Showing papers in "Thrombosis and Haemostasis in 2010"

Dabigatran etexilate - a novel, reversible, oral direct thrombin inhibitor: Interpretation of coagulation assays and reversal of anticoagulant activity

Abstract: Summary Dabigatran etexilate is an oral, reversible direct thrombin inhibitor that is approved in the EU and several other countries for the prevention of venous thromboembolism after elective hip and knee replacement, and is in advanced clinical development for other thromboembolic disorders. Dabigatran has a predictable pharmacokinetic profile, allowing for a fixed-dose regimen without the need for routine coagulation monitoring. In certain clinical situations such as serious bleeding into critical organs (e.g. intracerebral bleeding), potential overdose and emergency surgery, clinicians will need to make an assessment of the anticoagulant status of a patient receiving dabigatran before deciding on future management strategies. If available, thrombin clotting time (TT), ecarin clotting time (ECT) and TT determined by Hemoclot ® thrombin inhibitor assay are sensitive tests to evaluate the anticoagulant effects of dabigatran. Prothrombin time (INR) is less sensitive than other assays and cannot be recommended. The activated partial thromboplastin time (aPTT) can provide a useful qualitative assessment of anticoagulant activity but is less sensitive at supratherapeutic dabigatran

Assessment of laboratory assays to measure rivaroxaban--an oral, direct factor Xa inhibitor.

Abstract: Although there is no need for routine coagulation monitoring with rivaroxaban – an oral, direct factor Xa inhibitor – a haemostasis assay might be valuable to measure its pharmacodynamic effects. This study aimed to find assays, among those commercially available, to measure rivaroxaban pharmacodynamics. Several global conventional clotting tests, as well as clotting or chromogenic assays to measure anti-factor Xa activity, were studied. A thrombin generation test using calibrated automated thrombogram was also done. Tests were performed with the indirect factor Xa inhibitor fondaparinux for comparison. A concentration-dependent prolongation of prothrombin time (PT), dilute PT, and activated partial thromboplastin time was observed with rivaroxaban. The results varied depending on the reagents. This variability cannot be standardised with the international normalised ratio system commonly used for vitamin K antagonists. Using a standard calibration curve, PT test results can be expressed in plasma concentrations of rivaroxaban rather than PT seconds or ratio. Standard methods for HepTest and two-step prothrombinase-induced clotting time (PiCT) resulted in a paradoxical response, with low concentrations of rivaroxaban reducing clotting times. This was not observed with shorter incubation times, or when antithrombin-deficient (immunodepleted) plasma was used. The chromogenic tests found a dose-dependent relationship between anti-factor Xa activity and rivaroxaban concentration. Modified specific factor Xa chromogenic assays are being further investigated. One-step PiCT and HepTest with shortened incubation times, as well as the widely available PT assay (using a rivaroxaban calibrator) could be useful to monitor the pharmacodynamic effects of rivaroxaban accurately. Finally, all clotting and chromogenic assays showed a concentration-dependent effect induced by rivaroxaban.

Clinical laboratory measurement of direct factor Xa inhibitors: Anti-Xa assay is preferable to prothrombin time assay

Abstract: Apixaban and other factor Xa (FXa) inhibitors are in late-stage clinical development for prevention and treatment of thromboembolic diseases. Although routine monitoring will not be required, in certain situations assessment of drug level may be helpful. This study evaluated the suitability of commercially available prothrombin time/international normalised ratio (PT/INR) and anti-FXa activity assays to measure FXa inhibitors in plasma. Twelve PT (ISI 0.89-1.88) and three anti-Xa assays were evaluated in vitro using human plasma spiked with four FXa inhibitors (0-2,000 ng/ml). Assay variability and correlation with drug plasma exposure were evaluated in patients with venous thromboembolism (VTE) treated with apixaban. All FXa inhibitors prolonged PT; however, assay sensitivity was dependent on thromboplastin reagents used and FXa inhibitors tested. To achieve a doubling of PT, the concentration of each FXa inhibitor varied 2.6- to 8-fold between thromboplastin reagents. The rank order of a FXa inhibitor’s effect on PT ratio varied across thromboplastin reagents. Conversion to INR increased variability. Different anti-Xa assays showed different dynamic ranges for each FXa inhibitor; however, their rank order was consistent. For apixaban, the dynamic range of <7.8–240 ng/ml, and inter- and intra-assay precision of <6% coefficient of variation by Rotachrom assay appeared suitable for the anticipated apixaban plasma concentrations with 2.5 and 5 mg bid clinical doses. The stronger correlation between apixaban plasma concentration and anti-Xa activity (r2 = 0.88–0.89) compared with PT/INR (r2 = 0.36) in patients undergoing VTE treatment suggested that anti-Xa activity was the better indicator of apixaban plasma concentrations.

Randomised, parallel-group, multicentre, multinational phase 2 study comparing edoxaban, an oral factor Xa inhibitor, with warfarin for stroke prevention in patients with atrial fibrillation.

Abstract: The primary objective of this study was to compare the safety of four fixed-dose regimens of edoxaban with warfarin in patients with non-valvular atrial fibrillation (AF). In this 12-week, parallel-group, multicentre, multinational study, 1,146 patients with AF and risk of stroke were randomised to edoxaban 30 mg qd, 30 mg bid, 60 mg qd, or 60 mg bid or warfarin dose-adjusted to a target international normalised ratio of 2.0–3.0. The study was double-blind to edoxaban dose, but open-label to warfarin. Primary outcomes were occurrence of major and/or clinically relevant non-major bleeding and elevated hepatic enzymes and/or bilirubin. Mean age was 65 ± 8.7 years and 64.4% were warfarin-naive. Whereas major plus clinically relevant non-major bleeding occurred in 3.2% of patients randomised to warfarin, the incidence of bleeding was significantly higher with the edoxaban 60 mg bid (10.6%; p=0.002) and 30 mg bid regimens (7.8%; p=0.029), but not with the edoxaban 60 mg qd (3.8%) or 30 mg qd regimens (3.0%). For the same total daily dose of 60 mg, both bleeding frequency and trough edoxaban concentrations were higher in the 30-mg bid group than in the 60-mg qd group. There were no significant differences in hepatic enzyme elevations or bilirubin values among the groups. The safety profiles of edoxaban 30 and 60 mg qd in patients with AF were similar to warfarin. In contrast, the edoxaban bid regimens were associated with more bleeding than warfarin. These results suggest that in this three-month study, edoxaban 30 or 60 mg qd are safe and well-tolerated.

The majority of circulating platelet-derived microparticles fail to bind annexin V, lack phospholipid-dependent procoagulant activity and demonstrate greater expression of glycoprotein Ib

Abstract: It has been widely accepted that microparticles expose phosphatidylserine which in turn binds annexin V. It was the objective of this study to compare the antigenic characteristics and phospholipid-dependent procoagulant activity of annexin V positive and -negative subpopulations of platelet-derived microparticles. Annexin V positive and -negative microparticles were identified and characterised using flow cytometry and procoagulant activity was measured by a phospholipid-dependent assay (XACT). In unstimulated platelet-poor plasma, 80% of platelet-derived microparticles failed to bind annexin V. Varying the assay constituents (buffer, calcium and annexin V concentration) did not alter annexin V binding. The proportion of microparticles that bound annexin V was dependent upon the agonist, with physiological agonists such as collagen resulting in fewer annexin V binding microparticles than non-physiological agonists such as ionophore. CD42b (glycoprotein Ib) expression was significantly decreased and CD62p and CD63 expression were significantly increased in annexin V positive compared to annexin V negative subpopulations. There was no significant difference in CD41, CD61, CD42a and CD40L expression between annexin V positive and -negative subpopulations. A significant correlation between annexin V binding and XACT was found (p=0.033). Annexin V inhibited greater than 95% of phospholipid activity, suggesting that annexin V binding was a true reflection of procoagulant activity. The majority of platelet-derived microparticles in unstimulated plasma failed to bind annexin V and showed significantly increased levels of CD42b compared to annexin V positive events. Phospholipid-dependent procoagulant activity is limited to the annexin V positive subpopulation and is agonist-dependent. The significance of annexin V negative microparticles is unclear, however, it is possible that they possess other activities aside from procoagulant phospholipid activity.

Haemostatic reference intervals in pregnancy

Abstract: Haemostatic reference intervals are generally based on samples from non-pregnant women. Thus, they may not be relevant to pregnant women, a problem that may hinder accurate diagnosis and treatment of haemostatic disorders during pregnancy. In this study, we establish gestational age-specific reference intervals for coagulation tests during normal pregnancy. Eight hundred one women with expected normal pregnancies were included in the study. Of these women, 391 had no complications during pregnancy, vaginal delivery, or postpartum period. Plasma samples were obtained at gestational weeks 13–20, 21–28, 29–34, 35–42, at active labor, and on postpartum days 1 and 2. Reference intervals for each gestational period using only the uncomplicated pregnancies were calculated in all 391 women for activated partial thromboplastin time (aPTT), fibrinogen, fibrin D-dimer, antithrombin, free protein S, and protein C and in a subgroup of 186 women in addition for prothrombin time (PT), Owren and Quick PT, protein S activity, and total protein S and coagulation factors II, V, VII, VIII, IX, X, XI, and XII. The level of coagulation factors II, V, X, XI, XII and antithrombin, protein C, aPTT, PT remained largely unchanged during pregnancy, delivery, and postpartum and were within non-pregnant reference intervals. However, levels of fibrinogen, D-dimer, and coagulation factors VII, VIII, and IX increased markedly. Protein S activity decreased substantially, while free protein S decreased slightly and total protein S was stable. Gestational age-specific reference values are essential for the accurate interpretation of a subset of haemostatic tests during pregnancy, delivery, and puerperium.

Pre-analytical and analytical issues in the analysis of blood microparticles

Abstract: Results of plasma microparticles (MPs) measurements reported in the literature vary widely. This is clearly not only related to the lack of well-standardised MP assays, but also to variations in pre-analytical conditions. In this review we will discuss the pre-analytical variables related to plasma and MP preparation which may affect MP analysis. Additionally we will address several analytical issues in commonly used MP assays and briefly discuss some novel approaches for the detection and characterisation of MPs. Ideally MP measurements should be performed in plasma, freshly prepared directly after blood withdrawal. As platelet contamination seems to be one of the major pre-analytical problems in processing plasma for MP measurement, the use of platelet-free plasma may be preferred. When frozen-thawed plasma is used, especially PMP and annexinV-positive MP counts should be interpreted with caution. When flow cytometry is chosen as a method for quantification of MPs, some analytical conditions should be standardised, e.g. settings of the flow cytometer, quality of the antibodies, and use of counting beads. Fluorescence-nanoparticle tracking analysis and atomic force microscopy can accurately count nanosized MPs, but unfortunately the operational procedures of both methods are still time consuming and they give no information on the functional properties of MPs. The MP-TF activity assay provides information on MPs carrying active TF, regardless of their parental origin. Ultimately, standardisation of pre-analytical procedures and the introduction of reliable and rapid methods for the measurement of MPs are urgently needed to facilitate their use as biomarker in the pathophysiology of diseases.

Effects of the oral, direct thrombin inhibitor dabigatran on five common coagulation assays

Abstract: Dabigatran is an oral, reversible thrombin inhibitor that has shown promising results in large clinical trials. Laboratory monitoring is not needed but the effects on common coagulation assays are incompletely known. Dabigatran was added to plasma from healthy subjects in the concentration range 0–1,000 μg/l and analysed using several reagents for activated thromboplastin time (APTT), prothrombin time (PT), fibrinogen, antithrombin, and activated protein C resistance. Typical trough concentrations are about 50 μg/l, peak concentrations 100–300 μg/l. At 100 μg/l all APTT-results were prolonged. The concentration required to double APTT ranged between 227 and 286 μg/l, the responses for all five reagents were similar. PT-reagents were much less affected with almost no samples above INR 1.2 at 100 μg/l. The effect was sample dilution dependent with PT Quick type more sensitive than PT Owren type methods. If a patient on dabigatran has prolonged APTT, >90 seconds, and Quick PT INR>2 or Owren PT INR>1.5 over-dosing or accumulation of dabigatran should be considered. Two of four fibrinogen reagents underestimated the fibrinogen concentration considerably at expected peak concentration. Methods based on inhibition of thrombin over-estimated the antithrombin concentration, but not Xa-based. The APC-resistance methods over-estimated the APC-ratio, which may lead to miss-classification of factor V Leiden patients as being normal. Different coagulation assays, and even different reagents within an assay group, display variable effects at therapeutic concentrations of dabigatran. Some of these assay variations are of clinical importance, thus knowledge is needed for a correct interpretation of results.

Rivaroxaban for the prevention of venous thromboembolism after hip or knee arthroplasty. Pooled analysis of four studies.

Abstract: Four phase III studies compared oral rivaroxaban with subcutaneous enoxaparin for the prevention of venous thromboembolism (VTE) after total hip or knee arthroplasty (THA or TKA). A pooled analysis of these studies compared the effect of rivaroxaban with enoxaparin on symptomatic VTE plus all-cause mortality and bleeding events, and determined whether these effects were consistent in patient subgroups. Patients (N=12,729) aged ≥18 years and scheduled for elective THA or TKA received rivaroxaban 10 mg once daily or enoxaparin 40 mg once daily or 30 mg every 12 hours. The composite of symptomatic VTE and all-cause mortality, the prespecified primary efficacy endpoint and adjudicated bleeding events were analysed in the day 12± 2 active treatment pool. Subgroup analyses of these outcomes were performed over the total treatment period. In the day 12± 2 pool, the primary efficacy endpoint occurred in 29/6,183 patients receiving rivaroxaban (0.5%) versus 60/6,200 patients receiving enoxaparin (1.0%; p=0.001). Major bleeding occurred in 21 (0.3%) versus 13(0.2%) patients, p=0.23; major plus non-major clinically relevant bleeding in 176(2.8%) versus 152 (2.5%) patients, p=0.19; and any bleeding in 409 (6.6%) versus 384 (6.2%) patients, p=0.38, respectively. The reduction of symptomatic VTE plus all-cause mortality was consistent across prespecified subgroups (age, gender, body weight, creatinine clearance) in the total treatment period. Compared with enoxaparin regimens, rivaroxaban reduces the composite of symptomatic VTE and all-cause mortality after elective THA or TKA, with a small increase in bleeding, no signs of compromised liver safety and fewer serious adverse events.

New oral anticoagulant drugs in cardiovascular disease

Abstract: Oral anticoagulation has been limited to vitamin K antagonists (VKAs) for over 60 years. VKAs are effective and recommended for the prevention of venous and arterial thromboembolism in cardiovascular disease, but their pharmacodynamics are difficult to predict and the highly variable interindividual and intraindividual response to treatment accounts for the need of continuous monitoring. This prompted the intensive exploration of numerous substances within the last decade in an attempt to meet the shortcomings of current oral anticoagulation with VKAs. The development and clinical investigation of two novel groups of oral anticoagulants targeting central factors of the coagulation system either factor Xa or thrombin (factor IIa) has now reached the daily clinical practice with the approval of the oral direct thrombin inhibitor dabigatran etexilate and the oral direct factor Xa inhibitor rivaroxaban. Ongoing clinical trials are investigating these substances and other novel oral anticoagulants with similar mechanisms of action in patients with atrial fibrillation and acute coronary syndromes. This review article discusses the clinical evaluation and pharmacological properties of novel oral anticoagulants in late and earlier stages of clinical development, thereby providing a critical analysis and an outlook on the future of oral anticoagulation in cardiovascular disease.

Characterisation and potential diagnostic value of circulating matrix Gla protein (MGP) species.

Abstract: Matrix γ-carboxyglutamate (Gla) protein (MGP) is an important local inhibitor of vascular calcification, which can undergo two post-translational modifications: vitamin K-dependent γ-glutamate carboxylation and serine phosphorylation. While carboxylation is thought to have effects upon binding of calcium-ions, phosphorylation is supposed to affect the cellular release of MGP. Since both modifications can be exerted incompletely, various MGP species can be detected in the circulation. MGP levels were measured with two commercially available competitive and two novel sandwich assays in healthy controls, in patients with rheumatic disease, aortic valve disease, and end-stage renal disease, as well as in volunteers after vitamin K supplementation (VKS) and treatment with vitamin K antagonists (VKA). Major differences were found between the MGP assays, including significantly different behaviour with regard to vascular disease and the response to VKA and VKS. The dual-antibody assay measuring non-phosphorylated, non-carboxylated MGP (dp-ucMGP) was particularly sensitive for these changes and would be suited to assess the vascular vitamin K status. We conclude that the different assays for particular circulating MGP species allows the assessment of various aspects of the MGP system.

Clopidogrel non-responsiveness and risk of cardiovascular morbidity. An updated meta-analysis.

Abstract: We performed this meta-analysis to update the clinical evidences on the relation between clopidogrel non-responsiveness and clinical outcomes in patients with coronary artery disease (CAD) who underwent percutaneous coronary intervention. An electronic literature search through MEDLINE, EMBASE, Web of Science, and the Cochrane Library and bibliographies of retrieved articles up to January, 2009 was conducted. Studies were included if they had a cohort prospective design, if they analysed clopidogrel responsiveness in CAD patients in relation to death and/or occurrence of adverse coronary events during follow-up, and if they reported an adequate statistical analysis. Fourteen studies, totalling 4,564 CAD patients followed for a time ranging from 14 days to one year, were included. The cumulative analysis reported that residual platelet reactivity despite clopidogrel treatment was significantly associated with an increased risk of death and/or thrombotic recurrences (odds ratio [OR] 5.67, 95% confidence interval [CI] 2.97 to 10.84; p<0.00001). However, four studies contributed to a consistent heterogeneity of the model and evidenced a significant risk of publication bias, so were excluded from the analysis. This exclusion, however, did not influence the overall result, by confirming the increased risk of cardiovascular recurrences for patients with a poor response to clopidogrel treatment (OR 3.58, 95%CI 2.54 to 5.05; p<0.00001). The present updated meta-analysis documents a significant association between residual platelet reactivity under clopidogrel treatment and recurrent cardiovascular events, so suggesting the relevance of ongoing interventional studies aimed at tailoring the antithrombotic therapy in CAD patients.

C1 inhibitor, a multi-functional serine protease inhibitor.

Abstract: C1 inhibitor (C1INH) is a serpin that regulates both complement and contact (kallikrein-kinin) system activation. It consists of a serpin domain that is highly homologous to other serpins and an amino terminal non-serpin mucin-like domain. Deficiency of C1INH results in hereditary angioedema, a disease characterised by episodes of angioedema of the skin or the mucosa of the gastrointestinal tract or the oropharynx. Although early data suggested that angioedema was mediated via complement system activation, the preponderance of the data indicate that bradykinin is the mediator. In the past few years, it has become apparent that C1INH has additional anti-inflammatory functions independent of protease inhibition. These include interactions with leukocytes that may result in enhanced phagocytosis, with endothelial cells via E- and P-selectins that interfere with leukocyte rolling and in turn results in suppression of transmigration of leukocytes across the endothelium, and interactions with extracellular matrix components that may serve to concentrate C1INH at sites of inflammation. In addition, C1INH suppresses gram negative sepsis and endotoxin shock, partly via direct interaction with endotoxin that interferes with its interaction with macrophages, thereby suppressing tumour necrosis factor-a and other inflammatory mediators. C1INH treatment improves outcome in a number of disease models, including sepsis and other bacterial infections, possibly malaria, ischaemia-reperfusion injury (intestinal, hepatic, muscle, cardiac, brain), hyper-acute transplant rejection, and other inflammatory disease models. Recent data suggest that this effectiveness is the result of mechanisms that do not require protease inhibition, in addition to both complement and contact system activation.

Patients with severe factor XI deficiency have a reduced incidence of deep-vein thrombosis.

Abstract: Factor XI (FXI) plays a dual role in haemostasis and thrombosis. It contributes to thrombin generation and promotes inhibition of fibrinolysis. Severe FXI deficiency was shown to confer protection against arterial and venous thrombosis in animal models without compromising haemostasis. We have previously shown that patients with severe FXI deficiency have a low incidence of ischaemic stroke, but display the usual incidence of myocardial infarction. In the present study, we compared the incidence of deep-vein thrombosis (DVT) in 219 unrelated patients with severe FXI deficiency aged 20–94 to the incidence in a large population-based study. No cases of DVT were observed in the FXI-deficient cohort, a result that is significantly lower than the expected number (4.68) computed from the population-based study. The low incidence remains statistically significant when compared to three other population-based studies. These data suggest that severe FXI deficiency provides protection against DVT.

Endothelial-derived microparticles: Biological conveyors at the crossroad of inflammation, thrombosis and angiogenesis

Abstract: Endothelial microparticles (EMP) are complex vesicular structures that can be shed by activated or apoptotic endothelial cells. EMP are composed of a phospholipid bilayer that exposes transmembrane proteins and receptors and encloses cytosolic components such as enzymes, transcription factors and mRNA derived from their parent cells. Thus, EMP behave as biological conveyors playing a key role in the tuning of vascular homeostasis. This review focuses on the multifaceted roles of EMP, notably in coagulation, inflammation and angiogenesis and also on the mechanisms that trigger their formation. In this context, EMP could compromise vascular homeostasis and then represent key players in the pathogenesis of several inflammatory and thrombotic diseases. Consequently, elucidating their role and their mechanisms of formation will bring new insights into the understanding of endothelial-associated diseases. Moreover, in the future, it can open novel therapeutic perspectives based on the inhibition of EMP release.

Stem cell and progenitor cell therapy in peripheral artery disease. A critical appraisal.

Abstract: Atherosclerotic peripheral artery disease (PAD) is a common manifestation of atherosclerosis. The occlusion of large limb arteries leads to ischaemia with claudication which can progress to critical limb ischaemia (CLI) with pain at rest, and to tissue loss. At present, common therapy for CLI is either surgical or endovascular revascularisation aimed at improving blood flow to the affected extremity. However, major amputation and death are still frequent complications. Exploring new strategies for revascularisation of ischaemic limbs is thus of major importance. Bone marrow (BM)-derived stem and progenitor cells have been identified as a potential new therapeutic option to induce therapeutic angiogenesis. Encouraging results of preclinical studies have rapidly led to several small clinical trials, in which BM-derived mononuclear cells were administered to patients with limb ischaemia. Clinical benefits were reported from these trials including improvement of ankle-brachial index (ABI), transcutaneous partial pressure of oxygen (TcPO2), reduction of pain, and decreased need for amputation. Nonetheless, large randomised, placebo-controlled, double-blind studies are necessary and currently ongoing (BONMOT-CLI, JUVENTUS and NCT00498069). Further research relates to the optimal cell type and dosage, the isolation method, the role of colony-stimulating factors, administration route, and the supportive stimulation of cells with reduced functioning due to advanced PAD. Autologous stem cell therapy for ischaemic peripheral disease seems to be a promising new tool for the treatment of severe limb ischaemia. Preliminary evidence has established its safety, feasibility and effectiveness on several important endpoints. Several large endpoints studies are underway to further consolidate this evidence.

Tissue factor and thrombosis: The clot starts here.

Abstract: Thrombosis, or complications from thrombosis, currently occupies the top three positions in the cardiovascular causes of morbidity and mortality in the developed world. There are a limited number of safe and effective drugs to prevent and treat thrombosis. Animal models of thrombosis are necessary to better understand the complex components and interactions involved in the formation of a clot. Tissue factor (TF) is required for the initiation of blood coagulation and likely plays a key role in both arterial and venous thrombosis. Understanding the role of TF in thrombosis may permit the development of new antithrombotic drugs. This review will focus on the role of TF in in vivo models of thrombosis.

Thromboprophylaxis for recurrent miscarriage in women with or without thrombophilia. HABENOX: a randomised multicentre trial.

Abstract: Recurrent miscarriage affects 1–2% of women. In more than half of all recurrent miscarriage the cause still remains uncertain. Thrombophilia has been identified in about 50% of women with recurrent miscarriage and thromboprophylaxis has been suggested as an option of treatment. A randomised double-blind (for aspirin) multicentre trial was performed among 207 women with three or more consecutive first trimester (<13 weeks) miscarriages, two or more second trimester (13–24 weeks) miscarriages or one third trimester fetal loss combined with one first trimester miscarriage. Women were analysed for thrombophilia. After complete work-up, women were randomly allocated before seven weeks’ gestation to either enoxaparin 40 mg and placebo (n=68), enoxaparin 40 mg and aspirin 100 mg (n=63) or aspirin 100 mg (n=76). The primary outcome was live-birth rate. Secondary outcomes were pregnancy complications, neonatal outcome and adverse effects. The trial was ended prematurely because of slow recruitment. A live birth rate of 71% [relative risk (RR) 1.17, 95% confidence interval (CI) 0.92–1.48] was found for enoxaparin and placebo and 65% [RR 1.08, 95% CI 0.83–1.39] for enoxaparin and aspirin when compared to aspirin alone (61%, reference group). In the whole study group the live birth rate was 65% (95% CI 58.66–71.74) for women with three or more miscarriages (n=204). No difference in pregnancy complications, neonatal outcome or adverse effects was observed. No significant difference in live birth rate was found with enoxaparin treatment versus aspirin or a combination of both versus aspirin in women with recurrent miscarriage.

Oral direct factor Xa inhibition with edoxaban for thromboprophylaxis after elective total hip replacement. A randomised double-blind dose-response study.

Abstract: Edoxaban is a new oral direct factor Xa inhibitor. The purpose of this study was to evaluate the efficacy and safety of different doses of edoxaban for the prevention of venous thromboembolism (VTE) in patients undergoing elective total hip replacement. A total of 903 patients were randomised to oral edoxaban 15, 30, 60 or 90 mg once daily or subcutaneous dalteparin once daily (initial dose 2,500 IU, subsequent doses 5,000 IU). Both drugs were begun 6-8 hours postoperatively and continued for 7-10 days, when bilateral venography was performed. The primary efficacy endpoint was the incidence of total VTE, which included proximal and/or distal deep-vein thrombosis (DVT) by venography or symptomatic, objectively confirmed DVT or pulmonary embolism during the treatment period. The primary safety outcome was the incidence of the composite of major and clinically relevant non-major bleeding. All venograms and bleeding events were reviewed by a central independent adjudication committee blinded as to treatment allocation. Of the 903 patients randomised, 776 were evaluable for the primary efficacy analysis. The incidences of VTE were 28.2%, 21.2%, 15.2%, and 10.6% in patients receiving edoxaban 15, 30, 60 and 90 mg, respectively, compared with 43.8% in the dalteparin group (p<0.005 ). There was a statistically significant (p<0.001) dose-response for efficacy across the edoxaban dose groups for total VTE and for major VTE. The incidence of clinically relevant bleeding was low and similar across the groups. Oral edoxaban once daily is effective for preventing VTE after total hip replacement.

The CHADS2 score for stroke risk stratification in atrial fibrillation--friend or foe?

Abstract: The risk of stroke in patients with non-valvular atrial fibrillation (NVAF) varies widely depending on patient age and the presence of other risk factors such as hypertension, diabetes mellitus, congestive heart failure or prior stroke or transient ischaemic attack (TIA) (1, 2). Warfarin reduces the risk of stroke by about twothirds when compared to placebo or no treatment, and by about two-fifths when compared to aspirin, but substantially increases major bleeding (2, 3). The most feared complication of warfarin is intracranial bleeding which occurs at the rate of 2–5 per 1,000 patients per year and often results in disability or death (3). Consequently, the decision to use warfarin must balance the benefits of warfarin for stroke prevention against the risk of major bleeding. The goal of stroke prediction models is to help clinicians and patients select the most appropriate antithrombotic therapy for stroke prevention. Because the absolute benefit of warfarin for stroke prevention increases with increasing baseline stroke risk whereas the absolute risk of major bleeding is more constant (3, 4), the balance between benefits and risks of warfarin in individual patients is determined primarily by their baseline untreated stroke risk. In this paper we critically examine the value of the CHADS2 (acronym for recent Congestive heart failure, history of Hypertension, Age≥75 years, Diabetes mellitus, and past history of Stroke or TIA) risk index to estimate stroke risk in patients with NVAF.

Comparative efficacy and safety of the novel oral anticoagulants dabigatran, rivaroxaban and apixaban in preclinical and clinical development

Abstract: Therapeutic oral anticoagulation is still commonly achieved by administration of warfarin or other vitamin K antagonists that are associated with an untoward pharmacokinetic / pharmacodynamic (PK/PD) profile leading to a high incidence of bleeding complications or therapeutic failure. Hence, there is an unmet medical need of novel easy-to-use oral anticoagulants with improved efficacy and safety. Recent developments include the identification of non-peptidic small-molecules that selectively inhibit certain serine proteases within the coagulation cascade. Of these, the thrombin inhibitor dabigatran and factor Xa inhibitor rivaroxaban have recently been licensed for thromboprophylaxis after orthopaedic surgery mainly in Europe. In addition, the factor Xa inhibitor apixaban is in late-stage clinical development. Each drug is prescribed at fixed doses without the need of anticoagulant monitoring. Phase III trials in orthopaedic patients essentially resulted in non-inferior efficacy of dabigatran and superior efficacy of rivaroxaban over enoxaparin without any marked differences of drug safety, while apixaban data is still controversial. However, alterations of rivaroxaban and apixaban pharmacokinetics upon interactions with inhibitors and inducers of CYP3A4 or P-glycoprotein may complicate the use of these compounds in daily practice, whereas dabigatran elimination largely depends on renal function. Hence, this review reports PK/PD, efficacy and safety data of dabigatran, rivaroxaban and apixaban throughout preclinical and clinical development.

CC and CXC chemokines are pivotal mediators of cerebral injury in ischaemic stroke.

Abstract: The definition of ischaemic stroke has been recently updated as an acute episode of neurological dysfunction caused by focal brain, spinal cord, or retinal ischaemia in the presence of a cerebral infarction. This "tissular" definition has highlighted the importance of pathophysiological processes underlying cerebral damage. In particular, post- ischaemic inflammation in the brain and in the blood stream could influence crucial steps of the tissue injury/repair cascade. CC and CXC chemokines orchestrate the inflammatory response in atherosclerotic plaque vulnerability and cerebral infarction. These molecules exert their activities through the binding to selective transmembrane receptors. CC and CXC chemokines modulate crucial processes (such as inflammatory cell recruitment and activation, neuronal survival, neoangiogenesis). On the other hand, CXC chemokines could also modulate stem cell homing, thus favouring tissue repair. Given this evidence, both CC and CXC chemokines could represent promising therapeutic targets in primary and secondary prevention of ischaemic stroke. Only preliminary studies have been performed investigating treatments with selective chemokine agonists/antagonists. In this review, we will update evidence on the role and the potential therapeutic strategies targeting CC and CXC chemokines in the pathophysiology of ischaemic stroke.

A comparison of platelet function tests and thromboxane metabolites to evaluate aspirin response in healthy individuals and patients with coronary artery disease

Abstract: Individualised antiplatelet therapy and platelet function testing have attracted considerable clinical interest, but several aspects of test performance have not been thoroughly evaluated. We investigated repeatability and concordance of light transmission aggregometry (LTA) induced with arachidonic acid (AA) 1.0 mM, PFA-100 induced with collagen/epinephrine, multiple electrode aggregometry (MEA) induced with AA 0.5 or 0.75 mM and VerifyNow Aspirin. Patients with stable coronary artery disease (n=43) and healthy individuals (n=21) were included. All tests were performed in duplicate at baseline in healthy individuals and in duplicate for four days in all study participants during aspirin treatment. Serum and urinary thromboxane metabolites were measured several times to evaluate cyclooxygenase-1 inhibition by aspirin. MEA was most sensitive for aspirin as treatment induced a 12-fold difference in AA-induced platelet aggregation. Coefficients of variation for duplicate measurements at baseline (0.4-12%), during aspirin treatment (3-46%) and for day-to-day variability (3-37%) differed markedly between tests and were lowest for VerifyNow. The prevalence of aspirin low-responsiveness also differed between tests (0-9%) and the agreement was low: kappa

New-onset atrial fibrillation and warfarin initiation: High risk periods and implications for new antithrombotic drugs

Abstract: Atrial fibrillation is a common condition that increases the risk of stroke in many patients. Although warfarin has been shown to reduce the risk of stroke, many patients who might benefit from anticoagulation do not receive this therapy. Fear of bleeding is the most often cited reason. Several new anticoagulant medications are being studied to determine their efficacy and safety relative to warfarin. Unlike earlier trials that established the superiority of warfarin over placebo, recent trials in atrial fibrillation have enrolled a disproportionate number of patients already taking warfarin. This review suggests that the risk of both haemorrhage and stroke are highest when atrial fibrillation is newly diagnosed and during the initiation of anticoagulant medication. Randomised controlled trials designed to evaluate the safety and efficacy of new anti-thrombotic agents should include substantial numbers of patients without prior exposure to anticoagulation since these individuals are at the highest risk for bleeding and thromboembolism.

Treatments for stroke prevention in atrial fibrillation: a network meta-analysis and indirect comparisons versus dabigatran etexilate.

Abstract: Patients with atrial fibrillation at moderate to high risk of stroke are not always anticoagulated despite a lack of contraindications to vitamin K antagonists (VKAs) like warfarin. These patients are treated with aspirin, aspirin-clopidogrel combination therapy or even receive no thromboprophylaxis. The oral direct thrombin inhibitor, dabigatran etexilate 150 mg BID and 110 mg BID, might represent an alternative for these patients; however, no head-to-head clinical trial data exist versus these alternative treatments. A network meta-analysis (NMA) was performed to indirectly compare dabigatran etexilate with antiplatelets and placebo. Compared with placebo, dabigatran etexilate 150 mg BID was estimated to significantly reduce the risk of any stroke (ischaemic and haemorrhagic) by 75% (relative risk [RR] 0.25; 95% confidence interval [CI] 0.12–0.51), ischaemic stroke by 77% (RR 0.23; 95% CI 0.14–0.38), systemic embolism by 83% (RR 0.17; 95% CI 0.05–0.50) and mortality by 36% (RR 0.64; 95% CI 0.45–0.91). Dabigatran etexilate 150 mg BID was estimated to significantly reduce the risk of any stroke compared with aspirin monotherapy by 63% (RR 0.37; 95% CI 0.20–0.69) and aspirin plus clopidogrel by 61% (RR 0.39; 95% CI 0.21–0.72). Trends toward reduced risk with both dabigatran etexilate regimens were found for most clinical outcomes. Relative risk estimates of dabigatran etexilate versus adjusted-dose VKAs within the NMA were consistent with results from the head-to-head randomised trial of these two strategies. Indirect evidence suggests treatment with dabigatran etexilate offers benefit for the prevention of stroke, systemic embolism and mortality over antiplatelets and placebo. There was no indication of increased intracranial or extracranial haemorrhage with dabigatran etexilate compared to antiplatelet agents.

24-hour time-dependent aspirin efficacy in patients with stable coronary artery disease.

Abstract: Aspirin-induced cyclooxygenase (COX)-1 acetylation is irreversible and it is assumed that the platelet thromboxane-A2 aggregation pathway is inhibited for at least 24 hours (h) after aspirin ingestion. However, time course of biological efficacy of daily low-dose aspirin has rarely been assessed in patients with coronary artery disease (CAD). We aimed to assess the 24-h biological efficacy of daily low-dose aspirin in CAD patients. The peak and trough (2 h –24 h) effect of a chronic treatment with once daily dose aspirin were studied in 150 consecutive stable CAD patients. The main outcome measure waslight transmission aggregometry (LTA) triggered with 0.5 mg/ml arachidonic acid (AA). In the last 47 consecutive patients, additional tests were conducted at 6, 12, 16, 20 h after last aspirin administration. 4.7% of the patients had significant aggregation (>20% maximal intensity LTA-AA) 2 h after aspirin ingestion and 24.7% at 24 h (p 100 mg/day) dose aspirin. Such aspirin «resistance» at 24 h after ingestion was related to biological inflammatory markers, current smoking and diabetes. In conclusion, once daily aspirin does not provide stable 24-h antiplatelet protection in a significant proportion of CAD patients. Any biological assessment of aspirin efficacy should take time since last aspirin intake into consideration.

In vitro factor XIII supplementation increases clot firmness in Rotation Thromboelastometry (ROTEM

Abstract: Factor XIII (F XIII) is an essential parameter for final clot stability. The purpose of this study was to determine the impact of the addition of factor (F)XIII on clot stability as assessed by Rotation Thromboelastometry (ROTEM®). In 90 intensive care patients ROTEM® measurements were performed after in vitro addition of F XIII 0.32 IU, 0.63 IU, 1.25 IU and compared to diluent controls (DC; aqua injectabile) resulting in approximate F XIII concentrations of 150, 300 and 600%. Baseline measurements without any additions were also performed. The following ROTEM® parameters were measured in FIBTEM and EXTEM tests: clotting time (CT), clot formation time (CFT), maximum clot firmness (MCF), maximum lysis (ML), maximum clot elasticity (MCE) and α-angle (αA). Additionally, laboratory values for FXIII, fibrinogen (FBG), platelets and haematocrit were contemporaneously determined. In the perioperative patient population mean FBG concentration was elevated at 5.2 g/l and mean FXIII concentration was low at 62%. The addition of FXIII led to a FBG concentration-dependent increase in MCF both in FIBTEM and EXTEM. Mean increases in MCF (FXIII vs. DC) of approximately 7 mm and 6 mm were observed in FIBTEM and EXTEM, respectively. F XIII addition also led to decreased CFT, increased αA, and reduced ML in FIBTEM and EXTEM. In vitro supplementation of FXIII to supraphysiologic levels increases maximum clot firmness, accelerates clot formation and increases clot stability in EXTEM and FIBTEM as assayed by ROTEM® in perioperative patients with high fibrinogen and low FXIII levels.

An optimised, rapid chromogenic assay, specific for measuring direct factor Xa inhibitors (rivaroxaban) in plasma.

Abstract: An optimised, rapid chromogenic assay, specific for measuring direct factor Xa inhibitors (rivaroxaban) in plasma -

Phosphate and vascular calcification: Emerging role of the sodium-dependent phosphate co-transporter PiT-1.

Abstract: Elevated serum phosphate is a risk factor for vascular calcification and cardiovascular events in kidney disease as well as in the general population. Elevated phosphate levels drive vascular calcification, in part, by regulating vascular smooth muscle cell (VSMC) gene expression, function, and fate. The type III sodium-dependent phosphate co-transporter, PiT-1, is necessary for phosphate-induced VSMC osteochondrogenic phenotype change and calcification, and has recently been shown to have unexpected functions in cell proliferation and embryonic development.

Microparticle-associated tissue factor activity and venous thrombosis in multiple myeloma.

Abstract: Multiple myeloma (MM) is associated with an increased risk of venous thromboembolic (VTE) complications. Aim of this study was to measure microparticle-associated tissue factor (MP-TF) activity in patients with newly diagnosed MM before and after chemotherapy and to investigate whether MP-TF activity is associated with VTE. MP-TF activity was assessed in 122 newly diagnosed MM patients who were eligible for combination chemotherapy. MP-TF activity levels (17.6 fM Xa/min [8.6-33.2] (median [IQR]) were higher in untreated MM patients compared to normal healthy volunteers (4.1 fM Xa/min [2.3-6.6], p <0.001). MP-TF activity prior to the start of treatment was not different between patients who developed a VTE during follow-up (n=15) and those who did not (n=107). In 75 patients in whom plasma was obtained before and after chemotherapy, MP-TF activity decreased significantly (from 17.4 [10.2-32.8] to 12.0 [7.0-18.5] fM Xa/min, P=0.006). MP-TF activity remained, however, elevated in patients who developed VTE (15.1 [10.3-25.2]), in contrast to patients not developing VTE (11.4 [7.0-25.2], P<0.001). In conclusion, MP-TF activity is increased in patients with MM. Whether MP-TF activity has a pathogenetic role in VTE in MM patients remains to be established in future studies.