LAUSR

Introduction Atrial fibrillation (AF) is associated with an increased risk of stroke and thromboembolism. Despite best clinical care, patients on anticoagulation therapy still suffer from thrombosis and remain at risk of haemorrhage with devastating consequences. The assessment of different oral anticoagulants to identify the effects on plasma clots may help in identifying reasons for this. Aim To study how different oral anticoagulants affect plasma clot properties in patients with AF. Methods We studied 257 patients with AF receiving oral anticoagulants (Warfarin (n=184), Rivaroxaban (n=37), Apixaban (n=17) and Dabigatran (n=19)). Plasma sample was obtained from patients centrifuged to prepare platelet poor plasma. Assays were performed in 96-well polystyrene microtiter plates. Reagents were diluted in standard buffer (10 mM N-2-hydroxyethylpiperazine-N’-2-ethanesulphonic acid [HEPES], pH 7.4, 150 mM NaCl). Patient plasma samples (25 %) were incubated with tissue plasminogen activator (500 ng.mL-1) for 10 minutes at 37°C before the addition of CaCl2 (7.5 mM). Either PPP reagent (2.5 %), aPPT reagent (2.5 %), or thrombin (0.5 U.mL-1) were then added to initiate coagulation. Polymerisation of fibrin in plasma was monitored (ΔOD340 nm) using a Synergy H1 hybrid multi-mode plate reader, readings were taken in 12 second intervals for up to 60 minutes. Results Comparison between the 4 groups was performed using Kruskal-Wallis test with Dunn’s post-hoc analysis and Holm-Sidak adjustment. Optical density reflecting clot turbidity was highest in warfarin (0.58) followed by dabigatran (0.56), rivaroxaban (0.54) and apixaban (0.48) with the thrombin reagent (p=0.049) (table 1). The maximum rate of clot formation was significantly slower in the dabigatran subgroup with all reagents used (p<0.001). Plasma clot lysis time was prolonged with warfarin compared to other anticoagulants with all reagents (p=0.001). Time for 50% of the clot to lyse was significantly longer in warfarin group compared to non-vitamin K antagonist oral anticoagulants (NOACs), particularly with PPP and thrombin reagents (p=0.001 and <0.001 respectively). Abstract BS20 Table 1 Demographic, clinical and heamostatic characteristics of patients with atrial fibrillation receiving different oral anticoagulants Conclusion There were marked differences in the laboratory assessment of thrombogensis and fibrinolysis in patients on different oral anticoagulants. NOACs were found to be more effective in altering clot thickness, delaying clot formation and shortening clot lysis time compared to warfarin. Conflict of interest None