Genetic susceptibility, smoking, obesity and risk of venous thromboembolism

Association of Cardiovascular Health with the Incidence of Venous Thromboembolism: A Prospective Study of 275,149 Participants from the UK Biobank

BACKGROUND

 The Life's Essential 8 (LE8) score, recently proposed by the American Heart Association, represents a new paradigm for evaluating cardiovascular health (CVH). We aimed to explore the association between CVH, estimated using LE8, and venous thromboembolism (VTE) incidence.

METHODS

 A total of 275,149 participants were recruited from the UK Biobank and divided into high (LE8 score ≥ 80), moderate (LE8 score < 80 but ≥ 50), and low (LE8 score < 50) CVH groups. Restricted cubic spline analysis, the Kaplan-Meier method, and the Cox proportional hazards model were used to explore the association between CVH and VTE. The genetic predisposition to VTE was assessed with a polygenic risk score. Sensitivity analyses were performed to validate the results.

RESULTS

 During a median follow-up of 12.56 years, VTE developed in 506 (4.09%), 6,069 (2.78%), and 720 (1.66%) participants with low, moderate, and high CVH levels, respectively. Compared with the low CVH group, participants in the moderate and high CVH groups had a 23% (hazard ratio [HR]: 0.77; 95% confidence interval [CI]: 0.71-0.85) and 41% (HR: 0.59; 95% CI: 0.52-0.66) lower risk of VTE, respectively, after adjusting for demographic characteristics, medical history, socioeconomic status, and genetic predisposition. This association remained robust in multiple sensitivity analyses. Higher CVH levels led to a more pronounced reduction in the risk of VTE in females and could appreciably offset the genetic risk of VTE.

CONCLUSION

 Higher CVH levels were significantly associated with a lower incidence of VTE, encouraging efforts to increase LE8 scores in individuals.

From Risk Assessment to Intervention: A Systematic Review of Thrombosis in Plastic Surgery

Thromboembolism is a feared complication in plastic surgery and is linked to higher rates of morbidity and mortality. Despite extensive research, there is a lack of consistency between recommendations and clinical protocols to be implemented pre and post-surgery to reduce the incidence of thromboembolism. A systematic literature review was conducted using Pubmed and Scopus databases to determine the risk factors, screening methods, and existing treatment models for thromboembolism prevention. Articles in non-English languages were excluded. Analysis indicated that predominant risk factors include age (>35), elevated body mass index, coagulation disorders, smoking, estrogen therapies, genetic predisposition, vascular endothelium damage, stasis, and use of general anesthesia in patients with a history of cancer. Implementation of a proper prophylactic protocol is dependent on understanding the interplay between the aforementioned risk factors and the utilization of well-defined, evidence-based guidelines, such as the 2005 Caprini Risk Assessment Model and ultrasound surveillance. The literature review revealed that mechanical prophylaxis is the primary prevention method, followed by thromboprophylaxis for patients with higher Caprini scores. Plastic surgeons often underestimate the present risk stratification tools available for the prophylactic intervention of thromboembolism due to the fear of bleeding or hematoma complications postoperatively. In summary, this literature review emphasizes the importance of plastic surgeons selecting protocols that is inclusive of the patient's risk profile to yield a reduced risk of thromboembolism.

The utility of risk assessment tools for acute pulmonary embolism in children

BACKGROUND AND AIM: Pulmonary embolism (PE) is a potentially life-threatening disease in children. The objective of the study is to evaluate the utility of adult-based pulmonary embolism rule-out criteria (PERC), Pediatric PE Model, and D-dimer in the diagnosis of PE in children.

MATERIAL AND METHODS

The study consisted of patients under 18 years of age who were consulted to the Pediatric Pulmonology Clinic for the evaluation of PE. Patients were divided into two groups based on the confirmation of PE. The group with the presence of PE (n = 20) consisted of children who were diagnosed with PE. The group with the absence of PE (n = 28) consisted of children with clinically suspected PE but negative diagnostic imaging. Adult validated clinical decision PERC rule and Pediatric PE Model were retrospectively applied to the patients.

RESULTS

In the study, PERC demonstrated a sensitivity of 60% and a specificity of 46% for the diagnosis of PE in children. When PE Model was evaluated for the children, it was found a 50% sensitivity and 75% specificity. Combining PE Model and PERC rule with D-dimer did not increase the specificity and sensitivity. Smoking was found to be relevant for PE in the childhood. Twenty-five percent of the patients had a genetic tendency for PE. All of the patients had an underlying disease as well.

CONCLUSION

None of the current risk assessment tools (PE Model, PERC, D-dimer) were found to be accurate in predicting PE. Further larger population studies are still required to develop a better diagnostic approach.

Association of Combined Lifestyle and Polygenetic Risk with Incidence of Venous Thromboembolism: A Large Population-Based Cohort Study

As one of the fatal complications, venous thromboembolism (VTE) is associated with increased mortality. However, the combined effects of adopting multiple healthy lifestyles have not been firmly demonstrated. This study was to evaluate the association of combined healthy lifestyles and genetic risk factors with VTE and to investigate their interaction. A prospective cohort study from UK Biobank with a total of 442,963 men and women aged between 38 to 73 years were recruited from 2006 to 2010 and followed up through 2017 or 2018. A polygenic risk score was constructed and a weighted healthy lifestyle score, including no current smoking, regular physical exercises, healthy diet, and healthy body mass index, was categorized. During a median follow-up 9.0 years (3,912,396 person-years), there were 6,736 (172 per 100,000 person-years) incident VTE cases recorded. Among the participants with an unfavorable lifestyle, 1.80% developed VTE, versus 1.03% of the participants with a favorable lifestyle (hazard ratio [HR]: 1.58; 95% confidence interval [CI]: 1.48-1.68). Of the participants with high genetic risk, 2.42% developed VTE, versus 0.97% of the participants with low genetic risk (HR: 2.60; 95% CI: 2.39-2.81). Moreover, of the participants with high genetic risk and unfavorable lifestyle, 2.90% developed VTE, versus 0.66% of the participants with low genetic risk and favorable lifestyle (HR: 4.09; 95% CI: 3.48-4.79). No significant interaction between genetic risk and lifestyle factors was observed (p for interaction = 0.727). An unfavorable lifestyle was associated with a substantially higher risk of VTE, regardless of the genetic risk strata.

Association between cardiovascular risk factors and venous thromboembolism in the elderly

Background

The preponderance of the evidence supports no association between traditional cardiovascular risk factors and venous thromboembolism (VTE), other than obesity. There are limited data in older people.

Objectives

To investigate whether cardiovascular risk factors (body mass index, smoking, alcohol intake, hypertension, and diabetes) are associated with the risk of VTE in elderly and to assess the combined effect between cardiovascular risk factors and genetic risk factors for VTE (factor V Leiden/prothrombin 20210A, positive family history of VTE, and non‐O blood group).

Methods

The Age and Thrombosis, Acquired and Genetic risk factors in the Elderly study is a multicenter case‐control study performed in Vermont, USA and Leiden, the Netherlands, comprising 401 cases with first VTE and 431 control subjects, all aged ≥70 years. To assess the risk of VTE, odds ratios (OR) with 95% confidence intervals (CIs) were calculated, adjusting for potential confounders.

Results

Both height and weight were positively associated with VTE risk: the ORs were 2.2 (95% CI, 1.2–3.9) and 1.5 (95% CI, 1.0–2.4) in the top quartile for height and weight separately. This risk was more pronounced for unprovoked VTE. Smoking, alcohol intake, and diabetes were not associated with VTE. Higher systolic and diastolic blood pressure and hypertension were associated with a decreased risk of VTE. In the presence of a genetic predisposition, height and weight further increased the risk of VTE.

Conclusions

In the elderly, height and weight are positively associated with the risk of VTE. With genetic predisposition, higher levels of height and weight further increase the risk of VTE.

Association of smoking and cancer with the risk of venous thromboembolism: the Scandinavian Thrombosis and Cancer cohort

Smoking is a well-established risk factor for cancer, and cancer patients have a high risk of venous thromboembolism (VTE). Conflicting results have been reported on the association between smoking and risk of VTE, and the effect of smoking on VTE-risk in subjects with cancer is scarcely studied. We aimed to investigate the association between smoking and VTE in subjects with and without cancer in a large population-based cohort. The Scandinavian Thrombosis and Cancer (STAC) cohort included 144,952 participants followed from 1993-1997 to 2008-2012. Information on smoking habits was derived from self-administered questionnaires. Active cancer was defined as the first two years following the date of cancer diagnosis. Former smokers (n = 35,890) and those with missing information on smoking status (n = 3680) at baseline were excluded. During a mean follow up of 11 years, 10,181 participants were diagnosed with cancer, and 1611 developed incident VTE, of which 214 were cancer-related. Smoking was associated with a 50% increased risk of VTE (HR 1.49, 95% CI 1.12-1.98) in cancer patients, whereas no association was found in cancer-free subjects (HR 1.07, 95% CI 0.96-1.20). In cancer patients, the risk of VTE among smokers remained unchanged after adjustment for cancer site and metastasis. Stratified analyses showed that smoking was a risk factor for VTE among those with smoking-related and advanced cancers. In conclusion, smoking was associated with increased VTE risk in subjects with active cancer, but not in those without cancer. Our findings imply a biological interaction between cancer and smoking on the risk of VTE.

Community-Onset Venous Thromboembolism in Children: Pediatric Emergency Medicine Perspectives

Pediatric venous thromboembolism (VTE) is a condition increasingly encountered by emergency medicine physicians. Unfortunately, despite increased incidence, the diagnosis of pediatric VTE relies on a high index of suspicion from clinicians. Delays in diagnosis and initiation of treatment can lead to poor outcomes in children, including an increased risk of mortality from pulmonary embolism, increased risk of VTE recurrence, and the development of the post-thrombotic syndrome. The majority of pediatric VTE events are associated with the presence of at least one underlying prothrombotic risk. Timely recognition of these risk factors in the emergency department (ED) setting is paramount for a prompt diagnosis and treatment initiation. Compared with children with hospital-acquired VTE, children presenting to the ED with new onset VTE tend to be older (>11 years of age), have a lower incidence of co-morbidities, and present more frequently with a deep venous thrombosis of the lower extremity. Currently, there are no validated pediatric-specific VTE clinical pretest probability tools that reliably assist with the accurate and timely diagnosis of pediatric VTE. Compression ultrasound with Doppler is the most common imaging modality used for VTE diagnosis, and low molecular weight heparins are the most common anticoagulants initiated in children presenting with VTE in the ED. Special consideration should be given to patients who present to the ED already on anticoagulation therapy who may require acute management for clinically-significant bleeding or change in antithrombotic therapy approach for progression/recurrence of VTE.

Joint Effect of Multiple Prothrombotic Genotypes and Obesity on the Risk of Incident Venous Thromboembolism

BACKGROUND

 The impact of the combination of obesity and multiple prothrombotic genotypes on venous thromboembolism (VTE) risk remains unclear.

OBJECTIVE

 To investigate the joint effect of obesity and a genetic risk score (GRS) composed of established prothrombotic single nucleotide polymorphisms (SNPs) on VTE risk using a population-based case-cohort.

METHODS

 Cases with incident VTE (n = 1,470) and a subcohort (n = 12,826) were derived from the Tromsø Study (1994-2012) and the Trøndelag Health Study (HUNT) (1995-2008). Participants were genotyped for ABO (rs8176719), F5 (rs6025), F2 (rs1799963), FGG (rs2066865), and F11 (rs2036914) SNPs. Age- and sex-adjusted hazard ratios (HRs) were estimated according to body mass index (BMI) categories and number of risk alleles for individual SNPs and the GRS (0-1, 2, 3, ≥4 alleles).

RESULTS

 The combination of obesity (BMI ≥ 30kg/m²) and risk alleles, either as individual SNPs or as a GRS, had an additive effect on VTE risk (i.e., no biological interaction). Obese subjects who were carriers of ≥4 risk alleles had a 2.85-fold (95% confidence interval [CI]: 2.05-3.96) increased risk of overall VTE compared with those with BMI <25 kg/m² and 0 to 1 risk allele. However, in subgroups, the combination of obesity and ≥4 risk alleles was more pronounced for deep vein thrombosis (DVT) (HR: 3.20; 95% CI: 2.09-4.90) and unprovoked VTE (HR: 3.82; 95% CI: 2.25-6.47), suggesting a supra-additive effect.

CONCLUSION

 Our findings indicate that the combination of obesity and GRS has an additive effect on the risk of overall VTE. However, it may have a supra-additive effect on the risk of DVT and unprovoked VTE.

Physical Activity as an Effect Modifier of the Association Between Obesity and Venous Thromboembolism: A Danish Population-Based Cohort Study

Purpose

Obesity is an established risk factor for venous thromboembolism (VTE), while studies on physical inactivity and VTE risk show conflicting results. We examined whether physical activity modified the association between obesity and VTE.

Patients and Methods

We conducted a population-based cohort study by combining data on outcome diagnoses, comorbidities and medication from nationwide registries with self-reported lifestyle data from an extensive Danish lifestyle questionnaire (2001–2015). We computed incidence rates (IRs) and hazard ratios (HRs) of VTE for categories of body mass index (BMI), among the total study population (n=57,523) and for physically active (n=25,387) and inactive individuals (n=30,902) separately.

Results

Obesity (BMI ≥30 kg/m²) was as expected associated with increased VTE risk compared with normal weight (HR 1.62, 95% confidence interval (CI): 1.26–2.09). Independent of BMI category, the rate of VTE was higher for inactive than active individuals. Thus, among obese individuals, the IR per 1000 person-years was 2.03 (95% CI: 1.60–2.57) for inactive and 1.44 (95% CI: 0.97–2.15) for active individuals. In contrast, the HR for VTE comparing obese with normal weight individuals were higher for active (HR 2.19, 95% CI: 1.35–3.58) than inactive individuals (HR 1.36, 95% CI: 1.00–1.84).

Conclusion

Physical activity acts as an effect measure modifier of the association between obesity and VTE. Thus, physical activity reduced the absolute rate of VTE among obese individuals but increased the relative rate of VTE among obese compared with normal weight individuals.

Association Between Residual Platelet Reactivity on Clopidogrel Treatment and Severity of Coronary Atherosclerosis: Intrinsic Hypercoagulability as a Mediator

INTRODUCTION

High on-treatment residual platelet reactivity (HRPR) was associated with greater atherosclerosis burden. We examined whether intrinsic hypercoagulability (IHC) could be attributed to that association in patients treated by drug-eluting stents.

METHODS

This retrospective observation enrolled a total of 891 coronary artery disease (CAD) subjects. Platelet and coagulant reactivity was measured by thrombelastography. At least 24 h after a 300-mg dose of clopidogrel, adenosine diphosphate (ADP)-induced maximum amplitude of clot strength (MA_adp) > 47 mm represented HRPR. Thrombin-induced platelet-fibrin clot strength (MA_thrombin) and blood fibrinogen surrogated intrinsic coagulability. Using mediation analysis to evaluate the effect of IHC on the relationship between the number of narrowed coronaries and HRPR on clopidogrel.

RESULTS

More HRPR on clopidogrel and higher intrinsic coagulability were observed in more severe coronary atherosclerosis, especially in the three-vessel disease. After adjustment for confounding factors, the number of narrowed coronaries (OR_adj = 1.343, 95% CI 1.063-1.695, p = 0.013), MA_thrombin (OR_adj = 1.106, 95% CI 1.058-1.157, p < 0.001), and fibrinogen (OR_adj = 1.003, 95% CI 1.001-1.005, p = 0.012) were all independent positive predictors for HRPR. MA_thrombin and fibrinogen were meaningful mediators for the significant positive association of the number of narrowed vessels and HRPR on clopidogrel, which were enhanced by around 30% and 43%, respectively, for this effect.

CONCLUSIONS

This is the first study to demonstrate that the positive correlation between the number of stenotic coronaries and HRPR on clopidogrel may be partly attributed to IHC, which may enhance the risk stratification, guide more precise coagulation in multi-vessel disease after drug-eluting stents, and therefore deserve further study.

Interaction of a genetic risk score with physical activity, physical inactivity, and body mass index in relation to venous thromboembolism risk

INTRODUCTION

Venous thromboembolism (VTE) is highly heritable. Physical activity, physical inactivity and body mass index (BMI) are also risk factors, but evidence of interaction between genetic and environmental risk factors is limited.

METHODS

Data on 2,134 VTE cases and 3,890 matched controls were obtained from the Nurses' Health Study (NHS), Nurses' Health Study II (NHS II), and Health Professionals Follow-up Study (HPFS). We calculated a weighted genetic risk score (wGRS) using 16 single nucleotide polymorphisms associated with VTE risk in published genome-wide association studies (GWAS). Data on three risk factors, physical activity (metabolic equivalent [MET] hours per week), physical inactivity (sitting hours per week) and BMI, were obtained from biennial questionnaires. VTE cases were incident since cohort inception; controls were matched to cases on age, cohort, and genotype array. Using conditional logistic regression, we assessed joint effects and interaction effects on both additive and multiplicative scales. We also ran models using continuous wGRS stratified by risk-factor categories.

RESULTS

We observed a supra-additive interaction between wGRS and BMI. Having both high wGRS and high BMI was associated with a 3.4-fold greater risk of VTE (relative excess risk due to interaction = 0.69, p = 0.046). However, we did not find evidence for a multiplicative interaction with BMI. No interactions were observed for physical activity or inactivity.

CONCLUSION

We found a synergetic effect between a genetic risk score and high BMI on the risk of VTE. Intervention efforts lowering BMI to decrease VTE risk may have particularly large beneficial effects among individuals with high genetic risk.

Joint effects of prothrombotic genotypes and body height on the risk of venous thromboembolism: the Tromsø study

Essentials Body height and prothrombotic genotypes are associated with risk of venous thromboembolism (VTE). The joint effect of prothrombotic genotypes and tall stature on VTE risk is scarcely investigated. We investigated the joint effect of prothrombotic genotypes and tall stature on VTE risk. Prothrombotic genotypes did not yield excess risk of VTE in subjects with a tall stature.

SUMMARY

Background Studies have reported synergistic effects of prothrombotic single-nucleotide polymorphisms (SNPs) and obesity on the risk of venous thromboembolism (VTE). Tall stature is associated with an increased VTE risk, but the joint effect of prothrombotic genotypes and tall stature on the VTE risk is unknown. Aims To investigate the joint effects of prothrombotic genotypes and tall stature on the VTE risk. Methods Cases with incident VTE (n = 676) and a randomly selected age-weighted subcohort (n = 1842) were sampled from the Tromsø study (cohort follow-up: 1994-2012). DNA was genotyped for rs6025 (factor V Leiden), rs1799963 (FII), rs8176719 (ABO blood group), rs2066865 (fibrinogen-γ), and rs2036914 (FIX). Age-adjusted and sex-adjusted hazard ratios (HRs) of VTE were calculated by categories of risk alleles (de Haan 5-SNP score: 0-1, 2-3, and ≥ 4) and body height (< 40th, 40th-80th and > 80th percentiles). Results The VTE risk increased by increasing category of body height, and subjects with height ≥ 178 cm had a two-fold higher VTE risk (HR 2.03; 95% confidence interval [CI] 1.51-2.73) than those with height ≤ 165 cm. The VTE risk also increased across categories of risk alleles. However, the combination of a tall stature and risk alleles, either individual SNPs or risk score, did not result in an excess VTE risk. Subjects with four or more risk alleles and height ≥ 178 cm had a two-fold (HR 2.08; 95% CI 1.24-3.52) higher VTE risk than subjects ≤ 165 cm with no risk allele or one risk allele. Conclusions In contrast to obesity, the presence of prothrombotic genotypes did not result in an excess VTE risk in subjects with a tall stature.

Hypercoagulable state evaluated by thromboelastography in patients with idiopathic membranous nephropathy

The aims of this study were to evaluate the characteristics of hypercoagulable states in patients with membranous nephropathy (MN) via thromboelastography (TEG) and to identify risk factors. 235 MN patients who had undergone TEG examinations from 2011 to 2014 were included. An abnormality in at least two TEG parameters is considered a hypercoagulable state. Patient data was compared between the hypercoagulable and non-hypercoagulable groups. Potential risk factors for hypercoagulability were analyzed by logistic regression models. Subgroup analysis was performed in hypercoagulable patients. Compared to the non-hypercoagulable MN patients, the hypercoagulable patients showed a significantly higher proportion of female patients, urinary protein, platelet count, triglyceride and fibrinogen level, along with more severe hypoproteinemia and a reduction of serum antithrombin III. Correlation analysis showed that hypoproteinemia was the primary risk factor for hypercoagulability in MN patients. Among the hypercoagulable MN patients, a subgroup TEG parameter analysis showed that glucocorticoids-used subgroup and smoker subgroup had shortened time to initial fibrin formation (R value) and increased coagulation index respectively (P < 0.05), indicating a more serious hypercoagulable state. Meanwhile, the time to initial fibrin formation (R value) and time to clot formation (K value) of the statin-used patients were remarkably higher than those of the non-statin patients. TEG examinations facilitated the detection of hypercoagulable states in MN patients, and hypoproteinemia was the most important risk factor for hypercoagulability in these patients. The use of glucocorticoids and smoking may help to aggravate hypercoagulable states, while statin drugs may alleviate hypercoagulability.

Nutritional management of a patient with obesity and pulmonary embolism: a case report

Background

The aim of this case report is to discuss the issue of nutritional therapy in patients taking warfarin. Patients are often prescribed vitamin K free diets without nutritional counseling, leading to possible health consequences.

Case presentation

A 52-year-old woman with obesity and hypertension was prescribed a low calorie diet by her family doctor in an effort to promote weight loss. After a pulmonary embolism, she was placed on anticoagulant therapy and on hospital discharge she was prescribed a vitamin K free diet to avoid interactions. Given poor control of her anticoagulant therapy, she was referred to our Nutritional Unit outpatients’ service.

Conclusions

This case illustrates the importance of a thorough medical nutrition assessment in the management of patients with obesity and the need for a change in the dietary approach of nutritional therapy in the management of vitamin K anticoagulant therapy. In patients taking warfarin, evidence suggest that the aim of nutritional therapy should be to keep dietary intake of vitamin K constant.

Joint effects of cancer and variants in the factor 5 gene on the risk of venous thromboembolism

Venous thromboembolism occurs frequently in cancer patients. Two variants in the factor 5 gene (F5), rs6025 encoding for the factor V Leiden mutation R506Q, and rs4524 encoding K858R, have been found to be associated with venous thromboembolism. We assessed the joint effect of active cancer and these two F5 variants on venous thromboembolism risk in a case-cohort study. Cases with a first venous thromboembolism (n=609) and a randomly selected age-weighted cohort (n=1,691) were sampled from the general population in Tromsø, Norway. Venous thromboembolism was classified as cancer-related if it occurred in the period 6 months before to 2 years after a diagnosis of cancer. Active cancer was associated with an 8.9-fold higher risk of venous thromboembolism (95% CI 7.2-10.9). The risk of cancer-related venous thromboembolism was 16.7-fold (95% CI 9.9-28.0) higher in subjects heterozygous for rs6025 compared with non-carriers of this variant without active cancer. In subjects with active cancer the risk of venous thromboembolism was 15.9-fold higher (95% CI 9.1-27.9) in those with one risk allele at rs4524, and 21.1-fold (95% CI 12.4-35.8) higher in those with two risk alleles compared with non-carriers without active cancer. A synergistic interaction was observed between active cancer and factor V Leiden (relative excess risk due to interaction 7.0; 95% CI 0.5-14.4) and rs4524 (relative excess risk due to interaction 15.0; 95% CI 7.5-29.2). The incidence of venous thromboembolism during the initial 6 months following a diagnosis of cancer was particularly high in subjects with risk alleles at these loci. This implies that the combination of cancer and F5 variants synergistically increases venous thromboembolism risk.

Antithrombin Dublin (p.Val30Glu): a relatively common variant with moderate thrombosis risk of causing transient antithrombin deficiency

The key haemostatic role of antithrombin and the risk of thrombosis associated with its deficiency support that the low incidence of antithrombin deficiency among patients with thrombosis might be explained by underestimation of this disorder. It was our aim to identify mutations in SERPINC1 causing transient antithrombin deficiency. SERPINC1 was sequenced in 214 cases with a positive test for antithrombin deficiency, including 67 with no deficiency in the sample delivered to our laboratory. The p.Val30Glu mutation (Antithrombin Dublin) was identified in five out of these 67 cases, as well as in three out of 127 cases with other SERPINC1 mutations. Genotyping in 1593 patients with venous thrombosis and 2592 controls from two populations, revealed a low prevalent polymorphism (0.3 %) that moderately increased the risk of venous thrombosis (OR: 2.9; 95 % CI: 1.07-8.09; p= 0.03) and identified one homozygous patient with an early thrombotic event. Carriers had normal anti-FXa activity, and plasma antithrombin was not sensitive to heat stress or proteolytic cleavage. Analysis of one sample with transient deficit revealed a type I deficiency, without aberrant or increased latent forms. The recombinant variant, which lacked the two amino-terminal residues, had reduced secretion from HEK-EBNA cells, formed hyperstable disulphide-linked polymers, and had negligible activity. In conclusion, p.Val30Glu by affecting the cleavage of antithrombin's signal peptide, results in a mature protein lacking the N-terminal dipeptide with no functional consequences in normal conditions, but that increases the sensitivity to be folded intracellularly into polymers, facilitating transient antithrombin deficiency and the subsequent risk of thrombosis.

Epidemiology of venous thromboembolism

Thrombosis can affect any venous circulation. Venous thromboembolism (VTE) includes deep-vein thrombosis of the leg or pelvis, and its complication, pulmonary embolism. VTE is a fairly common disease, particularly in older age, and is associated with reduced survival, substantial health-care costs, and a high rate of recurrence. VTE is a complex (multifactorial) disease, involving interactions between acquired or inherited predispositions to thrombosis and various risk factors. Major risk factors for incident VTE include hospitalization for surgery or acute illness, active cancer, neurological disease with leg paresis, nursing-home confinement, trauma or fracture, superficial vein thrombosis, and-in women-pregnancy and puerperium, oral contraception, and hormone therapy. Although independent risk factors for incident VTE and predictors of VTE recurrence have been identified, and effective primary and secondary prophylaxis is available, the occurrence of VTE seems to be fairly constant, or even increasing.

Recurrent venous thromboembolism in a patient with heterozygous factor v leiden mutation

OBJECTIVE

To report a patient case identifying risk for recurrent venous thromboembolism (VTE) associated with heterozygous Factor V Leiden mutation.

CASE SUMMARY

A 54-year-old Caucasian male was diagnosed with heterozygous Factor V Leiden mutation in 2008 after experiencing a deep vein thrombosis (DVT) and bilateral pulmonary embolism. The patient was treated appropriately and started on anticoagulation therapy with warfarin through an anticoagulation management clinic. After approximately 17 months of warfarin therapy without incident, warfarin was discontinued. Within 2 months after discontinuation of anticoagulation therapy, the patient experienced his second DVT and left pulmonary artery embolus.

DISCUSSION

The risk of recurrent venous thromboembolism (VTE) in patients with heterozygous Factor V Leiden mutation is documented as an approximate 1.4-fold increase compared to patients without thrombophilia. However, the risk increases dramatically when nonreversible (age) or reversible risk factors (obesity, smoking, and long air flights) are present in this population.

CONCLUSION

Based on recent literature, heterozygous Factor V Leiden mutation exponentially increases the risk of recurrent VTE, especially in the presence of other risk factors. Health care providers should complete a comprehensive review of the patients' other risk factors when deciding on duration of anticoagulation therapy for patients with positive heterozygous Factor V Leiden mutation.

Impact of obesity on the risk of venous thromboembolism in an inpatient pediatric population

INTRODUCTION

The incidence of venous thromboembolism in children has increased significantly over the past 20 years. Over the same period of time, there was an increase in the prevalence of obesity in the pediatric population. Obesity is a known risk factor for VTE in adults, but little information is available in children.

METHODS

This study evaluates the relation between obesity and VTE using a retrospective, case-control design, comparing the body mass index (BMI) of patients admitted with a diagnosis of VTE versus patients admitted with other diagnoses, at a single institution, between 2007 and 2011.

RESULTS

We studied 48 inpatients diagnosed with deep venous thrombosis or pulmonary embolism and a control group of 274 age and gender matched patients admitted with other diagnoses. We found obese patients (BMI > 95th percentile) to have significantly higher risk of VTE (odds ratio 2.1, with 95% CI 1.1-4.2) than patients of normal weight (BMI < 85th percentile). Overweight patients (BMI 85th-95th percentile) did not demonstrate a significant change in risk. Most of the VTE patients were adolescents and the majority of them had other identifiable risk factors for thrombosis.

CONCLUSION

This study establishes a correlation between obesity and VTE in a group of hospitalized children, showing a risk for VTE in obese children similar to the one described in much larger adult cohorts.

The relationship between obesity and prescription of smoking cessation medications

The objective of this study was to examine the differences in prescription of smoking cessation medications among smokers with different body mass index (BMI) classifications. A retrospective cross-sectional study was conducted using National Ambulatory Medical Care Survey data (2006-2010). Self-reported current smokers aged 18 years and older were included in the study. The outcome of interest was receiving a prescription for a Food and Drug Administration-approved smoking cessation medication. Multivariate logistic regression was performed to assess the association between the outcome variable and the main independent variable (BMI classification), controlling for other covariates. The results showed that overweight, obese, and severely obese smokers were less likely to be prescribed a smoking cessation medication as compared to normal weight smokers. Although 5.11% of normal weight smokers were prescribed a smoking cessation medication, only 3.70% of overweight smokers, 3.41% of obese smokers, and 2.50% of severely obese smokers were prescribed a smoking cessation medication. In addition, older smokers, whites, smokers visiting primary care providers, smokers receiving tobacco counseling, and nondiabetic smokers were more likely to be prescribed a smoking cessation medication. Lower prescription of smoking cessation medications among overweight, obese, and severely obese smokers might be driven by patients' health concerns and behavioral factors or providers' treatment preferences or biases. The disparity in smoking cessation medication prescription among smokers with different BMI classifications raises quality of care and health care concerns for overweight, obese, and severely obese smokers.

Overview and assessment of risk factors for pulmonary embolism

Pulmonary embolism is one of the most common undiagnosed conditions affecting hospitalized patients. There are a plethora of risk factors for venous thromboembolism and pulmonary emboli. These factors are grouped under the broad triad of hypercoagulability, stasis and injury to provide a framework for understanding. Important risk factors include inherited thrombophilia, age, malignancy and estrogens. These risk factors are reviewed in detail and several risk assessment models are reviewed. These risk assessment models help identify those at risk for disease and therefore candidates for thromboprophylaxis. Diagnosis can be difficult and is aided by clinical decision rules that incorporate clinical scores that define the likelihood of pulmonary embolism. These are important considerations, not only for diagnostic purposes, but also to minimize excessive use of imaging, which increases exposure to and risks associated with radiation. A healthy index of suspicion is often the key to diagnosis.

Smoking, surgery, and venous thromboembolism risk in women: United Kingdom cohort study

BACKGROUND

Evidence about the effect of smoking on venous thromboembolism risk, generally and in the postoperative period, is limited and inconsistent. We examined the incidence of venous thromboembolism in relation to smoking habits, both in the absence of surgery and in the first 12 postoperative weeks, in a large prospective study of women in the United Kingdom.

METHODS AND RESULTS

During 6 years' follow-up of 1 162 718 women (mean age 56 years), 4630 were admitted to hospital for or died of venous thromboembolism. In the absence of surgery, current smokers had a significantly increased incidence of venous thromboembolism compared with never-smokers (adjusted relative risk 1.38, 95% confidence interval 1.28-1.48), with significantly greater risks in heavier than lighter smokers (relative risks 1.47 [95% confidence interval 1.34-1.62] and 1.29 [95% confidence interval 1.17-1.42] for ≥15 versus <15 cigarettes per day). Current smokers were also more likely to have surgery than never-smokers (relative risk 1.12, 95% confidence interval 1.12-1.13). Among women who had surgery, the incidence of venous thromboembolism in the first 12 postoperative weeks was significantly greater in current than never-smokers (relative risk 1.16, 95% confidence interval 1.02-1.30).

CONCLUSIONS

Venous thromboembolism incidence was increased in current smokers, both in the absence of surgery and in the 12 weeks after surgery. Smoking is another factor to consider in the assessment of venous thromboembolism risk in patients undergoing surgery.

Current and former smoking and risk for venous thromboembolism: a systematic review and meta-analysis

BACKGROUND

Smoking is a well-established risk factor for atherosclerotic disease, but its role as an independent risk factor for venous thromboembolism (VTE) remains controversial. We conducted a meta-analysis to summarize all published prospective studies and case-control studies to update the risk for VTE in smokers and determine whether a dose-response relationship exists.

METHODS AND FINDINGS

We performed a literature search using MEDLINE (source PubMed, January 1, 1966 to June 15, 2013) and EMBASE (January 1, 1980 to June 15, 2013) with no restrictions. Pooled effect estimates were obtained by using random-effects meta-analysis. Thirty-two observational studies involving 3,966,184 participants and 35,151 VTE events were identified. Compared with never smokers, the overall combined relative risks (RRs) for developing VTE were 1.17 (95% CI 1.09-1.25) for ever smokers, 1.23 (95% CI 1.14-1.33) for current smokers, and 1.10 (95% CI 1.03-1.17) for former smokers, respectively. The risk increased by 10.2% (95% CI 8.6%-11.8%) for every additional ten cigarettes per day smoked or by 6.1% (95% CI 3.8%-8.5%) for every additional ten pack-years. Analysis of 13 studies adjusted for body mass index (BMI) yielded a relatively higher RR (1.30; 95% CI 1.24-1.37) for current smokers. The population attributable fractions of VTE were 8.7% (95% CI 4.8%-12.3%) for ever smoking, 5.8% (95% CI 3.6%-8.2%) for current smoking, and 2.7% (95% CI 0.8%-4.5%) for former smoking. Smoking was associated with an absolute risk increase of 24.3 (95% CI 15.4-26.7) cases per 100,000 person-years.

CONCLUSIONS

Cigarette smoking is associated with a slightly increased risk for VTE. BMI appears to be a confounding factor in the risk estimates. The relationship between VTE and smoking has clinical relevance with respect to individual screening, risk factor modification, and the primary and secondary prevention of VTE. Please see later in the article for the Editors' Summary.

Body mass index, surgery, and risk of venous thromboembolism in middle-aged women: a cohort study

BACKGROUND

Obesity and surgery are known risk factors for venous thromboembolism (VTE), but there is limited information about the independent effects of obesity on the incidence of postoperative VTE. We linked questionnaire data from the Million Women Study with hospital admission and death records to examine the risk of VTE in relation to body mass index (BMI) both in the absence of surgery and in the first 12 weeks following an operation.

METHODS AND RESULTS

Overall, 1 170 495 women (mean age, 56.1 years) recruited in 1996 to 2001 through the National Health Service Breast Screening Programme in England and Scotland were followed for an average of 6 years, during which time 6438 were admitted to hospital or died of VTE. The adjusted relative risks of VTE increased progressively with increasing BMI and women with a BMI ≥ 35 kg/m(2) were 3-4 times as likely to develop VTE as those with a BMI 22.5 to 24.9 (relative risk 3.45 [95% CI 3.09-3.86]). Overweight and obese women were more likely than lean women to be admitted for surgery and also to develop postoperative VTE. During a 12-week period without surgery, the incidence rates of VTE per 1000 women with a BMI < 25 and ≥ 25 were 0.10 (0.09-0.10) and 0.19 (0.18-0.20); the corresponding rates in the 12 weeks following day and inpatient surgery were, respectively, about 4 and 40 times higher.

CONCLUSIONS

VTE risk increases with increasing BMI and the associated excess risk is much greater after surgery than without surgery.

The effects of obesity on venous thromboembolism: A review

Obesity has emerged as a global health issue that is associated with wide spectrum of disorders, including coronary artery disease, diabetes mellitus, hypertension, stroke, and venous thromboembolism (VTE). VTE is one of the most common vascular disorders in the United States and Europe and is associated with significant mortality. Although the association between obesity and VTE appears to be moderate, obesity can interact with other environmental or genetic factors and pose a significantly greater risk of VTE among individuals who are obese and who are exposed simultaneously to several other risk factors for VTE. Therefore, identification of potential interactions between obesity and certain VTE risk factors might offer some critical points for VTE interventions and thus minimize VTE morbidity and mortality among patients who are obese. However, current obesity measurements have limitations and can introduce contradictory results in the outcome of obesity. To overcome these limitations, this review proposes several future directions and suggests some avenues for prevention of VTE associated with obesity as well.

Venous thromboembolism in patients with membranous nephropathy

BACKGROUND AND OBJECTIVES

The aims of this study were to determine the frequency of venous thromboembolic events in a large cohort of patients with idiopathic membranous nephropathy and to identify predisposing risk factors.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We studied patients with biopsy-proven membranous nephropathy from the Glomerular Disease Collaborative Network (n=412) and the Toronto Glomerulonephritis Registry (n=486) inception cohorts. The cohorts were pooled after establishing similar baseline characteristics (total n=898). Clinically apparent and radiologically confirmed venous thromboembolic events were identified. Potential risk factors were evaluated using multivariable logistic regression models.

RESULTS

Sixty-five (7.2%) subjects had at least one venous thromboembolic event, and this rate did not differ significantly between registries. Most venous thromboembolic events occurred within 2 years of first clinical assessment (median time to VTE = 3.8 months). After adjusting for age, sex, proteinuria, and immunosuppressive therapy, hypoalbuminemia at diagnosis was the only independent predictor of a venous thromboembolic event. Each 1.0 g/dl reduction in serum albumin was associated with a 2.13-fold increased risk of VTE. An albumin level <2.8 g/dl was the threshold below which risk for a venous thromboembolic event was greatest.

CONCLUSIONS

We conclude that clinically apparent venous thromboembolic events occur in about 7% of patients with membranous nephropathy. Hypoalbuminemia, particularly <2.8 g/dl, is the most significant independent predictor of venous thrombotic risk.

Racial differences in venous thromboembolism

The incidence of venous thrombosis (VTE) varies by race, with African-Americans having over 5-fold greater incidence than Asian-ancestry populations, and an intermediate risk for European and Hispanic populations. Known racial differences in genetic polymorphisms associated with thrombosis do not account for this gradient of risk, nor do known racial variations in environmental risk factors. Data on the incidence of and risk factors for VTE outside of Europe and North America and in non-European ancestry populations are sparse. Common genetic polymorphisms in European-Ancestry populations, such as factor V Leiden and prothrombin G20210A, and environmental risk factors, such as obesity, may account for some of the increased risk in European populations, and high factor VIII, high von Willebrand factor and low protein C levels and increased prevalence of obesity may explain some of the increased risk in African-Americans. The low rates in Asian populations may be partially explained by low clinical suspicion in a perceived low-risk population and lack of access to healthcare in other populations. As risk factors for thrombosis, such as surgery and treatment for cancer, are applicable to more people, as obesity increases in prevalence in the developing world, and as surveillance systems for VTE improve, VTE may increase in previously low-risk populations. While differences in VTE by race due to genetic predisposition will probably always be present, understanding the reasons for racial differences in VTE will help providers develop strategies to minimize VTE in all populations.

Prevention of venous thromboembolism in obesity

Venous thromboembolism (VTE) is a significant cause of morbidity and mortality in hospitalized patients. Where appropriate, evidence-based methods of prophylaxis are implemented and the burden of VTE can be reduced substantially. Obesity, including morbid obesity, is associated with a high risk of VTE and, unfortunately, fixed doses of US FDA-approved anticoagulant regimens, including unfractionated heparins, low-molecular-weight heparins and factor Xa inhibitors, may not provide optimal VTE prophylaxis in these patients. Although the data are still limited, a rapidly growing body of literature and cumulative evidence suggests that anticoagulant dose adjustments in morbidly obese patients may optimize pharmacodynamic activity and reduce VTE risk. With the prevalence of morbid obesity continuing to rise, more high-quality clinical data are needed to better understand the pathobiology of VTE in obesity and provide effective, yet safe, prevention strategies.