bluuebunny/crossref_metadata_2025 huggingface dataset:
Dosing in Heavy-weight/Obese Patients with the LMWH, Tinzaparin: A Pharmacodynamic Study
Authors: Barrett Jeffrey , Assaid Christopher , Fossler Michael , Cox Donna , Leathers Todd , Leese Philip , Hainer James
Published: March 2018

This pharmacodynamic study examined weight-based dosing of the low molecular weight heparin (LMWH), tinzaparin, in heavyweight/obese subjects. Single doses (175 and 75 IU/kg) were administered subcutaneously (SC) to 37 healthy heavy-weight subjects (101-165 kg; 26-61 kg/m2). AUA and Amax values of anti-Xa and anti-IIa activities were consistent over these body weight and body mass index (BMI) ranges, indicating that tinzaparin pharmacodynamics are not influenced by body weight or BMI. The range of AUA and Amax values in the study population overlapped that of historical control normal-weight subjects (<100 kg), indicating that weightadjusted tinzaparin dosing yields a predictable response regardless of body weight or BMI. Tinzaparin was well tolerated, although injection site bruising was commonly reported. SC tinzaparin dosing in heavy or obese patients is appropriate based on body weight alone; the dose need not be capped at a maximal absolute dose.
Pharmacokinetics of Recombinant Factor IX after Intravenous and Subcutaneous Administration in Dogs and Cynomolgus Monkeys
Authors: McCarthy K. , Stewart P. , Sigman J. , Read M. , Keith J. C. , Brinkhous K. M. , Nichols T. C. , Schaub R. G.
Published: March 2018

Hemophilia B therapy requires intravenous (IV) infusions of large volumes of factor IX due to the low concentration of factor IX in concentrates (∼100 IU/mL). High concentration recombinant factor IX (rFIX) could be a significant advance since it would reduce the large volumes necessary for IV dosing and allow for low-volume subcutaneous (SC) administration. To evaluate high concentration factor IX, we produced formulations with either 2,000 or 4,000 IU/mL and studied the SC bioavailability in beagle dogs, cynomolgus monkeys and hemophilia B dogs along with efficacy in hemophilia B dogs. Beagle dog SC bioavailability was 86.4% using a 2000 IU/mL formulation and 77.0% using a 4000 IU/mL formulation. Monkey bioavailability of a 4000 IU/mL formulation of rFIX was 34.8%. A single SC administration of 200 IU/kg (4000 IU/mL) of rFIX to hemophilia B dogs, produced factor IX clotting activity above 5% for 5 days with a bioavailability of 48.6%. High concentration SC rFIX has an acceptable pharmacokinetic profile in monkeys and dogs, and produces a sustained FIX activity in hemophilic dogs.
Tirofiban Blocks Platelet Adhesion to Fibrin with Minimal Perturbation of GpIIb/IIIa Structure
Authors: Stahle Mary , Jerome Gray , Nagaswami Chandrasekaran , Weisel John , Hantgan Roy
Published: March 2018

A biophysical approach tested the hypothesis that tirofiban, like eptifibatide, perturbs GpIIb/IIIa structure. Tirofiban bound tightly to platelet GpIIb/IIIa (EC50 ∼ 24 nmol/L) and effectively inhibited platelet aggregation (IC50 ∼ 37 nmol/L) but blocked platelet adhesion to clotted fibrin only at much higher doses (IC50 ∼ 580 nmol/L). Electrophoretic analyses demonstrated that tirofiban protected GpIIb/IIIa from SDSinduced subunit dissociation. However, saturating tirofiban concentrations had little or no effect on GpIIb/IIIa secondary or tertiary structure, as determined by circular dichroic spectroscopy, dynamic light scattering, and sedimentation velocity measurements performed with purified receptors in octyl glucoside. Moderate dose-dependent effects on GpIIb/IIIa quaternary structure were detected by sedimentation equilibrium. Transmission electron microscopy showed minimal tirofiban-induced receptor activation or oligomerization. Thus, even at the increased concentrations needed to block platelet:fibrin adhesive interactions, tirofiban exhibited only limited effects on GpIIb/IIIa conformation and clustering. Our results provide new insights into the mechanisms and potential prothrombotic complications of integrin antagonists.
Genome-wide linkage analysis of von Willebrand factor plasma levels: results from the GAIT project
Authors: Almasy Laura , Manuel Soria Jose , Buil Alfonso , Stone William , Lathrop Mark , Blangero John , Fontcuberta Jordi , Carlos Souto Juan
Published: March 2018

High plasma levels of von Willebrand factor (vWF) have been associated with the risk of thromboembolic disease. As a complex trait, this phenotype must be influenced by genetic and environmental factors. Among the genetic factors, only the ABO gene located on chromosome 9q34 has been clearly linked to the plasma levels of vWF. This locus explains about 30-40% of the genetic variability. Therefore, the source of the majority of the genetic component remains to be identified.

To search for these unknown loci, we conducted a genome-wide linkage screen for genes affecting normal variation in vWF levels in 21 Spanish families as part of the GAIT (Genetic Analysis of Idiopathic Thrombophilia) Project.

The results showed that the strongest linkage signal (LOD = 3.46, p = 0.00003) for vWF was found on chromosome 9q34 at the DNA marker D9S290, where the ABO gene is located. Additional suggestive linkage signals were found on chromosomes 2q23.2 (LOD = 1.65, p = 0.003) and 1p36.13 (LOD = 1.32, p = 0.007). After refining the linkage analysis, conditional to the ABO genotype, three additional loci on chromosomes 5, 6 and 22 showed LOD scores higher than 1, suggesting the presence of other genes linked to vWF levels. Curiously, no linkage signals were detected in other chromosome regions previously associated with vWF levels (like the structural VWF gene on 12p13.2 or Lewis blood group gene on 19q13). These results indicate that these loci are not important genetic determinants of the normal variation of vWF levels.

Our results indicate that the ABO locus is the major genetic determinant of the plasma levels of the vWF in Spanish population. It is possible that there are other potential regions on chromosomes 1, 2, 5, 6 and 22 that influence this thrombosis risk factor. However, the structural vWF gene itself has a very low influence (if any) on the plasma levels of vWF.
Circulating microparticles: a marker of procoagulant state in normal pregnancy and pregnancy complicated by preeclampsia or intrauterine growth restriction
Authors: Bretelle Florence , Sabatier Florence , Desprez Dominique , Camoin Laurence , Grunebaum Leila , Combes Valérie , D’Ercole Claude , Dignat-George Françoise
Published: March 2018

In the present study, we explored the microparticles involved in the control of hemostatic equilibrium, i.e microparticles originating from platelet, endothelial cells and total MP defined as annexin V positive microparticles. Our aim was to analyze the level and procoagulant activity of these microparticles in normal pregnancy and pregnancies complicated with preeclampsia or isolated intrauterine growth restriction. We reported increased levels of platelet and endothelial microparticles in normal pregnancy compared to non pregnant healthy women. Number of annexin V microparticles was significantly increased together with their procoagulant activity. In pathological pregnancies, significant reduction in platelet microparticle number was found in preeclampsia. The procoagulant activity generated by the total annexin V MP was unchanged, suggesting that the microparticles remaining in the circulation were pro-coagulant. This study evidenced that microparticles constitute a cellular marker of a proinflammatory and procoagulant responses in normal pregnancy. In pregnancies with vascular complications, circulating MP with procoagulant potential may be part of the exacerbation of these responses.
Endothelial cell serine proteases expressed during vascular morphogenesis and angiogenesis
Authors: Aimes Ronald , Zijlstra Andries , Hooper John , Ogbourne Steven , Sit Mae-Le , Fuchs Simone , Gotley David , Quigley James , Antalis Toni
Published: March 2018

Many serine proteases play important regulatory roles in complex biological systems, but only a few have been linked directly with capillary morphogenesis and angiogenesis. Here we provide evidence that serine protease activities, independent of the plasminogen activation cascade, are required for microvascular endothelial cell reorganization and capillary morphogenesis in vitro. A homology cloning approach targeting conserved motifs present in all serine proteases, was used to identify candidate serine proteases involved in these processes, and revealed 5 genes (acrosin, testisin, neurosin, PSP and neurotrypsin), none of which had been associated previously with expression in endothelial cells. A subsequent gene-specific RT-PCR screen for 22 serine proteases confirmed expression of these 5 genes and identified 7 additional serine protease genes expressed by human endothelial cells, urokinase-type plasminogen activator, protein C, TMPRSS2, hepsin, matriptase/ MT-SP1, dipeptidylpeptidase IV, and seprase. Differences in serine protease gene expression between microvascular and human umbilical vein endothelial cells (HUVECs) were identified and several serine protease genes were found to be regulated by the nature of the substratum, ie. artificial basement membrane or fibrillar type I collagen. mRNA transcripts of several serine protease genes were associated with blood vessels in vivo by in situ hybridization of human tissue specimens. These data suggest a potential role for serine proteases, not previously associated with endothelium, in vascular function and angiogenesis.
Fibrin(ogen) in cardiovascular disease: an update
Authors: Koenig Wolfgang
Published: March 2018

The notion that fibrinogen is strongly, consistently, and independently related to cardiovascular risk has been widely accepted. The evidence is based on numerous prospective epidemiological studies and clinical observations. In meta-analysis, an association between even modest increases (10%) in fibrino-gen and future coronary heart disease (CHD) endpoints has been found with an odds ratio for CHD of 1.8; 95% CI, 1.6 to 2.0, if the top tertile of the fibrinogen distribution was compared to the bottom tertile; but fibrinogen levels were also associated with unstable and stable coronary artery disease, and coronary complications after interventions. Similar results have been obtained for incident stroke, progression of peripheral arterial disease, and finally for total mortality. The reasons however, why fibrinogen is elevated in cardiovascular disease and in atherosclerosis in general, are only incompletely under-stood; but all cells involved in the atherogenetic process are able to produce cytokines which induce an acute phase reaction, and thus increase fibrinogen plasma levels. The potential pathophysiological mechanisms by which elevated fibrinogen levels mediate cardiovascular risk are manyfold: It forms the substrate for thrombin and represents the final step in the coagulation cascade; it is essential for platelet aggregation; it modulates endothelial function;it promotes smooth muscle cell proliferation and migration; it interacts with the binding of plas-min with its receptor, and finally it represents a major acute phase protein. Whether or not fibrinogen is causally involved in atherothrombogenesis still remains to be determined, and even though other unsolved issues await conclusive answers, fibrino-gen has emerged as an important additional marker of cardiovascular risk.

Theme paper: Part of this paper was originally presented at the joint meetings of the 16th International Congress of the International Society of Fibrinolysis and Proteolysis (ISFP) and the 17th International Fibrinogen Workshop of the International Fibrinogen Research Society (IFRS) held in Munich, Germany, September, 2002.
Molecular and cellular modulation of fibrinolysis
Authors: Kolev Krasimir , Machovich Raymund
Published: March 2018

The structure of the fibrin network, the hemodynamic environment of the clot, the kinetic properties of the fibrinolytic enzymes and the balance of their formation and inactivation essentially determine the effectiveness of fibrinolysis in vivo. The fibrin structure and the action of proteases, however depend considerably on additional, apparently inert physiological and pathological factors, which are restricted to more or less transient compartments in fluid-solid interface, such as thrombus (fibrin with platelet membrane structures), endothelial cell surface, the environment of polymorphonuclear cells (PMN). In these compartments extreme changes in concentrations and rate enhancements are observed. Components released by endothelial cells, PMNs and platelets or molecules present in circulating blood create a heterogeneous milieu that modulates fibrinolysis. This review summarizes the effects, and where it is possible, explains the mechanism of modulators of the fibrinolytic processes, such as cell membrane and cellular contents of endothelium, PMN and platelets present in thrombi, the action of normal and pathological blood plasma- and extracellular matrix-components.
Monitoring of Aspirin (ASA) Pharmacodynamics with the Platelet Function Analyzer PFA-100®
Authors: Homoncik Monika , Hergovich Nicole , Stohlawetz Petra , Panzer Simon , Speiser Wolfgang , Jilma Bernd
Published: March 2018

Anti-platelet drug therapy is currently performed without monitoring, because the established method of platelet aggregometry is cumbersome. The recently developed platelet function analyzer PFA-100® measures shear stress dependent, collagen epinephrine (CEPI) and collagen adenosine diphosphate (CADP) induced platelet plug formation. As the PFA-100 provides a valuable tool to detect patients with platelet dysfunction more efficiently and cost-effectively than aggregometry, we investigated its potential to monitor the efficacy of aspirin treatment.

All healthy volunteers (n = 10) received a fractionated infusion of L-aspirin to establish individual dose-response curves. Further, in a randomized, double-blind, placebo controlled two-way cross over study the same volunteers received either 50 or 100 mg aspirin/day p.o. for a period of 11 days to determine the day-to-day variability CEPI induced closure time (CT) under constant intake of low dose aspirin, and to compare the efficacy of those two doses.

Intra- and intersubject variability of CEPI-CT averaged 9% and 22%, respectively. Seven volunteers exceeded the maximum of CEPI-CT (>300 s) already after infusion of 100 mg L-aspirin. Intake of 100 mg of aspirin elicited a more rapid onset of effect than 50 mg, which was only significant on days 3 and 4 of aspirin intake. The aspirin induced CEPI-CT prolongation correlated positively with basal CEPI-CT values (r = 0.86; p = 0.001) and were strongly dependent on von Willebrand Factor levels (r = -0.9; p = 0.001).

Thus, the PFA-100 system appears suitable to demonstrate an aspirin-induced platelet effect in a longitudinal study, and may be adequate to monitor a patient’s compliance. However, prospective trials have to be conducted to demonstrate whether the EPI-CT achieved under ASA-intake has predictive value for cardiovascular outcome.
Regional Variation in Plasminogen Activator Inhibitor-1 Expression in Adipose Tissue from Obese Individuals
Authors: Van Harmelen Vanessa , Hoffstedt Johan , Lundquist Per , Vidal Hubert , Stemme Veronika , Hamsten Anders , Arner Peter , Reynisdottir Signy , Eriksson Per
Published: March 2018

High plasma plasminogen activator inhibitor-1 (PAI-1) activity is a frequent finding in obesity and adipose tissue has recently been suggested to be a source of circulating PAI-1 in humans. In the present study, differences in adipose tissue gene expression and protein secretion rate of PAI-1 between subcutaneous and visceral adipose tissue was analysed in specimens obtained from 22 obese individuals. The secretion rate of PAI-1 was two-fold higher in subcutaneous adipose tissue than in visceral adipose tissue (292 ± 50 vs 138 ± 24 ng PAI-1/107 cells, P <0.05). In accordance with the secretion data, subcutaneous adipose tissue contained about three-fold higher levels of PAI-1 mRNA than visceral adipose tissue (2.43 ± 0.37 vs 0.81 ± 0.12 attomole PAI-1 mRNA/µg total RNA, P <0.001). PAI-1 secretion from subcutaneous but not from visceral adipose tissue correlated significantly with cell size (r = 0.43, P <0.05). In summary, subcutaneous adipose tissue secreted greater amounts of PAI-1 and had a higher PAI-1 gene expression than visceral adipose tissue from the same obese individuals. Bearing in mind that subcutaneous adipose tissue is the largest fat depot these finding may be important for the coagulation abnormalities associated with obesity.
The HR2 Haplotype of Factor V: Effects on Factor V Levels, Normalized Activated Protein C Sensitivity Ratios and the Risk of Venous Thrombosis
Authors: Guasch Joan , Kamphuisen Pieter , Vos Hans , Rosendaal Frits , Bertina Rogier , de Visser Marieke
Published: March 2018

We studied the HR2 haplotype of the factor V gene in a case-control study for venous thrombosis including 474 patients with a first deep-vein thrombosis and 474 age- and sex-matched healthy controls (Leiden Thrombophilia Study, LETS). We investigated both the original His1299Arg (A4070G) polymorphism and the Met385Thr (T1328C) polymorphism. This latter polymorphism, located in exon 8 (heavy chain), is always present in the HR2 haplotype, but also occurs on its own in a His1299 (wt) background. The HR2 haplotype was not associated with an increased risk of venous thrombosis (OR = 1.2, 95% confidence interval: 0.8-2.0). We did not find an association between the HR2 haplotype and a reduced sensitivity for activated protein C (APC) in non-carriers of factor V Leiden (FVL). However, in compound heterozygous FVL/HR2 carriers the sensitivity for APC was reduced. The HR2 haplotype was also associated with reduced factor V antigen levels in both patients and controls. Sequence analysis of the promoter region of factor V in HR2 homozygotes did not reveal any sequence variations that could explain the reduced FV levels. Our results show that the HR2 haplotype is not associated with an increased risk of venous thrombosis or with a reduced sensitivity for APC in non-FVL carriers. However, the HR2 haplotype is associated with a reduced sensitivity for APC in carriers of FVL and with reduced factor V antigen levels.
Prevalence of Factor V Leiden in Patients with Myocardial Infarction and Normal Coronary Angiography
Authors: Da Costa Antoine , Munier Stéphane , Mercier Bernard , Tardy Brigitte , Ferec Claude , Isaaz Karl , Blanc Jean-Jacques , Mansourati Jacques
Published: March 2018

Factor V Leiden is associated with an increased risk of venous thrombosis and myocardial infarction in young women, but not in men in this latter case. The aim of this study was to evaluate the prevalence of this mutation in patients with myocardial infarction but normal coronary angiography.

We compared 3 groups of patients: one group consisted of 107 patients with premature myocardial infarction but no significant coronary artery stenosis; another group of 244 patients with myocardial infarction and significant coronary artery stenosis; a third group of 400 healthy controls.

Factor V Leiden was found in 13 patients (12.1%) who had a myocardial infarction without significant coronary artery stenosis, 11 patients (4.5%) who had a myocardial infarction with significant coronary artery stenosis (p = 0.01) and in 20 controls (5%) (p = 0.01). Odds ratio associated with factor V Leiden were respectively 2.93 (CI95 : 1.18-7.31) and 2.63 (CI95 : 1.19-5.78) when we compared myocardial infarction patients without significant coronary artery stenosis to controls or to patients with significant coronary artery stenosis.

In myocardial infarction patients without significant coronary artery stenosis, prevalence of factor V Leiden is significantly higher than in controls. This new finding supports the hypothesis that thrombosis plays a key role in this selected situation.
A Computer Generated Induction System for Hospitalized Patients Starting on Oral Anticoagulant Therapy
Authors: Johnson Judith , Nowacki Barbara , Turpie Alexander , Ageno Walter
Published: March 2018

There is an increasing use of computer-based dosage programs to monitor oral anticoagulant therapy in outpatients. DAWN AC INDUCTION by 4S, UK, is a computer generated system to initiate oral anticoagulant therapy providing fast access to the maintenance program. This method of initiation of anticoagulant therapy has not been validated. We therefore randomized 50 hospitalized patients starting oral anticoagulation to control by the computer and 51 by manual dosing using a dosing schedule based on a locally defined algorithm. After a 7 days follow up, the daily mean INR was 2.09 and 2.07 and the proportion of dose adjustments was 48% and 45% in the computer and manually controlled groups respectively. Twenty-eight % of the patients monitored by the computer system required at least one manual overriding. DAWN AC INDUCTION provided a simple and accurate organization of the data, with an overall quality comparable to that of the manual system. Furthermore, the induction programme provided simple access to the maintenance programme. Although it required careful monitoring, the programme resulted in a significant saving in personnel time.
Induction of Tissue Factor Expression in Whole Blood: Lack of Evidence for the Presence of Tissue Factor Expression in Granulocytes
Authors: Østerud Bjarne , Olsen Jan , Rao L. Vijaya
Published: March 2018

The present investigation was undertaken to explore the effect of platelets, tumor necrosis factor (TNF) and phorbel ester [phorbol 12-myristate 13-acetate (PMA)] on lipopolysaccharide (LPS)-induced tissue factor (TF) activity and TF antigen by using Western blot and ELISA-techniques. LPS was found to induce correlating levels of TF antigen and the activity in monocytes. TNF and PMA, when used alone, failed to induce TF activity and the antigen in monocytes, but enhanced the LPS-induced TF activity and the antigen by 2 to 3-fold. Addition of platelet rich plasma to isolated blood cells enhanced the LPS-induced TF activity but not the antigen levels in monocytes. In contrast to whole platelets, platelet lysates enhanced both LPS-induced TF activity and the antigen. Granulocytes isolated from heparinized plasma incubated for 2 or 24 h with LPS alone or together with PMA, failed to generate TF antigen or the activity. Although granulocyte preparations isolated from whole blood that was incubated for 24 h with LPS and PMA apparently possessed a significant amount of TF activity and the antigen, this could be accounted for by trace levels of contaminating monocytes. Upregulation of LPS-induced TF activity but not the antigen by platelets in the presence of granulocytes suggests that the increased TF activity could be the result of PS enrichment of monocytes by fusion or platelets with activated monocytes.
Plasma TAFI Antigen Variations in Healthy Subjects
Authors: Chetaille P. , Alessi M. C. , Kouassi D. , Morange P. E. , Juhan-Vague I.
Published: March 2018

The Thrombin Activatable Fibrinolysis Inhibitor (TAFI) is a recently described inhibitor of fibrinolysis. The physiological variations of plasma TAFI antigen are not well known. We studied TAFI antigen values in healthy populations with a commercially available kit from Milan Analytica (Switzerland). Broad range of TAFI antigen values (from 41% to 259%) was found in a population of 249 healthy individuals. Gender as well as pregnancy did not influence mean values of TAFI antigen. There was a positive correlation between TAFI antigen and age in female (r = 0.28; p <0.05) but not in male populations. Mean TAFI antigen value of a black African male group [mean ± SD (range): 87 ± 23 (39-144%)] was significantly lower than the one of age matched Caucasian men [114 ± 34 (52-259%)] (p <0.0001). TAFI antigen values were very stable within individuals, they did not significantly vary on day time or at several months period.

Thus, in contrast to large inter-individual variations, TAFI antigen levels are quite stable within individuals.
Effects on Coagulation of Levonorgestrel- and Desogestrel-containing Low Dose Oral Contraceptives: a Cross-over Study
Authors: Meijers Joost , van den Ende Abraham , van Enk Adam , Bouma Bonno , Tans Guido , Rosing Jan , Prins Martin , Büller Harry , Middeldorp Saskia
Published: March 2018

Combined oral contraceptives (OC) are known to increase the risk of venous thromboembolism. The aim of this randomized, cycle-controlled, cross-over study in 28 healthy volunteers was to assess potential differences between the effects of an OC containing 150 µg levonorgestrel (as representative of the so-called second generation OC) and an OC containing 150 µg desogestrel (as representative of the third generation OC) in combination with 30 µg ethinylestradiol on several coagulation factors and markers of thrombin formation. All participants used each OC for two cycles, and were switched to the other OC after a washout period of two menstrual cycles. The plasma concentrations of factors II, VII, X, and fibrinogen significantly increased during use of both the levonorgestrel- and desogestrel-containing OC’s. The plasma concentrations of factor VIII increased, and of factor V decreased, changes which only reached statistical significance during the use of the desogestrel-containing OC. During exposure to the desogestrel-containing OC, as compared with the levonorgestrel-containing OC, both factor VII and factor II showed a greater increase (FVII: 32% and 12% respectively; p <0.0001; FII: 16% and 12% respectively; p = 0.048), whereas factor V showed a greater decrease (–11% and –3% respectively; p = 0.010). Only one of the markers for ongoing coagulation (prothrombin fragment 1+2) showed a significant increase during OC use, whereas concentrations of thrombin-antithrombin complexes and soluble fibrin remained unchanged. For these markers, there was no difference between the tested OC’s. We conclude that there are differences between the effects of levonorgestrel and desogestrel-containing OC’s on some coagulation factors. Whether these changes provide a biological explanation for the reported differences in venous thromboembolic risk is as yet unclear. The real challenge now becomes to define a pattern of changes in the various systems which, if affected simultaneously, may tip the hemostatic balance towards a prethrombotic state and may lead to overt clinical venous thromboembolism.
Rapid ELISA Assay for Plasma D-Dimer in the Diagnosis of Segmental and Subsegmental Pulmonary Embolism
Authors: van Ingen Huub , van Beek Edwin , Berghout Arie , Oudkerk Matthijs , Sijens Paul
Published: March 2018

Study objective To assess the accuracy of a rapid ELISA D-dimer assay for the exclusion of pulmonary embolism (PE) in patients suspected of PE, using pulmonary angiography alone as reference method rather than a diagnostic strategy including lung scintigraphy and leg vein ultrasonography. Methods In 342 patients who were examined by pulmonary angiography to diagnose or exclude PE, the accuracy of the quantitative rapid VIDAS D-dimer test for the exclusion of PE was evaluated retrospectively. D-dimer levels were assayed in frozen samples collected during the diagnostic work-up at the time of pulmonary angiography while on treatment with unfractionated heparin for 1-2 days. Results Mean plasma D-dimer concentrations were increased in patients with angiographic evidence of PE (P <0.0001). The sensitivity of D-dimer for segmental PE was 98%, its accuracy in excluding segmental PE was 99%, higher than the respective figures for subsegmental PE (76% and 94%; P <0.01, both). For both forms of PE combined the sensitivity was 90% and the negative predictive value 94%. Discussion The sensitivity and negative predictive values reported here, are low compared with previous studies using the same rapid ELISA D-dimer assay. This probably reflects an overlooking of mild cases of subsegmental PE in previous studies, although a reduction of D-dimer levels by the heparin pretreatment may have contributed to part of the discrepancy. Prospective studies are needed to clarify this issue.
Acquired von Willebrand Syndrome: from Pathophysiology to Management
Authors: Veyradier Agnès , Jenkins Charles , Fressinaud Edith , Meyer Dominique
Published: March 2018

Acquired von Willebrand syndrome (AvWS) is a rare and probably underestimated bleeding disorder which mimicks most of the clinical symptoms and laboratory features of hereditary von Willebrand disease (vWD) in patients devoid of both personal and familial history of bleeding diathesis (1). AvWS and congenital vWD both result from a defect in von Willebrand factor (vWF), a large multimeric glycoprotein present in megakaryocytes, platelets, endothelial cells, subendothelium and mainly in plasma (2). vWF is essential to platelet adhesion and aggregation at the site of vascular injury by acting as a bridge between platelet receptors and the collagen of the subendothelium as well as between platelets themselves. vWF binds to both platelet receptors glycoprotein (GP) Ib and GP IIb/IIIa and also to coagulation factor VIII (F.VIII) acting as a stabilizing carrier protein in plasma. The revised classification of hereditary vWD (3) includes three major types: type 1 and type 3 are respectively related to a partial or a total quantitative defect while type 2 (variants including several subtypes) results from a qualitative defect of vWF. Although vWD is well known to be the most common inherited bleeding disorder with a worldwide prevalence of 1 to 2% (1), more than 200 cases of AvWS have been reported since it was described in 1968 (4). It is likely, however, that this number is underestimated since isolated case-reports of AvWS tend to be less published and its diagnosis remains difficult. AvWS is most commonly found together with a variety of concurrent diseases which are mainly clonal hematoproliferative, neoplasia and autoimmune disorders (5-7). The pathophysiological basis of AvWS as well as its response to treatment depend clearly on the associated underlying disease. In this paper, we summarized all the situations where an AvWS may be observed as a function of the anamnestic and clinical data, the pathogenic mechanisms and the laboratory features. Moreover, we propose a therapeutic flow chart based on both data from the literature and personal experience.
Heparin-protamine Complexes and C-reactive Protein Induce Activation of the Classical Complement Pathway: Studies in Patients Undergoing Cardiac Surgery and In Vitro
Authors: Velthuis Henk , Eerenberg-Belmer Anke , Yazdanbakhsh Aria , de Beaumont Eddy , Eijsman León , Trouwborst Ad , Hack Erik , Bruins Peter
Published: March 2018

The administration of protamine to patients undergoing cardiopulmonary bypass (CPB) to neutralize heparin and to reduce the risk of bleeding, induces activation of the classical complement pathway mainly by heparin-protamine complexes. We investigated whether C-reactive protein (CRP) contributes to protamine-induced complement activation.

In 24 patients during myocardial revascularization, we measured complement, CRP, and complement-CRP complexes, reflecting CRPmediated complement activation in vivo. We also incubated plasma from healthy volunteers and patients with heparin and protamine in vitro to study CRP-mediated complement activation. During CPB, CRP levels remained unchanged while C3 activation products increased. C4 activation occurred after protamine administration. CRP-complement complexes increased at the end of CPB and upon protamine administration. Incubation of plasma with heparin and protamine in vitro generated complement-CRP complexes, which was blocked by phosphorylcholine and stimulated by exogenous CRP. C4d-CRP complex formation after protamine administration correlated clinically with the incidence of postoperative arrhythmia.

Protamine administration during cardiac surgery induces complement activation which in part is CRP-dependent, and correlates with postoperative arrhythmia.
Ultrastructural Analysis of Megakaryocytes in GPV Knockout Mice
Authors: Poujol Christel , Ramakrishnan Vanitha , DeGuzman Francis , Nurden Alan , Phillips David , Nurden Paquita
Published: March 2018

Lesions in the genes for GPIbα, GPIbβ or GPIX result in a bleeding diathesis, the Bernard-Soulier syndrome (BSS), which associates a platelet adhesion defect with thrombocytopenia, giant platelets and abnormal megakaryocytes (MK). The role of GPV, also absent in BSS, was recently addressed by gene targeting in mice. While a negative modulator function for GPV on thrombin-induced platelet responses was found in one model, the absence of GP V had no effect on GPIb-IX expression or platelet adhesion. Our study extends previous results and reports that electron microscopy of bone marrow from the GPV knockout mice revealed a normal MK ultrastructure and development of the demarcation membrane system (DMS). There was a usual presence of MK fragments in the bone marrow vascular sinus. Immunogold labelling of MK from the knockout mice showed a normal distribution of GPIb-IX in the DMS and on the cell surface. The distribution of fibrinogen, vWF and P-selectin was unchanged with, interestingly, P-selectin also localised within the DMS in both situations. Thus GPV is not crucial to MK development and platelet production, consistent with the fact that no mutation in the GPV gene has as yet been described in BSS.
Acquired von Willebrand Syndrome: Data from an International Registry
Authors: Rand Jacob , Bucciarelli Paolo , Budde Ulrich , van Genderen Perry , Mohri Hiroshi , Meyer Dominique , Rodeghiero Francesco , Sadler Evan , Federici Augusto
Published: March 2018

The acquired von Willebrand syndrome (AvWS) is a rare bleeding disorder with laboratory findings similar to those of congenital von Willebrand disease (vWD). Despite the numerous cases reported in the literature until 1999 (n = 266), large studies on AvWS are not available. Moreover, diagnosis of AvWS has been difficult and treatment empirical. These considerations prompted us to organize an international registry. A questionnaire, devised to collect specific information on AvWS, was sent to all the members of the International Society on Thrombosis and Haemostasis (ISTH), who were invited to respond if they had diagnosed cases with the AvWS cases. 156 members answered the questionnaire and 54 of them sent information on 211 AvWS cases from 50 centers. Data were compared with those already published in the literature and 25 cases already described or not correctly diagnosed were excluded. The 186 AvWS cases that qualified for the registry were associated with lymphoproliferative (48%) and myeloproliferative disorders (15%), neoplasia (5%), immunological (2%), cardiovascular (21%) and miscellaneous disorders (9%). Ristocetin cofactor activity (vWF:RCo) or collagen binding activity (vWF:CBA) were usually low in AvWS (median values 20 U/dL, range 3-150), while factor VIII coagulant activity was sometimes normal (median 25 U/dL, range 3-191). FVIII/vWF inhibiting activities were present in only a minority of cases (16%). Bleeding episodes in AvWS were mostly of mucocutaneous type (68%) and were managed by DDAVP (32%), FVIII/vWF concentrates (37%), intravenous immunoglobulins (33%), plasmapheresis (19%), corticosteroids (19%) and immunosuppressive or chemotherapic agents (35%). Based upon the data of this international registry, it appears that AvWS is especially frequent in lympho-or myeloproliferative and cardiovascular diseases. Therefore, AvWS should be suspected and searched with the appropriate laboratory tests especially when excessive bleeding occurs in patients with these disorders. On the basis of the information provided by this registry guidelines for diagnosis and management of the AvWS are given.
Blood Rheology, Cardiovascular Risk Factors, and Cardiovascular Disease: The West of Scotland Coronary Prevention Study
Authors: Rumley Ann , Norrie John , Ford Ian , Shepherd James , Cobbe Stuart , Macfarlane Peter , Packard Christopher , Lowe Gordon ,   The West of Scotland Coronary Prevention Study Group
Published: March 2018

The West of Scotland Coronary Prevention Study (WOSCOPS) showed that pravastatin reduced the risk of coronary heart disease (CHD) events in 6,595 middle-aged hypercholesterolaemic men aged 45–64 years without prior myocardial infarction followed for an average of 4.9 years. We hypothesised prospectively (a) that baseline levels of haemorheological variables were related to baseline and incident CHD and to mortality; and (b) that reduction in lipoproteins by pravastatin would lower plasma and blood viscosity, a potential contributory mechanism to CHD events. We therefore studied plasma and blood viscosity, fibrinogen, haematocrit, and blood cell counts at baseline and 1 year. At baseline, plasma and blood viscosity were related to risk factors, CHD measures, and claudication. On univariate analysis, baseline levels of all rheological variables (except platelet count) were related to incident CHD; CHD mortality; and total mortality. On multivariate analysis including baseline CHD and risk factors, plasma and blood viscosity, haematocrit and white cell count each remained significantly associated with incident CHD; while fibrinogen remained an independent predictor of mortality (all p < 0.03). After one year, lipoprotein reduction by pravastatin was associated with significant reductions (about one quarter of a standard deviation) in plasma viscosity (mean difference 0.02 mPa.s, p <0.001) and in blood viscosity (mean difference 0.06 mPa.s, p <0.001), but was not associated with significant changes in other rheological variables. We therefore suggest that pravastatin therapy, which reduces elevated lipoproteins in hypercholesterolaemic men, may lower risks of CHD and mortality partly by lowering plasma and blood viscosity. Further studies are required to test this hypothesis.
Effect of Factor Xa Inhibitors on the Platelet-derived Microparticles Procoagulant Activity In Vitro> and In Vivo in Rats
Authors: Hérault J. P. , Perrin B. , Jongbloet C. , Pflieger A. M. , Bernat A. , Herbert J. M.
Published: March 2018

The aim of this study was to investigate the effect of factor Xa inhibitors on the prothrombinase activity of platelet-derived microparticles in vitro and in vivo. The factor Xa inhibitors studied were DX9065A (a direct factor Xa inhibitor) and Sanorg34006 (an antithrombin (AT)-mediated factor Xa inhibitor). Microparticles formed from the platelet surface following activation were isolated by size exclusion gel chromatography. After purification, their presence was detected by their procoagulant activity and by flow cytometry. Our results show that factor Xa and/or factor Va were present at the surface of the platelet-derived microparticles. Prothrombinase formed on the microparticles was inhibited by factor Xa inhibitors at IC50 values of 0.45 ± 0.05 and 0.045 ± 0.005 µM for DX9065A and AT-Sanorg34006 respectively. In an experiment aimed at determining the kinetics of microparticles formation we demonstrated that thrombin traces were sufficient to induce the formation of a significant quantity of microparticles. Both factor Xa inhibitors delayed the formation of microparticles by delaying thrombin generation. The thrombogenic effect of the microparticles were studied in vivo in a modified arterio-venous shunt model in the rat. In this model, the increase in the thrombus weigh due to microparticles or phospholipids did not differ significantly (33% and 23% respectively). In these conditions, prothrombinase activity seemed to play a lesser role in the thrombogenic effect than phospholipids. Nevertheless, factor Xa inhibitors were efficient and inhibited thrombus formation in a dose-dependent manner.

These results demonstrate that platelet-derived microparticles display a potent prothrombotic effect in vivo and show that factor Xa inhibitors are potent antithrombotic compounds when thrombosis was induced by microparticles.
Regulation of Platelet Aggregation and Adenosine Triphosphate Release In Vitro by 17β-Estradiol and Medroxyprogesterone Acetate in Postmenopausal Women
Authors: Lahav J. , Hod M. , Ben-Rafael Z. , Weinberger I. , Brosens J. , Bar J.
Published: March 2018

Clinical studies have suggested that hormone replacement therapy (HRT) may reduce the risk of coronary heart disease in postmenopausal women. Although progestins are commonly added to HRT preparations for uteroprotection, the perceived beneficial cardiovascular effects of HRT are thought to be mediated predominantly by the estrogen component. Platelets play a critical role in the pathogenesis of atherosclerosis and cardiovascular disease and, hence, it is possible that the cardiovascular effects of estrogens are mediated, at least in part, through inhibition of illicit platelet activation. The aim of this study was to examine the effects of sex steroids on adenosine diphosphate (ADP)-induced platelet aggregation and adenosine triphosphate (ATP) release in vitro in postmenopausal women. In addition, the effects of antiestrogens [4-hydroxy tamoxifen (4-OHT) and ICI 182780] and antiprogestins (RU 486 and ZK 98299) were also investigated. Preincubation of platelet-rich plasma (PRP) with antiestrogens or antiprogestins did not alter subsequent platelet aggregation or ATP release in response to ADP. However, preincubation with 17β-estradiol (E2) significantly inhibited ADP-mediated platelet aggregation by a mean (±SEM) of 37% ± 6% (p = 0.02) and ATP release by 82% ± 6% (p = 0.03), an effect that was reversed by the addition of ICI 182780 or 4-OHT but not RU 486 and ZK 98299. Although the progestin medroxyprogesterone acetate (MPA) also significantly inhibited platelet aggregation (by 28% ± 5%, p = 0.02) and ATP release (by 63% ± 9%, p = 0.02), this inhibition was not reversed by the addition of antiprogestins or antiestrogens. These data show that sex steroids can modulate platelet function in vitro. Furthermore, as platelets are devoid of nuclear components, these findings indicate that estrogens may regulate platelet function through binding to a non-nuclear receptor with ligand-binding properties similar or identical to the wild-type receptor. By contrast, MPA appears to exert its effect through a mechanism that does not involve binding to the “classical” progesterone receptor.
Venous Thrombosis, Oral Contraceptives and High Factor VIII Levels
Authors: Bloemenkamp K. W. M. , Helmerhorst F. M. , Vandenbroucke J. P. , Rosendaal F. R.
Published: March 2018

Recently, it has been described that elevated plasma levels of factor VIII are a strong risk factor for venous thrombosis. We analysed the data of the Leiden Thrombophilia Study, a population based case-control study on the causes of venous thrombosis, to verify whether the risk due to oral contraceptive use was higher in women with higher factor VIII levels. Furthermore we investigated the joint risk of high factor VIII levels and oral contraceptive use.

We selected 155 premenopausal women with deep-vein thrombosis and 169 control subjects, aged 15-49, who were at the time of their thrombosis (or similar date in control) not pregnant, nor in the puerperium, did not have a recent miscarriage, and were not using injectable progestogens. Of the patients, 109 (70%) women had used oral contraceptives during the month preceding their deep-vein thrombosis, in contrast to 65 (38%) of the control subjects (index date), yielding an odds ratio for oral contraceptive use of 3.8 (95% CI 2.4-6.0). Of the women who suffered a deep-vein thrombosis 56 (36%) had high factor VIII levels (≥150 IU/dl) as compared with 29 (17%) of the control subjects, yielding an odds ratio for high factor VIII of 4.0 (95% CI 2.0-8.0), relative to factor VIII levels <100 IU/dl. The joint effect of oral contraceptive use and high factor VIII resulted in an odds ratio of 10.3 (95% CI 3.7-28.9), comparing women who had both with women who had neither. We conclude that there is an increase in risk due to oral contraceptive use in women with higher factor VIII levels and that both factors have additive effects.
Regular Exercise, Plasminogen Activator Inhibitor-1 (PAI-1) Activity and the 4G/5G Promoter Polymorphism in the PAI-1 Gene
Authors: Humphries Steve , Luong Le-Anh , Penttilä Ilkka , Bouchard Claude , Rauramaa Rainer , Väisänen Sari
Published: March 2018

The aim of this controlled randomised clinical trial was to investigate the effects of regular low to moderate intensity physical activity on plasminogen activator inhibitor-1 (PAI-1) activity during three years while taking into account the 4G/5G polymorphism in the promoter of the PAI-1 gene. Male subjects (age 52-62 years, n = 132) were randomised into an exercise or a (non-intervention) reference group. Aerobic threshold increased by 8.8% (p = 0.025) in the exercise group, and decreased by 1.1% in the non-intervention group, while PAI-1 activity did not change significantly in either study group. However, homozygotes for the 4G allele in the exercise group showed a 36% reduction in PAI-1 (p = 0.025). In conclusion, although regular moderate physical activity did not decrease PAI-1 activity in the whole group, regular exercise may be effective for controlling elevated PAI-1 level in subjects homozygous for the 4G allele.
Incidence of Venous Thromboembolism in Families with Inherited Thrombophilia
Authors: Simioni Paolo , Sanson Bernd-Jan , Tormene Daniela , Friederich Philip , Girolami Bruno , Gavasso Sabrina , Huisman Menno , Büller Harry , ten Cate Jan Wouter , Girolami Antonio , Prins Martin , Prandoni Paolo
Published: March 2018

The risk of spontaneous or risk-period related venous thromboembolism in family members of symptomatic carriers of antithrombin (AT), protein C (PC) or protein S (PS) defects, as well as of the Factor V Leiden mutation is still undefined. We performed a retrospective cohort study in family members (n = 793) of unselected patients with a documented venous thromboembolism and one of these deficiencies to make an estimate of this risk. The annual incidences of total and spontaneous venous thromboembolic events in carriers of AT, PC or PS defects (n = 181) were 1.01% and 0.40%, respectively, as compared to 0.10% and 0.04% in non-carriers, respectively (relative risks both 10.6). In carriers of Factor V Leiden (n = 224), the annual incidences of total and spontaneous venous thromboembolism were 0.28% and 0.11%, respectively, as compared to 0.09% and 0.04% in non-carriers, respectively (relative risks 2.8 and 2.5). Additional risk factors (immobilisation, surgery and trauma; oral contraceptive use; and pregnancy/ post-partum) increased the risk of thrombosis in carriers of AT, PC and PS defects as compared to non-carriers (relative risks 8.3, 6.4 and 8.2, respectively). Oral contraceptive use and pregnancy/ post-partum period increased the risk of thrombosis in carriers of Factor V Leiden to 3.3-fold and 4.2-fold, respectively, whereas other risk factors had only a minor effect.

These data lend some support to the practice of screening family members of symptomatic carriers of a AT, PC and PS deficiency. For family members of symptomatic carriers of Factor V Leiden, screening does not seem to be justified except for women in fertile age.