Antithrombin levels are associated with the risk of first and recurrent arterial thromboembolism at a young age.

BACKGROUND AND AIMS: It is as yet unknown whether antithrombin levels are associated with arterial thromboembolism (ATE) at a young age. To investigate the association between antithrombin levels and premature and recurrent ATE, we performed a case-control study and a subsequent nested cohort study of premature coronary heart disease (CHD) patients. METHODS: In the case-control study, we included 571 patients who had a recent premature ATE, including CHD and ischemic stroke (IS), and 461 healthy controls. The association between antithrombin levels (dichotomized: ≤median vs. >median) and ATE was investigated. Subsequently we studied the association between antithrombin levels and recurrent cardiac events, ATE or death in a nested cohort of 323 CHD patients. RESULTS: Low antithrombin levels (≤median, 1.04 IU/mL) are associated with an increased risk of ATE (OR 1.46; 95% CI:1.09-1.96), after adjustment for classical cardiovascular risk factors. This was observed in the subgroups of CHD patients (1.43; 1.01-2.02) and IS patients (1.48; 1.01-2.19). CHD patients with low antithrombin levels had a higher risk of recurrent cardiac events (HR 2.16, 95% CI:1.07-4.38). Especially in women with low antithrombin levels, the risk of recurrent cardiac events was high (HR 5.97, 95% CI 1.31-27.13) as was the risk of recurrent ATE or death (HR 4.22, 95% CI 1.19-15.00). CONCLUSIONS: Individuals with relatively low antithrombin levels have an increased risk for ATE at a younger age. CHD patients with low antithrombin levels, especially women, have a higher risk of recurrent cardiac events.

The effect of bioresorbable vascular scaffold implantation on distal coronary endothelial function in dyslipidemic swine with and without diabetes.

BACKGROUND: We studied the effect of bioresorbable vascular scaffold (BVS) implantation on distal coronary endothelial function, in swine on a high fat diet without (HFD) or with diabetes (DM+HFD). METHODS: Five DM+HFD and five HFD swine underwent BVS implantation on top of coronary plaques, and were studied six months later. Conduit artery segments >5mm proximal and distal to the scaffold and corresponding segments of non-scaffolded coronary arteries, and segments of small arteries within the flow-territory of scaffolded and non-scaffolded arteries were harvested for in vitro vasoreactivity studies. RESULTS: Conduit segments proximal and distal of the BVS edges showed reduced endothelium-dependent vasodilation as compared to control vessels (p≤0.01), with distal segments being most prominently affected(p≤0.01). Endothelial dysfunction was only observed in DM±HFD swine and was principally due to a loss of NO. Endothelium-independent vasodilation and vasoconstriction were unaffected. Surprisingly, segments from the microcirculation distal to the BVS showed enhanced endothelium-dependent vasodilation (p<0.01), whereas endothelium-independent vasodilation and vasoconstriction were unaltered. This enhanced vasorelaxation was only observed in DM+HFD swine, and did not appear to be either NO- or EDHF-mediated. CONCLUSIONS: Six months of BVS implantation in DM+HFD swine causes NO-mediated endothelial dysfunction in nearby coronary segments, which is accompanied by a, possibly compensatory, increase in endothelial function of the distal microcirculation. Endothelial dysfunction extending into coronary conduit segments beyond the implantation-site, is in agreement with recent reports expressing concern for late scaffold thrombosis and of early BVS failure in diabetic patients.

Genome-wide association studies identify genetic loci for low von Willebrand factor levels.

Low von Willebrand factor (VWF) levels are associated with bleeding symptoms and are a diagnostic criterion for von Willebrand disease, the most common inherited bleeding disorder. To date, it is unclear which genetic loci are associated with reduced VWF levels. Therefore, we conducted a meta-analysis of genome-wide association studies to identify genetic loci associated with low VWF levels. For this meta-analysis, we included 31 149 participants of European ancestry from 11 community-based studies. From all participants, VWF antigen (VWF:Ag) measurements and genome-wide single-nucleotide polymorphism (SNP) scans were available. Each study conducted analyses using logistic regression of SNPs on dichotomized VWF:Ag measures (lowest 5% for blood group O and non-O) with an additive genetic model adjusted for age and sex. An inverse-variance weighted meta-analysis was performed for VWF:Ag levels. A total of 97 SNPs exceeded the genome-wide significance threshold of 5 × 10(-8) and comprised five loci on four different chromosomes: 6q24 (smallest P-value 5.8 × 10(-10)), 9q34 (2.4 × 10(-64)), 12p13 (5.3 × 10(-22)), 12q23 (1.2 × 10(-8)) and 13q13 (2.6 × 10(-8)). All loci were within or close to genes, including STXBP5 (Syntaxin Binding Protein 5) (6q24), STAB5 (stabilin-5) (12q23), ABO (9q34), VWF (12p13) and UFM1 (ubiquitin-fold modifier 1) (13q13). Of these, UFM1 has not been previously associated with VWF:Ag levels. Four genes that were previously associated with VWF levels (VWF, ABO, STXBP5 and STAB2) were also associated with low VWF levels, and, in addition, we identified a new gene, UFM1, that is associated with low VWF levels. These findings point to novel mechanisms for the occurrence of low VWF levels.

Performance related factors are the main determinants of the von Willebrand factor response to exhaustive physical exercise.

BACKGROUND: Physical stress triggers the endothelium to release von Willebrand Factor (VWF) from the Weibel Palade bodies. Since VWF is a risk factor for arterial thrombosis, it is of great interest to discover determinants of VWF response to physical stress. We aimed to determine the main mediators of the VWF increase by exhaustive physical exercise. METHODS: 105 healthy individuals (18-35 years) were included in this study. Each participant performed an incremental exhaustive exercise test on a cycle ergometer. Respiratory gas exchange measurements were obtained while cardiac function was continuously monitored. Blood was collected at baseline and directly after exhaustion. VWF antigen (VWF:Ag) levels, VWF collagen binding (VWF:CB) levels, ADAMTS13 activity and common variations in Syntaxin Binding Protein-5 (STXBP5, rs1039084 and rs9399599), Syntaxin-2 (STX2, rs7978987) and VWF (promoter, rs7965413) were determined. RESULTS: The median VWF:Ag level at baseline was 0.94 IU/mL [IQR 0.8-1.1] and increased with 47% [IQR 25-73] after exhaustive exercise to a median maximum VWF:Ag of 1.38 IU/mL [IQR 1.1-1.8] (p<0.0001). VWF:CB levels and ADAMTS13 activity both also increased after exhaustive exercise (median increase 43% and 12%, both p<0.0001). The strongest determinants of the VWF:Ag level increase are performance related (p<0.0001). We observed a gender difference in VWF:Ag response to exercise (females 1.2 IU/mL; males 1.7 IU/mL, p = 0.001), which was associated by a difference in performance. Genetic variations in STXBP5, STX2 and the VWF promoter were not associated with VWF:Ag levels at baseline nor with the VWF:Ag increase. CONCLUSIONS: VWF:Ag levels strongly increase upon exhaustive exercise and this increase is strongly determined by physical fitness level and the intensity of the exercise, while there is no clear effect of genetic variation in STXBP5, STX2 and the VWF promoter.

Relationship of Von Willebrand Factor with carotid artery and aortic arch calcification in ischemic stroke patients.

BACKGROUND: Large population studies have revealed that increased von Willebrand Factor (VWF) levels are associated with an increased risk of ischemic stroke. In previous studies VWF was associated with atherosclerosis in healthy individuals. However, it is yet unknown what the association is between atherosclerosis and VWF levels in patients with ischemic stroke. OBJECTIVES: The aim of our study was to determine the association of atherosclerosis, measured with recent developed techniques, and VWF levels in a large, well characterized, cohort of ischemic stroke patients and to determine the prognostic value. METHODS: We included 925 consecutive patients with transient ischemic attack (TIA) or ischemic stroke. Calcification volumes (mm(3)) were scored in the aortic arch and both carotid arteries using multidetector computed tomography (CT) angiography. VWF antigen (VWF:Ag) levels were measured using ELISA. RESULTS: Mean VWF:Ag levels were significantly higher in the presence of calcification in either the aortic arch (1.47 vs. 1.37 IU/ml [P = 0.039]) or the carotid arteries (1.49 vs. 1.34 IU/ml [P = 0.001]). Patients with a large artery atherosclerosis ischemic stroke had significantly higher VWF:Ag levels then the other TOAST subtypes (P < 0.0001). High VWF:Ag levels were associated with an unfavorable outcome (modified Rankin Scale >2 vs. ≤2; 1.64 vs. 1.41 IU/ml, [P < 0.0001]). CONCLUSION: Our study showed a strong association between the extent of atherosclerosis in both the aortic arch and the carotid arteries and VWF levels in patients with TIA or ischemic stroke. Higher VWF levels are found in large artery atherosclerosis and are associated with a poor outcome.

Effect of genetic variation in STXBP5 and STX2 on von Willebrand factor and bleeding phenotype in type 1 von Willebrand disease patients.

BACKGROUND: In type 1 von Willebrand Disease (VWD) patients, von Willebrand Factor (VWF) levels and bleeding symptoms are highly variable. Recently, the association between genetic variations in STXBP5 and STX2 with VWF levels has been discovered in the general population. We assessed the relationship between genetic variations in STXBP5 and STX2, VWF levels, and bleeding phenotype in type 1 VWD patients. METHODS: In 158 patients diagnosed with type 1 VWD according to the current ISTH guidelines, we genotyped three tagging-SNPs in STXBP5 and STX2 and analyzed their relationship with VWF:Ag levels and the severity of the bleeding phenotype, as assessed by the Tosetto bleeding score. RESULTS: In STX2, rs7978987 was significantly associated with VWF:Ag levels (bèta-coefficient (ß) = -0.04 IU/mL per allele, [95%CI -0.07;-0.001], p = 0.04) and VWF:CB activity (ß = -0.12 IU/mL per allele, [95%CI -0.17;-0.06], p<0.0001). For rs1039084 in STXBP5 a similar trend with VWF:Ag levels was observed: (ß = -0.03 IU/mL per allele [95% CI -0.06;0.003], p = 0.07). In women, homozygous carriers of the minor alleles of both SNPs in STXBP5 had a significantly higher bleeding score than homozygous carriers of the major alleles. (Rs1039084 p = 0.01 and rs9399599 p = 0.02). CONCLUSIONS: Genetic variation in STX2 is associated with VWF:Ag levels in patients diagnosed with type 1 VWD. In addition, genetic variation in STXBP5 is associated with bleeding phenotype in female VWD patients. Our findings may partly explain the variable VWF levels and bleeding phenotype in type 1 VWD patients.

Prognostic markers in young patients with premature coronary heart disease.

OBJECTIVES: To evaluate the survival and prognostic implications of cardiovascular, inflammatory and prothrombotic risk factors in young patients with premature coronary heart disease (CHD). METHODS: Follow-up data were obtained from 353 young patients with a first cardiac event (men ≤45 years and women ≤55 years). Baseline characteristics on traditional risk factors were collected at the time of the first event, and plasma levels of C-reactive protein (CRP), von Willebrand Factor (VWF), and fibrinogen were measured one to three months after the first event to exclude an acute phase response. We performed age and sex adjusted Cox regression analyses to assess the relationship between these factors and recurrent events with three different endpoints: all cause mortality, recurrent cardiac event (myocardial infarction or revascularisation procedure), and any recurrent event (cardiac event, cerebrovascular event or all cause mortality). RESULTS: During a total follow-up time of 1483 person years (mean 4.2 years), 11 patients died (3%), 42 patients had a recurrent cardiac event (12%), and 53 patients had any recurrent event (15%). CRP was associated with an increased risk of any recurrent event (HR 1.28[95% CI = 1.02-1.59] per unit increase in lnCRP). Also, both CRP (5.00[1.04-24.04]) and fibrinogen (5.04[1.05-24.23]) were associated with all cause mortality when levels were above the 50th percentile. CONCLUSIONS: Fifteen percent of young patients with a first cardiac event have a recurrent event or die within a median follow-up of 4.2 years. In these young patients we have shown that, independently of cardiovascular risk factors, high CRP levels contribute to the risk of recurrent events, including all cause mortality, and high fibrinogen levels are associated with all cause mortality.

The in vitro effect of the new antithrombotic drug candidate ALX-0081 on blood samples of patients undergoing percutaneous coronary intervention.

Compound ALX-0081 is a bivalent humanised Nanobody® that binds the A1-domain of von Willebrand factor (VWF) with high affinity. Consequently, it can block the interaction between VWF and its platelet-receptor-glycoprotein Ib, which leads inevitably to formation of arterial thrombi. It was the objective of this study to assess the in vitro effects of ALX-0081 on platelet adhesion and aggregation in coronary artery disease (CAD) patients to determine the optimal concentration of ALX-0081 and the effect of co-medication. We included nine CAD patients, who were scheduled for elective percutaneous coronary intervention (PCI), and 11 healthy volunteers. At admission all patients received aspirin, clopidogrel and heparin. Blood was drawn 24 hours (h) before and 1 h after start of the PCI procedure and was subsequently spiked with different concentrations of ALX-0081 or buffer. The efficacy of ALX-0081 was assessed by in vitro experiments: flow chamber experiments, ristocetin-induced platelet aggregation (RIPA), and the platelet function analyser (PFA-100™). VWF levels in CAD patients were significantly higher than in healthy controls. During PCI VWF levels did not rise. In all in vitro experiments, ALX-0081 led to complete inhibition of platelet adhesion and aggregation. However, the required effective concentration was higher in patients than in controls and was related to plasma VWF levels. In conclusion, ALX-0081 is able to completely inhibit in vitro platelet adhesion and aggregation in CAD patients scheduled for elective PCI. The efficacy of ALX-0081 is not influenced by PCI or co-medication. However, due to higher VWF levels in CAD patients a higher effective concentration of ALX-0081 was required than in healthy individuals.

Effect of genetic variations in syntaxin-binding protein-5 and syntaxin-2 on von Willebrand factor concentration and cardiovascular risk.

BACKGROUND: Elevated von Willebrand factor (VWF) plasma levels are associated with an increased risk of cardiovascular disease. A meta-analysis of genomewide association studies on VWF identified novel candidate genes, that is, syntaxin-binding protein 5 (STXBP5) and syntaxin 2 (STX2), which are possibly involved in the secretion of VWF. We investigated whether VWF antigen levels (VWF:Ag), VWF collagen-binding activity (VWF:CB) and the risk of arterial thrombosis are affected by common genetic variations in these genes. METHODS AND RESULTS: In 463 young white subjects (men ≤45 years of age and women ≤55 years of age), who were included 1 to 3 months after a first event of arterial thrombosis, and 406 control subjects, we measured VWF:Ag and VWF:CB. Nine haplotype tagging single-nucleotide polymorphisms of STXBP5 and STX2 were selected and subsequently analyzed using linear regression with additive genetic models adjusted for age, sex, and ABO blood group. The minor alleles of rs9399599 and rs1039084 in STXBP5 were associated with lower VWF plasma levels and activity, whereas the minor allele of rs7978987 in STX2 was associated with higher VWF plasma levels and activity. The minor alleles of the single-nucleotide polymorphisms in STX2 were associated with a reduced risk of arterial thrombosis (rs1236: odds ratio, 0.73 [95% confidence interval, 0.59, 0.89]; rs7978987: odds ratio, 0.81 [95% confidence interval, 0.65, 1.00]; rs11061158: odds ratio, 0.69 [95% confidence interval, 0.55, 0.88]). CONCLUSIONS: Genetic variability in STXBP5 and STX2 affects both VWF concentration and activity in young individuals with premature arterial thrombosis. Furthermore, in our study, genetic variability in STX2 is associated with the risk of arterial thrombosis. However, at this point, the underlying mechanism remains unclear.