Factor VIII activity and blood coagulation in patients on long-term oral anticoagulation

Abstract number: P1929

Brzezinska-Kolarz^* B., Undas† A., Sydor† W. J., Iwaniec† T., Musial† J.

^*Jagiellonian University School of Medicine, Poland; †Poland

Recently, Brummel et al. (Circulation 2001; 104:2311) have reported that treatment with warfarin is associated with increased factor (F) VIII activity, which might be a compensatory mechanism during oral anticoagulation. The aim of our study was to evaluate changes in FVIII activity during long-term treatment with coumadin. We enrolled 35 patients (mean age, 48.4 ± 15.7 year), with a history of venous thromboembolism treated with acenocoumarol (mean = 19 months; stable INR values -2.0–3.0; normal C-reactive protein levels). The control group included 29 sex- and age-matched healthy subjects. Laboratory evaluation aPTT, activity of factor II, VII, IX, X, protein C and S levels, bleeding time (BT), levels of thrombin–anti-thrombin (TAT) complexes in blood samples taken every 30 s at the site of microvascular injury as described previously (Undas et al. Blood 2001). A significantly higher FVIII activity was observed in patients treated with acenocoumarol as compared to healthy individuals (162.2 ± 8.83% vs. 116.7 ± 5.9%; [mean ± SEM]; P = 0.007). However, FVIII activity showed no correlation with the duration of anticoagulation. A significant negative correlation between BT and FVIII activity (r = – 0.45; P = 0.006) was found in treated patients, but not in healthy controls. In both groups there was no correlation between INR and FVIII activity. Interestingly, in healthy subjects, but not anti-coagulated individuals FVIII activity was correlated positively with activity of prothrombin (P = 0.04) and factor VII (P = 0.003), but not other factors analyzed. The rate of increase in TAT levels measured in blood from skin incisions correlated significantly with FVIII activity in healthy subjects (r = 0.4; P = 0.04) only. In both groups FVIII activity did not influence the maximum TAT concentrations. In conclusion, our findings confirmed that long-term oral anticoagulation is accompanied by a markedly increased FVIII activity. However, we failed to show a correlation between its activity and the duration of anticoagulation.