Rationale: A reduced rate of myocardial infarction has been reported in patients with atrial fibrillation treated with FXa (factor Xa) inhibitors including rivaroxaban compared with vitamin K antagonists. At the same time, low-dose rivaroxaban has been shown to reduce mortality and atherothrombotic events in patients with coronary artery disease. Yet, the mechanisms underlying this reduction remain unknown. Objective: In this study, we hypothesized that rivaroxaban’s antithrombotic potential is linked to a hitherto unknown rivaroxaban effect that impacts on platelet reactivity and arterial thrombosis. Methods and Results: In this study, we identified FXa as potent, direct agonist of the PAR-1 (protease-activated receptor 1), leading to platelet activation and thrombus formation, which can be inhibited by rivaroxaban. We found that rivaroxaban reduced arterial thrombus stability in a mouse model of arterial thrombosis using intravital microscopy. For in vitro studies, atrial fibrillation patients on permanent rivaroxaban treatment for stroke prevention, respective controls, and patients with new-onset atrial fibrillation before and after first intake of rivaroxaban (time series analysis) were recruited. Platelet aggregation responses, as well as thrombus formation under arterial flow conditions on collagen and atherosclerotic plaque material, were attenuated by rivaroxaban. We show that rivaroxaban’s antiplatelet effect is plasma dependent but independent of thrombin and rivaroxaban’s anticoagulatory capacity. Conclusions: Here, we identified FXa as potent platelet agonist that acts through PAR-1. Therefore, rivaroxaban exerts an antiplatelet effect that together with its well-known potent anticoagulatory capacity might lead to reduced frequency of atherothrombotic events and improved outcome in patients.

In patients with atrial fibrillation, oral anticoagulation with oral thrombin inhibitors (OTIs), in contrast to vitamin K antagonists (VKAs), associates with a modest increase in acute coronary syndromes (ACSs). Whether this observation is causatively linked to OTI treatment and, if so, whether OTI action is the result of a lower antithrombotic efficacy of OTI compared to VKA or reflects a yet undefined prothrombotic activity of OTI remain unclear. We analyzed platelet function in patients receiving OTI or dose-adapted VKA under static and flow conditions. In vivo, we studied arterial thrombosis in OTI-, VKA-, and vehicle-treated mice using carotid ligation and wire injury models. Further, we examined thrombus formation on human atherosclerotic plaque homogenates under arterial shear to address the relevance to human pathology. Under static conditions, aggregation in the presence of ristocetin was increased in OTI-treated blood, whereas platelet reactivity and aggregation to other agonists were only marginally affected. Under flow conditions, firm platelet adhesion and thrombus formation on von Willebrand factor, collagen, and human atherosclerotic plaque were increased in the presence of OTI in comparison to VKA. OTI treatment was associated with increased thrombus formation in injured carotid arteries of mice. Inhibition or ablation of GPIbα-thrombin interactions abolished the effect of OTI on thrombus formation, suggesting a mechanistic role of the platelet receptor GPIbα and its thrombin-binding site. The effect of OTI was also abrogated in the presence of aspirin. In summary, OTI treatment has prothrombotic activity that might contribute to the increase in ACS observed clinically in patients.

Background: Even among biomarker-negative patients undergoing elective percutaneous coronary intervention (PCI), periprocedural thrombotic and bleeding complications can lead to increased morbidity and mortality. Whether stronger platelet inhibition by an intensified oral loading strategy (ILS) before PCI impacts on outcomes among these patients in contemporary practice remains unclear. Methods: This multicenter, randomized, assessor-blinded trial tested the hypothesis that in elective PCI prasugrel 60 mg (ILS) is superior to standard loading strategy with clopidogrel 600 mg regarding a composite primary end point of all-cause death, any myocardial infarction, definite/probable stent thrombosis, stroke, or urgent vessel revascularization. After PCI, all patients were on clopidogrel 75 mg/day and aspirin. The trial was terminated prematurely because of slower-than-expected recruitment and funding discontinuation. Results: Of 781 patients included in the final analysis, 382 were assigned to ILS and 399 to standard loading strategy. At 30 days, the primary end point occurred in 66 patients (17.3%) assigned to ILS and 74 patients (18.6%) assigned to standard loading strategy (odds ratio, 0.92 [95% CI, 0.63–1.32]; P =0.64). Any myocardial infarction and Bleeding Academic Research Consortium ≥2 bleeding rates were similar among ILS and standard loading strategy groups 16.2% versus 17.5%, odds ratio, 0.91 (95% CI, 0.62–1.32), P =0.62 and 4.2% versus 4.8%, odds ratio 0.87 (95% CI, 0.44–1.73), P =0.70, respectively. Conclusions: In biomarker-negative stable and unstable angina patients undergoing elective PCI, the trial did not find a conclusive difference in efficacy or safety. This observation should be interpreted in the context of wide CIs and premature termination of the trial. Registration: URL: https://www.clinicaltrials.gov . Unique identifier: NCT02548611.

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Venous thromboembolism (VTE) comprising deep venous thrombosis and pulmonary embolism is a major cause of morbidity and mortality. Short-term immobility-related conditions are a major risk factor for the development of VTE. Paradoxically, long-term immobilized free-ranging hibernating brown bears and paralyzed spinal cord injury (SCI) patients are protected from VTE. We aimed to identify mechanisms of immobility-associated VTE protection in a cross-species approach. Mass spectrometry–based proteomics revealed an antithrombotic signature in platelets of hibernating brown bears with heat shock protein 47 (HSP47) as the most substantially reduced protein. HSP47 down-regulation or ablation attenuated immune cell activation and neutrophil extracellular trap formation, contributing to thromboprotection in bears, SCI patients, and mice. This cross-species conserved platelet signature may give rise to antithrombotic therapeutics and prognostic markers beyond immobility-associated VTE.

Nonvitamin K oral anticoagulants (NOACs) or direct oral anticoagulants comprise inhibitors of factor Xa (rivaroxaban, apixaban, edoxaban) or factor IIa (dabigatran). Both classes efficiently interfere with the final or penultimate step of the coagulation cascade and showed superior net clinical benefit compared with vitamin K antagonists for prevention of thromboembolic events in patients with AF and for prevention and therapy of deep vein thrombosis and pulmonary embolism. None the less, accumulating data suggested, that there may be differences regarding the frequency of atherothrombotic cardiovascular events between NOACs. Thus, the optimal individualized NOAC for each patient remains a matter of debate. Against this background, some basic and translational analyses emphasized NOAC effects that impact on platelet activity and arterial thrombus formation beyond inhibition of plasmatic coagulation. In this review, we will provide an overview of the available clinical and translational evidence for so-called noncanonical NOAC effects on platelet activation and arterial thrombosis.

Dual platelet inhibition (DAPT) is crucial after percutaneous coronary intervention (PCI), especially for patients with diabetes mellitus. Guidelines recommend 3-12 months of DAPT post-PCI. 1 However, prolongation up to 30 months is discussed. Moreover, additional vascular-dose rivaroxaban has been shown to reduce mortality. 2 The associated increased bleeding risk, however, is fairly neglected. Several studies showed enhanced 3,4 while others found equal or decreased bleeding risk in diabetes mellitus. [5][6][7][8] This has direct implications for DAPT. Therefore, we investigated bleeding in post-PCI patients with diabetes mellitus.We conducted an observational analysis in the Department of Cardiology, University Hospital Duesseldorf, Germany including all PCI patients from 2016 to 2017 with a 3-year follow-up. The study conformed to the Declaration of Helsinki and was approved by the University of Duesseldorf Ethics Committee (vote no 2017-6166R). Diabetes was defined as pre-existing diabetes before PCI. Time since first onset was not known. Time until bleeding was measured in days

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