The EAHAD blood coagulation factor VII variant database

Hereditary blood coagulation factor VII (FVII) deficiency is a rare autosomal recessive bleeding disorder resulting from variants in the gene encoding FVII (F7). Integration of genetic variation with functional consequences on protein function is essential for the interpretation of the pathogenicity of novel variants. Here, we describe the integration of previous locus-specific databases for F7 into a single curated database with enhanced features. The database provides access to in silico analyses that may be useful in the prediction of variant pathogenicity as well as cross-species sequence alignments, structural information, and functional and clinical severity described for each variant, where appropriate. The variant data is shared with the F7 Leiden Open Variation Database. The updated database now includes 221 unique variants, representing gene variants identified in 728 individuals. Single nucleotide variants are the most common type (88%) with missense representing 74% of these variants. A number of variants are found with relatively high minor allele frequencies that are not pathogenic but contribute significantly to the likely pathogenicity of coinherited variants due to their effect on FVII plasma levels. This comprehensive collection of curated information significantly aids the assessment of pathogenicity.

The European Association for Haemophilia and Allied Disorders (EAHAD) Coagulation Factor Variant Databases: Important resources for haemostasis clinicians and researchers

INTRODUCTION

Advances in genomic sequencing have facilitated the sequencing of genes associated with disorders of haemostasis. The identification of variants within genes and access to curated data incorporating structural, functional, evolutionary as well as phenotypic data has become increasingly important in order to ascribe pathogenicity.

AIM

The European Association for Haemophilia and Allied Disorders (EAHAD) Coagulation Factor Variant Database Project aims to provide a single port of entry to a web-accessible resource for variants in genes involved in clinical bleeding disorders.

RESULTS

New databases have evolved from previously developed single gene variant coagulation database projects, incorporating new data, new analysis tools and a new common database architecture with new interfaces and filters. These new databases currently present information about the genotype, phenotype (laboratory and clinical) and structural and functional effects of variants described in the genes of factor (F) VII (F7), FVIII (F8), FIX (F9) and von Willebrand factor (VWF).

CONCLUSION

The project has improved the quality and quantity of information available to the haemostasis research and clinical communities, thereby enabling accurate classification of disease severity in order to make assessments of likely pathogenicity.

The Treatment of Bleeding in Acquired Haemophilia with Recombinant Factor VIIa: A Multicentre Study

Recombinant factor Vila was used to treat 38 patients with acquired haemophilia participating in the Novoseven compassionate-use program. 19 were male, median age 59, range 2-89 years. The median pre-treatment anti-human (H) and anti-porcine (P) inhibitor titre was H 43 BU/ml (range 1-4500) and P 4.5 BU/ml (range 0-1600). Recombinant factor VIIa was used as first-line therapy for 14 bleeding episodes and as salvage-therapy for 60 episodes which failed to respond to blood-product therapy given for a median of four days (range 1-21 days) prior to treatment with rVIIa. Pre-rVIIa treatment was not reported for four episodes. The indications for treatment were 7 haemarthroses, 40 muscle haematomas, 20 urinary or GI haemorrhages and 3 surgical interventions. The median starting dose of rVIIa was 90.4 ug/kg (range 45-181). A median of 28 doses (range 1-541) were given per episode, over a median 3.9 days (range 0-43).

Efficacy was assessed clinically 8 and 24 h after the start of rVIIa and at the end of treatment. A good response was obtained in all 14 bleeds for which rVIIa was used as first-line therapy. The response after 24 h of rVIIa salvage-therapy for 60 bleeds was good in 75%, partial in 17% and poor in 8%. Efficacy was unreported in 4 cases. The median prothrombin time (PTT) shortened from 12 s (range 9.3-20) pre-treatment to 8.8 s (range 6-14) during treatment. The clinical response did not correlate with the dose of rVIIa used, the type of bleed or the degree of shortening of the PTT following rVIIa infusion.

Three patients died from haemorrhagic complications of acquired haemophilia. This mortality of 7.9% is lower than previously reported for this condition. Although one patient developed DIC during treatment with rVIIa, this was probably attributable to hypovolaemic shock, massive transfusion and the use of PCCs. This study demonstrates that rVIIa is a safe, useful and effective treatment for bleeding in patients with acquired haemophilia.

Haemostatic Effects of Supraphysiological Levels of Testosterone in Normal Men

The effects of exogenous testosterone on the haemostatic system were studied in a group of 32 healthy men undergoing a clinical trial of hormonal male contraception. The men received 200 mg testosterone oenanthate (TE) weekly i.m., and plasma samples were taken pretreatment, at defined time points up to 52 weeks of treatment, and 4 and 8 weeks after discontinuing TE. This dose of TE caused a 2-fold increase in trough plasma testosterone levels.

TE caused a fall in plasma fibrinogen concentration after 16 weeks of treatment. This was sustained for the duration of TE treatment and recovered to pretreatment levels during the recovery phase. There was also a sustained fall in the level of C4b binding protein which showed a rebound to levels above pretreatment during recovery. Levels of antithrombin III and prothrombin fragment F1.2 rose initially during TE treatment, and levels of protein C, protein S (free) and plasminogen activator inhibitor fell, but the concentrations of these factors all returned to pretreatment levels during continued treatment. There was no change in the plasma concentrations of β-thromboglobulin, tissue plasminogen activator, protein S (total), or D-dimer. There was a sustained increase in haemoglobin concentration and haematocrit, without any change in platelet count.

The observed changes were consistent with mild activation of the haemostatic system during initial treatment with testosterone. After several months the raised activation markers had returned to pretreatment levels indicating that a new equilibrium had been established which did not appear to be prothrombotic. The increase in prothrombin fragment F1.2 for the first 32 weeks, and at four weeks after discontinuation of treatment, is consistent with prolonged mildly increased prothrombinase activity. The observed substantial fall in fibrinogen is likely to have reduced, whereas the small rise in haemoglobin will have increased, the tendency to arterial thrombosis. We conclude that supraphysiological doses of testosterone do not result in a sustained marked prothrombotic state, but these results do not exclude a small change in thrombotic risk.

A Comparative Study Using Immunological and Biological Assays of the Haemostatic Responses to DDAVP Infusion Venous Occlusion and Exercise in Normal Men

In a group of six normal male volunteers, infusion of DDAVP, venous occlusion and exercise were shown to increase plasma levels of factor VIII and plasminogen activator, activity and antigen, to different extents and at differing rates. Any mechanisms suggested to explain release of these proteins by various stimuli should account for such differences.

All three stimuli could also increase plasma levels of prostacyclin metabolites, although this was only significant for high doses of DDAVP. Other potential endothelial markers, such as fibronectin and thrombospondin, showed no specific increase after any of the stimuli.

An in vivo Model for the Assessment of Acute Fibrinolytic Capacity of the Endothelium

The effects on blood flow and plasma fibrinolytic and coagulation parameters of intraarterial substance P, an endothelium dependent vasodilator, and sodium nitroprusside, a control endothelium independent vasodilator, were studied in the human forearm circulation. At subsystemic locally active doses, both substance P (2-8 pmol/min) and sodium nitroprusside (2-8 μg/min) caused dose-dependent vasodilatation (p <0.001 for both) without affecting plasma concentrations of PAI-1, von Willebrand factor antigen or factor VIII:C activity. Substance P caused local increases in t-PA antigen and activity (p <0.001) in the infused arm while sodium nitroprusside did not. At higher doses, substance P increased blood flow and t-PA concentrations in the noninfused arm. We conclude that brief, locally active and subsystemic infusions of intraarterial substance P cause a rapid and substantial local release of t-PA which appear to act via a flow and nitric oxide independent mechanism. This model should provide a useful and selective method of assessing the in vivo capacity of the forearm endothelium to release t-PA acutely.

High Purity Factor IX and Prothrombin Complex Concentrate (PCC): Pharmacokinetics and Evidence that Factor IXa Is the Thrombogenic Trigger in PCC

Recent studies using assays for surrogate markers of thrombogenic-ity in man have demonstrated that activation of the coagulation system occurs following infusion of clinical doses of prothrombin complex concentrates (PCC) but not after the same doses of high-purity factor IX concentrates (HP-FIX) in patients with haemophilia B. Here we have investigated the mechanism of such thrombogenesis by applying assays that detect early-through to late-events in coagulation system activation in a pharmacokinetic cross-over study of 50 IU/kg PCC and a new HP-FIX product in haemophilia B patients. Satisfactory recoveries and half-lives were observed for both concentrates.

HP-FIX caused no increases in thrombin-antithrombin III complex (TAT), prothrombin activation peptide fragment F1+2 (F1+2), factor X activation peptide (FXAP) or factor Vila (FVIIa). In contrast the same dose of factor IX in the form of PCC was followed by significant increases over pre-infusion levels of TAT, F1+2 and FXAP, but not FVIIa. Elevations of FIXAP occurred after both HP-FIX and PCC but did not reach normal levels and were attributed to normalisation of the FIX concentration in those patients whose levels of FIXAP were initially low. We conclude that the thrombogenic trigger associated with PCC infusion occurs at the level of factor X activation. In the absence of any increase in FVIIa, we would attribute this to the likely presence of FIXa in the PCC.

Platelet and Coagulation Function in Patients with Abnormal Cardiac Valves Treated with Sulphinpyrazone

Eight patients on warfarin with rheumatic heart disease and prosthetic cardiac valves were selected for study on the basis of persistently elevated plasma β-thromboglobulin (β-tg) and platelet factor 4 (PF4) concentrations. Platelet mean lifespan and fibrinogen half life were short, and positively correlated, and both were inversely related to the Plasma concentrations of the platelet specific proteins. Antithrombin III (ATIII) levels were also reduced. Treatment with sulphinpyrazone resulted in lengthening of both platelet and fibrinogen survival, a rise in ATIII but no change in the βtg or PF4 concentrations. It is concluded that patients with abnormal cardiac valves and raised plasma levels of βtg or PF4 have, despite warfarin, a consumption coagulopathy that can be inhibited by sulphinpyrazone.

Reliability of a Single β-Thromboglobulin Measurement in a Diabetic Population : Importance of PGE1 in Anticoagulant Mixture

During the collection of samples for plasma β-thromboglobulin (β-TG) determination, it is well established that artificially high values can be observed due to in-vitro release. To estimate the reliability of a single β-TG measurement, blood samples were collected simultaneously from both arms on two separate occasions in 56 diabetic patients selected for a clinical trial. From each arm, blood was taken into two tubes containing an anticoagulant mixture with (tube A) and without (tube B) PGE!. The overall mean value of B-TG in tube B was 1.14 times higher than in tube A (p <0.01). The markedly large between-arms variation accounted for the most part of within-subject variation in both tubes and was significantly greater in tube B than in tube A. Based on the difference between B-TG values from both arms, the number of subjects with artifically high B-TG values was significantly higher in tube B than in tube A on each occasion (overall rate: 28% and 14% respectively). Estimate of between-occasions variation showed that B-TG levels were relatively stable for each subject between two occasions in each tube. It is concluded that the use of PGEi decreases falsely high B-TG levels, but a single measurement of B-TG does not provide a reliable estimate of the true B-TG value in vivo.

Endogenous tissue plasminogen activator enhances fibrinolysis and limits thrombus formation in a clinical model of thrombosis

OBJECTIVE

Using a clinical model of deep arterial injury, we assessed the ability of exogenous and endogenous tissue plasminogen activator (t-PA) to limit acute in situ thrombus formation.

APPROACH AND RESULTS

Ex vivo thrombus formation was assessed in the Badimon chamber at low and high shear rates in 2 double-blind randomized cross-over studies of 20 healthy volunteers during extracorporeal administration of recombinant t-PA (0, 40, 200, and 1000 ng/mL) or during endogenous t-PA release stimulated by intra-arterial bradykinin infusion in the presence or absence of oral enalapril. Recombinant t-PA caused a dose-dependent reduction in thrombus area under low and high shear conditions (P<0.001 for all). Intra-arterial bradykinin increased plasma t-PA concentrations in the chamber effluent (P<0.01 for all versus saline) that was quadrupled in the presence of enalapril (P<0.0001 versus placebo). These increases were accompanied by an increase in plasma D-dimer concentration (P<0.005 for all versus saline) and, in the presence of enalapril, a reduction in thrombus area in the low shear (16±5; P=0.03) and a trend toward a reduction in the high shear chamber (13±7%; P=0.07).

CONCLUSIONS

Using a well-characterized clinical model of coronary arterial injury, we demonstrate that endogenous t-PA released from the vascular endothelium enhances fibrinolysis and limits in situ thrombus propagation. These data support a crucial role for the endogenous fibrinolytic system in vivo and suggest that continued exploration and manipulation of its therapeutic potential are warranted.

Effects of acute insulin-induced hypoglycemia on indices of inflammation: putative mechanism for aggravating vascular disease in diabetes

OBJECTIVE

To examine the effects of acute insulin-induced hypoglycemia on inflammation, endothelial dysfunction, and platelet activation in adults with and without type 1 diabetes.

RESEARCH DESIGN AND METHODS

We studied 16 nondiabetic adults and 16 subjects with type 1 diabetes during euglycemia (blood glucose 4.5 mmol/l) and hypoglycemia (blood glucose 2.5 mmol/l). Markers of inflammation, thrombosis, and endothelial dysfunction (soluble P-selectin, interleukin-6, von Willebrand factor [vWF], tissue plasminogen activator [tPA], high-sensitivity C-reactive protein [hsCRP], and soluble CD40 ligand [sCD40L]) were measured; platelet-monocyte aggregation and CD40 expression on monocytes were determined using flow cytometry.

RESULTS

In nondiabetic participants, platelet activation occurred after hypoglycemia, with increments in platelet-monocyte aggregation and P-selectin (P <or= 0.02). Inflammation was triggered with CD40 expression increasing maximally at 24 h (3.13 +/- 2.3% vs. 2.06 +/- 1.0%) after hypoglycemia (P = 0.009). Both sCD40L and hsCRP (P = 0.02) increased with a nonsignificant rise in vWF and tPA, indicating a possible endothelial effect. A reduction in sCD40L, tPA, and P-selectin occurred during euglycemia (P = 0.03, P <or= 0.006, and P = 0.006, respectively). In type 1 diabetes, both CD40 expression (5.54 +/- 4.4% vs. 3.65 +/- 1.8%; P = 0.006) and plasma sCD40L concentrations increased during hypoglycemia (peak 3.41 +/- 3.2 vs. 2.85 +/- 2.8 ng/ml; P = 0.03). Platelet-monocyte aggregation also increased significantly at 24 h after hypoglycemia (P = 0.03). A decline in vWF and P-selectin occurred during euglycemia (P <or= 0.04).

CONCLUSIONS

Acute hypoglycemia may provoke upregulation and release of vasoactive substances in adults with and without type 1 diabetes. This may be a putative mechanism for hypoglycemia-induced vascular injury.

Acute endothelial tissue plasminogen activator release in pregnancy

OBJECTIVE

Pregnancy is associated with marked changes in vascular physiology and an increased risk of thrombosis. The aim of the study was to assess the effect of pregnancy on the acute release of tissue plasminogen activator (t-PA) from the endothelium.

METHODS AND RESULTS

Ten primigravida pregnant women were recruited in the third trimester of pregnancy (week 36 +/- 1) and compared with 20 age-matched non-pregnant women (day 9.8 +/- 0.3 of menstrual cycle). Blood flow and plasma fibrinolytic factors were measured in both forearms by venous occlusion plethysmography and blood sampling, respectively, during unilateral brachial artery infusions of bradykinin (100-1000 pmol min(-1)). Pregnant women had higher plasma plasminogen activator inhibitor type 1 (PAI-1) antigen concentrations (77.1 +/- 12.4 vs. 21.5 +/- 9.8 ng mL(-1); P = 0.004) that resulted in lower basal t-PA/PAI-1 ratios (0.2 +/- 0.1 vs. 0.6 +/- 0.1; P = 0.02) and plasma t-PA activity concentrations (0.17 +/- 0.02 vs. 0.58 +/- 0.06 IU mL(-1); P < 0.0004). In both groups, bradykinin caused dose-dependent increases in blood flow and local release of plasma t-PA antigen and activity (P < 0.005 for all). Both the plasma t-PA/PAI-1 ratios and the net release of active t-PA were markedly reduced in pregnant women (P < 0.05 for both). Area under the curve for net active t-PA release was reduced by 36%.

CONCLUSIONS

Pregnancy is associated with major perturbations of endogenous fibrinolytic capacity with an overwhelming increase in plasma PAI-1 concentrations and an inadequate release of active t-PA. These prothrombotic effects may, in part, explain the increased risk of arterial and venous thrombosis in pregnant women.

Role of the endothelium in the vascular effects of the thrombin receptor (protease-activated receptor type 1) in humans

OBJECTIVES

The purpose of this study was to determine the role of the endothelium in the vascular actions of protease-activated receptor type 1 (PAR-1) activation in vivo in man.

BACKGROUND

Thrombin is central to the pathophysiology of atherothrombosis. Its cellular actions are mediated via PAR-1. Protease-activated receptor type 1 activation causes arterial vasodilation, venoconstriction, platelet activation, and tissue-type plasminogen activator release in man.

METHODS

Dorsal hand vein diameter was measured in 6 healthy volunteers before and after endothelial denudation. Forearm arterial blood flow, plasma fibrinolytic factors, and platelet activation were measured in 24 healthy volunteers during venous occlusion plethysmography. The effects of inhibition of prostacyclin, nitric oxide (NO), and endothelium-derived hyperpolarizing factor on PAR-1 responses were assessed during coadministration of aspirin, the "NO clamp" (L-N(G)-monomethyl arginine and sodium nitroprusside), and tetraethylammonium ion, respectively.

RESULTS

Endothelial denudation did not affect PAR-1-evoked venoconstriction (SFLLRN; 0.05 to 15 nmol/min). Although aspirin had no effect, SFLLRN-induced vasodilation (5 to 50 nmol/min) was attenuated by the NO clamp (p < 0.0001) and tetraethylammonium ion (p < 0.05) and abolished by their combination (p < 0.01). The NO clamp augmented SFLLRN-induced tissue-type plasminogen activator and plasminogen activator inhibitor type 1 antigen (p < 0.0001) release, but tetraethylammonium ion and aspirin had no effect. SFLLRN-induced platelet activation was unaffected by NO or prostacyclin inhibition.

CONCLUSIONS

Acting via PAR-1, thrombin causes contrasting effects in the human vasculature and has a major interaction with the endothelium. This highlights the critical importance of endothelial function during acute arterial injury and intravascular thrombosis, as occurs in cardiovascular events including myocardial infarction and stroke.

Plasma microparticles and vascular disorders

Microparticles are circulating, phospholipid rich, submicron particles released from the membranes of endothelial cells, platelets, leucocytes and erythrocytes. Investigation into their biological activity has revealed diverse actions in coagulation, cell signalling and cellular interactions. These actions are mediated through their phospholipid rich surfaces and the expression of cell surface molecules which reflect their cell of origin and its state of activation. Microparticle numbers are reported to be elevated in a number of conditions where vascular dysfunction and inflammation are important pathophysiological mechanisms, for example coronary artery disease or thrombotic microangiopathies. Currently, there are a variety of different methods used for the quantitation of circulating microparticles; however with standardisation their assessment may prove to be of clinical value, reflecting the state of the vasculature. Knowledge of the functional properties of microparticles will contribute to our understanding of the mechanisms underlying vascular dysfunction and prothrombotic states.

Endothelial fibrinolytic capacity predicts future adverse cardiovascular events in patients with coronary heart disease

OBJECTIVE

The endothelium-derived fibrinolytic factor tissue plasminogen activator (t-PA) is a major determinant of vessel patency after coronary plaque rupture and thrombosis. We assessed whether endothelial fibrinolytic capacity predicts atherothrombotic events in patients with coronary heart disease.

METHODS AND RESULTS

Plasma t-PA and plasminogen activator inhibitor (PAI)-1 concentrations were measured during intrabrachial substance P infusion in 98 patients with angiographically proven stable coronary heart disease. Forearm blood flow was measured during infusion of substance P and sodium nitroprusside. Cardiovascular events (cardiovascular death, myocardial infarction [MI], ischemic stroke [CVA], and emergency hospitalization for unstable angina) were determined during 42 months of follow-up. Patients experiencing a cardiovascular event (n=19) had similar baseline characteristics to those free of events. Substance P caused a dose-dependent increase in plasma t-PA concentrations (P<0.001). However, net t-PA release was 72% lower in the patients who experienced death, MI, or CVA, and 48% lower in those who suffered death, MI, CVA or hospitalization for unstable angina (P<0.05). Major adverse cardiovascular events were most frequent in those with the lowest fibrinolytic capacity (P=0.03 for trend); patients with the lowest quartile of t-PA release had the highest rate of adverse events (P=0.01).

CONCLUSION

Endothelial fibrinolytic capacity, as measured by stimulated t-PA release, predicts the future risk of adverse cardiovascular events in patients with coronary heart disease. We suggest that endothelial fibrinolytic capacity is a powerful novel determinant of cardiovascular risk.

Mortality rates, life expectancy, and causes of death in people with hemophilia A or B in the United Kingdom who were not infected with HIV

Since the 1970s, mortality in the hemophilia population has been dominated by human immunodeficiency virus (HIV) and few reports have described mortality in uninfected individuals. This study presents mortality in 6018 people with hemophilia A or B in the United Kingdom during 1977 to 1998 who were not infected with HIV, with follow-up until January 1, 2000. Given disease severity and factor inhibitor status, all-cause mortality did not differ significantly between hemophilia A and hemophilia B. In severe hemophilia, all-cause mortality did not change significantly during 1977 to 1999. During this period, it exceeded mortality in the general population by a factor of 2.69 (95% confidence interval [CI]: 2.37-3.05), and median life expectancy in severe hemophilia was 63 years. In moderate/mild hemophilia, all-cause mortality did not change significantly during 1985 to 1999, and median life expectancy was 75 years. Compared with mortality in the general population, mortality from bleeding and its consequences, and from liver diseases and Hodgkin disease, was increased, but for ischemic heart disease it was lower, at only 62% (95% CI: 51%-76%) of general population rates, and for 14 other specific causes it did not differ significantly from general population rates. There was no evidence of any death from variant Creutzfeldt-Jakob disease or from conditions that could be confused with it.

Direct Vascular Effects of Protease-Activated Receptor Type 1 Agonism In Vivo in Humans

Background— Protease-activated receptor type 1 (PAR-1) has been proposed as the principal thrombin receptor in humans, although its actions in vivo have not been defined. The aim of the present study was to determine the direct vascular actions of PAR-1 agonism in humans.

Methods and Results— Dorsal hand vein diameter was measured by the Aellig technique in 14 healthy volunteers during local intravenous SFLLRN (PAR-1 agonist; 0.05 to 15 nmol/min) and SLIGKV (PAR-2 agonist; 1.6 to 160 nmol/min) infusions. The venous effects of SFLLRN were further assessed in the presence or absence of norepinephrine or the glycoprotein IIb/IIIa antagonist tirofiban. Forearm blood flow was measured by venous occlusion plethysmography in 16 volunteers during infusion of SFLLRN (1 to 50 nmol/min), SLIGKV (160 to 800 nmol/min), and the endothelium-dependent vasodilator bradykinin (100 to 1000 pmol/min). Platelet-monocyte binding (a sensitive measure of platelet activation) and plasma tissue plasminogen activator (tPA), plasminogen-activator inhibitor 1, and von Willebrand factor concentrations were measured at intervals throughout the study. SFLLRN caused dose-dependent venoconstriction ( P <0.001) that was unaffected by norepinephrine or tirofiban co-infusion. In forearm resistance vessels, SFLLRN increased forearm blood flow ( P <0.001), tPA release ( P <0.001), and platelet-monocyte binding ( P <0.0001) without affecting plasma plasminogen-activator inhibitor 1 or von Willebrand factor concentrations. SLIGKV caused venous ( P <0.001) and arterial ( P <0.01) dilatation without tPA release.

Conclusions— We have demonstrated that PAR-1 agonism causes platelet activation, venous constriction, arterial dilatation, and tPA release in vivo in humans. These unique and contrasting effects provide important insights into the physiological and pathophysiological role of thrombin in the human venous and arterial circulations.

Tissue plasminogen activator genetic polymorphisms do not influence tissue plasminogen activator release in patients with coronary heart disease

OBJECTIVES

To determine if polymorphisms of the tissue plasminogen activator (t-PA) gene influence acute endogenous t-PA release in patients with coronary heart disease (CHD).

METHODS

Forearm blood flow and plasma t-PA concentrations were measured in response to intra-brachial infusion of substance P and sodium nitroprusside in 96 patients with stable CHD. Genotyping was performed using a Taqman polymerase chain reaction assay specifically designed to detect the polymorphisms of interest: (i) Alu-repeat insertion/deletion sequence; (ii) C-->T substitution in an upstream enhancer region (-7351 C/T); (iii) T-->C in exon 6 (20 099 T/C); and (iv) T-->A (27 445 T/A) in intron 10.

RESULTS

Substance P and sodium nitroprusside caused dose-dependent increases in forearm blood flow in all patients (P < 0.001 for all) that were independent of the four genetic polymorphisms. Similarly, there were no differences in basal plasma t-PA antigen concentrations or net t-PA release between genotypes. Compared to non-smokers, smokers exhibited impaired substance P-induced vasodilatation (P < 0.001) and t-PA release (P = 0.05).

CONCLUSIONS

Despite confirming our previous findings in cigarette smokers, we have found no effect of polymorphisms of the t-PA gene on two complementary aspects of endothelial function. We conclude that genetic variation of the t-PA locus is unlikely to have a major influence on acute t-PA release in subjects with established CHD.

Vascular and fibrinolytic effects of intra-arterial tumour necrosis factor-alpha in patients with coronary heart disease

Elevated plasma t-PA (tissue plasminogen activator) and serum CRP (C-reactive protein) concentrations are associated with an adverse cardiovascular risk. In the present study, we investigated whether acute local inflammation causes vascular dysfunction and influences t-PA release in patients with stable coronary heart disease. Serum CRP, plasma t-PA and PAI-1 (plasminogen activator inhibitor type 1) concentrations were determined in 95 patients with stable coronary heart disease. A representative subpopulation of 12 male patients received an intra-brachial infusion of TNF-alpha (tumour necrosis factor-alpha) and saline placebo using a randomized double-blind cross-over study design. Forearm blood flow and plasma fibrinolytic and inflammatory variables were measured. Serum CRP concentrations correlated with plasma t-PA concentrations (r=0.37, P<0.001) and t-PA/PAI-1 ratio (r=-0.21, P<0.05). Intra-arterial TNF-alpha caused a rise in t-PA concentrations (P<0.001) without affecting blood flow or PAI-1 concentrations. TNF-alpha pretreatment impaired acetylcholine- and sodium nitroprusside-induced vasodilatation (P<0.001 for both) whilst doubling bradykinin-induced t-PA release (P=0.006). In patients with stable coronary heart disease, plasma fibrinolytic factors correlate with a systemic inflammatory marker and local vascular inflammation directly impairs vasomotor function whilst enhancing endothelial t-PA release. We suggest that the adverse prognosis associated with elevated plasma t-PA concentrations relates to the underlying causative association with vascular inflammation and injury.

Clinical perspectives of emerging pathogens in bleeding disorders

As a result of immunological and nucleic-acid screening of plasma donations for transfusion-transmissible viruses, and the incorporation of viral reduction processes during plasma fractionation, coagulation-factor concentrates (CFC) are now judged safe in terms of many known infectious agents, including hepatitis B and C viruses, HIV, and human T-cell lymphotropic virus. However, emerging pathogens could pose future threats, particularly those with blood-borne stages that are resistant to viral-inactivation steps in the manufacturing process, such as non-lipid-coated viruses. As outlined in this Review, better understanding of infectious diseases allows challenges from newly described agents of potential concern in the future to be anticipated, but the processes of zoonotic transmission and genetic selection or modification ensure that plasma-derived products will continue to be subject to infectious concerns. Manufacturers of plasma-derived CFC have addressed the issue of emerging infectious agents by developing recombinant products that limit the need for human plasma during production. Such recombinant products have extended the safety profile of their predecessors by ensuring that all reagents used for cell culture, purification steps, and stabilisation and storage buffers are completely independent of human plasma.

Managing the risk of transmission of variant Creutzfeldt Jakob disease by blood products

Whereas plasma-derived clotting factor concentrates now have a very good safety record for not being infectious for lipid enveloped viruses, concern has arisen about the possibility that prion diseases might be transmitted by blood products. There is epidemiological evidence that classical sporadic Creutzfeld Jakob disease (CJD) is not transmitted by blood transfusion. There is now good evidence that the abnormal prion associated with variant CJD can be transmitted by transfusion of fresh blood components and infect recipients. To reduce the risk of the pathological prion in the UK infecting recipients of clotting factor concentrates, these are now only manufactured from imported plasma collected from countries where there has not been bovine spongiform encephalopathy (BSE) in cattle and the risk of variant CJD in the population is, therefore, considered negligible. The safety of these concentrates is also enhanced because prion protein is, to an appreciable extent, excluded by the manufacturing process from the final product. To help reduce the chance of prion transmission by fresh blood products, donations are leucodepleted, there is increasing use of imported fresh frozen plasma (especially for treating children) and potential donors, who have been recipients of blood since 1980 (the beginning of the BSE epidemic in cattle) are deferred.

Management of acquired von Willebrand's sryndrome in a patient requiring major surgery

We present the case of a patient with acquired von Willebrand's syndrome and a monoclonal gammopathy of undetermined significance who required cystectomy for relapsed transitional cell carcinoma (TCC) of the bladder. We demonstrated that infused von Willebrand factor (VWF) containing factor VIII concentrates had an unacceptably short half-life, but that this was significantly prolonged following combined therapy with plasma exchange and intravenous immunoglobulin (IVIgG). This approach was successfully utilized peri-operatively, with the total surgical blood loss less than would be expected even for a haemostatically normal patient. Trough VWF antigen and Ristocetin co-factor activity levels fell on the second postoperative day and we therefore administered further IVIgG. Levels again fell on the fifth postoperative day with the development of a Staphylococcus aureus septicaemia. At this point bleeding occurred from a surgical drain site requiring 'factor VIII inhibitor bypass activity' to secure haemostasis while further plasma exchange and IVIgG were administered. Now 5 years later, there is no evidence of recurrence of the TCC or progression of the monoclonal gammopathy.

Addressing current challenges in haemophilia care: consensus recommendations of a European Interdisciplinary Working Group

Current challenges facing haemophilia care were identified and reviewed by an interdisciplinary group of experts in haemostasis and thrombosis, infectious disease, epidemiology, pharmacoeconomics and public health who met in February 2005 in Brussels. The outcome of this meeting was a series of consensus recommendations proposed to address the following three challenges: (i) developing the next generation of haemophilia specialists; (ii) reducing the risk that emerging pathogens present to safe haemophilia care and (iii) providing haemophilia care in an environment of cost constraint. It is intended that these consensus recommendations will form the basis of a concerted effort by leading haemophilia clinicians to secure future resources for the development and improvement of haemophilia care throughout Europe.

Plasma TAFI and soluble CD40 ligand do not predict reperfusion following thrombolysis for acute myocardial infarction

INTRODUCTION

Thrombolytic therapy fails to achieve reperfusion in almost a third of patients with acute myocardial infarction. Thrombin activatable fibrinolysis inhibitor (TAFI) and soluble CD40 ligand (sCD40L) are novel endogenous fibrinolytic and atherothrombotic factors that determine clot stability. We investigated whether admission plasma thrombin activatable fibrinolysis inhibitor (TAFI) and soluble CD40 ligand (sCD40L) concentrations predicted reperfusion following thrombolytic therapy in patients with acute myocardial infarction.

MATERIALS AND METHODS

Prior to administration of thrombolytic therapy, venous blood was collected from 110 patients presenting with acute ST segment elevation myocardial infarction and plasma assayed for tissue plasminogen activator (t-PA) antigen and activity, plasminogen activator inhibitor type-1 antigen (PAI-1), TAFI antigen and activity, C-reactive protein (CRP) and sCD40L concentrations. Reperfusion was determined using continuous ST segment monitoring.

RESULTS

Reperfusion occurred in 77 (70%) patients with a mean treatment to reperfusion time of 83 +/- 46 min. Peak creatine kinase was significantly lower in patients who reperfused (1578 +/- 1199 versus 2200 +/- 1744 U/L; P < 0.05) and correlated with time to reperfusion (r = 0.44 [95% CI: 0.23 - 0.61], P = 0.0001). There was a modest correlation between plasma TAFI antigen and activity (r = 0.3 [95% CI: 0.04 - 0.53]; P < 0.05). There were no significant associations between coronary reperfusion and plasma concentrations of t-PA, PAI-1, TAFI, CRP or sCD40L.

CONCLUSIONS

Systemic plasma TAFI, sCD40L and CRP concentrations do not predict reperfusion in patients receiving thrombolytic therapy for acute ST elevation myocardial infarction.

Phosphodiesterase type 5 inhibition does not reverse endothelial dysfunction in patients with coronary heart disease

OBJECTIVES

To investigate whether sildenafil citrate, a selective phosphodiesterase type 5 inhibitor, may improve endothelial vasomotor and fibrinolytic function in patients with coronary heart disease.

DESIGN

Randomised double blind placebo controlled crossover study.

PATIENTS AND METHODS

16 male patients with coronary heart disease and eight matched healthy men received intravenous sildenafil or placebo. Bilateral forearm blood flow and fibrinolytic parameters were measured by venous occlusion plethysmography and blood sampling in response to intrabrachial infusions of acetylcholine, substance P, sodium nitroprusside, and verapamil.

MAIN OUTCOME MEASURES

Forearm blood flow and acute release of tissue plasminogen activator.

RESULTS

Mean arterial blood pressure fell during sildenafil infusion from a mean (SEM) of 92 (1) to 82 (1) mm Hg in patients and from 94 (1) to 82 (1) mm Hg in controls (p < 0.001 for both). Sildenafil increased endothelium independent vasodilatation with sodium nitroprusside (p < 0.05) but did not alter the blood flow response to acetylcholine or verapamil in patients or controls. Substance P caused a dose dependent increase in plasma tissue plasminogen activator antigen concentrations (p < 0.01) that was unaffected by sildenafil in either group.

CONCLUSIONS

Sildenafil does not improve peripheral endothelium dependent vasomotor or fibrinolytic function in patients with coronary heart disease. Phosphodiesterase type 5 inhibitors are unlikely to reverse the generalised vascular dysfunction seen in patients with coronary heart disease.

B1 Kinin Receptor Does Not Contribute to Vascular Tone or Tissue Plasminogen Activator Release in the Peripheral Circulation of Patients With Heart Failure

Objective— Vascular expression of the B 1 kinin receptor is markedly upregulated with left ventricular dysfunction and angiotensin-converting enzyme (ACE) inhibition, but its function remains unclear. Inhibitors of ACE potentiate bradykinin-mediated B 2 receptor-dependent vasodilatation and tissue plasminogen activator (tissue-type plasminogen activator [t-PA]) release. We investigated the contribution of the B 1 receptor to the maintenance of vascular tone and t-PA release in patients with heart failure.

Methods and Results— Eleven patients were treated with enalapril (10 mg twice daily) or losartan (50 mg twice daily) in a randomized double-blind crossover trial. During week 6 of each treatment, patients received an intrabrachial infusion of Lys-des-Arg 9 -bradykinin (B 1 agonist; 1 to 10 nmol/min), bradykinin (30 to 300 pmol/min), Lys-[Leu 8 ]-des-Arg 9 -bradykinin (B 1 antagonist; 1 to 10 nmol/min), and norepinephrine (60 to 540 pmol/min). Blood flow and t-PA release were measured using venous occlusion plethysmography and blood sampling. Bradykinin ( P <0.001 for all), but not Lys-des-Arg 9 -bradykinin, caused vasodilatation and t-PA antigen and activity release. Norepinephrine ( P <0.001), but not Lys-[Leu 8 ]-des-Arg 9 -bradykinin, caused vasoconstriction. Compared with losartan, enalapril augmented bradykinin-mediated vasodilatation ( P <0.05) and t-PA release ( P <0.01 for all) but had no effect on B 1 receptor-mediated responses.

Conclusions— The B 1 kinin receptor does not have a major vasomotor or fibrinolytic role in patients with heart failure. Augmentation of kinin-mediated vasodilatation and t-PA release by ACE inhibition is restricted to the B 2 receptor.

The procoagulant potential of environmental particles (PM10)

BACKGROUND AND AIMS

Epidemiology studies have shown that cardiovascular (CV) disease is primarily responsible for the mortality associated with increased pulmonary environmental particle (PM10) exposure. The mechanisms involved in PM10 mediated CV effects are unknown although changes in plasma viscosity and in the homoeostasis of blood coagulation have been implicated. It was hypothesised that PM10 exposure would result in an inflammatory response and enhance the activation of the extrinsic coagulation mechanisms in pulmonary and vascular cells in culture.

METHODS

Primary human monocyte derived macrophages and human umbilical cord vein endothelial, human alveolar type II epithelial (A549), and human bronchial epithelial (16HBE) cells were tested for their inflammatory and procoagulant response to PM10 exposure. IL-8, tissue factor (TF), and tissue plasminogen activator (tPA) gene expression and protein release, and coagulation enhancing ability of culture media were determined 6 and 24 hours following exposure.

RESULTS

The culture media from macrophages and 16HBE bronchial epithelial cells, but not A549 cells, exposed to PM10 had an enhanced ability to cause clotting. Furthermore, H2O2 also increased the clotting activity. Apoptosis was significantly increased in macrophages exposed to PM10 and LPS as shown by annexin V binding. TF gene expression was enhanced in macrophages exposed to PM10, and HUVEC tissue factor and tPA gene and protein expression were inhibited.

CONCLUSIONS

These data indicate that PM10 has the ability to alter macrophage, epithelial, and endothelial cell function to favour blood coagulation via activation of the extrinsic pathway and inhibition of fibrinolysis pathways.

A framework for genetic service provision for haemophilia and other inherited bleeding disorders

This framework document offers guidance to patients, doctors, nurses, laboratory scientists, funders and hospitals on the provision of clinical and laboratory genetic services for haemophilia. With recent advances in molecular laboratory techniques it is now possible to give the vast majority of individual patients and family members very reliable genetic information. To enable these genetic data to be used for both the optimal treatment of patients with inherited bleeding disorders and for appropriate reproductive decisions in carriers, there needs to be a clear and robust framework for systematically acquiring the necessary clinical, personal, family and laboratory information upon which decisions can be made. This document provides guidance on the range and standards of clinical and laboratory genetic services which should be offered to patients and their families. Included are arrangements for genetic counselling and testing (including consent and confidentially issues), management of early pregnancy, standards for laboratory genetic services, as well as advice on data storage, security and retrieval.

Endothelial dysfunction in patients with recent myocardial infarction and hyperhomocysteinaemia: effects of vitamin supplementation

Hyperhomocysteinaemia is a prothrombotic condition that may cause oxidative endothelial injury and impair endogenous fibrinolysis. Vitamin supplementation enhances endothelial function in hyperhomocysteinaemic patients, but responses in patients with co-existing coronary artery disease have been variable. It is also unknown whether hyperhomocysteinaemia is associated with reduced fibrinolytic responses in patients with coronary artery disease. The study aims were to test the hypothesis that patients with recent myocardial infarction and hyperhomocysteinaemia have impaired endothelium-dependent vasomotion and fibrinolysis that is rectified by vitamin supplementation. From a cohort of 120 patients admitted with acute myocardial infarction, 18 patients were recruited from the upper (n=9) and lower (n=9) plasma homocysteine quartiles into a randomized double-blind placebo-controlled crossover trial. Following a 4-week course of placebo or folate/cyanocobalamin/pyridoxine supplements, FBF (forearm blood flow) was measured using venous occlusion plethysmography during intra-arterial substance P (4–16 pmol/min), acetylcholine (5–20 μg/min) and sodium nitroprusside (2–8 μg/min) infusions. All vasodilators caused dose-dependent increases in infused FBF (P<0.05). Patients in the upper homocysteine quartile (16.8±2.9 compared with 7.9±0.7 μmol/l; P=0.003) had reduced vasodilatation to acetylcholine (P=0.01) and substance P (P<0.05), but not sodium nitroprusside. There were no differences in substance P-induced tissue plasminogen activator release. Vitamin supplementation increased serum folate and vitamin B12 concentrations (P<0.05), but did not significantly lower homocysteine, or affect FBF or fibrinolytic responses. In patients with recent myocardial infarction, hyperhomocysteinaemia is associated with impaired endothelium-dependent vasodilatation, but no alteration in the acute fibrinolytic capacity. This endothelial vasomotor dysfunction is unaltered by vitamin supplementation.

Neutral Endopeptidase Inhibition Augments Vascular Actions of Bradykinin in Patients Treated With Angiotensin-Converting Enzyme Inhibition

Angiotensin-converting enzyme and neutral endopeptidase (EC 3.4.24.11; neprilysin) are metallopeptidases present on the endothelium that metabolize bradykinin. Inhibitors of angiotensin-converting enzyme potentiate bradykinin-mediated vasodilatation and endothelial tissue plasminogen activator release. Combined angiotensin-converting enzyme and neutral endopeptidase inhibition may have additional beneficial cardiovascular effects mediated through bradykinin potentiation. We investigated the effects of local neutral endopeptidase inhibition on the vascular actions of bradykinin in heart failure patients maintained on chronic angiotensin-converting enzyme inhibition. Ten patients received intrabrachial infusion of thiorphan (30 nmol/min), a neutral endopeptidase inhibitor, in a randomized double-blind placebo-controlled crossover trial. Thiorphan was coinfused with Lys-des-Arg9-bradykinin (1 to 10 nmol/min), bradykinin (30 to 300 pmol/min), atrial natriuretic peptide (10 to 100 pmol/min), and sodium nitroprusside (2 to 8 mug/min). Bradykinin, atrial natriuretic peptide, and sodium nitroprusside caused dose-dependent vasodilatation (peak blood flow 14.4+/-2.2, 3.6+/-0.6, and 8.6+/-1.3 mL per 100 mL/min, respectively; P<0.0001). Bradykinin caused dose-dependent increases in tissue plasminogen activator antigen and activity (peak concentration 31.8+/-3.4 ng/mL and 21.9+/-7.6 IU/mL, respectively; P<0.001) and estimated antigen and activity release (peak release 152+/-46 ng per 100 mL/min and 154+/-22 IU/100 mL/min, respectively; P<0.005). Compared with placebo, thiorphan augmented bradykinin-mediated vasodilatation (1.4-fold; P<0.0001) and net tissue plasminogen activator release (1.5-fold; P<0.005). Neutral endopeptidase contributes to bradykinin metabolism in heart failure patients maintained on angiotensin-converting enzyme inhibitor therapy. Our findings may explain some of the clinical effects of combined angiotensin-converting enzyme and neutral endopeptidase inhibition, including the greater vasodepressor effect observed with combined therapy when compared with angiotensin-converting enzyme inhibition alone.

Coagulopathy and Hyperfibrinolysis in Ruptured Abdominal Aortic Aneurysm Repair

Perioperative hemorrhage is one of the principal causes of death in patients with ruptured abdominal aortic aneurysm (AAA). This study examines perioperative coagulation and fibrinolysis in patients undergoing ruptured AAA repair complicated by coagulopathy. Eight patients (8 men of median age 74, range 69-87, years) who developed clinical and laboratory evidence of coagulopathy during attempted repair of ruptured infrarenal AAA were prospectively studied. Platelet count, fibrinogen, clotting times, prothrombin fragment (PF) 1+2, and tissue plasminogen activator (t-PA) and plasminogen activator inhibitor (PAI) activities were measured preoperatively, immediately before, and 5 min and 24 hr after aortic declamping. Six patients died, three intraoperatively, one within 24 hr, and two in the late postoperative period. All patients had thrombocytopenia and prolonged clotting times intraoperatively with evidence of increased thrombin generation (as demonstrated by elevated PF 1+2). Five patients had increased systemic fibrinolysis (as demonstrated by elevated t-PA activity) preoperatively and/or before aortic declamping and all of these patients died. Three patients had perioperative inhibition of systemic fibrinolysis (as demonstrated by elevated PAI activity) and two survived. These data demonstrate that coagulopathy in ruptured AAA repair may be associated with a hyperfibrinolytic state. Further research is required to determine if (a) a causal relationship exists between hyperfibrinolysis and coagulopathy and (b) whether antifibrinolytic agents can improve outcome if targeted at this group of patients.

Effects of a brief course of azithromycin on soluble cell adhesion molecules and markers of inflammation in survivors of an acute coronary syndrome: A double-blind, randomized, placebo-controlled study

BACKGROUND

The anti-chlamydial antibiotic, azithromycin, may improve outcome in patients who survive an acute coronary syndrome. The mechanisms are, however, poorly understood. The aims of this study were to define any relationship between Chlamydia pneumoniae seropositivity and levels of specific markers of endothelial activation (soluble cell adhesion molecules) and more general markers of inflammation (C-reactive protein [CRP] and interleukin-6 [IL-6]) and to assess whether azithromycin had any effect on such markers.

METHODS

Patients who survived an acute coronary syndrome were randomized to receive treatment with azithromycin (n = 72) or placebo (n = 69) for 5 days. Before therapy, C pneumoniae IgA and IgG titers were checked, with serum levels of soluble intercellular adhesion molecule-1 (sICAM-1), soluble vascular cell adhesion molecule-1, soluble E-selectin (sE-selectin), soluble P-selectin, high-sensitivity CRP, and IL-6. They were rechecked 3 months later.

RESULTS

There were no significant correlations between C pneumoniae titers and levels of CRP, IL-6, or soluble cell adhesion molecules. However, azithromycin treatment significantly reduced mean sICAM-1 levels (P =.006). This effect was more marked in patients with elevated titers of C pneumoniae IgA and IgG. Soluble E-selectin levels were also reduced in patients who were seropositive, but no effects were seen on other endothelial or inflammatory markers.

CONCLUSIONS

After an acute coronary syndrome, a 5-day course of azithromycin reduces levels of sICAM-1, a marker of endothelial cell activation. Although these data suggest a potentially beneficial role for azithromycin, they should be interpreted with caution.

von Willebrand Factor and Platelet Count in Ruptured Abdominal Aortic Aneurysm Repair

OBJECTIVE

von Willebrand factor (vWF) is essential for the formation of platelet aggregates at sites of vascular endothelial cell (EC) injury. Peri-operative thrombocytopenia is associated with poor outcome in ruptured abdominal aortic aneurysm (AAA) repair. This prospective study examines the relationship between vWF and platelet count (PC) in ruptured AAA repair.

METHODS

plasma vWF antigen, PC and C-reactive protein (CRP) were measured pre-operatively, and immediately before and 5 min after aortic clamp release, and on post-operative days 1 and 2 in 20 patients (18 men and 2 women of median age 74, range 63-86, years) with ruptured AAA.

RESULTS

elevated vWF was present in 13 (65%) patients pre-operatively, and 14 of 16 (88%) survivors at 24 h post-operatively. All patients demonstrated an intra-operative fall in vWF. There was no significant difference in vWF levels between survivors and non-survivors. PC was below the normal range in 8 (40%) patients pre-operatively and all patients at 24 h. Eighteen (90%) patients demonstrated an intro-operative fall in PC. PC was significantly lower in non-survivors pre-operatively (p=0.007), immediately before (p=0.009) and 5 min (p=0.009) and 24 h (p=0.02) after clamp release. There was a significant positive correlation between vWF and PC pre-operatively (r= +0.48, p=0.033), and immediately before (r= +0.47, p=0.044) and 5 min after clamp release (r= +0.5, p=0.043). There was a significant positive correlation between peak vWF level and the greatest fall in PC (r= +0.65, p=0.006). There was a significant negative correlation between vWF and CRP and operative blood loss; and between PC and CRP, operative blood loss and aortic clamp time.

CONCLUSIONS

these data demonstrate that EC activation, the acute phase protein response, operative blood loss and aortic clamp time all contribute to the peri-operative fall in PC in patients with ruptured AAA. The peri-operative fall in circulating levels of vWF and PC may represent consumption secondary to macro- and microvascular thrombus formation. The resultant procoagulant state may partly explain the association between low PC and poor outcome in ruptured AAA.

Bradykinin receptor antagonism and endothelial tissue plasminogen activator release in humans

OBJECTIVE

We sought to assess pharmacodynamic responses to the bradykinin antagonist B9340 and to determine the contribution of the endothelial bradykinin receptor to stimulated tissue plasminogen activator (t-PA) release in humans.

METHODS AND RESULTS

Bilateral forearm blood flow and plasma fibrinolytic variables were measured in 8 volunteers during 100 minutes of intrabrachial infusions of saline placebo, B9340 at 4.5 nmol/min, or B9340 at 13.5 nmol/min. On each occasion, intra-arterial bradykinin (30 to 3000 pmol/min) and substance P (4 to 16 pmol/min) were coinfused for 10 minutes at each dose. To assess the onset and offset of action, 6 additional subjects on 2 occasions received intra-arterial bradykinin (100 pmol/min) for 60 minutes with a coinfusion of either saline placebo or B9340 (13.5 nmol/min) for 12 minutes. During placebo infusion, bradykinin and substance P caused dose-dependent vasodilatation in the infused forearm (P<0.001). B9340 caused a dose-dependent inhibition of bradykinin-induced forearm vasodilatation and t-PA release (P<0.001) without affecting substance P-induced vasodilatation or t-PA release (P=NS). B9340 caused a reversible inhibition of bradykinin-induced vasodilatation (P<0.001) with a rapid onset and offset of action.

CONCLUSIONS

B9340 is a potent, reversible, and selective competitive receptor antagonist of bradykinin-induced vasodilatation and t-PA release in humans.

The evidence behind inhibitor treatment with recombinant factor VIIa

Over the past 10 years considerable use has been made of recombinant factor VIIa (rFVIIa) for the treatment of patients with inhibitors to coagulation factors. During this time, its place in the management of acute bleeds and surgery has become better defined. Although pharmacokinetic studies report the half-life of rFVIIa as 2.7 h, there is considerable intersubject variability. Moreover, rFVIIa is cleared more rapidly in children than in adults. Assays for the measurement of rFVIIa plasma levels are not readily available in clinical diagnostic laboratories, although there is evidence that plasma FVII:C levels, measured by a one-stage prothombin-based assay, reflect the plasma concentration of rFVIIa:C. The level of FVII:C required to achieve haemostasis in different clinical circumstances remains uncertain. In order to overcome the logistic difficulties of repeated frequent bolus injections, and potentially to minimise usage, administration of rFVIIa by continuous infusion has been reported. However, there is some uncertainty as to whether continuous infusion of rFVIIa has similar therapeutic efficacy to an equivalent total dose administered by bolus injections. The extensive clinical experience with rFVIIa in haemophilic patients with inhibitors has been recorded in descriptive accounts of the Compassionate Use Programme and the Emergency Use Study. On the basis of the apparent clinical efficacy and safety reported in these studies, prospective randomised trials of different dose regimens have been undertaken for the treatment of acute bleeds and surgery. These have helped to define the minimum dose needed to achieve haemostasis. There remains considerable uncertainty about the minimal effective dose and appropriate duration of therapy in different clinical circumstances. There is therefore a need for the development of evidence-based guidelines for the use of rFVIIa in bolus and continuous infusion regimens in different settings, and for the therapeutic value of measuring plasma concentrations of rFVIIa, to facilitate the optimal use of this product. Furthermore, additional randomised clinical trials will help ensure that rFVIIa is used in the most clinically and cost effective way.

Intra-arterial tumor necrosis factor-alpha impairs endothelium-dependent vasodilatation and stimulates local tissue plasminogen activator release in humans

OBJECTIVE

Inflammation contributes to the pathogenesis of cardiovascular disease, potentially through the actions of proinflammatory cytokines. We assessed the direct effects of local intra-arterial tumor necrosis factor-alpha (TNF-alpha), interleukin-6, and endotoxin on blood flow and endogenous tissue plasminogen activator (t-PA) release in vivo in humans.

METHODS AND RESULTS

In a double-blind, randomized, placebo-controlled trial, blood flow, plasma cytokine, and fibrinolytic parameters were measured using venous occlusion plethysmography and blood sampling. Ten subjects received intrabrachial TNF-alpha, interleukin-6, and endotoxin infusions, and 8 additional subjects received intrabrachial infusions of bradykinin, acetylcholine, and sodium nitroprusside after pretreatment with TNF-alpha. TNF-alpha but not interleukin-6, endotoxin, or placebo caused a gradual and sustained approximately 20-fold increase in plasma t-PA concentrations (P<0.001) that was associated with elevated plasma interleukin-6 concentrations (P<0.05) but without an effect on blood flow or plasminogen activator inhibitor type 1 antigen. Compared with placebo, TNF-alpha pretreatment impaired bradykinin- and acetylcholine-induced vasodilatation (P<0.03) and resulted in a doubling of bradykinin-induced t-PA release (P<0.05).

CONCLUSIONS

Intra-arterial TNF-alpha causes an acute local vascular inflammation that is associated with impaired endothelium-dependent vasomotion as well as a sustained and substantial increase in endothelial t-PA release. TNF-alpha has potentially both adverse vasomotor and beneficial profibrinolytic effects on endothelial function.

Effects of acute liver injury on blood coagulation

The mechanisms leading to the hemostatic changes of acute liver injury are poorly understood. To study these further we have assessed coagulation and immune changes in patients with acute paracetamol overdose and compared the results to patients with chronic cirrhosis and normal healthy controls. The results demonstrate that in paracetamol overdose coagulation factors (F)II, V, VII and X were reduced to a similar degree and were significantly lower than FIX and FXI (mean levels 0.28, 0.16, 0.13, 0.19, 0.51 and 0.72 IU mL(-1), respectively). In cirrhosis, by contrast, FII, FV, FVII, FIX and FX were equally reduced whilst FXI was lower than the other factors (mean levels 0.64, 0.69, 0.62, 0.60, 0.66 and 0.40 IU mL-1, respectively). FVIII was raised in paracetamol overdose patients but normal in those with cirrhosis (mean levels 1.95 and 1.01 IU mL(-1), respectively). Interleukin-6 and tumor necrosis factor-alpha levels were raised in both patient groups, but higher levels were found in paracetamol overdose, compared to cirrhosis. Thrombin-antithrombin and soluble tissue factor levels were higher in those with acute liver injury but normal in cirrhosis. Antithrombin levels were reduced in both acute liver injury and cirrhosis. From these data we put forward a novel mechanism for the coagulation changes in acute paracetamol induced liver injury. We propose that immune activation leads to tissue factor-initiated consumption of FII, FV, FVII and FX, but that levels of FIX and FXI are better preserved because antithrombin inhibits the thrombin induced positive feedback loop that activates these latter factors.