Relative effects of different non-vitamin K antagonist oral anticoagulants on global thrombotic status in atrial fibrillation

Non-vitamin K antagonist oral anticoagulants (NOACs) reduce the risk of thromboembolism in patients with atrial fibrillation (AF). There has been no head-to-head comparison of the effect of these agents on ex vivo thrombotic and thrombolytic status. Enhanced platelet reactivity and impaired endogenous thrombolysis are risk factors for recurrent thrombotic events. We aimed to assess the comparative effect of NOACs and warfarin using an ex vivo test of thrombosis and thrombolysis. Eighty patients with newly diagnosed non-valvular AF were tested before, and after being established on apixaban (n = 20), dabigatran (n = 20), rivaroxaban (n = 20), or warfarin (n = 20). Thrombotic status was assessed with the automated, point-of-care Global Thrombosis Test (GTT) that assesses both platelet reactivity and endogenous thrombolysis from native blood. The time taken to form an occlusive thrombus (occlusion time, OT) and the time required to restore flow through endogenous thrombolysis (lysis time, LT) were measured. All anticoagulants caused OT prolongation compared to baseline (apixaban 403 +/- 102s vs. 496 +/- 125s, p = 0.006; dabigatran 471 +/- 106s vs. 656 +/- 165s, p < 0.00001; rivaroxaban 381 +/- 119s vs. 579 +/- 158, p < 0.00001; warfarin 420 +/- 145s vs. 604 +/- 124s, p < 0.00001). Apixaban reduced LT from baseline (1895[1702-2167] s vs. 1435[347-1990] s; p = 0.006). A trend for LT reduction was seen with other NOACs (dabigatran 1594[1226-2069] s vs. 1539[561-2316] s, p = 0.499; rivaroxaban 2085[1366-2428] s vs. 1885[724-2420] s, p = 0.295) but not with warfarin (1490[1206-1960] s vs. 1776[1545-2334], p = 0.601). Our results suggest that NOACs and warfarin have a similar favorable effect on reducing platelet reactivity. All NOACs exhibited a trend toward enhancing endogenous thrombolytic status, although this was significant only for apixaban. This raises the possibility of using NOACs to enhance impaired endogenous fibrinolysis in patients at high-thrombotic risk.