Effects of HeartWare ventricular assist device on the von Willebrand factor: results of an academic Belgian center.

BACKGROUND: Left Ventricular Assist Device (LVAD) is a promising therapy for patients with advanced heart failure (HF), but bleeding complications remain an important issue. Previous series show that acquired von Willebrand syndrome was present in up to 100 % of first generation LVAD recipients. We report the effects of new generation LVADs on vW factor (vWF) metabolism and activity in our center. METHODS: Fifteen LVAD recipients (HeartWare®, Framingham, MA, USA) were compared to 12 HF patients, matched for age and body mass index. vWF antigen and activity, as well as D-dimers, were measured on hemostasis analyzers. A vWF LVAD-induced alteration was evocated when the [vWF activity]/[vWF antigen] ratio was <0.6. ADAMTS13 and high molecular weight multimers of vWF were also assessed. RESULTS: LVAD recipients had similar levels of endothelial vWF production than the HF subjects (137 ± 14.5 vs. 147 ± 11.7 %; respectively, p = 0.611) but a decreased vWF activity (90 ± 11 vs. 132.6 ± 13 %; respectively, p = 0.017). [vWF activity]/[vWF antigen] ratio was 0.65 ± 0.02 in the LVAD recipients and 0.92 ± 0.06 in the subjects with HF (p = 0.001). ADAMTS13 activity was 80.3 ± 4.7 % in LVAD recipients and 96.2 ± 3.5 % in the HF patients (p = 0.016). LVAD patients disclosed markedly elevated D-dimers (3217.7 ± 735 vs. 680.6 ± 223.2 ng/mL FEU in the HF patients, p = 0.006). The LVAD patients experienced one major hemorrhagic event and one systemic thrombotic event during the median follow-up of 345 days. CONCLUSIONS: LVAD recipients achieved a new hemostatic equilibrium characterized by infrequent major hemorrhagic and thrombotic events, despite a mildly impaired vWF function and a markedly enhanced thrombin formation. TRIAL REGISTRATION: ISRCTN39517567.

Thrombophilic factors in Stage V chronic kidney disease patients are largely corrected by renal transplantation.

BACKGROUND: The aim of our study was to evaluate the prevalence of acquired thrombophilic factors in Stage V chronic kidney disease (CKD) patients according to dialysis modality, the rate of correction of these factors 1 month after renal transplantation and their impact on cardiovascular or thromboembolic events at 1 year. METHODS: Three hundred and ten patients were prospectively screened for seven thrombophilic factors at transplantation; 215 of them were also assayed 1 month after. All the patients received prophylactic acetylsalicylic acid, started before transplantation. RESULTS: The prevalence of thrombophilic factors was significantly higher in patients under dialysis (n = 289) than in patients not yet on dialysis (n = 21) (74 versus 52.4%; P = 0.03) but was similar in haemodialysis and peritoneal dialysis patients (74.2 versus 73.2%). One month after transplantation, the global prevalence of thrombophilic factors had dropped from 74.4 to 44.7% (P < 0.001). Most thrombophilic factors had disappeared after transplantation: antithrombin deficiency: 13.5 versus 0.9%; P < 0.001, protein C deficiency: 12.1 versus 1.9%; P < 0.001, protein S deficiency: 3.7 versus 1.4%; P = 0.1, lupus anticoagulant: 37.7 versus 8.4%; P < 0.001 and antiphospholipid antibodies: 29.3 versus 12.6%; P < 0.001. The prevalence of activated protein C resistance, which reflects inherited factor V (FV) Leiden, was unchanged (1.9%), while the prevalence of elevated factor VIIIc increased from 20.9 to 30.7%, P < 0.001. The incidence of cardiovascular or thromboembolic events 1 year after transplantation was similar in patients with more than or equal to one thrombophilic factor at 1 month (5.2%) versus thrombophilic-free patients (6.7%). CONCLUSION: Acquired thrombophilic factors are highly prevalent among Stage V CKD patients. Most thrombophilic factors are corrected 1 month after transplantation.

Thrombin generation in plasma of healthy adults and children: chromogenic versus fluorogenic thrombogram analysis.

Coagulation tests and coagulation factor assays have been complemented recently with experimental tests to measure the total amount of thrombin formed. We have presently analyzed thrombin generation of healthy adult and paediatric plasma samples via a fluorogenic and a chromogenic method. The chromogenic method was performed on the fully automated Behring Coagulation System (BCS) and fluorogenic assays via Calibrated Automated Thrombography (CAT), after coagulation induction by various tissue factor (TF) concentrations. Sample distribution and variability were analyzed for the four main coagulation parameters, derived via computerized curve analysis in each method. Results for both methods were correlated. At the recommended TF concentration (300 pM), thrombin generation via BCS was less variable than via CAT (1-6 pM), but at comparable TF concentrations (1-6 pM), the CAT sensitivity was higher than that of BCS. Inhibition of intrinsic coagulation with the anti-factor VIII antibody BO2C11 revealed that the BCS detected extrinsic coagulation exclusively, at all TF concentrations tested. In contrast, at low TF concentrations (1 and 2.5 pM), via CAT, intrinsic coagulation pathway amplification was measured. At standardized TF concentrations (300 pM in BCS vs. 2.5 pM in CAT), different reference values between adults and children were found, for all parameters, except Tmax. In adult samples, the best correlation between both methods was observed for ETP(CAT) versus ETP(BCS) and for Peak height(CAT) versus Cmax(BCS), when thrombin generation was exclusively extrinsic (300 pM in BCS vs. 6 pM in CAT). In conclusion, differential thrombin generation characteristics in BCS and CAT are relevant for their clinical applicability.

Pro-thrombotic effect of exercise in a polluted environment: a P-selectin- and CD63-related platelet activation effect.

Exposure to diesel exhaust is an important cardiovascular risk factor and may promote atherothrombotic events. Some data suggest that polluted air exposure could affect haemostasis through platelet activation. The aim of the study was to investigate the effects of acute exposure to diesel exhaust on platelet activation and platelet function. We tested the hypothesis in a randomised, crossover study in 25 healthy men exposed to ambient and polluted air; 11 of the subjects also performed exercise during exposure sessions. Platelet activation was evaluated by surface expression of CD62P (P-selectin) and CD63 (dense granule glycoprotein) using flow cytometry of labelled platelets. Platelet function was measured using the PFA-100 platelet function analyser and by Multiplate whole blood impedance platelet aggregometry. Acute diesel exhaust exposure had no effect on platelet activation at rest, but exercise in polluted air increased the collagen-induced expression of CD62P and CD63 (both p< 0.05). The increase in the expression of CD62P and CD63 was related to the total amount of PM2.5 inhaled during the exercise sessions (r=+0.58 and +0.60, respectively, both p< 0.05). Platelet aggregation was not impaired after polluted air exposure at rest or during exercise. In conclusion, in healthy subjects, diesel exhaust exposure induces platelet activation as illustrated by a dose-response increase in the release of CD62P and CD63. This platelet priming effect could be a contributor to the triggering of atherothrombotic events related to air pollution exposure.

Influence of dabigatran and rivaroxaban on routine coagulation assays. A nationwide Belgian survey.

The Belgian national External Quality Assessment Scheme performed a nationwide survey using lyophilised plasma samples spiked with dabigatran or rivaroxaban to demonstrate to the Belgian clinical laboratories how these drugs affect their routine coagulation assays prothrombin time (PT), activated partial thromboplastin time (aPTT), fibrinogen and antithrombin. Virtually all Belgian laboratories performing routine coagulation testing (189/192) participated in the survey. Both, dabigatran and rivaroxaban significantly prolonged the PT and aPTT in a concentration- and reagent-dependent manner. PT reagents were more influenced by rivaroxaban than by dabigatran and aPTT reagents more influenced by dabigatran than by rivaroxaban. Among PT reagents, Neoplastin R® was the most sensitive to rivaroxaban and Innovin® and Thromborel S® the least sensitive. Converting PT results to INR only increased the variability between reagents. Among aPTT reagents, Actin FSL® was the least sensitive to dabigatran while the other aPTT reagents showed slightly higher sensitivities. The presence of dabigatran led to falsely reduced fibrinogen concentrations when measured with a low thrombin concentration reagent. The presence of dabigatran caused an overestimation of the antithrombin level when measured with a thrombin-based activity assay and the presence of rivaroxaban an overestimation of the antithrombin level when measured with a FXa-based assay. Instrument-related differences were found for all tested parameters. In conclusion, this paper provides detailed information on the effect of dabigatran and rivaroxaban on routine coagulation assays as performed with a large number of reagent/instrument combinations.

Tissue factor-dependent procoagulant activity of isolated human hepatocytes: relevance to liver cell transplantation.

Liver cell transplantation (LCT) aims to correct inborn liver function defects by infusing metabolically active cells into the diseased liver. Further improvement in LCT might depend on the prevention of early loss of transplanted cells. As tissue factor (TF)-dependent activation of coagulation was found to contribute to a low rate of beta cell engraftment in islet transplantation, we investigated the potential procoagulant activity (PCA) of hepatocyte preparations. TF expression on hepatocyte preparations was assessed by flow cytometry, reverse-transcription polymerase chain reaction and immunofluorescence. PCA depending on TF was evaluated in human plasma and in whole blood systems. Coagulation parameters were followed by routine techniques in a LCT recipient Crigler-Najjar patient. We determined that hepatocytes express soluble and membrane-bound forms of TF. We showed that hepatocytes exert a TF-dependent PCA. In parallel, delayed increase in D-dimer levels was observed following the hepatocyte infusions in the Crigler-Najjar patient. Furthermore, in vitro experiments demonstrated that TF-dependent PCA of hepatocytes is inhibited by N-acetyl-L-cysteine. In conclusion, hepatocytes exert TF-dependent PCA, which may contribute to early loss of infused cells. Addition of N-acetyl-L-cysteine to the suspensions of hepatocytes might be beneficial in LCT by inhibiting activation of coagulation.

Comparison of the effects of aprotinin and tranexamic acid on blood loss and red blood cell transfusion requirements during the late stages of liver transplantation.

BACKGROUND: During liver transplantation (LT), profound activation of the fibrinolytic system can contribute significantly to perioperative bleeding. Prophylactic administration of antifibrinolytic agents has been shown to reduce blood loss and the need for allogeneic transfusion in these conditions. STUDY DESIGN AND METHODS: This prospective randomized trial included 51 cirrhotic patients undergoing LT. Patients were randomly assigned to receive either 280 mg of aprotinin (AP) followed by 70 mg per hour or 40 mg per kg tranexamic acid (TA) followed by 40 mg per kg per hour, administered from the end of the anhepatic phase until 2 hours after reperfusion of the graft, and the effects on blood loss and red blood cell (RBC) transfusion requirements were compared. Transfusion policy was standardized in all patients. In addition, the biological effects of the two drugs, as assessed by coagulation and fibrinolytic markers obtained during surgery, were evaluated in a subgroup of patients from each treatment group and compared with an historical control group that did not receive antifibrinolytic drugs. RESULTS: There was no significant difference between the two groups in perioperative blood losses (AP, 6200 [4620-8735] mL; TA, 5945 [4495-8527] mL; median [range]) or in RBC transfusions requirements (AP, 9 [6.75-15.25] units; TA, 10 [6.5-13.5] units). Inhibition of fibrinolysis was observed with both drugs compared with the control group. Coagulation appeared to be activated more with AP, however, whereas fibrinolysis was inhibited more by TA. CONCLUSION: Blood losses and RBC transfusion requirements were comparable regardless of the drug administered. TA may be as valuable as AP for controlling fibrinolysis in LT.