Comparative study of the effect of rivaroxaban and fondaparinux on monocyte's coagulant activity and cytokine release

Acute Pulmonary Embolism and Immunity in Animal Models

Venous thromboembolism, encompassing acute pulmonary embolism (APE) and deep vein thrombosis (DVT), is a potentially fatal disease with complex pathophysiology. Traditionally, the Virchow triad provided a framework for understanding the pathogenic contributors to thrombus formation, which include endothelial dysfunction, alterations in blood flow and blood hypercoagulability. In the last years, it has become apparent that immunity plays a central role in thrombosis, interacting with classical prothrombotic mechanisms, oxidative stress and vascular factors. Thrombosis amplifies inflammation, and exaggerated inflammatory processes can trigger thrombosis mainly due to the activation of leukocytes, platelets, and endothelial cells. APE-related endothelium injury is a major trigger for immune system activation. Endothelium is also a key component mediating inflammatory reaction and it is relevant to maintain vascular permeability. Exaggerated right ventricular wall stress and overload, with coexisting systemic hypotension and hypoxemia, result in myocardial injury and necrosis. Hypoxia, tissue factor activation and cytokine storm are engaged in the thrombo-inflammatory processes. Thrombus development is characterized by inflammatory state vascular wall caused mainly by an early extravasation of leukocytes and intense selectins and cytokines production. Nevertheless, immunity of DVT is well described, little is known about potential chemokine and cellular differences between thrombus that develops in the vein and thrombus that detaches and lodges in the pulmonary circulation being a cause of APE. There is a paucity of data considering inflammatory state in the pulmonary artery wall during an acute episode of pulmonary embolism. The main aim of this review is to summarize the knowledge of immunity in acute phase of pulmonary embolism in experimental models.

TILE pilot trial study protocol: Tinzaparin Lead-in to Prevent the Post-Thrombotic syndrome study protocol

INTRODUCTION

The post-thrombotic syndrome (PTS) is a form of chronic venous insufficiency due to a prior ipsilateral deep venous thrombosis (DVT). This is a frequent complication that develops in 20%-50% of patients after a proximal DVT and is associated with significant healthcare, economic and societal consequences. In the absence of effective and well-tolerated treatment options for established PTS, effective preventative measures are needed. Anticoagulation itself reduces the risk of PTS, and low-molecular-weight heparin may reduce this further through anti-inflammatory properties targeting the initial acute inflammatory phase of DVT.

METHODS AND ANALYSIS

The Tinzaparin Lead-In to Prevent the Post-Thrombotic syndrome pilot trial is an investigator-initiated, multicentre, open-label assessor-blinded trial that will randomise patients with first acute symptomatic common femoral or iliac DVT to receive either a 3-week lead-in course of tinzaparin, followed by rivaroxaban (experimental arm) or rivaroxaban alone (control arm). Its primary objectives are to assess: (1) proportion of PTS at 6 months using the Villalta scale and (2) study feasibility, which consists of (a) the proportion of screened patients eligible for the study, (2) the proportion of eligible patients recruited and (c) the proportion of recruited patients adherent to treatment (defined as at least 80% of drug taken). This study will determine the feasibility of a subsequent larger definitive trial. Secondary outcomes include change of quality of life scores, PTS severity, global improvement, patient satisfaction, bleeding, recurrent venous thromboembolism, leg pain, death and lost to follow-up. Target recruitment will be a total of 60 participants, recruited at 5-6 centres.

ETHICS AND DISSEMINATION

Primary ethics approval was received from the Sunnybrook Health Sciences Center Research Ethics Board (approval ID 3315). Results of the study will be disseminated via peer-reviewed presentation at scientific conferences and open access publication.

TRIAL REGISTRATION NUMBER

NCT04794569.

The effect of rivaroxaban on biomarkers in blood and plasma: a review of preclinical and clinical evidence

Rivaroxaban is a direct, oral factor Xa inhibitor that is used for the prevention and treatment of various thromboembolic disorders. Several preclinical and clinical studies have utilized specific molecules as biomarkers to investigate the potential role of rivaroxaban beyond its anticoagulant activity and across a range of biological processes. The aim of this review is to summarize the existing evidence regarding the use of blood-based biomarkers to characterize the effects of rivaroxaban on coagulation and other pathways, including platelet activation, inflammation and endothelial effects. After a literature search using PubMed, almost 100 preclinical and clinical studies were identified that investigated the effects of rivaroxaban using molecular biomarkers. In agreement with the preclinical data, clinical studies reported a trend for reduction in the blood concentrations of D-dimers, thrombin-antithrombin complex and prothrombin fragment 1 + 2 following treatment with rivaroxaban in both healthy individuals and those with various chronic conditions. Preclinical and also some clinical studies have also reported a potential impact of rivaroxaban on the concentrations of platelet activation biomarkers (von Willebrand factor, P-selectin and thrombomodulin), endothelial activation biomarkers (matrix metalloproteinase-9, intercellular adhesion molecule-1 and vascular cell adhesion molecule-1) and inflammation biomarkers (interleukin-6, tumor necrosis factor-α and monocyte chemoattractant protein-1). Based on the results of biomarker studies, molecular biomarkers can be used in addition to traditional coagulation assays to increase the understanding of the anticoagulation effects of rivaroxaban. Moreover, there is preliminary evidence to suggest that rivaroxaban may have an impact on the biological pathways of platelet activation, endothelial activation and inflammation; however, owing to paucity of clinical data to investigate the trends reported in preclinical studies, further investigation is required to clarify these observations.

Rivaroxaban as Therapy for Saphenous Venous Graft Failure due to Venous Outflow Mismatch

Background

Recurrent angina and long-term occlusion following coronary artery bypass graft surgery is often treated with percutaneous coronary intervention, a high-risk intervention for distal embolization. Here, we present the utilization of the novel oral anticoagulant, rivaroxaban, in the treatment of saphenous vein graft thrombosis with complete resolution of the thrombus secondary to graft outflow mismatch. Case Presentation. A 69-year-old man with triple coronary artery bypass grafting using a saphenous vein and left internal mammary artery, performed in 2017, presented at our hospital for recurrent angina. Coronary angiography revealed a patent LIMA to LAD and a large clot burden in the venous conduit to the first OM/terminal circumflex—theorized to be due to an outflow mismatch of the large saphenous vein to the native artery resulting in stasis. Instead of percutaneous coronary intervention, he was treated with rivaroxaban 20 mg once a day. The angiography 4 weeks after starting rivaroxaban showed complete resolution of the thrombus.

Conclusion

Rivaroxaban could become a potential treatment option in thrombus reversal due to static venous flow with subsequent long-term patency of the graft. Additionally, its use may be indicated in the generalized prevention of VGF.

Prevention of the post thrombotic syndrome with anticoagulation: a narrative review

The post thrombotic syndrome (PTS) is chronic venous insufficiency secondary to a prior deep vein thrombosis (DVT). It is the most common complication of VTE and, while not fatal, it can lead to chronic, unremitting symptoms as well as societal and economic consequences. The cornerstone of PTS treatment lies in its prevention after DVT. Specific PTS preventative measures include the use of elastic compression stockings (ECS) and pharmacomechanical catheter directed thrombolysis (PCDT). However, the efficacy of these treatments has been questioned by large RCTs. So far, anticoagulation, primarily prescribed to prevent DVT extension and recurrence, appears to be the only unquestionably effective treatment for the prevention of PTS. In this literature review we present pathophysiological, biological, radiological and clinical data supporting the efficacy of anticoagulants to prevent PTS and the possible differential efficacy among available classes of anticoagulants (vitamin K antagonists (VKA), low molecular weight heparins (LMWHs) and direct oral anticoagulants (DOACs)). Data suggest that LMWHs and DOACs are superior to VKAs, but no head-to-head comparison is available between DOACs and LMWHs. Owing to their potentially greater anti-inflammatory properties, LMWHs could be superior to DOACs. This finding may be of interest particularly in patients with extensive DVT at high risk of moderate to severe PTS, but needs to be confirmed by a dedicated RCT.

The Potential Role of Coagulation Factor Xa in the Pathophysiology of COVID-19: A Role for Anticoagulants as Multimodal Therapeutic Agents

SARS-CoV-2 infection (COVID-19) results in local and systemic activation of inflammation and coagulation. In this review article, we will discuss the potential role of coagulation factor Xa (FXa) in the pathophysiology of COVID-19. FXa, a serine protease, has been shown to play a role in the cleavage of SARS-CoV-1 spike protein (SP), with the inhibition of FXa resulting in the inhibition of viral infectivity. FX is known to be primarily produced in the liver, but it is also expressed by multiple cells types, including alveolar epithelium, cardiac myocytes, and macrophages. Considering that patients with preexisting conditions, including cardiopulmonary disease, are at an increased risk of severe COVID-19, we discuss the potential role of increased levels of FX in these patients, resulting in a potential increased propensity to have a higher infectious rate and viral load, increased activation of coagulation and inflammation, and development of fibrosis. With these observations in mind, we postulate as to the potential therapeutic role of FXa inhibitors as a prophylactic and therapeutic treatment for high-risk patients with COVID-19.

Expression of pro-inflammatory genes in human endothelial cells: Comparison of rivaroxaban and dabigatran

INTRODUCTION

In addition to its central role in coagulation, thrombin is involved in non-hemostatic activities such as inflammation. Direct inhibition of thrombin activity (e.g. with dabigatran) or reducing its generation by inhibition of Factor Xa (e.g. with rivaroxaban) may therefore have anti-inflammatory effects.

MATERIALS AND METHODS

Microarray experiments were performed to identify transcriptome-wide changes in mRNA expression levels induced by thrombin in the presence and absence of the PAR-1 antagonist vorapaxar in primary human umbilical vein endothelial cells (HUVECs). On this basis, HUVECs were incubated with recalcified plasma, with or without rivaroxaban (0.3-3000nM), dabigatran (0.3-10,000nM), or vorapaxar (0.3-10nM). Expression levels of preselected pro-inflammatory genes were quantified by real-time PCR.

RESULTS

Vorapaxar abolished 67 of the 69 transcripts altered by more than twofold on addition of thrombin to HUVECs. ELAM-1, VCAM-1, ICAM-1, MCP-1, IL-8, CXCL1, and CXCL2 were among the genes most strongly induced by thrombin. Inflammatory gene expression after stimulation of thrombin generation was concentration-dependently suppressed by vorapaxar, dabigatran, and rivaroxaban. However, dabigatran at low concentrations (3-300nM) increased significantly the expression levels of CXCL1, CXCL2, IL-8, ELAM-1, MCP-1, and tissue factor.

CONCLUSION

In HUVECs, plasma-induced transcriptional changes are mediated by thrombin-induced PAR-1 activation. Rivaroxaban downregulated the expression of pro-inflammatory markers and tissue factor to a similar extent to dabigatran.