Background: Anticoagulation control quality affects the incidence of thromboembolic events in atrial fibrillation (AF) patients. However, the effects of anticoagulation control quality on the prothrombotic state of AF patients are unclear.
Methods and results: Ninety-five AF patients who had been treated with warfarin were prospectively followed-up for 449 ± 92 days. We analyzed whether time in the therapeutic range (TTR) of the international normalized ratio (INR) of prothrombin time, percentage of INR values in the range (%INR), and coefficient of variation of INR values (CV-INR) were related to D-dimer levels. The mean values of TTR, %INR, and CV-INR were 62%, 59%, and 0.19, respectively, and their median values were 67%, 63%, and 0.19, respectively. TTR was significantly correlated with %INR (R(2) = 0.917, P<0.01), but not with CV-INR (R(2) = 0.050, P = 0.26). The mean and median D-dimer levels were 0.79 and 0.60 µg/ml, respectively. Low TTR, low %INR, and high CV-INR were found to contribute to high D-dimer levels (P = 0.02, 0.03, and 0.02, respectively).
Conclusions: In AF patients treated with warfarin, not only the duration outside the target INR range, but also the fluctuation in INR level may influence the prothrombotic state.