Category: Professional Posters
Purpose: Tissue factor–initiated thrombin generation (TF-TG) is dependent on several key enzyme complexes (e.g., factor Xa [FXa]/factor Va [FVa], IIase), leading to the activation of prothrombin to thrombin. Inherited or acquired (e.g., anticoagulation) deficiencies in these factors can lead to bleeding. Whereas factor replacement therapies have established clinical benefit for hemophilia and vitamin K antagonist–treated patients due to factor deficiencies, the effectiveness of this strategy (use of prothrombin complex concentrates [PCCs]) is unclear for reversing the direct FXa inhibitor (DOAC)-induced anticoagulation. The aim of this study was to establish the relationship between DOAC concentration and PCC-mediated TF-TG in vitro.
Methods: TF-TG was measured using a calibrated automated thrombogram (CAT, 5 pM TF, Diagnostica Stago). Purified plasma proteins, human plasma (PPP), and a commercially available 4-factor PCC (Kcentra) were used. TF-TG was measured in PPP spiked with purified plasma proteins, PCC (0-1.0 IU/mL), PCC + rivaroxaban (0-250 ng/mL) or apixaban (0-125 ng/mL). Five CAT parameters were collected, and the endogenous thrombin potential (ETP) was used for the comparisons.
Results: In normal PPP, addition of prothrombin or PCC caused similar broadening of the CAT profiles and increased ETP (~2x at 1.0U/mL), whereas FIX/FX increased mainly peak thrombin. Therefore, TF-TG was dependent on both the prothrombin concentration and the IIase activity. Inhibition of IIase by rivaroxaban and apixaban dose-dependently dampened ETP, with IC50 being 116 ng/mL and 158 ng/mL, respectively. PCC (up to 1.0 IU/mL) showed no apparent reversal activity with inhibitor concentrations at 250-75 ng/mL. ETP increased only when the inhibitor concentrations were sufficiently low (≤37.5 ng/mL, < 30% inhibition of ETP), likely due to increased prothrombin level from PCC addition.
Conclusion: TF-TG at therapeutic levels of FXa inhibitors was limited by the level of active FXa, which limits the contribution of PCC to thrombin generation. Effective and rapid reversal of DOACs likely requires direct sequestration of the inhibitors and restoration of the FXa enzymatic activity.