Mechanisms and mitigating factors for venous thromboembolism in chronic kidney disease: the REGARDS study

Concerns about the application of resistance exercise with blood-flow restriction and thrombosis risk in hemodialysis patients

BACKGROUND

Hemodialysis (HD) per se is a risk factor for thrombosis. Considering the growing body of evidence on blood-flow restriction (BFR) exercise in HD patients, identification of possible risk factors related to the prothrombotic agent D-dimer is required for the safety and feasibility of this training model. The aim of the present study was to identify risk factors associated with higher D-dimer levels and to determine the acute effect of resistance exercise (RE) with BFR on this molecule.

METHODS

Two hundred and six HD patients volunteered for this study (all with a glomerular filtration rate of <15 mL/min/1.73 m2). The RE + BFR session consisted of 50% arterial occlusion pressure during 50 min sessions of HD (intradialytic exercise). RE repetitions included concentric and eccentric lifting phases (each lasting 2 s) and were supervised by a strength and conditioning specialist.

RESULTS

Several variables were associated with elevated levels of D-dimer, including higher blood glucose, citrate use, recent cardiovascular events, recent intercurrents, higher inflammatory status, catheter as vascular access, older patients (>70 years old), and HD vintage. Furthermore, RE + BFR significantly increases D-dimer after 4 h. Patients with borderline baseline D-dimer levels (400-490 ng/mL) displayed increased risk of elevating D-dimer over the normal range (≥500 ng/mL).

CONCLUSION

These results identified factors associated with a heightened prothrombotic state and may assist in the screening process for HD patients who wish to undergo RE + BFR. D-dimer and/or other fibrinolysis factors should be assessed at baseline and throughout the protocol as a precautionary measure to maximize safety during RE + BFR.

Combined effect of high factor VIII levels and high mean platelet volume on the risk of future incident venous thromboembolism

BACKGROUND

High factor VIII (FVIII) levels and large platelets, as reflected by a high mean platelet volume (MPV), are separately associated with increased risk of venous thromboembolism (VTE). Whether the combination of high FVIII levels and large platelets has a supra-additive effect on VTE risk is unknown.

OBJECTIVES

We aimed to investigate the joint effect of high FVIII levels and large platelets, as reflected by high MPV, on the risk of future incident VTE.

METHODS

A population-based nested case-control study with 365 incident VTE cases and 710 controls was derived from the Tromsø study. FVIII antigen levels and MPV were measured in blood samples drawn at baseline. Odds ratios with 95% CIs were estimated across FVIII tertiles (<85%, 85%-108%, and ≥108%) and within predefined MPV strata (<8.5, 8.5-9.5, and ≥9.5 fL).

RESULTS

VTE risk increased linearly across FVIII tertiles (Ptrend < .001) in models adjusted for age, sex, body mass index, and C-reactive protein. In the combined analysis, participants with FVIII levels in the highest tertile and an MPV of ≥9.5 fL (ie, joint exposure) had an odds ratio for VTE of 2.71 (95% CI, 1.44-5.11) compared with those with FVIII levels in the lowest tertile and an MPV of <8.5 fL (reference). In the joint exposure group, 52% (95% CI, 17%-88%) of VTEs were attributable to the biological interaction between FVIII and MPV.

CONCLUSION

Our results suggest that large platelets, as reflected by high MPV, might play a role in the mechanism by which high FVIII level increases the risk of incident VTE.

Unsupervised clustering of venous thromboembolism patients by clinical features at presentation identifies novel endotypes that improve prognostic stratification

BACKGROUND

Individuals with acute venous thromboembolism (VTE) constitute a heterogeneous group of patients with diverse clinical characteristics and outcome.

OBJECTIVES

To identify endotypes of individuals with acute VTE based on clinical characteristics at presentation through unsupervised cluster analysis and to evaluate their molecular proteomic profile and clinical outcome.

METHODS

Data from 591 individuals from the Genotyping and Molecular phenotyping of Venous thromboembolism (GMP-VTE) project were explored. Hierarchical clustering was applied to 58 variables to define VTE endotypes. Clinical characteristics, three-year incidence of thromboembolic events or death, and acute-phase plasma proteomics were assessed.

RESULTS

Four endotypes were identified, exhibiting different patterns of clinical characteristics and clinical course. Endotype 1 (n = 300), comprising older individuals with comorbidities, had the highest incidence of thromboembolic events or death (HR [95 % CI]: 3.76 [1.96-7.19]), followed by endotype 4 (n = 127) (HR [95 % CI]: 2.55 [1.26-5.16]), characterised by men with history of VTE and provoking risk factors, and endotype 3 (n = 57) (HR [95 % CI]: 1.57 [0.63-3.87]), composed of young women with provoking risk factors, vs. reference endotype 2 (n = 107). The reference endotype was constituted by individuals diagnosed with PE without comorbidities, who had the lowest incidence of the investigated endpoint. Differentially expressed proteins associated with the endotypes were related to distinct biological processes, supporting differences in molecular pathophysiology. The endotypes had superior prognostic ability compared to existing risk stratifications such as provoked vs unprovoked VTE and D-dimer levels.

CONCLUSION

Four endotypes of VTE were identified by unsupervised phenotype-based clustering that diverge in clinical outcome and plasmatic protein signature. This approach might support the future development of individualized treatment in VTE.

Procoagulant factors and future risk of arterial cardiovascular disease in patients with prior venous thrombosis: A cohort study

Patients with venous thrombosis (VT) are at increased risk of future arterial cardiovascular disease (CVD) (i.e., myocardial infarction, ischemic stroke or peripheral artery disease). We investigated whether shared risk factors for VT and CVD are associated with the levels of procoagulant factors (fibrinogen, factor VIII, and von Willebrand factor), and whether the relationship between these risk factors and subsequent CVD was mediated through these procoagulant factors in patients with VT. In a follow-up study consisting of 4956 patients with VT, 2176 patients (44%) provided blood samples and were linked to the Dutch Hospital registry of Statistics Netherlands to identify hospital admissions or procedures for subsequent CVD. In total, 52 CVD events occurred over a follow-up of 11,124 years, with an incidence rate of 4.7 per 1000 patient years (95% confidence intervals 3.5-6.1). Increasing age, male sex, smoking history, major illnesses, dyslipidemia, and impaired fasting glucose levels were associated with increased CVD risk. Procoagulant factor levels were also associated with CVD risk. When adjusted for these procoagulant factors, the association between the risk factors and CVD attenuated partially. This study provides evidence that procoagulant factors can partially explain the association between increased risks of subsequent CVD in patients with previous VT.

Long-term clinical outcomes in older patients with acute venous thromboembolism who have renal impairment

INTRODUCTION

Renal impairment (RI) may induce an inflammatory/procoagulant state as well as platelet dysfunction. Little is known on the prevalence of RI and long-term prognosis of older patients with venous thromboembolism (VTE) who have concomitant RI.

METHODS

In a prospective multicenter cohort, we analyzed 912 patients aged ≥65 years with acute VTE. Using the CKD-EPI formula, we defined three categories of baseline renal function: estimated glomerular filtration rate ≥60 ml/min/1.73m² (no RI), 30-59 ml/min/1.73m² (moderate RI), and <30 ml/min/1.73m² (severe RI). The outcomes were VTE recurrence, major bleeding, and overall mortality. We examined the association between renal function and clinical outcomes using competing risk regression models, adjusting for relevant confounders and periods of anticoagulation.

RESULTS

We followed 912 patients over a median duration of 29.6 months. Overall, 313 (34%) patients had moderate and 51 (6%) severe RI. One hundred and seven patients (12%) had VTE recurrence, 125 (14%) had major bleeding, and 186 (20%) died during follow-up. After adjustment, severe RI was associated with a 2-fold increased risk of major bleeding (sub-hazard ratio [SHR] 2.1, 95% CI 1.1-4.0) compared to no RI, but not with VTE recurrence (SHR 0.6, 95% CI 0.2-1.8) or overall mortality (hazard ratio 1.0, 95% CI 0.6-1.9). Moderate RI was not significantly associated with adverse clinical outcomes.

CONCLUSIONS

RI was common among older patients with acute VTE. Severe RI was associated with a 2-fold increased long-term risk of major bleeding, without a risk increase in terms of VTE recurrence and overall mortality. Older patients with moderate RI did not carry worse prognosis.

Venous Thromboembolism in Kidney Diseases and Genetic Predisposition

BACKGROUND

Many renal diseases have been associated with profound clinical effects on thrombosis. To our knowledge, patients with nephrotic syndrome (NS) and chronic kidney disease (CKD) display an elevated risk of vein thrombosis, which is among the common causes of mortality in patients with renal diseases. In addition, venous thrombosis, as a complication, has also been reported in a variety of other renal diseases such as glomerulonephritis without the NS, hypertensive nephropathy, and polycystic kidney disease. With the increasing incidence of kidney diseases and the deeper understanding of the disease, clinicians are becoming more and more aware of the complications of thrombus formation in kidney disease.

SUMMARY

We reviewed recent publications of vein thrombosis in kidney diseases, including primary and secondary glomerular diseases, CKD, hereditary kidney disease, renal transplantation, and hemodialysis-induced, catheter-related thrombus, focusing mainly on the main clinical manifestations, possible mechanisms, related risk factors as well as hereditary influencing factors.

KEY MESSAGES

Vein thrombosis is a complicated complication of a wide spectrum of kidney diseases due to different possible underlying mechanisms.

Tryptophan Metabolites Regulate Neuropentraxin 1 Expression in Endothelial Cells

In patients with chronic kidney disease (CKD) and in animal models of CKD, the transcription factor Aryl Hydrocabon Receptor (AhR) is overactivated. In addition to the canonical AhR targets constituting the AhR signature, numerous other genes are regulated by this factor. We identified neuronal pentraxin 1 (NPTX1) as a new AhR target. Belonging to the inflammatory protein family, NPTX1 seems of prime interest regarding the inflammatory state observed in CKD. Endothelial cells were exposed to tryptophan-derived toxins, indoxyl sulfate (IS) and indole-3-acetic acid (IAA). The adenine mouse model of CKD was used to analyze NPTX1 expression in the burden of uremia. NPTX1 expression was quantified by RT-PCR and western blot. AhR involvement was analyzed using silencing RNA. We found that IS and IAA upregulated NPTX1 expression in an AhR-dependent way. Furthermore, this effect was not restricted to uremic indolic toxins since the dioxin 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) and the tryptophan photoproduct 6-formylindolo[3,2-b]carbazole (FICZ) do the same. In CKD mice, NPTX1 expression was increased in the aorta. Therefore, NPTX1 is a new target of AhR and further work is necessary to elucidate its exact role during CKD.

Biomarkers as MEDiators of racial disparities in risk factors (BioMedioR): Rationale, study design, and statistical considerations

PURPOSE

Relative to White adults, Black adults have a substantially higher prevalence of hypertension and diabetes, both key risk factors for stroke, cardiovascular disease, cognitive impairment, and dementia. Blood biomarkers have shown promise in identifying contributors to racial disparities in many chronic diseases.

METHODS

We outline the study design and related statistical considerations for a nested cohort study, the Biomarker Mediators of Racial Disparities in Risk Factors (BioMedioR) study, within the 30,239-person biracial REasons for Geographic And Racial Differences in Stroke (REGARDS) study (2003-present). Selected biomarkers will be assessed for contributions to racial disparities in risk factor development over median 9.4 years of follow-up, with initial focus on hypertension, and diabetes. Here we outline study design decisions and statistical considerations for the sampling of 4,400 BioMedioR participants.

RESULTS

The population for biomarker assessment was selected using a random sample study design balanced across race and sex to provide the optimal opportunity to describe association of biomarkers with the development of hypertension and diabetes. Descriptive characteristics of the BioMedioR sample and analytic plans are provided for this nested cohort study.

CONCLUSIONS

This nested biomarker study will examine pathways with the target to help explain racial differences in hypertension and diabetes incidence.

Causal effect of renal function on venous thromboembolism: a two-sample Mendelian randomization investigation

Whether renal function is causally associated with venous thromboembolism (VTE) is not yet fully elucidated. We conducted a two-sample Mendelian randomization (MR) study to determine the causal effect of renal function, measured as estimated glomerular filtration rate (eGFR), on VTE. Single-nucleotide polymorphisms associated with eGFR were selected as instrumental variables at the genome-wide significance level (p < 5 × 10⁻⁸) from a meta-analysis of 122 genome-wide association studies including up to 1,046,070 individuals. Summary-level data for VTE were obtained from the FinnGen consortium (6913 VTE cases and 169,986 non-cases) and UK Biobank study (4620 VTE cases and 356,574 non-cases). MR estimates were calculated using the random-effects inverse-variance weighted method and combined using fixed-effects meta-analysis. Genetically predicted decreased eGFR was significantly associated with an increased risk of VTE in both FinnGen and UK Biobank. For one-unit decrease in log-transformed eGFR, the odds ratios of VTE were 2.93 (95% confidence interval (CI) 1.25, 6.84) and 4.46 (95% CI 1.59, 12.5) when using data from FinnGen and UK Biobank, respectively. The combined odds ratio was 3.47 (95% CI 1.80, 6.68). Results were consistent in all sensitivity analyses and no horizontal pleiotropy was detected. This MR-study supported a casual role of impaired renal function in VTE.

Thrombolome and Its Emerging Role in Chronic Kidney Diseases

Patients with chronic kidney disease (CKD) are at an increased risk of thromboembolic complications, including myocardial infarction, stroke, deep vein thrombosis, and pulmonary embolism. These complications lead to increased mortality. Evidence points to the key role of CKD-associated dysbiosis and its effect via the generation of gut microbial metabolites in inducing the prothrombotic phenotype. This phenomenon is known as thrombolome, a panel of intestinal bacteria-derived uremic toxins that enhance thrombosis via increased tissue factor expression, platelet hyperactivity, microparticles release, and endothelial dysfunction. This review discusses the role of uremic toxins derived from gut-microbiota metabolism of dietary tryptophan (indoxyl sulfate (IS), indole-3-acetic acid (IAA), kynurenine (KYN)), phenylalanine/tyrosine (p-cresol sulfate (PCS), p-cresol glucuronide (PCG), phenylacetylglutamine (PAGln)) and choline/phosphatidylcholine (trimethylamine N-oxide (TMAO)) in spontaneously induced thrombosis. The increase in the generation of gut microbial uremic toxins, the activation of aryl hydrocarbon (AhRs) and platelet adrenergic (ARs) receptors, and the nuclear factor kappa B (NF-κB) signaling pathway can serve as potential targets during the prevention of thromboembolic events. They can also help create a new therapeutic approach in the CKD population.

Clinical factors associated with massive pulmonary embolism and PE-related adverse clinical events

Background

Clinicians evaluating acute PE patients often have to identify risks for massive PE, a measure of hemodynamic instability and its consequence, massive PE related adverse clinical events (PEACE). We investigated the association of these risk factors with massive PE and PEACE in a consecutive PE cohort (n = 364).

Methods

Massive PE was defined as an acute central clot (proximal to the lobar artery) in a patient with right heart strain and systolic blood pressure ≤ 90 mg. PEACE was defined as any massive PE who died or required one or more of the following: ACLS, assisted ventilation, vasopressor use, thrombolytic therapy, or invasive thrombectomy, within seven days of PE diagnosis. Univariate and multivariate analysis assessing associations between the risk factors (age, gender, comorbidities, PE provoking risks, and whether the PE was felt to be idiopathic) and massive PE or PEACE were performed. Significance was determined at p < 0.05.

Results

Thirteen percent (n = 48) of patients presented with massive PE, and 9% (n = 32) had PEACE. In the final multivariate model, recent invasive procedure (RR = 7.4, p = 0.007), recent hospitalization (RR = 7.3, p = 0.002), and idiopathic PE (RR = 6.5, p = 0.003) were associated with massive PE. Only idiopathic PE (RR = 5.7, p = 0.005) was significantly associated with PEACE. No comorbidities or other PE provoking risks were associated with massive PE or PEACE.

Conclusions

As a take-home message, recent invasive procedure, recent hospitalization, and idiopathic PE were associated with massive PE, and only idiopathic PE was associated with PEACE. Simultaneously, comorbidities like age or chronic cardiopulmonary disease seem not to be associated with massive PE or PEACE.

Statins and risk of thromboembolism: A meta-regression to disentangle the efficacy-to-effectiveness gap using observational and trial evidence

BACKGROUND AND AIMS

Meta-analyses of randomised controlled trials (RCTs) and observational studies indicate a lower risk of venous thromboembolism (VTE) associated with statin treatment. We aimed to compare the effect of statin therapy in these two settings and to identify and quantify potential factors to explain statin efficacy and effectiveness.

METHODS AND RESULTS

We electronically searched on December 11th, 2018, articles reporting on first VTE events in RCTs (statin vs placebo) and in observational studies (participants exposed vs non-exposed to statin). We performed Knapp-Hartung random-effect meta-analyses to calculate pooled relative risks (RRs) of VTE events associated with statin treatment, separately for RCTs and observational studies; and estimated the ratio of the relative risk (RRR) comparing RCTs and observational studies using meta-regressions, progressively adjusted for study-level characteristics. Twenty-one RCTs (115,107 participants; 959 events) and 8 observational studies (2,898,096 participants; 19,671 events) were included. Pooled RRs for RCTs and observational studies were 0.82 (95% confidence interval (CI): 0.67-1.00; I² 19.2%) and 0.60 (95% CI: 0.42-0.86; I² 86.3%), respectively. In meta-regressions, the unadjusted RRR indicated a nonsignificant 23% smaller benefit in RCTs (RRR 0.77; 95% CI: 0.52-1.13); accounting for age, sex, geographical region, and duration of follow-up, there was a sensible change of the RRR which resulted 0.30 (95% CI: 0.13-0.68).

CONCLUSION

Differences in the characteristics between patients included in RCTs and those in observational studies may account for the differential effect of statins in preventing VTE in the two settings.

Inhibition of Soluble Epoxide Hydrolase for Renal Health

A soluble epoxide hydrolase (sEH) mediates the metabolism of epoxy fatty acids to form the corresponding vicinal diols, which are usually inactive or less active than the epoxide substrates. The sEH enzyme presents in many organs, including but not limited to the liver, heart, spleen, lung, and kidney. Here we summarized the changes in the expression and activity of sEH in multiple renal diseases, such as acute kidney injury (AKI), diabetic nephrology (DN), chronic kidney diseases (CKD), hypertension-mediated renal damage, and other renal dysfunctions. We also discussed the pharmacologic effects and the underlying mechanisms of sEH inhibition by using an inhibitor of sEH and/or the generic deletion of sEH on multiple renal diseases. We believe that sEH is a potential therapeutic target for renal dysfunction although the target disease needs further investigation.

Venous thromboembolism, factor VIII and chronic kidney disease

Chronic kidney disease (CKD) affects 30 million Americans and is associated with approximately a two-fold increased risk of venous thromboembolism (VTE). There is a graded increased risk of VTE across declining kidney function, as measured by estimated glomerular filtration rate (eGFR) and albuminuria. When patients with end-stage kidney disease (ESKD) experience VTE they are more likely than the general population to be hospitalized and they have a higher mortality. The incidence and consequences of VTE may also differ depending on the cause of kidney disease. In addition, kidney transplant patients with VTE are at a greater risk for death and graft loss than transplant patients without VTE. The reasons that patients with CKD are at increased risk of VTE are not well understood, but recent data suggest that factor VIII is a mediator. Factor VIII is an essential cofactor in the coagulation cascade and a strong risk factor for VTE in general. It is inversely correlated with eGFR and prospective studies demonstrate that factor VIII activity predicts incident CKD and rapid eGFR decline. The etiology of CKD may also influence factor VIII levels. This review summarizes the epidemiology VTE in CKD and reviews the biochemistry of factor VIII and determinants of its levels, including von Willebrand factor and ABO blood group. We explore mechanisms by which the complications of CKD might give rise to higher factor VIII and suggests future research directions to understand how factor VIII and CKD are linked.