A functional haplotype in the 5' flanking region of the factor VII gene is associated with an increased risk of coronary heart disease

Summary.  Aims : The aim of this study was to investigate associations between coronary heart disease risk and polymorphisms in the coagulation factor (F)VII gene in participants of a large prospective study. Methods : One thousand nine hundred and fifty-seven men were genotyped for four FVII polymorphisms, −670A→C, −402G→A, a 10 base pair insertion at −323 (0 > 10) in the promoter, and R353Q in the structural gene. Associations among genotypes and estimated haplotypes, plasma FVII levels, and coronary heart disease risk were evaluated, and the function of the promoter polymorphisms was assessed in reporter gene assays. Results : The −670A→C and −402G→A polymorphisms were in complete allelic association. The haplotype containing −670C and −402A (frequency =0.23) was associated with significantly increased plasma FVII coagulant activity and increased risk of an initial coronary event, particularly acute myocardial infarction, which remained after correction for conventional risk factors. In contrast, the −323 insertion and Q353 alleles (frequency =0.11 and 0.10, respectively) were associated with decreased plasma FVII levels, but hazard ratios for coronary events in carriers of these alleles were not significantly different from unity. In transiently transfected hepatoma cells, increased basal expression of the reporter gene was directed by a promoter fragment with rare haplotype −670C/−630G/−402A rather than by a promoter fragment with common haplotype −670A/−630A/−402G; −402A was not responsible for this effect. Conclusions : The promoter haplotype, −670C/−630G/402A, was associated with significantly increased plasma FVII coagulant activity, risk of an initial coronary event, particularly acute myocardial infarction, and reporter gene expression.     

Coagulation factor VII gene haplotypes, obesity-related traits, and cardiovascular risk in young women

BACKGROUND: Associations between common F7 haplotypes, plasma factor VII (FVII) levels, and cardiovascular risk have recently been reported in population studies involving predominantly European men. METHODS: We assessed associations between F7 haplotypes and cardiovascular risk in two US population-based studies: a case-control study of these alleles related to a decreased risk of arterial thrombotic outcomes such as myocardial infarction (MI) in young-to-middle-aged women (n = 671), and a cohort study of cardiovascular disease risk factors in young women (n = 1040). RESULTS: The high-expression F7 haplotype B (containing the promoter variant allele -402A) was associated with an increased FVII level among controls, but not with MI risk. Women carrying a> or =1 copy of the low FVII expression level haplotype C (containing the -401T/-323del/-122C and Gln353 alleles) had decreased FVII levels and decreased risk of MI (odds ratio 0.54, 95% CI 0.31-0.93) compared with women homozygous for the most common haplotype A. Haplotype C was also associated with a decreased body mass index (BMI) and an increased high-density lipoprotein (HDL) cholesterol level, but not with MI risk after adjustment for these metabolic risk factors. In a cohort study composed of young US women, individuals homozygous for haplotype C had a lower BMI and lower systolic blood pressure, but the association between the F7 haplotype and HDL cholesterol was not confirmed. CONCLUSION: Common FVII haplotypes may contribute to the risk of MI in women, but the mechanisms appear complex. The association between F7 haplotypes and MI susceptibility may be mediated in part through an influence on atherogenic risk factors such as BMI.     

冠心病患者血浆凝血因子Ⅶ水平及其基因多态性研究

目的：研究冠心病（CHD）患者血浆凝血因子Ⅶ（FⅦ）水平及其基因多态性。方法：对60例CHD患者[其中急性心肌梗死（AMI）33例]及正常对照者149名的血浆活化因子Ⅶ（FⅦa)、FⅦ活性（FⅦc）与FⅦ抗原（FⅦ：Ag)进行测定。应用PCR、限制性片段长度多态性分析及琼脂糖凝胶电泳的方法鉴定Ⅶ基因中的5个可能与血栓有关的多态性位点：－401G/T、－402G／A、5′F7 A1/A2、IVS7 H5/H6/H7/H8和R335Q M1／M2。结果：与正常对照组相比，CHD组的FⅦa、FⅦc与FⅦAg平均值均有升高，但仅AMI组FⅦa与FⅦc的增高有统计学意义（P＜0．05）；AMI组IVS7基因型频率与正常对照组比较差异有显著性（P＜0．05），其余各组间各基因型频率与等位基因频率差异均无显著性；－402A纯合子与－402G纯合子相比，血浆FⅦ：Ag水平显著升高（P＜0．05）。结论：血浆FⅦa与FⅦc增高，可能对AMI时冠状动脉血栓形成有促进作用；AMI组IVS7基因型频率与正常对照组比较差异有显著性；而且－402A纯合子血浆FⅦ：Ag水平显著高于－402G纯合子，故－402G／A多态性可能主要是影响血浆FⅦ：Ag水平，进而影响血栓形成。     

Factor VII gene haplotypes and risk of ischemic stroke

BACKGROUND: Coagulation factor VII (FVII) plays an important role in the activation of blood coagulation and clot formation. Recent studies have provided evidence for an association between common polymorphic markers in the FVII gene and plasma FVII concentrations. The 353R>Q sequence variation, and 3 common sequence variations in the promoter of the FVII gene-the 10-bp insertion/deletion at position -323 and the -401G>T and -402G>A sequence variations-are well-known determinants of circulating FVII concentrations. METHODS: To clarify the role of these sequence variations in the pathogenesis of ischemic stroke, we performed a case-control study with 242 patients with ischemic stroke before the age of 60 years and 239 healthy controls. RESULTS: The -323 insertion/deletion and the 353R>Q and -401G>T sequence variations were in strong linkage disequilibrium, and the resulting haplotypes occurred with equal frequencies in patients and controls. The variant form of FVII (-402G>A) occurred only in combination with the common (wild-type) sequences at all other loci. This haplotype was more frequent in patients than in healthy controls (28% vs 22%). The difference in the prevalence of carriers of this haplotype among patients and controls was statistically significant (P = 0.03; odds ratio = 1.6; 95% confidence interval, 1.1-2.6). CONCLUSION: According to our results, the FVII -402A allele seems to increase the risk of early ischemic cerebrovascular events, whereas the 353R>Q, G-401T, and -323ins/del sequence variations, which are in close linkage disequilibrium, apparently do not influence the risk of stroke.     

Prevalence in a Tunisian Arabic population of factor VII DNA variants and relation to factor VII plasma levels

BACKGROUND: A raised plasma factor VII (FVII) level is a risk factor for coronary heart disease. DNA variants have been described to be associated with alteration in FVII levels. The prevalence of FVII polymorphisms is unknown in the Tunisian Arab population. METHODS: In a group of 240 healthy Tunisians, we examined the relationship between levels of FVII coagulant activity (FVIIc) and two polymorphisms in the FVII gene. One polymorphism alters arginine at position 353 to glutamine (R/Q) and the other is a 10 base pair insertion (0/10 bp). RESULTS: The FVII distribution was in accordance with the Hardy-Weinberg equilibrium. The allele frequencies of Q and 10 bp were 0.212 and 0.235, respectively. There were significant differences in these allelic frequencies between Tunisian and other populations (p<0.001). We observed lower FVIIc levels among subjects with the Q allele compared to RR subjects (RR: 98.17%, RQ/QQ: 57.41%, p<0.0001). For the 0/10 polymorphism, no statistically difference was observed. CONCLUSION: The prevalence of the Q allele which was found to be associated with lower plasma FVIIc levels is high in Tunisian population. Further analyses should yield information on the protective role of carrying the Q allele for coronary heart disease.     

静脉血栓栓塞症患者活化蛋白C抗性及凝血因子V活性和基因多态性研究

本研究旨在观察静脉血栓栓塞患者凝血因子V(Factor V,F V)活性改变,检测活化蛋白C抗性(activated protein C resistance,APCR)和凝血因子V基因F V Leiden、F V Cambridge、F V Hong Kong、F V Asp79His和F V I359T多态性.对95例静脉血栓栓塞患者(其中下肢深静脉血栓79例,肺栓塞4例,下肢深静脉血栓合并肺栓塞12例)和95例正常对照者.应用限制性内切酶片段长度多态性测定FV Leiden、F V Cambridge和F V Hong Kong多态性,用MassARRAYTM技术检测F V Asp79His、F V I359T多态性.以一期法和校正的APTT试验分别对其中的65例静脉血栓栓塞患者和60例正常对照者行凝血因子V活性水平和活化蛋白C抵抗检测.结果表明静脉血栓栓塞患者血浆凝血因子V活性水平(108.03%±28.29%)高于对照组(95.17%±29.75%),差异有显著性统计学意义(P=0.008);静脉血栓栓塞组活化蛋白C抵抗阳性13例(20.0%),对照组3例(5.0%),二组比较,有统计学意义(P=0.012).二组均未发现FV Leiden、F V Cambridge、F V Hong Kong、FV Asp79His和FV I359T多态性.结论凝血因子V活性升高和活化蛋白C抵抗是静脉血栓栓塞的危险因素,但APCR与F V Leiden、F V Cambridge、F V HongKong、F V Asp79His和F V I359T多态性无关.     

Haplotype and genotype effects of the F7 gene on circulating factor VII,coagulation activation markers and incident coronary heart disease in UK men

Background: Evidence for the associations of single nucleotide polymorphisms (SNPs) in the F7 gene and factor (F)VII levels and with risk of coronary heart disease (CHD) is inconsistent. We examined whether F7 tagging SNPs (tSNPs) and haplotypes were associated with FVII levels, coagulation activation markers (CAMs) and CHD risk in two cohorts of UK men. Methods: Genotypes for eight SNPs and baseline levels of FVIIc, FVIIag and CAMs (including FVIIa) were determined in 2773 healthy men from the Second Northwick Park Heart Study (NPHS‐II). A second cohort, Whitehall II study (WH‐II, n = 4055), was used for replication analysis of FVIIc levels and CHD risk. Results: In NPHS‐II the minor alleles of three SNPs (rs555212, rs762635 and rs510317; haplotype H2) were associated with higher levels of FVIIag, FVIIc and FVIIa, whereas the minor allele for two SNPs (I/D323 and rs6046; haplotype H5) was associated with lower levels. Adjusted for classic risk factors, H2 carriers had a CHD hazard ratio of 1.34 [95% confidence interval (CI): 1.12–1.59; independent of FVIIc], whereas H5 carriers had a CHD risk of 1.29 (95% CI: 1.01–1.56; not independent of FVIIc) and significantly lower CAMs. Effects of haplotypes on FVIIc levels were replicated in WH‐II, as was the association of H5 with higher CHD risk [pooled‐estimate odds ratio (OR) 1.16 (1.00–1.36), P = 0.05], but surprisingly, H2 exhibited a reduced risk for CHD. Conclusion: tSNPs in the F7 gene strongly influence FVII levels. The haplotype associated with low FVIIc level, with particularly reduced functional activity, was consistently associated with increased risk for CHD, whereas the haplotype associated with high FVIIc level was not.     

Relation of psychological distress to the international normalized ratio in patients with venous thromboembolism with and without oral anticoagulant therapy

Summary. Background: Psychological distress might affect the international normalized ratio (INR), but effects might vary depending on oral anticoagulant (OAC) therapy. Objectives: To investigate the association of psychological distress with INR and clotting factors of the extrinsic pathway in patients with and without OAC therapy. Patients and methods: We studied 190 patients with a previous venous thromboembolism (VTE); 148 had discontinued OAC therapy and 42 had ongoing OAC therapy. To assess psychological distress, all patients completed validated questionnaires to measure symptoms of depression, anxiety, worrying, anger and hostility. INR, fibrinogen, factor (F)II:C, FV:C, FVII:C and FX:C were measured as part of outpatient thrombophilia work‐up. Results: In VTE patients without OAC therapy, the odds of a reduced INR (< 1.00) were significantly increased from 1.5 to 1.8 times for an increase of 1 standard deviation (SD) in symptoms of depression, anxiety, worrying and anger, respectively, after adjusting for gender, age, body mass index, socioeconomic status, hematocrit and C‐reactive protein. Worrying, anger and hostility also showed significant direct associations with FVII:C. In patients with OAC therapy, INR was unrelated to a negative affect; however, lower FVII:C related to anxiety and worrying as well as lower FX:C related to anger and hostility were observed in patients with OAC therapy compared with those without OAC therapy. Conclusions: Psychological distress was associated with a reduced INR in VTE patients without OAC therapy. The direction of the association between psychological distress and activity in some clotting factors of the extrinsic coagulation pathway might differ depending on whether VTE patients are under OAC therapy or not.     

Post-thrombotic syndrome, recurrence, and death 10 years after the first episode of venous thromboembolism treated with warfarin for 6 weeks or 6 months

BACKGROUND: The influence of the duration of anticoagulant therapy after venous thromboembolism (VTE) on the long-term morbidity and mortality is unclear. AIM: To investigate the long-term sequelae of VTE in patients randomized to different duration of secondary prophylaxis. METHODS: In a multicenter trial comparing secondary prophylaxis with vitamin K antagonists for 6 weeks or 6 months, we extended the originally planned 2 years follow-up to 10 years. The patients had annual visits and at the last visit clinical assessment of the post-thrombotic syndrome (PTS) was performed. Recurrent thromboembolism was adjudicated by a radiologist, blinded to treatment allocation. Causes of death were obtained from the Swedish Death Registry. RESULTS: Of the 897 patients randomized, 545 could be evaluated at the 10 years follow-up. The probability of developing severe PTS was 6% and any sign of PTS was seen in 56.3% of the evaluated patients. In multivariate analysis, old age and signs of impaired circulation at discharge from the hospital were independent risk factors at baseline for development of PTS after 10 years. Recurrent thromboembolism occurred in 29.1% of the patients with a higher rate among males, older patients, those with permanent triggering risk factor - especially with venous insufficiency at baseline - signs of impaired venous circulation at discharge, proximal deep vein thrombosis, or pulmonary embolism. Death occurred in 28.5%, which was a higher mortality than expected with a standardized incidence ratio (SIR) of 1.43 (95% CI 1.28-1.58), mainly because of a higher mortality than expected from cancer (SIR 1.83; 95% CI 1.44-2.23) or from myocardial infarction or stroke (SIR 1.28; 95% CI 1.00-1.56). The duration of anticoagulation did not have a statistically significant effect on any of the long-term outcomes. CONCLUSION: The morbidity and mortality during 10 years after the first episode of VTE is high and not reduced by extension of secondary prophylaxis from 6 weeks to 6 months. A strategy to reduce recurrence of VTE as well as mortality from arterial disease is needed.     

Prospective study of subclinical atherosclerosis as a risk factor for venous thromboembolism

BACKGROUND: Whether atherosclerotic disease predisposes to venous thrombosis is uncertain. OBJECTIVE: To determine whether subclinical atherosclerosis, manifested as increased carotid intima-media thickness (IMT) or presence of carotid plaque, is associated with increased incidence of venous thromboembolism (VTE). PATIENTS AND METHODS: The Atherosclerosis Risk in Communities study is a prospective cohort of adults aged 45-64 years, examined at baseline (1987-89) and followed for cardiovascular events. Bilateral carotid ultrasound for IMT measurements was done at baseline for portions of the common and internal carotid arteries, and carotid bifurcation and also to detect the presence of carotid plaque. Exclusion criteria included baseline anticoagulant use, history of coronary heart disease, stroke, or VTE, and incomplete data. First VTE during follow-up was validated using abstracted medical records. RESULTS: Among 13,081 individuals followed for a mean of 12.5 years, 225 first VTE events were identified. Unadjusted hazard ratios (HR) (95% CI) of VTE across quartiles of baseline IMT were 1.0, 1.16 (0.77-1.75), 1.64 (1.12-2.40), and 1.52 (1.03-2.25). However, this association disappeared after adjustment for age, sex, and ethnicity (HRs: 1.0, 1.06, 1.40, and 1.18). Further adjustment for body mass index and diabetes weakened the relative risks even further. Presence of carotid plaque at baseline also was not associated with VTE occurrence; adjusted HR = 0.97, 95% CI = 0.72-1.29. CONCLUSION: Increased carotid IMT or presence of carotid plaque was not associated with an increased incidence of VTE in this middle-aged cohort, suggesting subclinical atherosclerosis itself is not a VTE risk factor.     

A multi‐stage multi‐design strategy provides strong evidence that the BAI3 locus is associated with early‐onset venous thromboembolism

Summary. Background: Factor VIII (FVIII) and von Willebrand factor (VWF) are two known quantitative risk factors for venous thromboembolism (VTE). Objectives: To identify new loci that could contribute to VTE susceptibility and to modulating FVIII and/or VWF levels. Patients/Methods: A pedigree linkage analysis was first performed in five extended French‐Canadian families, including 253 individuals, to identify genomic regions linked to FVIII or VWF levels. Identified regions were further explored using ‘in silico’ genome‐wide association studies (GWAS) data on VTE (419 patients and 1228 controls), and two independent case‐control studies (MARTHA and FARIVE) for VTE, gathering 1166 early‐onset patients and 1408 healthy individuals. Single nucleotide polymorphisms (SNPs) associated with VTE risk were further investigated in relation to plasma levels of FVIII and VWF in a cohort of 108 healthy nuclear families. Results: Four main linkage regions were identified, among which the well‐characterized ABO locus, the recently identified STAB 2 gene, and a third one, on chromosome 6q13‐14, harbouring four non‐redundant SNPs, associated with VTE at P < 10^?4 in the GWAS dataset. The association of one of these SNPs, rs9363864, with VTE was further replicated in the MARTHA and FARIVE studies. The rs9363864‐AA genotype was associated with a lower risk for VTE (OR = 0.58 [0.42–0.80], P = 0.0005) but mainly in non‐carriers of the FV Leiden mutation. This genotype was further found to be associated with the lowest levels of FVIII (P = 0.006) and VWF (P = 0.001). Conclusions: The BAI3 locus where the rs9363864 maps is a new candidate for VTE risk.     

Thrombosis risk and survival in cancer patients with elevated C‐reactive protein

Summary. Background: The incidence of venous thromboembolism (VTE) is increased among cancer patients. Objective: We assessed serum levels of C‐reactive protein (CRP) in order to study their prognostic significance for VTE and survival in the prospective observational Cancer and Thrombosis Study (CATS). Patients and methods: This study includes patients with recently diagnosed cancer or progression of disease after remission. Occurrence of VTE and information on the patients’ anti‐cancer‐treatment are recorded. Observation ends with occurrence of objectively confirmed VTE, death or after 2 years. CRP levels were determined by an immunonephelometric method. Results: We included 705 consecutive patients with solid tumors. During the observation period, VTE occurred in 43 (6.1%) patients and 413 (58.6%) died. The cumulative probability of VTE was 6.6% after 1 year. In univariate analysis, CRP (as metric variable, per double increase) was associated with VTE [hazard ratio (HR) 1.2, 95% confidence interval (CI) 1.1–1.3 P = 0.048]. However, in multivariable analysis including chemotherapy, surgery and radiotherapy, metastasis, cancer‐site and sP‐selectin the association with VTE (HR 1.0, 95% CI 0.9–1.2 P = 0.932) was no longer observed. CRP was clearly associated with worse survival probability with a HR of 1.3 (95% CI 1.2–1.3, P < 0.0001) in multivariable analysis. The cumulative survival after 12 months was 43% in patients with CRP above the 75th percentile (1.8 mg dL^?1) and 82% in those below the 75th percentile. Conclusions: In cancer patients elevated CRP was not independently associated with VTE. CRP was significantly associated with worse survival.     

D-dimer, factor VIII coagulant activity, low-intensity warfarin and the risk of recurrent venous thromboembolism

BACKGROUND: Elevated plasma D-dimer and factor VIII coagulant activity (FVIIIc) may be associated with the risk of recurrent venous thromboembolism (VTE). OBJECTIVES: To evaluate D-dimer and FVIIIc as risk factors for recurrent VTE and assess the efficacy of extended low-intensity warfarin (target International Normalized Ratio 1.5-2.0) in preventing recurrence by biomarker level. PATIENTS AND METHODS: In the Prevention of Recurrent Venous Thromboembolism trial, 508 idiopathic VTE patients treated for > or = 3 months with full-intensity warfarin, and who had stopped warfarin for 7 weeks on average, were randomized to low-intensity warfarin or placebo and followed for 2.1 years for recurrent VTE. Prerandomization blood samples were analysed for D-dimer and FVIIIc. RESULTS: One-third of participants had elevated baseline D-dimer (> or = 500 ng mL(-1)) and one-fourth, elevated FVIIIc (> or = 150 IU dL(-1)). Adjusting for other risk factors, the hazard ratios (HRs) for recurrent VTE with elevated D-dimer or FVIIIc were 2.0 [95% confidence interval (CI) 1.2-3.4] and 1.5 (95% CI 0.8-2.8), respectively. The association of elevated D-dimer with recurrence was larger among patients with one prior VTE (HR 3.2, 95% CI 1.3-8.0) than in patients with more than one event (HR 1.4, 95% CI 0.7-2.2). For patients with one prior VTE on placebo, the annual recurrence incidence was 10.9% with elevated D-dimer and 2.9% with normal values. Low-intensity warfarin was equally effective in recurrence risk reduction in those with normal or elevated biomarkers. CONCLUSIONS: Among patients with idiopathic VTE, measurement of D-dimer, but not FVIIIc, might be useful for risk stratification. The efficacy of extended low-intensity warfarin therapy did not vary by biomarker level.     

Plasma concentrations of blood coagulation factor VII measured by immunochemical and amidolytic methods

Ever since the coagulant activity of blood coagulation factor VII (FVII:C) was identified as a risk indicator of cardiac death, a large number of studies have measured FVII protein concentrations in plasma. FVII protein concentrations are either measured immunologically with an ELISA method (FVII:Ag) or estimated with an amidolytic method (FVII:Am). We have investigated whether FVII:Am is a valuable alternative to FVII:Ag. FVII:Ag and FVII:Am were measured in 147 plasma samples from blood donors, patients on oral anticoagulant therapy, postmenopausal women on hormone replacement therapy, in postprandial plasma, in cold activated plasma and in FVII deficient plasma. There was a positive correlation (r=0.96) between FVII:Ag and FVII:Am with slightly but significantly higher values for FVII:Ag (FVII:Ag= 106 U/ml and FVII:Am=100 U/ml; p <0.001). A significant correlation (r=0.93) was still observed after omitting the data from patients on oral anticoagulant therapy, with mean values of 113 U/ml for FVII:Ag and 110 U/ml for FVII:Am (p < 0.01). In a linear regression analysis, the intercept (alpha=-21.50) was different from zero (p < 0.0001) and the slope (beta=1.16) was different from 1.0 (p < 0.001). Only a few points (3.1%) in a difference plot were present outside the expected 95% interval calculated from the analytical imprecision of the two methods. Therefore, we consider the amidolytic method an acceptable alternative to the ELISA method when analysing citrated plasma samples containing only enzymatically functional FVII protein, but the results cannot be directly transferred from one method to the other.     

Single intravenous administration of TB‐402 for the prophylaxis of venous thromboembolism after total knee replacement: a dose‐escalating,randomized, controlled trial

Summary. Background: TB‐402 is a novel anticoagulant monoclonal antibody with a prolonged antithrombotic effect resulting from its partial factor (F)VIII inhibition and long half‐life. We evaluated the efficacy and safety of a single administration of TB‐402 for the prevention of venous thromboembolism (VTE) after total knee replacement (TKR). Patients and methods: This was a phase II, dose‐escalating, randomized, enoxaparin‐controlled, open‐label study. Patients were post‐operatively assigned to a single dose of TB‐402 (0.3, 0.6 or 1.2 mg kg^?1) or enoxaparin 40 mg for at least 10 days (n = 75 per group; 3:1 TB‐402 to enoxaparin). The primary efficacy outcome was total VTE defined as asymptomatic deep vein thrombosis (DVT) detected by bilateral venography and symptomatic VTE by day 7 to 11. The principal safety outcome was the incidence of major bleeding and clinically relevant non‐major bleeding. Results: Total VTE was lower in all TB‐402 groups compared with enoxaparin: 16.7%(95% CI 9.8–26.9), 23.9%(95% CI 15.3–35.3), 24.1%(95% CI 16.0–34.5) and 39.0%(95% CI 28.8–50.1) for TB‐402 0.3, 0.6, 1.2 mg kg^?1 and enoxaparin, respectively (P = 0.003 for TB‐402 0.3 mg kg^?1 vs. enoxaparin). The incidence of total VTE in the pooled TB‐402 groups was 21.6% (95%CI 16.6–27.5), an absolute risk reduction vs. enoxaparin of 17.4% (95% CI 5.2–29.6). Major or clinically relevant non‐major bleeding was observed in 3/75(4.0%), 4/74(5.4%), 7/87(8.0%) and 3/79(3.8%) patients for TB‐402 0.3, 0.6, 1.2 mg kg^?1 and enoxaparin, respectively. Conclusions: TB‐402, as a single post‐operative administration, was associated with a lower rate of VTE in all doses tested, compared with enoxaparin. The incidence of major and clinically relevant non‐major bleeding was similar to enoxaparin 40 mg for TB‐402 0.3 and 0.6 mg kg^?1.     

Combined factor VII/protein C deficiency results in intrauterine coagulopathy in mice

To determine whether an additional loss of the coagulation factor VII (FVII) gene influenced the coagulopathy observed in protein C gene-deficient (PC(-/-)) embryos and neonates, we crossed mice doubly heterozygous for the factor VII (FVII(+/-)) and protein C (PC(+/-)) genes to produce offspring possessing the 9 predicted genotypic combinations. FVII(-/-)/PC(-/-) embryos, although present at their expected Mendelian frequency, displayed a phenotype that had not been observed in either the FVII or PC singly deficient embryos. At E12.5 days postcoitum (dpc), FVII(-/-)/PC(-/-) embryos demonstrated an intra- and extravascular coagulopathy that progressed with substantial concomitant hemorrhage and peripheral edema by E17.5dpc, resulting in mortality immediately after birth. FVII(+/-)/PC(-/-) embryos showed a less severe phenotype, suggesting a gene dosage effect. The lack of rescue of PC(-/-) embryos and neonates and augmented coagulopathy resulting from an additional heterozygous or homozygous FVII deficiency are probably due to increased factor Xa and thrombin generation, resulting from loss of FVIIa-dependent tissue factor pathway inhibitor function and the absence of control at the levels of factors Va and VIIIa. The presence of fibrin in embryos in the absence of fetal FVII suggests that significant clot-generating potential exists outside of the embryonic factor VII-dependent pathway.     

Thrombomodulin gene polymorphisms or haplotypes as potential risk factors for venous thromboembolism: a population-based case–control study

Dysfunction of the protein C anticoagulant system is associated with venous thromboembolism (VTE) and thrombomodulin (TM) is a critical cofactor within the protein C system. The aim of this study was to test the hypotheses that polymorphisms or haplotypes within the TM gene are common risk factors for VTE. We screened the TM putative promoter, exon and 3'-untranslated region for sequence variations in a random sample (n = 266) of consecutive idiopathic, objectively confirmed non-Olmsted County VTE patients referred to the Mayo Clinic. We then genotyped a sample of Olmsted County, MN residents with a first lifetime, objectively confirmed VTE in the 25-year period, 1966-90 (n = 223), and a sample of Olmsted County residents without VTE (n = 237) for polymorphisms either discovered in the screening population or previously published, and tested for an association of VTE with TM genotype or haplotypes using unconditional logistic regression and generalized linear models, respectively. We also genotyped these Olmsted County cases and controls at 20 'null' genetic maker loci and tested for population admixture. Nine novel and three previously described mutations were identified in the screening population. Mutations within the TM promoter, EGF(1-5), serine/threonine-rich, transmembrane, and cytoplasm regions were absent or uncommon. TM845G-->A (Ala25Thr; lectin region), TM2136T-->C (Ala455Val; EGF(6) region), TM2470C deletion (3'-untranslated region), and 4363A-->G (3'-flanking region) were more common, but were not associated with VTE by genotype or haplotype. Null genetic marker allele frequencies did not differ significantly among cases and controls. We conclude that polymorphisms or haplotypes within the TM gene are not common risk factors for incident VTE.     

Low-density lipoprotein receptor-related protein 1 polymorphism 663 C > T affects clotting factor VIII activity and increases the risk of venous thromboembolism

BACKGROUND: Clotting factor (F) VIII is an independent risk factor for primary and recurrent venous thromboembolism (VTE). The causes for high plasma FVIII levels are not fully understood, but an involvement of genetic factors has been demonstrated. A multifunctional endocytic receptor, low-density lipoprotein receptor-related protein 1 (LRP1), mediates cellular uptake and subsequent degradation of FVIII and may contribute to variations in FVIII levels. OBJECTIVE: We assessed the association of a genetic variation of LRP1 (663C > T) with basal FVIII levels and the risk of venous thrombosis in a group of high-risk patients and in healthy controls. PATIENTS AND METHODS: One hundred and fifty-two patients with a history of recurrent VTE (median age 56 years, 47% women) were compared with 198 age- and sex-matched controls (median age 53 years, 50% women). The LRP1 663C > T genotype was analyzed by mutagenic separated polymerase chain reaction assay and heterozygosity was confirmed by sequence analysis. RESULTS: LRP1 663C > T genotype distribution differed significantly between patients (663CC n = 138, 663CT n = 14) and controls (663CC n = 190, 663CT n = 8; P = 0.048). In multivariable linear regression analysis including LRP1 663C > T, ABO blood group, von Willebrand factor antigen, C-reactive protein and age, LRP1 663CT was independently associated with FVIII activity (P = 0.02). LRP1 663CT was also associated with increased odds for VTE following adjustment for blood group O, FV Leiden and the prothrombin variation 20210G > A in multivariate analysis (odds ratio 3.3, 95% CI 1.3-8.5). CONCLUSIONS: According to our data the LRP1 663C > T polymorphism influences plasma FVIII levels independently of blood group, C-reactive protein and von Willebrand factor and is significantly associated with the risk of VTE.     

Factor VII –323 decanucleotide D/I polymorphism in atrial fibrillation: Implications for the prothrombotic state and stroke risk

There are limited data on the influence of genetic polymorphisms in atrial fibrillation (AF) stroke risk. We hypothesized that a functional haemostatic polymorphism, that is, the factor VII ?323 Del/Ins polymorphism, would influence the prothrombotic state associated with AF, as well as stroke risk. Other functional polymorphisms were also tested.

Methods. We performed a cross-sectional study of 119 AF patients, who were compared to 96 patients with stroke secondary to AF. In the first patient group, we analysed plasma prothrombin fragment 1+2 levels (F1+2, an index of thrombin generation) to reflect the prothrombotic state of AF.

Results. AF patients carrying the ?323 Ins allele had lower plasma F1+2 levels (P=0.015). After multivariate analysis adjusted by age, sex and clinical risk factors, advanced age and 807C/T polymorphism of glycoprotein Ia (GPIa) gene were associated with higher risk of ischaemic stroke (OR: 1.06; P=0.003 and OR: 1.91; P=0.025), whilst FVII Ins ?323 allele was associated with lower stroke risk (OR: 0.41; P=0.017).

Conclusion. FVII ?323 Ins allele may modulate the prothrombotic state associated with AF. Despite the small sample size, we found that FVII Ins ?323 allele could be associated with a lower stroke risk in AF, whereas the 807C/T polymorphism may increase the risk.     

Hyperhomocysteinemia and low B vitamin levels are independently associated with venous thromboembolism: results from the EDITH study: a hospital-based case–control study

BACKGROUND: Moderate hyperhomocysteinemia and B vitamins deficiency are thought to be risk factors for venous thromboembolism (VTE). The causality and independence of those associations are still questioned. METHODS: We measured fasting serum total homocysteine, folates, and vitamin B12 levels as well as 5,10-methylenetetrahydrofolate reductase (MTHFR) C677T genotypes in 467 patients hospitalized with a first well-documented deep vein thrombosis and/or pulmonary embolism not related to a major acquired risk factor and 467 controls matched for gender and age. RESULTS: Mild hyperhomocysteinemia, low serum folates, and vitamin B12 were associated with VTE independently of each other. In multivariate analysis, odds ratios (OR) (95% CI) for VTE associated with mild hyperhomocysteinemia (>15 micromol L(-1)), low serum folates (< or = 4.9 nmol L(-1)), and vitamin B12 (< or = 253 pmol L(-1)) were 1.48 (1.05-2.08), 3.14 (1.35-7.32) and 1.42 (1.03-1.98), respectively. An MTHFRC677T genotype was not significantly associated with VTE; OR (95% CI): 1.13 (0.70-1.81) CONCLUSIONS: The current data provides further knowledge in the complex relationship between hyperhomocysteinemia, low vitamin levels, and VTE.