Plasma factor Xa inhibition can predict antithrombotic effects of oral direct factor Xa inhibitors in rabbit atherothrombosis models

Pleiotropic Effects of Direct Oral Anticoagulants in Chronic Heart Failure and Atrial Fibrillation: Machine Learning Analysis

Oral anticoagulant therapy (OAT) for managing atrial fibrillation (AF) encompasses vitamin K antagonists (VKAs, such as warfarin), which was the mainstay of anticoagulation therapy before 2010, and direct-acting oral anticoagulants (DOACs, namely dabigatran etexilate, rivaroxaban, apixaban, edoxaban), approved for the prevention of AF stroke over the last thirteen years. Due to the lower risk of major bleeding associated with DOACs, anticoagulant switching is a common practice in AF patients. Nevertheless, there are issues related to OAT switching that still need to be fully understood, especially for patients in whom AF and heart failure (HF) coexist. Herein, the effective impact of the therapeutic switching from warfarin to DOACs in HF patients with AF, in terms of cardiac remodeling, clinical status, endothelial function and inflammatory biomarkers, was assessed by a machine learning (ML) analysis of a clinical database, which ultimately shed light on the real positive and pleiotropic effects mediated by DOACs in addition to their anticoagulant activity.

Vascular protection with rivaroxaban in the comprehensive management of atrial fibrillation

INTRODUCTION

In addition to an increased risk of thromboembolic complications, patients with atrial fibrillation (AF) are at risk for vascular events. Consequently, complete vascular protection is warranted in these patients.

AREAS COVERED

A narrative search was conducted on PubMed (MEDLINE), using the MeSH terms [Rivaroxaban] + [Atrial fibrillation] + [Cardiovascular] + [Vascular] + [Treatment]. Original data from clinical trials, prospective and retrospective studies, useful reviews and experimental studies, were selected.

EXPERT OPINION

The ROCKET-AF trial showed that rivaroxaban is effective in reducing the risk of stroke, with a lower risk of fatal and intracranial bleeding compared to warfarin. Remarkably, experimental data have provided a number of pathogenic mechanisms through which rivaroxaban could provide beneficial vascular properties beyond its antithrombotic activity. Moreover, in the AF population, additional to its ability to reduce the risk of thromboembolic complications, rivaroxaban is associated with a lower risk of myocardial infarction, major adverse cardiac and limb events, and vascular mortality in patients with diabetes, also attenuating renal impairment during follow-up. These findings suggest that rivaroxaban may provide a comprehensive vascular protection in patients with AF.

Underlying mechanisms of thrombus formation/growth in atherothrombosis and deep vein thrombosis

Thrombosis remains a leading cause of death worldwide despite technological advances in prevention, diagnosis, and treatment. The traditional view of arterial thrombus formation is that it is a platelet-dependent process, whereas that of venous thrombus formation is a coagulation-dependent process. Current pathological and basic studies on atherothrombosis and venous thrombosis have revealed the diverse participation of platelet and coagulation activation mechanisms in both thrombus initiation and growth processes during clinical thrombotic events. Atherosclerotic plaque cell-derived tissue factor contributes to fibrin formation and platelet aggregation. The degree of plaque disruption and a blood flow alteration promote atherothrombotic occlusion. While blood stasis/turbulent flow due to luminal stenosis itself initiates venous thrombus formation. The coagulation factor XI-driven propagation phase of blood coagulation plays a major role in venous thrombus growth, but a minor role in hemostasis. These lines of evidence indicate that atherothrombosis onset is affected by the thrombogenic potential of atherosclerotic plaques, the plaque disruption size, and an alteration in blood flow. Upon onset of venous thrombosis, enhancement of the propagation phase of blood coagulation under blood stasis and a hypercoagulable state contribute to large thrombus formation.

Rivaroxaban: searching the integral vascular protection

INTRODUCTION

Residual cardiovascular risk remains high in patients with atherosclerotic cardiovascular disease despite current antithrombotic therapy. On the other hand, patients with atrial fibrillation have an increased risk of myocardial infarction and cardiovascular death. As a result, a new antithrombotic approach appears necessary to reduce this risk. Areas covered: In this article, the role of rivaroxaban on vascular protection in patients with cardiovascular disease and/or atrial fibrillation was reviewed, with a particular focus, but not limited, on clinical trials. Expert commentary: Previous data have shown that factor Xa plays a key role in the etiopathogenesis of atherothrombosis. Experimental data suggest that rivaroxaban exhibits antiinflammatory and antioxidative stress properties, and may improve endothelial dysfunction. The COMPASS trial showed that among patients with stable atherosclerotic vascular disease, the addition of rivaroxaban 2.5 mg twice daily (vascular dose) to aspirin provided a higher cardiovascular protection than aspirin alone. In ROCKET-AF trial, compared with warfarin, rivaroxaban 20 mg once daily (15 mg if moderate renal dysfunction) (anticoagulant dose) was, at least, as effective as warfarin for the prevention of stroke or systemic embolism among patients with nonvalvular atrial fibrillation, with a trend toward a reduction in the risk of cardiovascular outcomes. All these data suggest that rivaroxaban might have a vascular protective effect beyond its stroke/systemic embolism preventive activity.

Darexaban: anticoagulant effects in mice and human plasma in vitro, antithrombotic effects in thrombosis and bleeding models in mice and effects of anti-inhibitor coagulant complex and recombinant factor VIIa

Here, we investigated the anticoagulant effects of darexaban in mice and human plasma in vitro, effects of darexaban in thrombosis and bleeding models in mice, and reversal effects of anti-inhibitor coagulant complex (ACC) and recombinant factor VIIa (rFVIIa) on anticoagulant effects of darexaban. In mice, darexaban inhibited FXa activity in plasma with an ED50 value of 24.8 mg/kg. Both darexaban and warfarin prolonged prothrombin time (PT) at 3 mg/kg and 0.3 mg/kg/day, respectively. PT and activated partial thromboplastin time (aPTT) prolonged by darexaban were dose-dependently reversed by intravenously-administered rFVIIa, significantly so at 1 mg/kg. In a pulmonary thromboembolism (PE) mouse model, both darexaban and warfarin dose-dependently reduced the mortality rate, significantly so at 10 mg/kg and 3 mg/kg/day, respectively. In a FeCl3-induced venous thrombosis (VT) mouse model, darexaban (0.3-10 mg/kg) dose-dependently decreased the thrombus protein content, significantly so at doses of 3 mg/kg or higher. In a tail-transection mouse model, darexaban had no significant effect on the amount of blood loss at doses up to 10 mg/kg, while warfarin showed a dose-dependent increase in blood loss, significantly so from 1 mg/kg/day. Darexaban and its metabolite darexaban glucuronide significantly prolonged PT and aPTT in human plasma in vitro, and while rFVIIa concentration-dependently reversed the prolonged PT in this plasma, ACC dose-dependently reversed both PT and aPTT changes prolonged by darexaban. Taken together, these results suggest that darexaban has a potential to be an oral anticoagulant with a better safety profile than warfarin, and that rFVIIa and ACC may be useful as antidotes to darexaban in cases of overdose.