Venous and arterial thrombosis – pathogenesis and the rationale for anticoagulation

Arterial Thrombosis in Acute Respiratory Infections: An Underestimated but Clinically Relevant Problem

During the COVID-19 pandemic, there was increased interest in the issue of thrombotic complications of acute respiratory infections. Clinical reports and pathological studies have revealed that thrombus formation in COVID-19 may involve the venous and arterial vasculature. As thrombotic complications of infectious respiratory diseases are increasingly considered in the context of COVID-19, the fact that thrombosis in lung diseases of viral and bacterial etiology was described long before the pandemic is overlooked. Pre-pandemic studies show that bacterial and viral respiratory infections are associated with an increased risk of thrombotic complications such as myocardial infarction, ischemic stroke, pulmonary embolism, and other critical illnesses caused by arterial and venous thrombosis. This narrative review article aims to summarize the current evidence regarding thrombotic complications and their pathogenesis in acute lower respiratory tract infections.

Spectrum of Thrombotic Complications in Fatal Cases of COVID-19: Focus on Pulmonary Artery Thrombosis In Situ

COVID-19-related thrombosis affects the venous and arterial systems. Data from 156 autopsies of COVID-19 patients were retrospectively analyzed to investigate the pattern of thrombotic complications and factors associated with pulmonary artery thrombosis and thromboembolism. Thrombotic complications were observed in a significant proportion (n = 68, 44%), with pulmonary artery thrombosis the most frequently identified thrombotic event (42, 27%). Multivariate analysis revealed that the length of hospital stay (OR 1.1, p = 0.004), neutrophil infiltration in the alveolar spaces (OR 3.6, p = 0.002), and the absence of hyaline membranes (OR 0.1, p = 0.01) were associated with thrombotic complications. Neutrophil infiltration in the alveolar spaces (OR 8, p < 0.001) and the absence of hyaline membranes (OR 0.1, p = 0.003) were also independent predictors of pulmonary artery thrombosis. The association of pulmonary artery thrombosis with an absence of hyaline membranes suggests it occurs later in the course of COVID-19 infection. As neutrophil infiltration in the alveolar spaces may indicate bacterial infection, our studies suggest the consideration of bacterial infections in these critically ill patients.

Venous thrombosis: a mimic of musculoskeletal injury on MR imaging

Clinical signs and symptoms of venous thrombosis and musculoskeletal pathologies frequently overlap. Sometimes, patients with venous thrombosis undergo MR examinations under an equivocal suspicion of muscle, tendon or articular injury. A low pretest clinical suspicion and lack of familiarity with the conventional MR imaging signs of venous thrombosis may result in failure to diagnose venous thrombosis, delaying treatment and raising morbimortality. In MR imaging, thrombosis presents as venous ectasia with intraluminal heterogeneous content. Small vein thrombosis is often identified as having a branching aspect. Perivenous edema and inflammatory soft tissue changes may be the most prominent findings. The purpose of this paper is to illustrate MR findings of venous thrombosis in patients who underwent MR examinations due to suspected musculoskeletal pathologies. Cases of venous thrombosis in different sites of the body diagnosed through MR are presented.

Pleiotropic Effects of Ticagrelor: Influence on CYP4F2 Gene and Protein Expression in HUVEC and HepG2, and Escherichia coli Bacterial Survival

Background

Antiplatelet drugs, such as ticagrelor, which target platelet P2Y₁₂ receptors, are used for prevention of ischemic heart disease. Ticagrelor is also known to have pleiotropic effects of unknown mechanisms. Ticagrelor could influence the expression of molecules involved in resolution of inflammation. This study aimed to investigate if ticagrelor could change the expression of CYP4F2 and its encoded protein concentration and, additionally, to determine ticagrelor possible antibacterial activity against gram-negative bacteria.

Methods

CYP4F2 expression was determined in HUVEC and HepG2 cell lines by qPCR. CYP4F2 protein concentration was determined by ELISA. Antibiotic susceptibility testing was performed using a disc diffusion method.

Results

Ticagrelor was observed to reduce the expression of CYP4F2 in HUVEC and HepG2 cell lines. It also reduced CYP4F2 protein levels in HUVEC cells. Ticagrelor had no bactericidal activity against gram-negative third generation cephalosporin resistant E. coli.

Conclusion

Ticagrelor reduced CYP4F2 protein concentration in HUVEC, and CYP4F2 expression in HUVEC and HepG2 cells, but had no effect on third-generation cephalosporin-resistant E. coli strains.

The Biofabrication of Diseased Artery In Vitro Models

As the leading causes of global death, cardiovascular diseases are generally initiated by artery-related disorders such as atherosclerosis, thrombosis, and aneurysm. Although clinical treatments have been developed to rescue patients suffering from artery-related disorders, the underlying pathologies of these arterial abnormalities are not fully understood. Biofabrication techniques pave the way to constructing diseased artery in vitro models using human vascular cells, biomaterials, and biomolecules, which are capable of recapitulating arterial pathophysiology with superior performance compared with conventional planar cell culture and experimental animal models. This review discusses the critical elements in the arterial microenvironment which are important considerations for recreating biomimetic human arteries with the desired disorders in vitro. Afterward, conventionally biofabricated platforms for the investigation of arterial diseases are summarized, along with their merits and shortcomings, followed by a comprehensive review of advanced biofabrication techniques and the progress of their applications in establishing diseased artery models.

Stroke of antiplatelet and anticoagulant therapy in patients with coronary artery disease: a meta-analysis of randomized controlled trials

BACKGROUND

We performed a meta-analysis sought to investigate the risk of stroke with antiplatelet and anticoagulant therapies among patients with coronary artery disease (CAD).

METHODS

We searched PubMed, EMBASE, and Cochrane Library for randomized controlled trials from January 1995 to March 2020. Studies were retrieved if they reported data of stroke for patients with CAD and were randomized to receive intensive versus conservative antithrombotic therapies, including antiplatelet and oral anticoagulant (OAC). Analyses were pooled by random-effects modeling. A total of 42 studies with 301,547subjects were enrolled in this analysis.

RESULTS

Intensive antithrombotic therapy significantly reduced risk of all stroke (RR 0.86, 95% CI 0.80-0.94) and ischemic stroke (RR 0.80, 95% CI 0.71-0.91), but increased risk of hemorrhagic stroke (RR 1.36, 95% CI 1.00-1.86) and intracranial hemorrhage (RR 1.46, 95% CI 1.17-1.81). Subgroup analyses indicated that OAC yields more benefit to all stroke than antiplatelet therapy (OAC: RR 0.73, 95% CI 0.58-0.92; Antiplatelet: RR 0.90, 95% CI 0.83-0.97; Between-group heterogeneity P value = 0.030). The benefit of antiplatelet therapy on all stroke and ischemic stroke were mainly driven by the studies comparing longer versus shorter duration of dual antiplatelet therapy (All stroke: RR 0.86, 95% CI 0.78-0.95; ischemic stroke: RR 0.84, 95% CI 0.75-0.94).

CONCLUSIONS

Among CAD patients who have already received antiplatelet therapy, either strengthening antiplatelet or anticoagulant treatments significantly reduced all stroke, mainly due to the reduction of ischemic stroke, although it increased the risk of hemorrhagic stroke and intracranial hemorrhage. OAC yields more benefit to all stroke than antiplatelet therapy.

Thrombolytic Agents: Nanocarriers in Targeted Release

A thrombus, known as a blood clot, may form within the vascular system of the body and impede blood flow. Thrombosis is the most common underlying pathology of cardiovascular diseases, contributing to high morbidity and mortality. However, the main thrombolytic drugs (urokinase, streptokinase, etc.) have shortcomings, including a short half-life, serious side effects and a lack of targeting, that limit their clinical application. The use of nano-drug delivery systems is expected to address these problems and a variety of approaches, including biological and physical responsive systems, have been explored. In this report, recent advances in the development of targeted nano-drug delivery systems are thoroughly reviewed.

Incidence and Risk Factors of Lower-Extremity Deep Vein Thrombosis After Thrombolysis Among Patients with Acute Ischemic Stroke

Background

Deep vein thrombosis (DVT) is common among patients with stroke. However, the incidence of DVT in acute ischemic stroke patients treated with thrombolytic therapy and the risk factors associated with this condition are unknown.

Objective

This study aimed to investigate the incidence and risk factors of DVT after thrombolysis in patients with acute ischemic stroke.

Settings and Methods

We retrospectively reviewed the medical records of all patients with acute ischemic stroke who underwent ultrasonic examination after intravenous thrombolysis between April 2017 and December 2019 at the stroke center of the First Hospital of Jilin University, China. Color duplex ultrasound was used to diagnosis DVT in all patients within 72 h after intravenous thrombolysis. Univariate and multivariate logistic regression analyses were performed to identify the risk factors for DVT.

Results

Overall, 474 patients were included in the study. Of these, 75 (15.8%) developed DVT (95% confidence interval 12.5–19.1). Older age was the risk factor that most significantly affected the development of DVT (p = 0.001). Compared to patients younger than 60 years old, those aged 60–69 years and ≥70 years had a higher risk of DVT, at rates of 2.201 (95% CI: 1.033–4.689; p < 0.05) and 4.241 (95% CI: 2.016–8.922; p < 0.001) times higher, respectively. Patients with higher triglyceride levels (odds ratio 0.545, 95% CI: 0.372–0.799, p = 0.002) and longer activated partial thromboplastin time (OR 0.927, 95% CI: 0.862–0.996, p = 0.040) were less likely to have DVT.

Conclusion

DVT is a common complication among patients undergoing intravenous thrombolysis after acute ischemic stroke. Advanced age may increase the occurrence of DVT to some extent. For these patients, safe antiplatelet therapy should be explored and implemented as soon as possible.

Significance of CHA2DS2-VASC on the severity and hemorrhagic transformation in patients with non-valvular atrial fibrillation-induced acute ischemic stroke

Atrial fibrillation causes a fivefold increase of stroke risk. CHA₂DS₂-VAS_C is widely used to evaluate the risk of cardiac embolism in patients with non-valvular atrial fibrillation (NVAF) and identify the patients eligible for anticoagulation therapy. This study aimed to identify the significance of CHA₂DS₂-VAS_C score on the severity and hemorrhagic transformation (HT) in patients with NVAF-induced acute ischemic stroke (NVAF-AIS). Total 113 patients diagnosed as NVAF-AIS were included in this study. Patients were categorized into severe stroke group (NIHSS > 10) and non-severe group (NIHSS ≤ 10), and the risk factors for severe stroke were investigated. Based on the results of repeated brain CT/MRI examination performed within 14 days from stroke onset or immediately in case of clinical worsening, patients were divided into HT group and non-HT group, and the predictors for HT were then analyzed. CHA₂DS₂-VAS_C score [median (interquartile range) 5 (3-5) vs. 3 (2-4); p = 0.002] in severe stroke group was significantly higher than that in non-severe group. The severe stroke group showed significantly increased prevalence of heart failure (20% vs. 48.5%, p = 0.002) and decreased hemoglobin (136.4 ± 18.0 vs.143.6 ± 15.6 g/L, p = 0.031) compared with non-severe group. Multivariate regression analysis revealed that CHA₂DS₂-VASc score was a powerful predictor for the severity of NVAF-AIS. Forty-seven of total recruited patients (43.2%) developed HT within 14 days after the onset of NVAF-AIS. CHA₂DS₂-VASc score as well as elevated glycated hemoglobin and intravenous rt-PA were the independent risk factors of HT. CHA₂DS₂-VAS_C score was closely associated with the severity of NVAF-AIS. Patients with higher CHA₂DS₂-VAS_C score were more likely to develop HT after NVAF-AIS.

Simultaneous Bilateral Total Knee Arthroplasty Becomes Safer after Institution of Optimal Perioperative Management: A Longitudinal Cohort Study

Simultaneous bilateral total knee arthroplasty (SBTKA) increases the rates of procedure-related complications and mortality compared with unilateral TKA. There are no well-defined guidelines for selecting patients to avoid mortality and proposing an upgrade treatment to decrease complication rates. This study aimed to evaluate whether optimal perioperative management could improve the safety of SBTKA. From 2005 to 2017, 1,166 cases of SBTKA were identified from 14,209 TKA procedures. We retrospectively examined the SBTKA patients' demographics, comorbidity profiles, procedure-related complications, and perioperative management during two time periods. Optimal perioperative workup for managing SBTKA significantly decreased the incidences of major complication from 6.2 to 2.4% (p = 0.001) and minor complications from 28.9 to 21.5% (p = 0.004) during period I and period II, respectively. The efficiency of less tourniquet use along with intraarticular tranexamic acid injection was demonstrated by the decreases of hemoglobin (Hb) change in the first 2 days after surgery (p = 0.005) and blood transfusion requirement (p = 0.035) during the SBTKA. Furthermore, the less tourniquet use group had less thigh pain (visual analog scale decreased from 6.0 to 4.2, p = 0.003), shorter duration of hospital stay (decreased from 7.8 to 7.1, p < 0.001), and lower coagulation time (decrease from 3.5 to 2.9, p < 0.001) than the routine tourniquet use group. Patient's screening must be performed carefully for cardiopulmonary compromise in patients aged >80 years and with an American Society of Anesthesiologists score of 3. Additionally, hospitalists should consider developing methods for the eligibility, testing, and perioperative monitoring of patients who undergo SBTKA with the aim of avoiding complications and improving outcomes.

Phase I clinical trial of an antithrombotic drug protocol combining apixaban and clopidogrel in dogs

INTRODUCTION

Combining an antiplatelet drug, clopidogrel, with the direct oral Factor Xa inhibitor, apixaban, could provide an effective antithrombotic strategy in dogs. Thus, a limited 3 + 3 phase I dose-escalation clinical trial in healthy dogs was conducted to evaluate bleeding (primary end-point) and pharmacodynamic (PD)/pharmacokinetic (PK) parameters (secondary end-point).

ANIMALS

Eleven beagle dogs, median body weight 10.2 kg (9.7-10.9 kg), were enrolled.

METHODS

Four doses of apixaban (three dogs/dose) administered for eight days. Clopidogrel dose was fixed at 18.75 mg per os (PO) q 24 h with escalation of apixaban dose at 5 mg PO q 12 h, 5 mg PO q 8 h, 10 mg PO q 12 h, and 10 mg PO q 8 h. Laboratory testing included fecal occult blood, coagulation parameters, Factor X activity, apixaban concentration, platelet aggregometry, and thromboelastography on days 1, 3, and 8.

RESULTS

Evidence of bleeding was not observed at any dosage. Dose-dependent changes in PD/PK parameters between baseline and 3 h post-medication were observed including a prolongation of prothrombin time, a prolongation of activated partial thromboplastin time, a decrease of Factor X activity level, and increased apixaban concentration.

CONCLUSIONS

The combination of apixaban at a dosage range of approximately 0.5 mg/kg PO q 12 h to 1 mg/kg PO q 8 h and clopidogrel at approximately 1.8 mg/kg PO q 24 h did not cause bleeding over a one-week period in healthy dogs. Clinically relevant changes in PD/PK data occur at all dosage levels. This study provides a starting point for longer-term clinical trials to determine safety and efficacy.

Venous thromboembolism after fast-track elective revision hip and knee arthroplasty - A multicentre cohort study of 2814 unselected consecutive procedures

BACKGROUND

Venous thromboembolism (VTE) prophylaxis is much debated within total hip and knee arthroplasty (THA/TKA). Revision hip and knee arthroplasty (rTHA/rTKA) are more extensive procedures, but data on the risk of postoperative VTE is conflicting and there are no specific guidelines for thromboprophylaxis. Furthermore, data on rTHA/rTKA within a fast-track protocol is sparse. Thus, we aimed at evaluating the incidence and time course of VTE in unselected elective rTHA/rTKA within our established multicentre fast-track collaboration with in-hospital only thromboprophylaxis if length of stay (LOS) ≤ 5 days.

METHODS

We used an observational study design of unselected consecutive fast-track elective major component rTHA/rTKA from 6 dedicated fast-track centres between 2010 and 2018. We obtained information on revisions through Danish hip and knee arthroplasty registers and complete (>99%) 90 days follow-up through the Danish National Patient Registry in combination with chart review.

RESULTS

We included 2814 procedures with median LOS 3 days [2-5] and 21% had LOS >5 days. The 90-day incidence of VTE was 0.42% (n = 12), with 8 (0.28%) DVT and 4 (0.14%) PE, after median 14 days [IQR: 11-23] with the latest on day 31.

CONCLUSION

The 90-day incidence of VTE after elective fast-track rTHA and rTKA was about 0.4% which is comparable to the 90-day VTE incidence after primary fast-track THA, TKA and unicompartmental knee arthroplasty. Future investigations should focus on identification of high-risk patients while the surgical trauma per se may be less important.

The Use of Antithrombotics in Critical Illness

Hypercoagulable tendencies may develop in critically ill dogs and to a less known extent, cats. Although the use of antithrombotics is well-established in critically ill people, the indications and approach are far less well-known in dogs and cats. The goal of this article was to review the relevant CURATIVE guidelines, as well as other sources, and to provide recommendations for critically ill patients with directions for future investigation.

Assessment of Dose Proportionality of Rivaroxaban Nanocrystals

Rivaroxaban (RXB) is a class II drug, according to the Biopharmaceutics Classification System. Since its bioavailability is low at high doses, dose proportionality is not achieved for pharmacokinetic parameters. However, when taken with food, its bioavailability increases at high doses. In this study, nanocrystal technology was used to increase the solubility and, hence, the bioavailability of RXB. Pluronic F127, pharmacoat 603, and PVP K-30 were used as stabilizers to prepare RXB nanosuspension, combining ball mill and high pressure homogenization methods. Particle sizes of RXB in nanosuspension (formulation A:348 nm; formulation B:403 nm) and nanocrystal formulations (formulation A:1167 nm; formulation B:606 nm) were significantly reduced (p < 0.05) compared to those of bulk RXB. In both formulations, 80% of the drug dissolved in 30 min. For dose proportionality evaluation, 3, 10, and 15 mg/kg of RXB nanosuspensions (formulation B) were administered to rabbits. The dose proportionality for AUC and C_max of RXB nanocrystals was assessed by the power model, variance analysis of pharmacokinetic parameters, linear regression, and equivalence criterion methods. Dose proportionality for AUC was achieved at doses between 10-15 and 3-15 mg/kg. In conclusion, the preparation of a nanocrystal formulation of RXB improved its dissolution rate and pharmacokinetic profile.

Effects of Rivaroxaban on Biomarkers of Coagulation and Inflammation: A Post Hoc Analysis of the X-VeRT Trial

Introduction  This X-VeRT (eXplore the efficacy and safety of once-daily oral riVaroxaban for the prevention of caRdiovascular events in patients with nonvalvular aTrial fibrillation scheduled for cardioversion) substudy evaluated the effects of treatment with rivaroxaban or a vitamin-K antagonist (VKA) on levels of biomarkers of coagulation (D-dimer, thrombin–antithrombin III complex [TAT] and prothrombin fragment [F1.2]) and inflammation (high sensitivity C-reactive protein [hs-CRP] and high-sensitivity interleukin-6 [hs-IL-6]) in patients with atrial fibrillation (AF) who were scheduled for cardioversion and had not received adequate anticoagulation at baseline (defined as, in the 21 days before randomization: no oral anticoagulant; international normalized ratio <2.0 with VKA treatment; or <80% compliance with non-VKA oral anticoagulant treatment).

Methods  Samples for biomarker analysis were taken at baseline ( n  = 958) and treatment completion (42 days after cardioversion; n  = 918). The influence of clinical characteristics on baseline biomarker levels and the effect of treatment on changes in biomarker levels were evaluated using linear and logistic models.

Results  Baseline levels of some biomarkers were significantly associated with type of AF (D-dimer and hs-IL-6) and with history of congestive heart failure (hs-CRP, D-dimer, and hs-IL-6). Rivaroxaban and VKA treatments were associated with reductions from baseline in levels of D-dimer (−32.3 and −37.6%, respectively), TAT (−28.0 and −23.1%, respectively), hs-CRP (−12.5 and −17.9%, respectively), and hs-IL-6 (−9.2 and −9.8%, respectively). F1.2 levels were reduced from baseline in patients receiving a VKA (−53.0%) but not in those receiving rivaroxaban (2.7%).

Conclusion  Anticoagulation with rivaroxaban reduced levels of key inflammation and coagulation biomarkers to a similar extent as VKAs, with the exception of F1.2. Further investigation to confirm the value of these biomarkers in patients with AF is merited.

Citrullinated histone H3, a biomarker for neutrophil extracellular trap formation, predicts the risk of mortality in patients with cancer

Prior studies indicate that neutrophil extracellular traps (NETs) are associated with arterial thromboembolism (ATE) and mortality. We investigated the association between NET formation biomarkers (citrullinated histone H3 [H3Cit], cell-free DNA [cfDNA], and nucleosomes) and the risk of ATE and all-cause mortality in patients with cancer. In this prospective cohort study, H3Cit, cfDNA and nucleosome levels were determined at study inclusion, and patients with newly diagnosed cancer or progressive disease after remission were followed for 2 years for ATE and death. Nine-hundred and fifty-seven patients were included. The subdistribution hazard ratios for ATE of H3Cit, cfDNA and nucleosomes were 1·0 per 100 ng/ml increase (95% confidence interval [95% CI]: 0·7-1·4, P = 0·949), 1·0 per 100 ng/ml (0·9-1·2, P = 0·494) increase and 1·1 per 1-unit increase (1·0-1·2, P = 0·233), respectively. Three-hundred and seventy-eight (39·5%) patients died. The hazard ratio (HR) for mortality of H3Cit and cfDNA per 100 ng/ml increase was 1·1 (1·0-1·1, P < 0·001) and 1·1 (1·0-1·1, P < 0·001), respectively. The HR for mortality of nucleosome levels per 1-unit increase was 1·0 (1·0-1·1, P = 0·233). H3Cit, cfDNA and nucleosome levels were not associated with the risk of ATE in patients with cancer. Elevated H3Cit and cfDNA levels were associated with higher mortality in patients with cancer.

Impact of Tissue Factor Localization on Blood Clot Structure and Resistance under Venous Shear

The structure and growth of a blood clot depend on the localization of tissue factor (TF), which can trigger clotting during the hemostatic process or promote thrombosis when exposed to blood under pathological conditions. We sought to understand how the growth, structure, and mechanical properties of clots under flow are shaped by the simultaneously varying TF surface density and its exposure area. We used an eight-channel microfluidic device equipped with a 20- or 100-μm-long collagen surface patterned with lipidated TF of surface densities ∼0.1 and ∼2 molecules/μm². Human whole blood was perfused at venous shear, and clot growth was continually measured. Using our recently developed computational model of clot formation, we performed simulations to gain insights into the clot’s structure and its resistance to blood flow. An increase in TF exposure area resulted not only in accelerated bulk platelet, thrombin, and fibrin accumulation, but also in increased height of the platelet mass and increased clot resistance to flow. Moreover, increasing the TF surface density or exposure area enhanced platelet deposition by approximately twofold, and thrombin and fibrin generation by greater than threefold, thereby increasing both clot size and its viscous resistance. Finally, TF effects on blood flow occlusion were more pronounced for the longer thrombogenic surface than for the shorter one. Our results suggest that TF surface density and its exposure area can independently enhance both the clot’s occlusivity and its resistance to blood flow. These findings provide, to our knowledge, new insights into how TF affects thrombus growth in time and space under flow.

Rivaroxaban plasma levels in patients admitted for bleeding events: insights from a prospective study

Background

Serious bleeding events have been frequently described in patients taking direct oral anticoagulants (DOAC). In secondary analyses of phase 3 trials, DOAC plasma concentrations were shown to correlate with bleeding outcomes. This study aimed to describe rivaroxaban plasma levels in patients admitted to the emergency department (ED) for bleeding events. For each patient, risk factors for experiencing bleeding events were also investigated.

Methods

This analysis was part of an observational study conducted in the ED of two teaching hospitals. Plasma samples from 10 rivaroxaban-treated patients admitted for bleeding events were collected. Rivaroxaban plasma concentrations were determined by calibrated chromogenic anti-Xa assay. The measured rivaroxaban levels were then extrapolated at trough using a published population pharmacokinetic (PopPK) model, and compared to on-therapy ranges observed in large clinical trials. For each patient, clinical, medication and ABCB1 genotype data were collected.

Results

Rivaroxaban measurements varied from 5 to 358 ng/ml, with a post-intake delay ranging from 9 to 38 h. At trough, estimated plasma concentrations were between 12 and 251 ng/ml (median value 94 ng/ml). Four patients had higher-than-expected rivaroxaban levels. Inadequate dose regimen, excessive alcohol consumption and lack of treatment reassessment were observed in several patients. Half of patients were taking ≥1 drug with potential pharmacokinetics interactions (e.g. amiodarone, diltiazem), while half of patients were taking ≥1 drug increasing the risk of bleeding. All 3 patients with available genotyping data and higher-than-expected rivaroxaban levels were heterozygous or homozygous mutated for the ABCB1 1236C > T, 2677G > T, 3435 C > T and rs4148738 single nucleotide polymorphisms (SNP).

Conclusions

Rivaroxaban patients admitted to the ED for bleeding events showed highly variable plasma concentrations. This analysis underlines the usefulness of rapid DOAC measurement and the value of PopPK models to estimate concentrations at trough in a context where the post-intake delay is unmanageable. Close patient follow-up, including renal function assessment and drug interactions review, is essential for bleeding risk minimization.

Effect of a new inhibitor of factor Xa zifaxaban, on thrombosis in the inferior vena cava in rabbits

In recent years, oral factor Xa inhibitors have become a research focus as anticoagulant drugs. Zifaxaban is the first oral FXa inhibitor to enter clinical trials in China. The aim of this study was to determine the inhibitory effect of zifaxaban on thrombosisthrough a model ofinferior vena cava (IVC) thrombosis in rabbits. IVC thrombosis model was established by electrical injury and stenosis, and zifaxaban was administered (p.o.) for 5 consecutive days, then coagulation indicators and bleeding were observed. The results showed that zifaxaban had obvious inhibitory effects on FXa, and had a significant inhibitory effect on IVC thrombosis induced by electrical damage and stenosis. The effect of zifaxaban was similar to that of rivaroxaban, but the bleeding side-effects of zifaxaban were less severe than those of rivaroxaban. Zifaxaban could prolong the prothrombin time and activated partial thromboplastin time of plasma similar to that of other oral FXa inhibitors. Zifaxaban had a significant inhibitory effect on FXa, but it had no obvious effect on other coagulation factors, major anticoagulant factors or fibrinolytic indices. Our results suggest that zifaxaban had specific inhibitory effects on FXa and inhibited IVC thrombosis in rabbits with its hemorrhagic effect was less than that of rivaroxaban. Zifaxaban is ecpected to be developed as a new drug for the prevention of deep venous thrombosis, providing more medication options for patients with such disease, more research is required to support it in the future.

Discovery of novel limonin derivatives as potent anti-inflammatory and analgesic agents

Novel series of limonin derivatives (V-A-1-V-A-8, V-B-1-V-B-8) were synthesized by adding various tertiary amines onto the C (7)-position of limonin. The synthesized compounds possessed favorable physicochemical property, and the intrinsic solubility of the novel compounds were significantly improved, compared with limonin. Different pharmacological models were used to evaluate the analgesic and anti-inflammatory activities of the target compounds. Compound V-A-8 exhibited the strongest in vivo activity among the novel limonin analogs; its analgesic activity was more potent than aspirin and its anti-inflammatory activity was stronger than naproxen under our testing conditions.

Novel microspheres reduce the formation of deep venous thrombosis and repair the vascular wall in a rat model

L-Arginine (L-arg), widely known as a substrate for endogenous nitric oxide synthesis, can improve endothelial function associated with the vasculature, inhibit platelet aggregation, and alter the activity of vascular smooth muscle cells. P-selectin is a membrane component of the platelet alpha-granule and the endothelial cell-specific Wiebel–Palade body that plays a central role in mediating interactions between platelets and both leukocytes and the endothelium. The experiment was designed to evaluate the effect of novel microspheres with L-arg targeting P-selectin on the formation of deep vein thrombosis and repair of vascular wall in a rat model. Thrombosis of the inferior vena cava was induced by applying a piece of filter paper (5 mm × 10 mm) saturated with 10% FeCl₃ solution for 5 min. Targeted microspheres with L-arg, targeted microspheres with water, and saline were injected into the tail veins of the rats after 30 min of applying the filter paper saturated with 10% FeCl₃ solution. The dry weight and length of the thrombus isolated from the inferior vena cava were significantly decreased in the group with L-arg in microsphere after 24 h. No significant differences in prothrombin time, activated partial thromboplastin time, thrombin time, and fibrinogen among the groups were indicated. Images revealed that apoptosis in the vascular wall was less in the group injected with targeted microspheres with L-arg than in the other two groups at 1 and 8 d postsurgery. Meanwhile, cell proliferation was considerably excessive in the group injected with L-arg wrapped in targeted microspheres. Therefore, these novel microspheres could decrease the formation of thrombus in the early stages and in the subsequent periods of thrombosis. The microspheres can also enhance the vitality of impaired endothelial cells and reduce cell apoptosis.

Complete resolution of extensive thrombosis of atheromatous non-aneurysmal descending aorta and pulmonary embolism with warfarin therapy

A 54-year-old man underwent decompressive craniectomy following a stroke. He further developed right lower limb ischaemia, and CT aortography revealed extensive aortic atherosclerotic disease. Urgent embolectomy prevented him from having a major amputation. He subsequently developed pulmonary embolism. This was initially treated with heparin followed by warfarin apart from antiplatelets and statin. A follow-up aortography at 3 months interval showed near complete resolution of atheromatous disease of the aorta. This report raises the possibility that apart from antiplatelets and lipid-lowering agents, anticoagulation may be responsible for resolution of such an extensive atheromatous disease and whether this can be considered as part of regular treatment.

Epidemiology and pathophysiology of venous thromboembolism: similarities with atherothrombosis and the role of inflammation

Venous thromboembolism (VTE) is a multifactorial disease. Major provoking factors (e. g. surgery, cancer, major trauma, and immobilisation) are identified in 50–60 % of patients, while the remaining cases are classified as unprovoked. However, minor predisposing conditions may be detectable in these patients, possibly concurring to the pathophysiology of the disease, especially when co-existing. In recent years, the role of chronic inflammatory disorders, infectious diseases and traditional cardiovascular risk factors has been extensively investigated. Inflammation, with its underlying prothrombotic state, could be the potential link between these risk factors, as well as the explanation for the reported association between arterial and venous thromboembolic events.

Animal Models of Thrombosis From Zebrafish to Nonhuman Primates: Use in the Elucidation of New Pathologic Pathways and the Development of Antithrombotic Drugs

Thrombosis is a leading cause of morbidity and mortality worldwide. Animal models are used to understand the pathological pathways involved in thrombosis and to test the efficacy and safety of new antithrombotic drugs. In this review, we will first describe the central role a variety of animal models of thrombosis and hemostasis has played in the development of new antiplatelet and anticoagulant drugs. These include the widely used P2Y12 antagonists and the recently developed orally available anticoagulants that directly target factor Xa or thrombin. Next, we will describe the new players, such as polyphosphate, neutrophil extracellular traps, and microparticles, which have been shown to contribute to thrombosis in mouse models, particularly venous thrombosis models. Other mouse studies have demonstrated roles for the factor XIIa and factor XIa in thrombosis. This has spurred the development of strategies to reduce their levels or activities as a new approach for preventing thrombosis. Finally, we will discuss the emergence of zebrafish as a model to study thrombosis and its potential use in the discovery of novel factors involved in thrombosis and hemostasis. Animal models of thrombosis from zebrafish to nonhuman primates are vital in identifying pathological pathways of thrombosis that can be safely targeted with a minimal effect on hemostasis. Future studies should focus on understanding the different triggers of thrombosis and the best drugs to prevent each type of thrombotic event.

Differential inhibitory action of apixaban on platelet and fibrin components of forming thrombi: Studies with circulating blood and in a platelet-based model of thrombin generation

Introduction

Mechanisms of action of direct oral anticoagulants (DOAC) suggest a potential therapeutic use in the prevention of thrombotic complications in arterial territories. However, effects of DOACs on platelet activation and aggregation have not been explored in detail. We have investigated the effects of apixaban on platelet and fibrin components of thrombus formation under static and flow conditions.

Methods

We assessed the effects of apixaban (10, 40 and 160 ng/mL) on: 1) platelet deposition and fibrin formation onto a thrombogenic surface, with blood circulating at arterial shear-rates; 2) viscoelastic properties of forming clots, and 3) thrombin generation in a cell-model of coagulation primed by platelets.

Results

In studies with flowing blood, only the highest concentration of apixaban, equivalent to the therapeutic C_max, was capable to significantly reduce thrombus formation, fibrin association and platelet-aggregate formation. Apixaban significantly prolonged thromboelastometry parameters, but did not affect clot firmness. Interestingly, results in a platelet-based model of thrombin generation under more static conditions, revealed a dose dependent persistent inhibitory action by apixaban, with concentrations 4 to 16 times below the therapeutic C_max significantly prolonging kinetic parameters and reducing the total amount of thrombin generated.

Conclusions

Our studies demonstrate the critical impact of rheological conditions on the antithrombotic effects of apixaban. Studies under flow conditions combined with modified thrombin generation assays could help discriminating concentrations of apixaban that prevent excessive platelet accumulation, from those that deeply impair fibrin formation and may unnecessarily compromise hemostasis.

Clinical benefit of graduated compression stockings for prevention of venous thromboembolism after total knee arthroplasty: post hoc analysis of a phase 3 clinical study of edoxaban

Background

Guidelines from the Japanese Circulation Society recommend prophylaxis with anticoagulation plus intermittent pneumatic compression or graduated compression stockings (GCS) among patients at the highest risk for developing venous thromboembolism (VTE). However, the benefits of concomitant GCS use for patients undergoing total knee arthroplasty (TKA) and receiving anticoagulation remain unknown. In this study, the efficacy of GCS plus anticoagulation compared with anticoagulation alone was evaluated among patients undergoing TKA.

Methods

This study is a post hoc analysis of a previously reported phase 3 trial involving patients undergoing TKA. In the primary study, which permitted the use of GCS for mechanical prophylaxis, patients were randomized to receive edoxaban 30 mg once daily or enoxaparin 20 mg twice daily for 11 to 14 days following TKA. The primary endpoint was the incidence of VTE, a composite of symptomatic deep vein thrombosis (DVT), symptomatic pulmonary embolism (PE), and asymptomatic DVT. Treatment comparisons were performed using the chi-square test, and the 95 % confidence intervals were calculated.

Results

Among patients receiving edoxaban, the incidence of VTE was 3.8 and 5.8 % for patients with and without GCS, respectively. For patients receiving enoxaparin, VTE incidence was 8.4 and 20.8 % among those with and without GCS, respectively. Overall, VTE incidence was 6.0 and 13.0 % for anticoagulated patients with and without GCS mechanical prophylaxis, respectively. No deaths or symptomatic PE were reported during this study.

Conclusions

Although the incidence of VTE was >2-fold lower among patients receiving anticoagulation plus GCS compared with those receiving anticoagulation alone, statistical significance was not achieved. Further studies are required to confirm the findings of this preliminary analysis.

Trial registration

ClinicalTrials.gov Identifier: NCT01181102

Detection of Serum Interleukin-6/10/18 Levels in Sepsis and Its Clinical Significance

OBJECTIVE

To explore the clinical significance of serum levels of IL-6/10/18 in sepsis.

METHODS

Sixty-six patients with sepsis were selected to be the case group. Additionally, 42 healthy adults were selected to be the control group. ELISA was used to measure the serum levels of IL-6/10/18, and ROC was utilized to evaluate the diagnostic values of IL-6/10/18 in sepsis.

RESULTS

The heart rate, respiratory rate, WBC count and APACHE II score in the sepsis group were significantly higher than those in the control group, and these indexes were increased in turn in the mild sepsis group, severe sepsis group, and septic shock group (all P < 0.05 after correction). The serum IL-6/18 levels in sepsis patients were significantly higher than those in the control group, and both of the levels were increased in turn in the mild sepsis group, severe sepsis group, and septic shock group (both P < 0.05). However, no significant difference was found in serum IL-10 level between groups (P > 0.05). The cut-off points of IL-6 and IL-18 were 109.19 pg/ml (sensitivity: 94.4%; specificity: 83.3%) and 116.01 pg/ml (sensitivity: 77.8%; specificity: 83.3%), respectively. Serum IL-6 levels were positively correlated with the APACHE II score and heart rate (both P < 0.001).

CONCLUSION

Serum levels of IL-6/8 are up-regulated in sepsis patients. Additionally, IL-6 has a greater sensitivity than IL-18. Serum IL-6 levels were positively correlated with the APACHE II score and heart rate, indicating that IL-6 could be used as a potential biomarker for sepsis.

Greater Severity of Neurological Defects in Women Admitted With Atrial Fibrillation-Related Stroke

BACKGROUND

The magnitude of the CHA2DS2-VASc score is associated with not only stroke incidence but also long-term outcomes. The association between sex and initial stroke severity in AF-related cardioembolic stroke patients has not been clarified. The present study aimed to elucidate the risk factors for initial stroke severity among patients with cardioembolic stroke enrolled in a multicenter registry.

METHODS AND RESULTS

We selected 12,701 patients (age, 77±10 years; 5,653 women) with AF-related cardioembolic stroke from the Japan Standard Stroke Registry Study between January 2000 and July 2013. Indicators of National Institutes of Health Stroke Scale (NIHSS) scores at admission were identified using a multiple linear regression. Increased NIHSS scores positively correlated with CHA2DS2-VASc score (ρ=0.197; P<0.001). The initial neurological deficits were more severe in women than in men (NIHSS scores, median [interquartile range] 14 [5-22] vs. 8 [3-18]; P<0.001). Multiple regression analysis revealed that higher age (standardized partial regression coefficient [β] 0.162; P<0.001), female sex (β 0.120; P<0.001), diabetes mellitus (β 0.020; P=0.019), dyslipidemia (β -0.076; P<0.001), congestive heart failure (β 0.039; P<0.001), vascular disease (β 0.030; P=0.001), prior stroke/TIA (β 0.085; P<0.001) and prior anticoagulant use (β -0.020; P=0.028) were associated with the NIHSS score at admission.

CONCLUSIONS

Female sex was independently associated with the initial neurological severity among AF-related cardioembolic stroke patients.

The simultaneous occurrence of both hypercoagulability and hypofibrinolysis in blood and serum during systemic inflammation, and the roles of iron and fibrin(ogen)

Although the two phenomena are usually studied separately, we summarise a considerable body of literature to the effect that a great many diseases involve (or are accompanied by) both an increased tendency for blood to clot (hypercoagulability) and the resistance of the clots so formed (hypofibrinolysis) to the typical, 'healthy' or physiological lysis. We concentrate here on the terminal stages of fibrin formation from fibrinogen, as catalysed by thrombin. Hypercoagulability goes hand in hand with inflammation, and is strongly influenced by the fibrinogen concentration (and vice versa); this can be mediated via interleukin-6. Poorly liganded iron is a significant feature of inflammatory diseases, and hypofibrinolysis may change as a result of changes in the structure and morphology of the clot, which may be mimicked in vitro, and may be caused in vivo, by the presence of unliganded iron interacting with fibrin(ogen) during clot formation. Many of these phenomena are probably caused by electrostatic changes in the iron-fibrinogen system, though hydroxyl radical (OH˙) formation can also contribute under both acute and (more especially) chronic conditions. Many substances are known to affect the nature of fibrin polymerised from fibrinogen, such that this might be seen as a kind of bellwether for human or plasma health. Overall, our analysis demonstrates the commonalities underpinning a variety of pathologies as seen in both hypercoagulability and hypofibrinolysis, and offers opportunities for both diagnostics and therapies.

Dosing of rivaroxaban by indication: getting the right dose for the patient

INTRODUCTION

Vitamin K antagonists were the only oral anticoagulants available for several decades, but they require frequent coagulation monitoring and dose adjustment. The direct oral anticoagulants rivaroxaban , dabigatran, apixaban, and, most recently, edoxaban have been approved for the management of specific thromboembolic indications.

AREAS COVERED

This review will provide a brief overview of the cell-based coagulation model, the main determinants of arterial and venous thrombosis, and the pharmacological rationale and clinical evidence for the different dosing regimens of rivaroxaban. Published articles indexed on PubMed and Medline covering arterial and venous thrombi pathophysiology, pharmacokinetics, and pharmacodynamics of rivaroxaban, and Phase II and Phase III clinical studies with rivaroxaban as well as real-world evidence were analyzed.

EXPERT OPINION

Education on pharmacokinetic/pharmacodynamic characteristics, as well as how to manage adverse events, is needed to increase physician knowledge and confidence in using direct oral anticoagulants, as specifically discussed for rivaroxaban in this article. The continued uptake of direct oral anticoagulants in clinical practice depends on understanding of the clinical evidence and reassurance provided by emerging real-world data.

Natural Products for Antithrombosis

Thrombosis is considered to be closely related to several diseases such as atherosclerosis, ischemic heart disease and stroke, as well as rheumatoid arthritis, hyperuricemia, and various inflammatory conditions. More and more studies have been focused on understanding the mechanism of molecular and cellular basis of thrombus formation as well as preventing thrombosis for the treatment of thrombotic diseases. In reality, there is considerable interest in the role of natural products and their bioactive components in the prevention and treatment of thrombosis related disorders. This paper briefly describes the mechanisms of thrombus formation on three aspects, including coagulation system, platelet activation, and aggregation, and change of blood flow conditions. Furthermore, the natural products for antithrombosis by anticoagulation, antiplatelet aggregation, and fibrinolysis were summarized, respectively.

A clinical and pharmacologic assessment of once-daily versus twice-daily dosing for rivaroxaban

Altering doses and regimens of a drug has consequences for the drug's pharmacokinetic and pharmacodynamic profile. Based on a half-life of 5-13 h, it is expected that the Factor Xa inhibitor rivaroxaban would be best suited to a twice-daily rather than a once-daily dose regimen. However, although rivaroxaban is used as a twice-daily regimen for the initial treatment of venous thromboembolism (VTE) and secondary prevention after acute coronary syndromes, the approved dosing is once-daily for prevention of VTE after orthopaedic surgery, long-term secondary prevention of VTE and stroke prevention in patients with non-valvular atrial fibrillation. Rivaroxaban dosing was based on the evaluation of the efficacy and safety of several rivaroxaban doses and regimens in phase II trials. A clear overall advantage of twice-daily dosing compared with once-daily dosing was not documented for indications for which once-daily dosing was subsequently selected. Once-daily dosing was therefore selected for these indications because it is expected to be associated with better compliance than twice-daily dosing, and potentially, with improved outcomes. These studies and data obtained with another Factor Xa inhibitor, edoxaban, in addition to previous experience with low molecular weight heparins, indicate that the clinical impact of once-daily versus twice-daily doses on outcome in terms of efficacy and safety cannot be reliably predicted from pharmacology data, e.g. elimination half-life, obtained during pre-clinical and early phase I clinical studies but rather should be ascertained empirically in phase II and III clinical trials.

Rivaroxaban: a review of its use in the treatment of deep vein thrombosis or pulmonary embolism and the prevention of recurrent venous thromboembolism

Rivaroxaban (Xarelto(®)), an oral direct factor Xa inhibitor, is approved for the initial treatment of deep vein thrombosis (DVT) and pulmonary embolism (PE), as well as the prevention of recurrent DVT and PE. It is administered at a fixed oral dose and does not require routine coagulation monitoring. In the EINSTEIN-DVT and EINSTEIN-PE trials, in over 8,000 patients with DVT and/or PE, a single-drug approach with rivaroxaban was shown to be noninferior to standard therapy consisting of subcutaneous enoxaparin sodium overlapping with and followed by an oral dose-adjusted vitamin K antagonist (enoxaparin-VKA) with regard to the incidence of symptomatic recurrent venous thromboembolism (VTE) after 3, 6 or 12 months of treatment. Rivaroxaban was generally well tolerated in patients with DVT or PE, with no significant between-group differences in clinically relevant bleeding between the rivaroxaban and enoxaparin-VKA groups. Notably, rivaroxaban was associated with a significantly lower rate of major bleeding compared with enoxaparin-VKA when EINSTEIN-DVT and EINSTEIN-PE data were pooled. Pharmacoeconomic analyses indicated that rivaroxaban may be a cost-effective alternative to enoxaparin-VKA for the treatment of DVT or PE and prevention of recurrent VTE. Extended prophylaxis with rivaroxaban reduced the incidence of symptomatic recurrent VTE to a greater extent than placebo in the EINSTEIN-Extension trial, but was associated with a non-significant increase in the risk of clinically relevant bleeding compared with placebo. In conclusion, rivaroxaban is a reasonable alternative to standard therapy for the treatment of DVT and PE, and as extended thromboprophylaxis.

The potential role of anticoagulant therapy for the secondary prevention of ischemic events post-acute coronary syndrome

Abstract The use of dual antiplatelet therapy has led to a substantial reduction in ischemic events post-acute coronary syndrome (ACS). Despite this, recurrent event rates remain high. Recent research has combined antiplatelet with anticoagulant therapy to reduce recurrent event rates further. Compared with standard medical therapy, rivaroxaban demonstrated improved efficacy outcomes and significantly reduced mortality after an ACS. Although clear benefits of novel oral anticoagulants post-ACS have been proven, concerns regarding bleeding are still a barrier to widespread use. This review explores key trials of dual antiplatelet therapy and examines the latest research in anticoagulation aiming to optimize clinical outcomes post-ACS.

Anticoagulation in heart failure: current status and future direction

Despite therapeutic advances, patients with worsening heart failure (HF) requiring hospitalization have unacceptably high post-discharge mortality and re-admission rates soon after discharge. Evidence suggests a hypercoagulable state is present in patients with HF. Although thromboembolism as a direct consequence of HF is not frequently clinically recognized, it may contribute to mortality and morbidity. Additionally, many patients with HF have concomitant disorders conferring additional thrombotic risk, including atrial fibrillation (AF) and coronary artery disease (CAD). Acute coronary syndrome (ACS), a known consequence of coronary thrombosis, is a common precipitating factor for worsening HF. Coronary thrombosis may also cause sudden death in patients with HF and CAD. Because data are largely derived from observational studies or trials of modest size, guideline recommendations on anticoagulation for HF vary between organizations. The recently presented Warfarin versus Aspirin in Reduced Cardiac Ejection Fraction trial of HF patients in sinus rhythm suggested anticoagulation reduces the risk of stroke, although rates of the combined primary endpoint (death, ischemic stroke, or intracerebral hemorrhage) were similar for acetylsalicylic acid and warfarin. Newer oral anticoagulants dabigatran, apixaban, and rivaroxaban have successfully completed trials for the prevention of stroke in patients with AF and have shown benefits in the subpopulation of patients with concomitant HF. Positive results of the Anti-Xa Therapy to Lower Cardiovascular Events in Addition to Standard Therapy in Subjects with Acute Coronary Syndrome-Thrombolysis in Myocardial Infarction 51 (ATLAS ACS 2-TIMI 51) trial of rivaroxaban in ACS are also encouraging. These data suggest there is a need to assess the potential role for these newer agents in the management of patients hospitalized for HF who continue to have a high post-discharge event rate despite available therapies.

Rivaroxaban in patients with a recent acute coronary syndrome event: integration of trial findings into clinical practice

Despite significant advances in the management of acute coronary syndrome (ACS) and long-term antiplatelet therapy after an ACS event, patients continue to be at risk of further cardiovascular events. There is evidence that recurrent events are at least partly attributed to the persistent activation of the coagulation system after ACS. Various anticoagulants, including vitamin K antagonists (VKAs) and non-VKA oral anticoagulants, have been evaluated in patients post-ACS, in combination with antiplatelet therapy. The desired outcome would be a further reduction of recurrent cardiovascular events with low or acceptable levels of bleeding complications. Here, we provide an overview of the current clinical trial data of non-VKA oral anticoagulants, focusing on rivaroxaban in particular, for secondary prevention in patients with a recent ACS event.

Cross-modulatory effects of clopidogrel and heparin on platelet and fibrin incorporation in thrombosis

Pharmacologic inhibition of platelet activation and aggregation is a mainstay for reducing the incidence of arterial thrombosis, whereas anticoagulation is the primary approach for preventing the development of venous thrombosis. The effect of standard pharmacologic agents on their reciprocal vessel - anticoagulants on arterial thrombosis and platelet inhibitor on venous thrombosis - is relatively understudied. This study was designed to evaluate murine large-vessel arterial or venous thrombosis under conditions of either fibrin or platelet inhibition. In this study, heparin and clopidogrel were used as standard anticoagulant and platelet inhibitor, respectively, evaluating both large artery and vein thrombosis in mice, using in-vivo fluorescence imaging to simultaneously measure fibrin and platelet levels at the thrombus induction site. Heparin reduced both fibrin and platelet development in both arteries and veins, with stronger influences on fibrin accrual. Clopidogrel had a stronger effect in arteries, reducing both platelet and fibrin accumulation. Clopidogrel also reduced platelet accumulation with venous thrombosis, but the reductions in fibrin formation did not reach statistical significance. These findings illustrate the interactive role of platelet activity and coagulation in the development of large-vessel thrombosis, with inhibition of one thrombotic component showing profound effects on the other component in both arterial and venous thrombosis.

Common polymorphisms in the interleukin-6 gene and myocardial infarction risk: a meta-analysis

BACKGROUND

Interleukin-6 (IL-6) plays a critical role in the development and progression of cardiovascular disease. Emerging evidence suggests that two common polymorphisms (-174 G/C and -572 G/C) in the IL-6 gene might have an impact on an individual's susceptibility to myocardial infarction (MI), but individually published results are inconclusive. This meta-analysis aimed to derive a more precise estimation of the relationship between IL-6 -174 G/C and -572 G/C polymorphisms and MI risk.

METHOD

An extensive literary search for relevant studies was conducted in PubMed, Embase, Web of Science, Cochrane Library, CISCOM, CINAHL, Google Scholar, China BioMedicine (CBM), and China National Knowledge Infrastructure (CNKI) databases from their inception through August 1st, 2013. A meta-analysis was then performed using the STATA 12.0 software. The crude odds ratios (OR) with 95% confidence intervals (CI) were calculated.

RESULTS

Eleven case-control studies were included with a total of 10,252 subjects, including 5429 MI patients and 4823 healthy controls. Our meta-analysis results indicated that IL-6 -174 G/C polymorphism may increase the risk of MI (C allele vs. G allele: OR=1.07, 95% CI: 1.01-1.14, p=0.018; GC+CC vs. GG: OR=1.14, 95% CI: 1.04-1.24, p=0.003; respectively). However, our results showed no significant association between IL-6 -572 G/C polymorphism and MI risk (C allele vs. G allele: OR=0.88, 95% CI: 0.75-1.03, p=0.098; GC+CC vs. GG: OR=0.87, 95% CI: 0.70-1.07, p=0.173; respectively). No publication bias was detected in this meta-analysis.

CONCLUSION

The current meta-analysis suggests that IL-6 -174 G/C polymorphism may contribute to MI susceptibility. Thus, detection of IL-6 -174 G/C polymorphisms may be a promising biomarker for the early detection of MI. However, IL-6 -572 G/C polymorphism may not associate with the risk of MI.

SPECT imaging of fibrin using fibrin-binding peptides

Noninvasive detection of fibrin in vivo using diagnostic imaging modalities may improve clinical decision-making on possible therapeutic options in atherosclerosis, cancer and thrombus-related pathologies such as pulmonary embolism and deep venous thrombosis. The aim of this study was to assess the potential of a novel (111)In-labeled fibrin-binding peptide (FibPep) to visualize thrombi in mice noninvasively using single-photon emission computed tomography (SPECT). FibPep and a negative control peptide (NCFibPep) were synthesized and their fibrin-binding properties were assessed in vitro. FibPep showed enhanced binding compared with NCFibPep to both fibrin and blood clots. FibPep bound to fibrin with a dissociation constant (K(d)) of 0.8 μ m, whereas NCFibPep displayed at least a 100-fold lower affinity towards fibrin. A FeCl3 -injury carotid artery thrombosis mouse model was used to evaluate the peptides in vivo. FibPep and NCFibPep displayed rapid blood clearance and were eliminated via the renal pathway. In vivo SPECT imaging using FibPep allowed clear visualization of thrombi. Ex vivo biodistribution showed significantly increased uptake of FibPep in the thrombus-containing carotid in comparison to the noninjured carotid (5.7 ± 0.7 and 0.6 ± 0.4% injected dose per gram (%ID g(-1)), respectively; p < 0.01; n = 4), whereas nonspecific NCFibPep did not (0.4 ± 0.2 and 0.3 ± 0.0%ID g(-1), respectively; n = 4). In conclusion, FibPep displayed high affinity towards fibrin in vitro and rapid blood clearance in vivo, and allowed sensitive detection of thrombi using SPECT imaging. Therefore, this particular imaging approach may provide a new tool to diagnose and monitor diseases such as atherosclerosis and cancer.

Myxomavirus-derived serpin prolongs survival and reduces inflammation and hemorrhage in an unrelated lethal mouse viral infection

Lethal viral infections produce widespread inflammation with vascular leak, clotting, and bleeding (disseminated intravascular coagulation [DIC]), organ failure, and high mortality. Serine proteases in clot-forming (thrombotic) and clot-dissolving (thrombolytic) cascades are activated by an inflammatory cytokine storm and also can induce systemic inflammation with loss of normal serine protease inhibitor (serpin) regulation. Myxomavirus secretes a potent anti-inflammatory serpin, Serp-1, that inhibits clotting factor X (fX) and thrombolytic tissue- and urokinase-type plasminogen activators (tPA and uPA) with anti-inflammatory activity in multiple animal models. Purified serpin significantly improved survival in a murine gammaherpesvirus 68 (MHV68) infection in gamma interferon receptor (IFN-γR) knockout mice, a model for lethal inflammatory vasculitis. Treatment of MHV68-infected mice with neuroserpin, a mammalian serpin that inhibits only tPA and uPA, was ineffective. Serp-1 reduced virus load, lung hemorrhage, and aortic, lung, and colon inflammation in MHV68-infected mice and also reduced virus load. Neuroserpin suppressed a wide range of immune spleen cell responses after MHV68 infection, while Serp-1 selectively increased CD11c(+) splenocytes (macrophage and dendritic cells) and reduced CD11b(+) tissue macrophages. Serp-1 altered gene expression for coagulation and inflammatory responses, whereas neuroserpin did not. Serp-1 treatment was assessed in a second viral infection, mouse-adapted Zaire ebolavirus in wild-type BALB/c mice, with improved survival and reduced tissue necrosis. In summary, treatment with this unique myxomavirus-derived serpin suppresses systemic serine protease and innate immune responses caused by unrelated lethal viral infections (both RNA and DNA viruses), providing a potential new therapeutic approach for treatment of lethal viral sepsis.

Open-label, randomized study of the effect of rivaroxaban with or without acetylsalicylic acid on thrombus formation in a perfusion chamber

INTRODUCTION

Rivaroxaban, a direct factor Xa inhibitor, has demonstrated effectiveness for the management of both venous and arterial thrombosis. This study was designed to investigate the antithrombotic effect of rivaroxaban, with or without acetylsalicylic acid (ASA), in an ex vivo perfusion chamber at both low and high shear rates.

MATERIALS AND METHODS

Healthy subjects (N=51) were enrolled in a randomized, crossover (rivaroxaban 5, 10 or 20mg with or without ASA), and parallel-group (compared with ASA plus clopidogrel) study. Thrombi formed on pig aorta strips were measured after a 5-minute perfusion at low and high shear rates with blood from the subjects by measuring D-dimer concentration (for fibrin deposition) and P-selectin content (for platelet deposition).

RESULTS

ASA alone had no impact on thrombus D-dimer levels, whereas rivaroxaban alone at peak concentrations decreased D-dimer levels by 9%, 84% and 65% at low shear rate and 37%, 73% and 74% at high shear rate after doses of 5, 10 and 20mg, respectively. Steady-state ASA plus rivaroxaban 5mg caused a greater reduction in D-dimer levels (63%) than monotherapy at low shear rate. Co-administration of ASA with clopidogrel was associated with a 30% decrease in D-dimer levels at low shear rate and a 14% decrease at high shear rate. No conclusive effect on P-selectin content was observed across the treatment groups.

CONCLUSIONS

Rivaroxaban dose-dependently inhibited ex vivo thrombus formation under low and high shear rates. Co-administration of ASA had an additional effect on the antithrombotic action of low-dose rivaroxaban.

Elevated prothrombin promotes venous, but not arterial, thrombosis in mice

OBJECTIVE

Individuals with elevated prothrombin, including those with the prothrombin G20210A mutation, have increased risk of venous thrombosis. Although these individuals do not have increased circulating prothrombotic biomarkers, their plasma demonstrates increased tissue factor-dependent thrombin generation in vitro. The objectives of this study were to determine the pathological role of elevated prothrombin in venous and arterial thrombosis in vivo, and distinguish thrombogenic mechanisms in these vessels.

APPROACH AND RESULTS

Prothrombin was infused into mice to raise circulating levels. Venous thrombosis was induced by electrolytic stimulus to the femoral vein or inferior vena cava ligation. Arterial thrombosis was induced by electrolytic stimulus or ferric chloride application to the carotid artery. Mice infused with prothrombin demonstrated increased tissue factor-triggered thrombin generation measured ex vivo, but did not have increased circulating prothrombotic biomarkers in the absence of vessel injury. After venous injury, elevated prothrombin increased thrombin generation and the fibrin accumulation rate and total amount of fibrin ≈ 3-fold, producing extended thrombi with increased mass. However, elevated prothrombin did not accelerate platelet accumulation, increase the fibrin accumulation rate, or shorten the vessel occlusion time after arterial injury.

CONCLUSIONS

These findings reconcile previously discordant findings on thrombin generation in hyperprothrombinemic individuals measured ex vivo and in vitro, and show elevated prothrombin promotes venous, but not arterial, thrombosis in vivo.

Rivaroxaban: a novel oral anticoagulant for the prevention and treatment of several thrombosis-mediated conditions

The development of rivaroxaban (XARELTO®) is an important new medical advance in the field of oral anticoagulation. Thrombosis-mediated conditions constitute a major burden for patients, healthcare systems, and society. For more than 60 years, the prevention and treatment of these conditions have been dominated by oral vitamin K antagonists (such as warfarin) and the injectable heparins. Thrombosis can lead to several conditions, including deep vein thrombosis, pulmonary embolism, myocardial infarction, stroke, and/or death. Prevention and treatment of thrombosis with an effective, convenient-to-use oral anticoagulant with a favorable safety profile is critical, especially in an aging society in which the risk of thrombosis, and the potential for bleeding complications, is increasing. Rivaroxaban acts to prevent and treat thrombosis by potently inhibiting coagulation Factor Xa in the blood. Factor Xa converts prothrombin to thrombin, which initiates the formation of blood clots by converting fibrinogen to clot-forming fibrin and leads to platelet activation. After a large and novel clinical development program in over 75,000 patients to date, rivaroxaban has received approval for multiple indications in the United States, European Union, and other countries worldwide to prevent and treat several thrombosis-mediated conditions. This review will highlight some of the unique aspects of the rivaroxaban development program.

The skin and hypercoagulable states

Hypercoagulable states (HS) are inherited or acquired conditions that predispose an individual to venous and/or arterial thrombosis. The dermatologist can play a vital role in diagnosing a patient's HS by recognizing the associated cutaneous manifestations, such as purpura, purpura fulminans, livedo reticularis, livedo vasculopathy (atrophie blanche), anetoderma, chronic venous ulcers, and superficial venous thrombosis. The cutaneous manifestations of HS are generally nonspecific, but identification of an abnormal finding can warrant a further workup for an underlying thrombophilic disorder. This review will focus on the basic science of hemostasis, the evaluation of HS, the skin manifestations associated with hypercoagulability, and the use of antiplatelet and anticoagulant therapy in dermatology.

Targeting Therapy to the Fibrin-Mediated Pathophysiology of Acute Coronary Syndrome

Acute coronary syndrome (ACS) encompasses a spectrum of diseases, ranging from ST-elevation myocardial infarction to non-ST-elevation myocardial infarction and unstable angina. A key initiating event in the pathology of ACS is atheromatous plaque disruption, in which the exposure of thrombogenic material triggers simultaneous activation of primary and secondary hemostatic pathways. Targeting platelet-mediated thrombus formation with dual antiplatelet therapy comprising acetylsalicylic acid and a P2Y12 antagonist is the current mainstay for management of ACS. However, a significant proportion of patients remain at risk of cardiovascular events. Fibrin is an important contributor to thrombogenesis and may account for the residual event rates. This review examines evidence for the role of the coagulation cascade in thrombus formation in ACS, which provides a rationale for the use of anticoagulation therapy. The current status of research with novel oral anticoagulants in combination with dual antiplatelet therapy for the secondary prevention of ACS is also discussed.