The in vitro analysis of the coagulation mechanism of activated factor VII using thrombelastogram

We investigated the effects of addition of recombinant activated coagulation factor VII (rFVIIa) to coagulation factor-deficient plasma and whole blood, using thrombelastograms (TEGs). The addition of rFVIIa to factor II- or X-deficient plasma did not correct hemostatic parameters, whereas it produced partial responses in factor V, VIII- or IX-deficient plasma and good responses in factor VII-, XI- or XII-deficient plasma. Furthermore, the addition of rFVIIa and platelets (30-100 X 10(3)/mul) to platelet-poor plasma produced marked corrections, producing TEGs similar to those of platelet-rich plasma. These results indicate that factors II and X are essential for the hemostatic effects of rFVIIa, and that factors V and VIII promote these effects. We believe that TEGs are, at present, one of the most useful tools for evaluating in vitro hemostatic effects of rFVIIa.