Background: Dabigatran and Rivaroxaban are new oral anticoagulants that offer an alternative to vitamin K antagonists for the prevention of ischemic stroke in patients with non valvular atrial fibrillation. Several studies suggest that dabigatran, a direct thrombin inhibitor, may be associated with a higher risk of ischemic events in patients with atrial fibrillation. Such association has not been reported for rivaroxaban, a factor Xa inhibitor. A potential explanation for increased risk of ischemic events is heightened platelet reactivity. We, therefore, aimed to assess the effect of dabigatran and rivaroxaban on platelet reactivity in patients with atrial fibrillation.
Methods: Patients with non-valvular atrial fibrillation who either began treatment with dabigatran or rivaroxaban, or renewed treatment after a discontinuation period were recruited for the study. All patients were tested at two time-points: before the first dose, and after at least 7 days of treatment. Platelet reactivity was evaluated using multiple electrode aggregometry(MEA) in response to various agonists, the Impact-R device which measures flow dependent platelet adhesion to a surface, and the proportion of membrane bound P-selectin using flow cytometry.
Results: Seventeen patients treated with dabigatran (mean age 69±7years, 35% women, mean CHADS2 score 2.6±1.2), and 9 patients treated with rivaroxaban (mean age 72.9±9years, 22.2% women, mean CHADS2 score 2.7±1.6) were included in the study. No significant differences were found between the baseline and the "on treatment" tests for all the parameters evaluated using Wilcoxon Tests (Table). There was a trend for increased arachidonic acid induced platelet reactivity in patients treated with both dabigatran and rivaroxaban which can be explained by the cessation of aspirin treatment by some of the patients after starting the anticoagulant drug
Conclusion: From these preliminary results it appears that dabigatran or rivaroxaban do not affect platelet reactivity in patients with atrial fibrillation.
