Real-Life Peak and Trough Dabigatran Plasma Measurements over Time in Hospitalized Geriatric Patients with Atrial Fibrillation.

BACKGROUND: Few geriatric patients were included in studies on direct oral anticoagulants and data on dabigatran concentration and safety are needed in this population. Our objectives were to evaluate peak and trough dabigatran plasma concentrations over time in a geriatric population and to identify factors associated with dabigatran plasma concentrations and to assess the relationship with bleeding events. METHODS: Peak and trough dabigatran plasma concentration were performed 4,8,15,30,45 days after inception of dabigatran treatment in 68 consecutive patients ≥75 years old hospitalized in a geriatric hospital with atrial fibrillation. Bleeding events were monitored for 1 year. RESULTS: Mean age was 85.8(5.1) years old and 76.5% were women. Overall, 541 dabigatran plasma measurements (270 peak, 271 trough) were performed. Mean dabigatran concentrations of the 5 sequential measurements ranged 106-146ng/mL for peak and 66-84ng/mL for trough. Renal failure was associated with high peak and trough dabigatran concentration. Inter- and intra-individual coefficients of variation were 59.5% and 44.7% for peak and 74.5% and 44.6% for trough. Participants in the lower two tertiles of dabigatran concentration at day 8 (D8) remained below the 90th percentile (243.9ng/ml) on the next measurements. Bleeding events were associated with high trough dabigatran concentrations. Trough dabigatran concentration at D8>243.9ng/mL significantly predicted bleeding. CONCLUSION: In this geriatric population, renal function and low albumin were associated with dabigatran concentrations. Despite large variability, participants in the lower two tertiles of dabigatran concentration at D8 remained below the 90th percentile on the following measurements. D8 dabigatran trough concentration≥243.9ng/mL identified patients at risk of bleeding.

OC-03 - Modelisation of the procoagulant properties of cancer cells and their capacity to alter the antithrombotic efficiency of LMWHs and specific inhibitors of factor Xa.

INTRODUCTION: The risk of venous thromboembolism varies according to the histological type of cancer. The failure of antithrombotic treatment is more frequent in cancer patients as compared to non-cancer ones. AIM: We aimed to elucidate the mechanism of activation of blood coagulation induced by cancer, the impact of chemo-resistance phenotype on the capacity of cancer cells to trigger thrombin generation and the alterations of the efficiency of LMWHs and the specific inhibitors of factor Xa (fondaparinux and apixaban) in the presence of cancer cells. MATERIALS AND METHODS: Thrombin generation of human plasma was assessed in the presence of various cancer cell lines. The model of cancer-induced hypercoagulability was coupled to the research for the expression of procoagulant molecules by cancer cells. RESULTS: The pancreatic adenocarcinoma cells BXPC3 and the breast adenocarcinoma cells MCF7 were initially tested. The BXPC3 cells induce significantly higher thrombin generation as compared to the MCF7 cells. In the same line Marchetti et al. showed that malignant hematologic cells (NB4, HEL, and K562) and H69 small cell lung cells express different procoagulant potential on triggering thrombin generation of human plasma. The comparison of the procoagulant activity has been extended to cancer cell lines from various cancers (i.e. colon, ovarian and prostatic cancer) as well as to different cell lines of the same type of cancer. The differences of the cancer cell lines to trigger thrombin generation are mainly due to the expression of TF. The acquisition of chemoresistant phenotype by cancer cells is correlated with increased TF expression and enhancement of theit procoagulant activity. The ability of cancer cells to activate FXII is an alternative pathway of significant importance for some cancer cell lines (i.e. MCF7). Clinically relevant concentrations of LMWH and specific direct and indirect inhibitors of FXa (apixaban and fondaparinux) inhibit thrombin generation induced by cancer cells. The synergy between the anti-Xa and anti-IIa activities of LMWHs rather than the AT-dependent selective inhibition of FXa results in profound inhibition of thrombin generation induced by BXPC3 cells. This experimental model allowed the functional distinction between the two specific FXa inhibitors (apixaban and fondaparinux). CONCLUSIONS: The cancer cell-based model of hypercoagulability is suitable for the identification of the prothrombotic fingerprint of various cancer types. This experimental model allows to perform pharmacological studies for the evaluation of the efficiency of the antithrombotic drugs in cancer-induced hypercoagulability. It is suitable for the study of the impact of anticancer drugs on the procoagulant properties of the cancer cells.

PO-53 - Prospective evaluation of risk assessment models and biological markers of hypercoagulability for the identification of high VTE risk patients with lung adenocarcinoma. The ROADMAP study.

INTRODUCTION: In patients with lung adenocarcinoma (LA), metastasis (MTS), advanced stage and chemotherapy (CTx) are risk factors for thromboembolism (VTE). Routine thromboprophylaxis is not recommended but individualized risk assessment is encouraged. AIM: The selection of the most relevant hypercoagulability biomarkers (HB) for incorporation into the risk assessment models (RAM) for VTE. MATERIALS AND METHODS: Patients with documented LA eligible for CTx at distance of at least 3months from surgery or hospitalization were included. They were either CTx naive (NG) or had received CTx (OTG). Control group (CG) consisted of 30 healthy age & sex-matched individuals. We assessed them for thrombin generation (TG), P-Selectin, heparanase (HPA), procoagulant phospholipids (PPL), factor VIIa, D-Dimers (DDi) and Tissue Factor activity (TFa). RESULTS: Patients showed significantly shortened PPL and higher levels of TFa, DDi and HPA as compared to the CG. FVIIa levels were lower in patients compared to CG. The NG showed significantly shorter lag-time and lower ETP as compared to the OTG. It also showed significantly higher levels of HPA as compared to the OTG.The increase of TG and of HPA, P-Selectin, FVIIa was associated with the stage. Patients with MTS had higher levels of P-Selectin, TFa, DDi, FVIIa, TGT and HPA than those with localized or advanced disease.Patients with VTE had higher baseline levels of DDi, TGT, shorter PPL and lower levels of HPA as compared to those without. Patients who died within 3-months had higher baseline levels of DDi and lower HPA levels as compared to those who were alive. CONCLUSIONS: Increased PPL, TF pathway up regulation, DDi and HPA increase is a universal phenomenon in LA. CTx has an impact on TGT and HPA levels. Baseline values of TGT, PPL, HPA, DDi were related with mortality and thrombosis. The incorporation of HB in VTE-RAMs might improve their predictive value. This concept is being studied on an ongoing trial.

Prevention and treatment of venous thromboembolism--International Consensus Statement.

The aim of this document is to provide a clear and concise account of the evidence regarding efficacy or harm for various methods available to prevent and manage venous thromboembolism (VTE).

[Acquired hemophilia A in prepartum: case report and literature review]. / Hémophilie A acquise découverte au cours de la grossesse : à propos d'un cas et revue de la littérature.

INTRODUCTION: Acquired hemophilia A (AH) is a rare hemorrhagic disorder, secondary to the occurrence of factor VIII inhibitor. In young patients, this disorder is commonly observed during the post-partum period, and has been rarely documented in the prepartum. We report a new case of a prepartum AH and review literature data. CASE REPORT: An isolated prolongation of the activated partial thromboplastin time (APTT) was fortuitously discovered in a 31-year-old pregnant women, with spontaneous ecchymosis of her lower limbs few days prior to delivery. Coagulation tests revealed decreased factor VIII activity (18%) and the presence of factor VIII inhibitor (1,4 Bethesda unit). In order to eradicate the autoantibody, the patient was first treated with prednisone and then with rituximab. CONCLUSION: Prepartum factor VIII inhibitors need to be precociously recognized to allow prophylactic management of the delivery bleeding.

[Pathogenesis of venous thromboembolic disease in cancer]. / Physiopathogénie de la maladie thromboembolique veineuse au cours du cancer.

Cancer is a real model of acquired hypercoagulable state. A close interaction exists between venous thromboembolic disease and cancer. Tumor progression is associated with an activation of coagulation and fibrinoformation which are both implicated in cancer proliferation and metastasis dissemination. The pathogenesis of haemostatic troubles described in cancer patients is particularly complex and it reflects the multiple connexions with inflammation and hemostasis systems. In this review, we will identify the numerous factors inducing such a prothrombotic state and the reason why their combined action contributes to cancer development. The relation between cancer and thrombosis seems reciprocal: cancer predisposes to thrombosis and tumor progression is deeply linked to this hypercoagulable state.

Circulating platelet-leukocyte aggregates: a marker of microvascular injury in diabetic patients.

Diabetes is associated with multiple disorders including metabolic, cellular and blood disturbances leading to vascular complications. Increased circulating levels of platelet-leukocyte aggregates (PLA) have been described in several thrombotic diseases. In this study, we have evaluated circulating PLA in diabetic patients and we have investigated whether they may be a marker of vascular complications. Using flow cytometry assay, we have quantified PLA percentages in 65 diabetics including 20 patients with type I and 45 with type II diabetes, and 25 healthy subjects. Specific labelling identified platelet-polymorphonuclear aggregates (PPA) and platelet-monocyte aggregates (PMA). We have observed a significant increase of PPA and PMA levels in diabetics (22+/-12% and 45+/-18%, respectively) compared to controls (7+/-4% and 19+/-10%, respectively) (p<0.01). However, both PPA and PMA values were similar in the two diabetes types. Circulating PPA and PMA were significantly enhanced in diabetics with vascular lesions (PPA: 24+/-13%; PMA: 50+/-18%) than in diabetics without vascular lesions (PPA: 18+/-8%; PMA: 38+/-15%) (p<0.05 and p<0.01). Patients with PPA>18% and/or PMA>38% showed a more important vascular injury (OR: 6; 95% CI: 1.6-23). Increased PMA circulating rate is particularly correlated to retinopathic injury (OR: 19; 95% CI: 2.3-154). Our findings established a relationship between increased circulating PLA levels, particularly PMA, and the incidence of microvascular complications in diabetes. They reinforce the concept of pro-inflammatory cells involvement in diabetic retinopathy pathogenesis and their link with thrombotic process.

[New antitoagulants]. / Les nouveaux anticoagulants.

In contrast to older anticoagulant agents vitamin K antagonists and heparins, the new ones are directed towards a single target in general. The main characteristics of the new agents are: their site of action in the coagulation cascade and their mechanism of action which is indirect, antithrombin dependent, most often such as Fondaparinux and Idraparinux or direct such as Dabigatran, Rivaroxaban; the specificity of the new molecules, since they must not interact with other enzymes: trypsin, kallikrein, t-PA, etc...; their mode of administration parenteral and/or oral; their pharmacokinetics and their clearance frequently by the kidney (Hirudin, fondaparinux) or through hepatic metabolism (argatroban); tolerance including for all compounds the bleeding risk or an unexpected hepatic intolerance for Ximelagatran; the availability of a specific antidote and the cost of the drug; one compound is registered in France Arixtra Fondaparinux in major orthopedic surgery and in the treatment of venous thromboembolism and in prophylactic treatment in medical patients. However, the main indications of interest for these new drugs is atrial fibrillation. There is a real need in this indication and the number of patients to treat is growing with the longer life expectancy.

Effect of the anti-factor Xa and anti-factor IIa activities of low-molecular-weight heparins upon the phases of thrombin generation.

BACKGROUND: Low-molecular-weight heparins (LMWHs), derived from unfractionated heparin (UFH) by different depolymerization procedures, vary in both their relative abilities to enhance the inhibition of FXa (anti-FXa) and thrombin (anti-FIIa), and in their physicochemical properties. OBJECTIVE: We aimed to profile the inhibition of thrombin generation induced by bemiparin, enoxaparin, nadroparin, dalteparin and tinzaparin in platelet-rich plasma (PRP), and to compare them with UFH and fondaparinux (a synthetic pentasaccharide that specifically enhances FXa inhibition). METHODS: Different LMWHs, UFH or fondaparinux were added to normal PRP. Thereafter, tissue factor-triggered thrombin generation was assessed using the Thrombogram-Thrombinoscope assay. RESULTS: At equivalent anti-FIIa activity concentrations, LMWHs and UFH exhibited similar inhibitory effects upon thrombin generation. However, when used at equivalent anti-FXa activity concentrations, tinzaparin was significantly more active than the other LMWHs at inhibiting thrombin generation, and had similar activity to that of UFH. Enoxaparin, nadroparin and dalteparin all showed similar inhibitory activities. In these experiments, bemiparin exhibited the lowest inhibitory effect on thrombin generation of all the LMWHs. At 0.1 microg mL(-1) (0.093 anti-FXa IU mL(-1)), fondaparinux inhibited the rate of thrombin generation by 50%. A 7-fold higher concentration of fondaparinux was required to inhibit the endogenous thrombin potential by 50%. CONCLUSIONS: LMWHs have a variable inhibitory effect on thrombin generation in vitro when compared by anti-FXa activity, but are similar when compared by their anti-FIIa activities. The rate of thrombin generation during the propagation phase, rather than the endogenous thrombin potential, is more sensitive to the anticoagulant activity of fondaparinux and the polysaccharide chains of LMWHs possessing only anti-FXa activity.

Thrombophilia and venous thromboembolism. International consensus statement. Guidelines according to scientific evidence.

Thrombophilia is the term now used to describe predisposition to increased risk of venous and occasionally arterial thromboembolism due to hematological abnormalities. It can be a multifactorial disorder where congenital defects of anticoagulant or procoagulant factors may be combined with acquired hematological abnormalities. It should be considered in patients with a documented unexplained thrombotic episode or a positive family history. The aim of this document is to provide guidelines for investigation and management of patients with thrombophilia in the presence or absence of venous thromboembolism (VTE).

Risk factors for venous thromboembolism in children.

The incidence of venous thromboembolism (VTE) is increasing in children as a result of therapeutic advances and improved clinical outcome in primary illnesses that previously caused mortality. VTE is mostly diagnosed in hospitalized children, especially sick newborns with central venous catheters and older children with a combination of risk factors. Infants older than 3 months and teenagers are the largest groups developing VTE. The most important triggering risk factors are the presence of central venous lines, cancer and chemotherapy. Pathological conditions such as severe infection, sickle cell disease, trauma and antiphospholipid syndrome are associated with the presence of a hypercoagulable state in children. The thrombotic risk in otherwise healthy children with a single identified thrombophilic defect appears to be extremely low. Venous thromboembolism in pediatric patients is mainly caused by combinations of at least 2 prothrombotic risk factors for venous thromboembolic events in children are usually associated with underlying clinical conditions and a triggering risk factor. In addition, recurrence of VTE after withdrawal of anticoagulant treatment occurs in about 20% of patients after re-exposure to a triggering risk factor. A non negligible mortality and morbidity is related to VTE in childhood. This supports the need for international multicenter randomized clinical trials to determine optimal prophylactic and therapeutic treatment for children with VTE. Risk factor assessment for VTE in children has to be improved in order to optimize the prophylactic and therapeutic strategies. The specific evolutionary characteristics of the hemostasis in children has to be taken into consideration when a prophylactic or therapeutic strategy is applied.The incidence of venous thromboembolism (VTE) is increasing in children as a result of therapeutic advances and improved clinical outcome in primary illnesses that previously caused mortality. VTE is mostly diagnosed in hospitalized children, especially sick newborns with central venous catheters and older children with a combination of risk factors. Infants older than 3 months and teenagers are the largest groups developing VTE. The most important triggering risk factors are the presence of central venous lines, cancer and chemotherapy. Pathological conditions such as severe infection, sickle cell disease, trauma and antiphospholipid syndrome are associated with the presence of a hypercoagulable state in children. The thrombotic risk in otherwise healthy children with a single identified thrombophilic defect appears to be extremely low. Venous thromboembolism in pediatric patients is mainly caused by combinations of at least 2 prothrombotic risk factors for venous thromboembolic events in children are usually associated with underlying clinical conditions and a triggering risk factor. In addition, recurrence of VTE after withdrawal of anticoagulant treatment occurs in about 20% of patients after re-exposure to a triggering risk factor. A non negligible mortality and morbidity is related to VTE in childhood. This supports the need for international multicenter randomized clinical trials to determine optimal prophylactic and therapeutic treatment for children with VTE. Risk factor assessment for VTE in children has to be improved in order to optimize the prophylactic and therapeutic strategies. The specific evolutionary characteristics of the hemostasis in children has to be taken into consideration when a prophylactic or therapeutic strategy is applied.

The combination of intermediate doses of thalidomide and dexamethasone reduces bone marrow micro-vessel density but not serum levels of angiogenic cytokines in patients with refractory/relapsed multiple myeloma.

The aim of the study was the evaluation of anti-angiogenic activity of the combination of intermediate doses of thalidomide and dexamethasone in patients with refractory/relapsed myeloma. Twenty-five patients were included in the study. Microvessel density (MVD) was evaluated in marrow biopsies before and after treatment. Serum levels of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (b-FGF), tumor necrosis factor-alpha (TNF-alpha), which have angiogenic potential and interleukin-6 (IL-6), IL-1beta, soluble IL-6 receptor (sIL-6R), and transforming growth factor-beta (TGF-beta) which are involved in the disease biology, were measured before treatment and then every 2 weeks for 8 weeks. Pretreatment levels of MVD, VEGF, b-FGF, IL-6, sIL-6R were increased in the patients compared to controls. The overall response rate to therapy was 72%. The administration of the combined regimen produced a significant reduction in MVD in responders. However, an increase in serum levels of VEGF, b-FGF, IL-6, sIL-6R was observed post-treatment in responders. In contrast, serum levels of TNF-alpha, TGF-beta, IL-1beta did not differ between patients and controls and remained unchanged during the study. These results suggest that the combination of thalidomide plus dexamethasone is an effective treatment for myeloma reducing MVD marrow levels but not serum levels of angiogenic cytokines or cytokines implicated in myeloma biology.

[Biological markers for acute phase hemostasis in coronary thrombosis]. / Les marqueurs biologiques de l'hémostase à la phase aiguë de la thrombose coronaire.

Associated with rheological conditions, multiple factors regarding haemostasis and fibrinolysis contribute to the instability and rupture of atherosclerotic plaque. Various biological parameters are modified during the occurrence of a coronary thrombotic episode, but do these increasingly identified alterations constitute a cause or a direct consequence of this accident? With the increasing identification of markers more and more sensitive but of limited specificity, the relative abundance of studies in the literature contrasts with the paucity of effective assets for everyday clinical practice. In fact, the potential use of these indicators in the evaluation of the pathogenesis of vascular accident, their eventual prognostic value, their predictive nature in therapeutic strategy, and their relevance for patient classification and follow up remain to be established on a wider scale. There is growing interest in the detection of evidence of cellular cooperation or a vascular compartment lesion thanks to the development of new diagnostic tools such as flux cytometry or immunoenzymology. While advances in biology have allowed undeniable clarifications of the physiopathology of coronary accidents and in the management of thrombotic pathology, it must nevertheless be endeavoured to give a practical response to the numerous questions where doubt remains, and to pursue the search for markers or tests clinically relevant.

The role of platelet factor 4 in platelet aggregation induced by the antibodies implicated in heparin-induced thrombocytopenia.

Heparin-induced thrombocytopenia (HIT) is a severe side effect of heparin treatment. Recent studies using immunological methods demonstrated that antibodies contained in plasma, or in purified total immunoglobulin (Ig)G from patients suffering HIT, recognize as target antigen the complex heparin/platelet factor (PF4). In the present study, the role of PF4 in in-vitro platelet aggregation induced by purified total IgG or platelet-poor plasma from patients suffering HIT was investigated. In order to demonstrate the functional role of PF4, an anti-PF4 antibody that specifically blocked PF4 was used. In an experimental system composed of washed platelet suspension, incubation of F(ab')2 fragments (0.125 microg/ml) of the polyclonal anti-PF4 antibody resulted in complete inhibition of platelet aggregation triggered by purified total IgG from patients suffering HIT and heparin. In platelet-rich plasma, a significantly higher concentration (4.25 microg/ml) of the anti-PF4 F(ab')2 was required to inhibit platelet aggregation induced by HIT-PPP and heparin. Intermediate concentrations of the anti-PF4 antibody partially inhibited platelet aggregation. In plasma milieu, the concentration of PF4 was about five-fold higher in comparison with that measured in the purified system. The intensity of platelet aggregation depended on the concentration of HIT-IgG. Platelet aggregation was abolished in the presence of high concentrations of heparin (superior or equal to 10 IU/ml). The present study shows that PF4 is essential for platelet aggregation triggered by the antibodies related to HIT in the presence of heparin. The concentration of PF4 that is available to bind with heparin or with the HIT-related antibodies is critical for platelet aggregation induced by HIT antibodies.