BS42 How warfarin and antiplatelets affect clot structure in atrial fibrillation

<h3>Introduction</h3> Atrial fibrillation (AF) and coronary artery disease (CAD) are two common cardiovascular conditions associated with increased morbidity and mortality. Both conditions bring a risk of thrombosis and thus antithrombotic therapy is indicated. Despite recognised treatment, stroke and myocardial infarctions still occur. Accordingly, the identification of patients whose haemostasis remains unimpaired by treatment is valuable. <h3>Purpose</h3> To investigate differences in plasma clot properties in patients with AF and CAD and compare the effect of warfarin and antiplatelets on clot structure in AF population. <h3>Methods</h3> We studied 270 patients and divided them into 3 groups: AF on warfarin (n=184), AF on antiplatelets (n=46) and CAD (n=40). Plasma samples were obtained from participants and 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. <h3>Results</h3> Comparisons between the 3 groups was performed using Kruskal-Wallis test, with Dunn’s post-hoc analysis and Holm-Sidak adjustment. There were no significant differences in clot structure between 3 subgroups. The maximum rate of clot formation was significantly delayed in the warfarin subgroup with all reagents used (p&lt;0.001) (table 1). Plasma clot susceptibility to fibrinolysis increased with warfarin compared to antiplatelets but was significant only with APPT and thrombin reagents (p&lt;0.001 and 0.04 respectively). <h3>Conclusion</h3> Warfarin was effective in delaying clot formation compared to antiplatelets and also resulted in increased susceptibility of plasma clot to fibrinolysis. <h3>Conflict of interest</h3> None