Observations on clot properties in atrial fibrillation: Relation to renal function and choice of anticoagulant.

INTRODUCTION Atrial fibrillation (AF) is associated with increased risk of stroke and thromboembolism. Patients with AF have a higher incidence of renal impairment, which may influence the risks of systemic thromboembolism or bleeding. We determined how different oral anticoagulants affect plasma clot properties and whether progressive renal dysfunction affects plasma clot properties in patients on warfarin. MATERIALS AND METHODS We studied 257 patients with AF receiving oral anticoagulants. Furthermore, we recruited 192 separate patients with AF on warfarin and divided them in 4 groups based on estimated glomerular filtration rate (eGFR). Platelet poor plasma was prepared and clot formation and fibrinolysis was monitored kinetically up to 1 h. RESULTS Rate of clot formation was significantly slower with dabigatran and rivaroxaban. Time between 50% clotting and 50% lysis was prolonged in patients receiving warfarin compared to NOACs. Time to 50% lysis from maximum absorbance was significantly shorter in patients receiving rivaroxaban. Time between 50% clotting and 50% lysis became significantly prolonged with worsening eGFR. Time to 50% lysis from maximum absorbance was prolonged as renal function worsened. CONCLUSIONS Compared to warfarin, NOACs differently modulate coagulation and fibrinolysis under ex vivo conditions. Worsening renal function in AF patients on warfarin prolongs fibrinolysis, potentially increasing the risk of thrombosis.