Application of clot‐fibrinolysis waveform analysis to assessment of in vitro effects of direct oral anticoagulants on fibrinolysis

Introduction Acceleration of fibrinolysis by direct oral anticoagulants (DOACs) has been reported by several groups, suggesting contribution of not only anticoagulant but also fibrinolytic effects to the therapeutic efficacy. The present study aims to evaluate the usability of clot‐fibrinolysis waveform analysis (CFWA) for assessment of in vitro effects of DOACs on fibrinolysis. Methods The experimental conditions were optimized according to how t‐PA concentrations and a time length after t‐PA adjustment affect parameters of CFWA. Addition of the activated partial thromboplastin time (APTT) reagent followed by that of calcium and t‐PA was done to obtain clotting and fibrinolytic reaction curves which were mathematically differentiated for CFWA (APTT‐CFWA). The positive and negative modes of waveforms were defined as the direction toward fibrin generation and that toward fibrin degradation, respectively. The maximum positive and negative values (Maxp1 and Maxn1) correspond to the maximum coagulation velocity and the maximum fibrinolysis velocity, respectively. Plasma spiked with each of DOACs (rivaroxaban, apixaban, edoxaban, and dabigatran) was subjected to APTT‐CFWA. Results Optimization of t‐PA use was based on Maxn1. Roughly biphasic effects of rivaroxaban and dabigatran but not apixaban or edoxaban on fibrinolysis were observed through Maxn1 and the fibrinolysis peak time, which was defined as a time length from the time when Maxp1 (Maxp1 time) to the time when Maxn1 appears (Maxn1 time). Conclusion The results suggest the usability of CFWA for assessment of DOAC effects and provide insights into relevance of anticoagulation to therapeutic efficacy and bleeding risk from the perspective of fibrinolysis.