesis prothrombin fragment 1 + 2, thrombin-antithrombin III complexes and D-dimer have been determined in order to assess the residual coagulation activation and the extent of the reactive fibrinolysis. The patients were divided into three subgroups of 20 patients each with different intensities of oral anticoagulation as indicated by International Normalized Ratio (INR) values in the ranges 4.8-3.6, 3.5-2.5 and 2.4-2.1. From the two markers of coagulation activation studied (prothrombin fragment 1 + 2 and thrombin-antithrombin III (TAT)) the prothrombin fragment 1 + 2 was dependent on the INR level in all groups, although the median values were still significantly beneath the lower limit of the reference range. The D-dimer concentrations were unexpectedly high with respect to the low coagulation activation levels, as indicated by the D-dimer/TAT and D-dimer/F 1 + 2 ratios. This demonstrates the enhanced presence of fibrin degradation products as a scarcely described side-effect of oral anticoagulation. The anticoagulant properties of fibrin degradation products might contribute partly to the in vivo haemorrhagic risk in high-intensity oral anticoagulation. These results show, inasmuch as the prothrombin fragment 1 + 2 is concerned, that from the laboratory point of view the residual thrombin activity is low enough to be adequate under the therapeutical regimen followed in this study. However, the question of the efficacy of anticoagulation intensities can only be finally answered by clinical trials.