Thrombophilia and the Risk for Hemodialysis Vascular Access Thrombosis

Heterogeneous gene expression during early arteriovenous fistula remodeling suggests that downregulation of metabolism predicts adaptive venous remodeling

Clinical outcomes of arteriovenous fistulae (AVF) for hemodialysis remain inadequate since biological mechanisms of AVF maturation and failure are still poorly understood. Aortocaval fistula creation (AVF group) or a sham operation (sham group) was performed in C57BL/6 mice. Venous limbs were collected on postoperative day 7 and total RNA was extracted for high throughput RNA sequencing and bioinformatic analysis. Genes in metabolic pathways were significantly downregulated in the AVF, whereas significant sex differences were not detected. Since gene expression patterns among the AVF group were heterogenous, the AVF group was divided into a 'normal' AVF (nAVF) group and an 'outliers' (OUT) group. The gene expression patterns of the nAVF and OUT groups were consistent with previously published data showing venous adaptive remodeling, whereas enrichment analyses showed significant upregulation of metabolism, inflammation and coagulation in the OUT group compared to the nAVF group, suggesting the heterogeneity during venous remodeling reflects early gene expression changes that may correlate with AVF maturation or failure. Early detection of these processes may be a translational strategy to predict fistula failure and reduce patient morbidity.

Antiphospholipid Antibodies Associated with Native Arteriovenous Fistula Complications in Hemodialysis Patients: A Comprehensive Review of the Literature

Antiphospholipid antibody (aPL)-persistent positivity is frequent in hemodialysis (HD) patients. Native arteriovenous fistula (AVF) complications such as stenosis and thrombosis are among the most important causes of morbidity and mortality in hemodialysis patients. The association between aPL positivity and AVF thrombosis seems to now be well established. However, whether aPL positivity is associated with other AVF complications, such as maturation failure or stenosis, is not well known. Given the significant impact of AVF failure on patient's prognosis, it is of interest to further investigate this particular point in order to improve prevention, surveillance and treatment, and, ultimately, the patient's outcome. This literature review aims to report the recent literature on aPL-associated native AVF complications.

Frequent vascular access thrombosis in a patient with end stage kidney disease on hemodialysis

Vascular access thrombosis (VAT) is common among patients receiving hemodialysis and leads to missed dialysis treatments, hospitalizations, catheter placement, and graft/fistula abandonment. This article reviews the association between hypercoagulability and VAT and the high prevalence of hypercoagulable states in end-stage kidney disease (ESKD). This article reviews the role of antithrombotic and anticoagulant medications in preventing VAT. The article concludes by reviewing the unique challenges of using vitamin K antagonists in patients with ESKD.

HD, Sarma P, Srikanth L, V. SK. Thrombophilic risk factors and ABO blood group profile for arteriovenous access failure in end stage kidney disease patients: a single-center experience

INTRODUCTION

Thrombosis of fistula occurs most frequently in end-stage kidney disease (ESKD) patients receiving hemodialysis. However, the role of thrombophilia in arteriovenous fistula (AVF) failure has not been well established. Hence, this study was aimed at assessing the roles of hereditary and acquired thrombophilic factors in association with AVF failure among patients with ESKD undergoing hemodialysis.

METHODS

A cross-sectional study was conducted on 100 ESKD patients, of whom 50 patients with well-functioning AVFs with no fistula failures earlier were enrolled as Group 1, and 50 patients who have had AVF failure were enrolled as Group 2. The hereditary factors as factor V Leiden, factor XIII, prothrombin, and methylene tetrahydrofolate reductase and the acquired factors as lipoprotein (a), fibrinogen, homocysteine, and anticardiolipin antibodies IgG and IgM were studied.

RESULTS

Among the hereditary factors, no statistically significant difference was observed in relation to factor V Leiden and Prothrombin (p > 0.05). However, for factor XIII and methylene tetrahydrofolate reductase, a statistically significant difference was observed between patients with well-functioning AVFs and patients who have had AVF failure (p < 0.05). We found a statistically significant increase in all the acquired factors in patients who have had AVF failure in comparison with patients with well-functioning AVFs (p < 0.001). Association between ABO blood groups and thrombophilic factors showed significant association between factor V Leiden, anticardiolipin antibody IgG and IgM and ABO blood groups (p < 0.05), whereas none of the other thrombophilic factors showed significant association (p > 0.05).

CONCLUSION

Thus, our study suggests significant role of acquired factors in causing AVF failure.

Medical Adjuvant Therapy in Reducing Thrombosis With Arteriovenous Grafts and Fistulae Use: A Meta-Analysis of Randomized Controlled Trials

Hemodialysis is required for patients with end-stage renal disease (ESRD) that require arteriovenous (AV) grafts or fistulas for vascular access. These access points are prone to thrombosis. To determine the effect of medical adjuvant therapy on AV graft/fistula patency among patients with ESRD on hemodialysis. Adhering to the PRISMA 2020 statement, a systematic search was conducted until August 20, 2021, with keywords including arteriovenous graft, fistula, patency, thrombosis, hemodialysis, adjuvant treatment. The following databases were searched: PubMed, Scopus, Web of Science, CINAHL Plus, and Cochrane. A random-effects model was employed using Review Manager 5.4 for data analysis. The meta-analysis pooled in 1985 participants with 1000 (50.4%) in the medical adjuvant treatment group. At a snapshot, medical adjuvant therapy reduced the risk for graft thrombosis (RR = 0.64, P = .02). Notable medications included aspirin for graft thrombosis (RR = 0.36, P = .006) and ticlopidine for fistula thrombosis (RR = 0.53, P = .01). Certain antiplatelet therapies (aspirin and ticlopidine) reduced the number of patients with AV fistula/graft thrombosis among patients with high heterogeneity among the trials. Other therapies (fish oil, sulfinpyrazone, clopidogrel, and aspirin/dipyridamole) did not demonstrate significant improvement but may be promising once concrete evidence is available. Potential benefits of anti-platelet therapies may be explored to maintain the potency of AV grafts/fistulas through well-designed placebo-controlled trials and long-term follow-up.

Hereditary thrombophilia and thrombosis of tunneled hemodialysis catheters: A single center study

Introduction: Vascular access thrombosis increases the risk of mortality and morbidity in end-stage renal disease (ESRD) patients on hemodialysis (HD). This study aimed to evaluate hereditary thrombophilia factors in HD patients and its association with tunneled cuffed catheters’ thrombosis.

Methods: In this cross-sectional study, 60 consecutive patients with ESRD on HD with tunneled cuffed catheters were selected. Inherited thrombophilia factors (Anti-thrombin III, Protein C, Protein S, and Factor V Leiden) were measured and the patients were followed for 3 months to evaluate the incidence of catheter-related thrombosis. The association between these factors and catheter thrombosis was assessed.

Results: The mean age of patients was 60.30 ± 8.69 years. Forty-seven patients (78.30%) were female and thirteen patients (21.70%) were male. The most common cause of ESRD was diabetes mellitus (41.67%). The most catheter site was the right internal jugular vein (55%). There were 22 (36.67%) and 8 (13.33%) cases of thrombosis and mortality, respectively. The association between hereditary thrombophilia factors and catheter thrombosis was not statistically significant (P > 0.05).

Conclusion: In this small group of our patients, the frequency of hereditary thrombophilia was not significantly different between those with and without thrombosis of tunneled HD catheter.

Association of Dysfunction of Vascular Access for Hemodialysis With Major Adverse Cardiovascular Events - A Group-Based Trajectory Model Analysis

BACKGROUND

An unconventional risk factor, "dysfunction of hemodialysis vascular access", was demonstrated to be associated with subsequent major adverse cardiovascular events (MACE) in our previous study. However, applying this suggestion in a clinical scenario may be not intuitive. A group-based trajectory model was applied to further recognize those patients with the highest risks for MACE.Methods and Results:In a cohort of patients who received hemodialysis from 2001 to 2010, we identified 9,711 cases that developed MACE in the stage of stable maintenance dialysis, and 19,422 randomly selected controls matched to cases on age, gender and duration of dialysis. Events of vascular access dysfunction in the 6-month period before MACE for cases and index dates for controls were evaluated. By group-based trajectory modeling, patients according to their counts of vascular access dysfunction in each month over the 6-month period prior to MACE or index dates were categorized. There were 26,744 patients in group 1 (no dysfunction), 650 in group 2 (escalating dysfunction) and 1,739 in group 3 (persistent dysfunction). Logistic regression analysis indicated that patients in group 3 had the highest chance of subsequent MACE (odds ratio 2.47, in comparison with group 1) after controlling for all the available potential confounders.

CONCLUSIONS

Uninterrupted clusters of vascular access dysfunction are associated with a higher risk of subsequent MACE.

Plasma D-Dimer Level and the Failure of Forearm Autologous Arteriovenous Fistula in Patients With End-Stage Renal Disease

Failed autologous arteriovenous fistula (AVF) is a major issue in the creation of functional hemodialysis vascular access. To date, the relationship between D-dimer and AVF failure is still uncertain. Hence, we conducted a retrospective cohort study to explore the patency rate of forearm AVFs and to clarify whether plasma D-dimer level can predict the failure of AVFs. In this study, 290 ESRD patients (the mean age 54.1 ± 14.6 years, 63.8% of them were males) receiving forearm AVFs surgery were consecutively enrolled with a median follow-up time of 34 months. Primary patency rates and risk factors associated with AVFs failure were explored by the Kaplan-Meier method or Cox proportional hazards model. Patients were divided into two groups based on the median level of D-dimer (group 1 <1.1 mg/L and group 2 ≥1.1 mg/L). The Kaplan-Meier survival analysis demonstrated that the patency of AVF in group 1 was similar in group 2, which were 92.4% versus 88.9%, 84.8% versus 84.0%, 80.0% versus 79.2%, 76.7% versus 78.5%, and 76.7% versus 78.5% at 12, 24, 36, 48, and 60 months (Log-rank test, P = 0.8), respectively. In the crude analysis, D-dimer (per 1 mg/L increase) was independently associated with AVFs failure, with OR of 1.08 (95% CI, 1.02-1.15). However, after adjusting for potential confounders, the D-dimer (per 1 mg/L increase) was not associated with the AVFs failure (OR = 1.06, 95% CI = 0.99-1.13). This study did not find that the plasma D-dimer level can predict the failure of forearm AVFs.

Determinants of successful arteriovenous fistulae creation including intraoperative transit time flow measurement

BACKGROUND

The prevalence of hemodialysis patients is increasing, and it is important to create the arteriovenous fistula as early as possible to avoid hemodialysis by central venous catheter. International guidelines recommend arteriovenous fistula as the vascular access of first choice. Arteriovenous fistulae are associated with a failure rate of 23%. The success of an arteriovenous fistula can be evaluated intraoperatively by physical examination and by measuring the blood flow.

OBJECTIVES

The aim of the study is to describe the predictive value of various factors for fistula maturation in the context to the current literature.

METHODS

We report on a prospective cohort study of 41 patients, undergoing a primary arteriovenous fistula at the upper extremity. The primary endpoint of the study was the successful fistula maturation after 6 weeks.

RESULTS

The intraoperative measurement of the blood flow in the outflow vein has been identified as the unique significant parameter for the fistula maturation.

CONCLUSION

The predictive value of intraoperative flow measurement is superior to intraoperative physical examination and could help reduce the fistula dysmaturation rate. Intraoperative transit time flow measurement is an easy method and can be used to predict successful fistula maturation in a high percentage rate.

Thrombophilic risk factors in hemodialysis: Association with early vascular access occlusion and patient survival in long-term follow-up

Objective

Thrombophilic risk factors (TRFs) occur rather frequently in hemodialysis (HD) patients. However, little is known about their significance in HD patients, besides their potential impact on arteriovenous (AV) access failure, with varying results. We examined the effects of a wide variety of TRFs on both early AV fistula occlusion and survival among HD patients in long-term follow-up.

Methods

In this single-center, observational study, 70 consecutive HD patients from our dialysis center were examined with respect to shunt occlusion within the first 2 years after fistula creation and patient survival in a long-term follow-up (at least 16 years). We examined the presence of factor V, prothrombin, and MTHFR mutations using real-time fluorescence polymerase chain reaction. Furthermore, antithrombin (AT), protein C, protein S, and antiphospholipid antibodies (APL-Abs) were assessed.

Results

Among the 70 patients, 32 had MTHFR mutations, 10 had heterozygous factor V Leiden mutations, 4 had prothrombin mutations, 4 had protein S deficiency, 2 had protein C deficiency, 9 had AT deficiency, and 14 had APL-Abs. 40 patients had shunt occlusion. TRFs were associated with a significantly increased risk for shunt thrombosis (P<0.02). Kaplan–Meier analysis with a log-rank test revealed significantly shorter survival in HD patients with TRFs (P<0.02). Cox regression analysis showed that the presence of TRFs (P<0.05; hazard ratio, 1.94; 95% CI: 1.07–3.56), but not early shunt occlusion, was associated with short patient survival.

Conclusions

TRFs in hemodialysis patients have a strong impact on patient survival and early AV fistula failure; however, patient survival is not significantly affected by early shunt occlusion.

Primary antiphospholipid syndrome in a hemodialysis patient with recurrent thrombosis of arteriovenous fistulas

INTRODUCTION

The antiphospholipid syndrome is a systemic autoimmune disease defined by recurrent vascular and/or obstetrical morbidity that occurs in patients with persistent antiphospholipid antibodies.

CASE PRESENTATION

A patient on hemodialysis with a primary antiphospholipid syndrome presented with recurrent vascular access thrombosis, obstetrical complications, and positive lupus anticoagulant. The patient had multiple arteriovenous fistulas that failed due to thrombosis. The obstetrical morbidity was defined by one miscarriage at the 7th week of gestation and a pregnancy complicated by pre-eclampsia with preterm delivery at the 28th week of gestation. A thorough thrombophilia screening confirmed the presence of antiphospholipid antibody. Lupus anticoagulant was present in plasma, measured on two occasions 12 weeks apart.

CONCLUSION

Thrombophilias are inherited or acquired predispositions to vascular thrombosis and have been associated with thrombosis of the arteriovenous fistula. Patients on hemodialysis with recurrent vascular access thrombosis and presence of thrombophilia should be evaluated about the need for anticoagulant therapy with a vitamin K antagonist.

Protein C and protein S deficiencies may be related to survival among hemodialysis patients

Background

Thrombophilia due to protein C (PC) and protein S (PS) deficiencies is highly prevalent among patients with stage 5 chronic kidney disease and is reported to arise due to extracorporeal circulation during hemodialysis (HD). This study aimed to evaluate the relationship between HD treatment and thrombophilia.

Methods

A total of 114 Japanese patients on maintenance HD (62 men, 52 women) were followed during 2008–2011. Their survival rates were compared against the duration of HD. Prior to each HD, coagulation/fibrinolysis parameters and PC and PS activities were measured using standard techniques. The patients were divided into two groups: Group 1, with PC and/or PS deficiencies (n = 32), and Group 2, without PC and PS deficiencies (n = 82). The influence of such deficiencies and duration of dialysis on survival was examined. Time-to-event analysis was applied using Kaplan-Meier estimates, and the log-rank test was proposed to test the equivalence of relative survival data. Hazard ratios and 95% confidence intervals (CI) were calculated.

Results

Of the 114 patients, 37 died (Group 1, 22; Group 2, 15). The hazard ratio (95% CI) was higher (p = 0.004) in Group 1 than Group 2. Gene analyses of PC and PS were performed in 14 patients from Group 1. No mutations in either protein were observed. We analyzed the causes of death in both groups; however, the estimated thrombophilia-related incidence of death could not be determined due to small sample size of HD patients.

Conclusions

Our results suggest that PC and PS deficiencies may be related to survival in HD patients. However, this finding warrants additional research.

Thrombophilia Associated with Early Post-angioplasty Thrombosis of Dialysis Vascular Access

AIM

Percutaneous transluminal angioplasty (PTA) is widely used as the primary treatment for dialysis vascular access dysfunction. Nonetheless, many patients develop early occlusion after angioplasty. Thus, we investigated the role of thrombophilia in access occlusion within 30 days of angioplasty.

MATERIALS AND METHODS

This case-control study included patients who underwent PTA for dialysis vascular access dysfunction. Patients who experienced occlusion within 30 days of angioplasty were included in the case group and those without occlusion for at least 30 days after angioplasty were included in the control group. All patients were tested for protein C, protein S, antithrombin III, lupus anticoagulant, and anticardiolipin antibodies.

RESULTS

From February to October 2015, 462 patients underwent PTA for dialysis vascular access dysfunction. Forty-one patients (8.9%) had early occlusion within 30 days of angioplasty. The case group had more graft accesses (73 vs. 31%, P < 0.001) and thrombotic occlusions (67 vs. 15%, P < 0.001). A higher incidence of protein C (10 vs. 2%), protein S (15 vs. 5%), and antithrombin III (10 vs. 2%) deficiency and elevated anticardiolipin antibody (22 vs. 10%) levels were observed in the case group. Overall, 26 patients (63%) in the case group had at least one thrombophilic factor, compared with 15 patients (37%) in the control group (unadjusted odds ratio [OR], 3.004; 95% confidence interval [CI], 1.223-7.380; P = 0.027). After adjustment for confounding factors, the association between thrombophilic factors and early occlusion remained (adjusted OR, 3.806; 95% CI, 1.018-14.220; P = 0.047).

CONCLUSION

Thrombophilia is associated with early occlusion after angioplasty for hemodialysis vascular access.

Risk of Vascular access Thrombosis in Patients with Systemic Lupus Erythematosus on Hemodialysis

Introduction

Anticardiolipin antibody is associated with increased risk of vascular access thrombosis (VAT) in hemodialysis (HD) patients. Systemic lupus erythematous (SLE) patients have a high prevalence of anticardiolipin antibodies, but it is not clear whether these patients are at high risk of developing vascular access thrombosis.

Methods

Thirty six SLE patients on HD, who had either an arterio-venous (AV) graft or AV fistula as vascular access, and were not on anticoagulation treatment, were retrospectively identified at Henry Ford Hospital. A similar number of patients without SLE, matched for age, sex, race and type of vascular access were selected as a control population. Vascular access thrombosis rate at one year was compared between two groups.

Results

Mean age at dialysis was 36±10 years in 36 SLE patients (28 females, 8 males) and was 38±6.4 years in 36 non-SLE patients (29 females, 7 males). Of all patients, 29/36 (80.5%) SLE and 27/36 (75%) non-SLE patients had AV grafts, whereas the rest had AV fistulas as vascular access (19.5% SLE and 25% non-SLE patients). Out of 36 SLE patients, 24 (66.6%) patients developed VAT at one year as compared to 14 (38.9%) patients in non-SLE group (p<0.05). The odds ratio of VAT in SLE patients was 3.1 (95% CI 1.2–8.2).

Conclusion

SLE patients on hemodialysis are more likely to develop vascular access thrombosis as compared to non-SLE patients.

The association of genotype polymorphisms with vascular access patency in hemodialysis patients

Some hemodialysis patients suffer from repeat dysfunction of dialysis vascular access and need procedures of angioplasty, thrombectomy, and even temporary catheter use. Why these patients are vulnerable to vascular access dysfunction and how to improve its patency are imperative to be discovered. Traditional risk factors for vascular access function had been widely investigated but could not fully explain this question. Several genotype polymorphisms were demonstrated to increase the incidence of cardiovascular disease and might also be linked to higher risk of vascular access dysfunction. As the major causes of arteriovenous access thrombosis are hypercoagulable status and arteriovenous access stenosis, the investigated genes mainly focus on the mediators of the coagulation cascade, inflammatory process, and endothelial dysfunction. The reported polymorphisms of genes significantly associated with arteriovenous access dysfunction included genes encoding methylene tetrahydrofolate reductase, coagulation factors, heme oxygenase-1, matrix metalloproteinase, transforming growth factor-β1, tumor necrosis factor-α, vascular endothelial growth factor-A, renin-angiotensin-aldosterone system, and protein methyl transferase. However, further prospective study is indispensable to elucidate the association between the genotype polymorphisms and the outcome of vascular access. More and more therapeutic options that focus on genotype polymorphisms may generate a great benefit to the patency of vascular access of uremic patients.

Hemodialysis access thrombosis

For the over 400,000 patients in the United States dependent on hemodialysis, arteriovenous (AV) access thrombosis may lead to missed dialysis sessions, inpatient admissions and the need for placement of temporary dialysis catheters. It is also the leading cause of permanent access loss. Percutaneous declotting is generally preferred over surgical thrombectomy. Various percutaneous approaches can be employed including the lyse-and-wait technique, thromboaspiration, pulse spray aided pharmacomechanical thrombolysis, and use of mechanical thrombectomy device.

Preoperative management of arteriovenous fistula (AVF) for hemodialysis

Native arteriovenous fistula (AVF) is the favorite access for hemodialysis (HD). The National Kidney Foundation's Kidney Disease Outcomes Quality Initiative (KDOQI) recommends its creation in most patients with renal failure. Unfortunately, intensive efforts to promote native AVF in patients with marginal vessels have increased the rate of primary fistula failure. A non-functioning fistula prompts the use of central venous catheter (CVC) that, unlike AVF, has been associated with an increased risk of morbidity and mortality among patients receiving HD. We believe that successful and timely AVF placement relies on the development of a multidisciplinary integrated preoperative program divided into five stages: (i) management of patients with advanced chronic kidney disease (CKD), (ii) management of preoperative risk factors for AVF failure, (iii) planning of native AVF, (iv) assessment of patient eligibility and (v) preoperative vascular mapping. Focusing specifically on native AVF, we review scientific evidence regarding preoperative management of this vascular access in order to favor construction of long-term functioning fistula minimizing development of severe complications.

Comparison of Complications of Arteriovenous Fistula with Permanent Catheter in Hemodialysis Patients: A Six-month Follow-up

Background:

Arteriovenous fistula (AVF), permanent catheter (PC), and vascular graft are three vascular access types used for hemodialysis procedure. Due to insufficient reliable information on the comparison between AVF and PC, this study was conducted to compare AVF and PC regarding dialysis adequacy.

Materials and Methods:

This prospective study was carried out from March, 2013 to September, 2013. In this study, 76 hemodialysis patients were enrolled and assigned to two unequal groups of AVF and PC. Before and after the dialysis session, blood samples were taken for laboratory examinations and measurement of urea reduction ratio (URR) and Kt/V. The patients were followed up for six months, and then laboratory examinations were repeated.

Results:

Of the 76 hemodialysis patients, 30 had AVF and others PC. During the 6-month follow-up, 24 patients in PC group but only one patient in AVF group showed infection (P = 0.006), while in each group, three cases of thrombosis were seen (P = 0.58); however, catheter dysfunction was seen in 13 patients of PC group but no patients of AVF group (P = 0.004). There was no difference between the two groups in Kt/V and URR at the beginning of the study; however, after six months, Kt/V and URR were greater in AVF group (P < 0.05).

Conclusions:

In addition to some advantages of AVF over PC, such as lower rate of infection and thrombosis, we also found better dialysis adequacy in AVF group. We recommend that AVF be created in all of patients with chronic kidney disease who are candidates for hemodialysis.

The molecular mechanisms of hemodialysis vascular access failure

The arteriovenous fistula has been used for more than 50 years to provide vascular access for patients undergoing hemodialysis. More than 1.5 million patients worldwide have end stage renal disease and this population will continue to grow. The arteriovenous fistula is the preferred vascular access for patients, but its patency rate at 1 year is only 60%. The majority of arteriovenous fistulas fail because of intimal hyperplasia. In recent years, there have been many studies investigating the molecular mechanisms responsible for intimal hyperplasia and subsequent thrombosis. These studies have identified common pathways including inflammation, uremia, hypoxia, sheer stress, and increased thrombogenicity. These cellular mechanisms lead to increased proliferation, migration, and eventually stenosis. These pathways work synergistically through shared molecular messengers. In this review, we will examine the literature concerning the molecular basis of hemodialysis vascular access malfunction.

Impact of Indoxyl Sulfate on Progenitor Cell-Related Neovascularization of Peripheral Arterial Disease and Post-Angioplasty Thrombosis of Dialysis Vascular Access

Patients with chronic kidney disease (CKD) have an increased risk of vascular disease, which is associated with considerable health care costs. Vascular disease in CKD differs clinically and pathobiologically from that in patients with normal renal function. Besides the traditional risk factors, retention of uremic toxins contributes to the pathogenesis of vascular disease in patients with CKD. Indoxyl sulfate is a protein-bound uremic toxin and is inefficiently removed by conventional dialysis. Accumulating evidence suggests that indoxyl sulfate is a vascular toxin involved in atherosclerosis, arteriosclerosis, vascular calcification and vascular repair. Clinically, indoxyl sulfate is associated with total and cardiovascular mortality in patients with CKD. Recent studies have indicated that in addition to coronary and cerebral arteries, indoxyl sulfate plays a role in peripheral artery disease (PAD) and dialysis graft thrombosis. Emerging evidence suggests that indoxyl sulfate is implicated via novel mechanisms, including progenitor cell-related neovascularization and tissue factor-related hypercoagulability. These findings raise the possibility that strategies targeting serum indoxyl sulfate may have the potential to improve the outcomes of PAD and dialysis vascular access in patients with CKD.

Coagulation, thrombophilia and patency of arteriovenous fistula in children undergoing haemodialysis compared with healthy volunteers: a prospective analysis

This study aimed to assess whether markers of coagulation, fibrinolysis or thrombophilia are increased in children on haemodialysis compared with controls and whether measurement of any of these factors could help to identify patients at an increased risk of arteriovenous fistula (AVF) occlusion. Blood samples were taken from 55 children immediately before a session of haemodialysis and from 20 healthy volunteers. Thrombin-antithrombin (TAT), D-dimer, plasmin-antiplasmin (PAP) and anticardiolipin immunoglobulin G (ACA-Ig G) were measured by ELISA. Factor V Leiden mutation (G1691A) was determined by gene polymorphism [restriction fragment length polymorphism (RFLP)]. Determination of the patency of the AVF was prospectively followed up for a minimum of 4 years or until the AVF was nonfunctioning. Fifty-five patients were studied with a median follow-up of 659 days (range 30-1670 days). A significant increase was found in the levels of D-dimer, PAP and ACA-Ig G in haemodialysis patients with thrombosed and nonthrombosed native AVFs vs.

CONTROLS

There was a significant difference between both chronic haemodialysis patients with thrombosed and nonthrombosed native AVF with regard to ACA-IgG levels. At 1 year follow-up, primary patency was 61.4% (27 patients). In multivariate analysis, D-dimer was inversely associated with secondary patency.Thrombophilia may predispose children with end stage renal disease to access failure. The promising finding is that in children on haemodialysis, D-dimer levels were increased and inversely correlated with secondary patency. Further evaluation is required into the possible role of D-dimer as a biomarker of AVF occlusion.

Future research directions to improve fistula maturation and reduce access failure

With the increasing prevalence of end-stage renal disease, there is a growing need for hemodialysis. Arteriovenous fistulae (AVF) are the preferred type of vascular access for hemodialysis, but maturation and failure continue to present significant barriers to successful fistula use. AVF maturation integrates outward remodeling with vessel wall thickening in response to drastic hemodynamic changes in the setting of uremia, systemic inflammation, oxidative stress, and pre-existent vascular pathology. AVF can fail due to both failure to mature adequately to support hemodialysis and development of neointimal hyperplasia that narrows the AVF lumen, typically near the fistula anastomosis. Failure due to neointimal hyperplasia involves vascular cell activation and migration and extracellular matrix remodeling with complex interactions of growth factors, adhesion molecules, inflammatory mediators, and chemokines, all of which result in maladaptive remodeling. Different strategies have been proposed to prevent and treat AVF failure based on current understanding of the modes and pathology of access failure; these approaches range from appropriate patient selection and use of alternative surgical strategies for fistula creation, to the use of novel interventional techniques or drugs to treat failing fistulae. Effective treatments to prevent or treat AVF failure require a multidisciplinary approach involving nephrologists, vascular surgeons, and interventional radiologists, careful patient selection, and the use of tailored systemic or localized interventions to improve patient-specific outcomes. This review provides contemporary information on the underlying mechanisms of AVF maturation and failure and discusses the broad spectrum of options that can be tailored for specific therapy.

Association Between Thrombophilic Gene Mutations and the Risk of Vascular Access Thrombosis in Hemodialysis Patients

The cause of thrombosis in hemodialysis vascular access is considered to be of a multifactorial nature, including stenosis of the venous or arterial connection. Therefore, identification of relevant thrombotic risk factors could lead to an improved antithrombotic therapy. This case control study was performed to evaluate the relationship between Factor V (G1691A and A4070G) and Factor II polymorphisms and vascular access thrombosis in hemodialysis patients. One hundred and twenty-one patients undergoing dialysis were selected as subjects. This sample was divided into two groups; a case group of 60 patients who had sustained one or more thrombotic events that resulted in vascular access failure and a control group of 61 patients, who never had a thrombotic occlusion of a functioning permanent dialysis access. Our data demonstrated a significantly increased risk of vascular access thrombosis in carriers of the mutant FV (G1691A and A4070G) polymorphisms (P < 0.05).Further studies on a large-scale population and other genetic variants will be needed to find candidate genes for vascular access thrombosis in hemodialysis patients.

The Reasons for the Failure of the Primary Arteriovenous Fistula Surgery in Patients with End-Stage Renal Disease

Purpose

To analyze the reasons for the failure of the primary arteriovenous fistula surgery and explore preventive measures.

Methods

A total of 819 patients with end-stage renal disease were enrolled in the study. Autologous arteriovenous fistula surgery was performed on all patients. Their clinical data of hemoglobin (HB), albumin (ALB), cholesterol (CHOL), parathyroid hormone (PTH), blood glucose and blood pressure were collected before surgery, while the diameters of the radial artery and cephalic vein were measured by ultrasound.

Results

The operations in 742 patients were successful, but failed in 77 cases (accounting for 7.07%). The failure group was significantly older (61.3 ± 13.4 years) than the successful group (45.6 ± 11.2 years). The ratio of diabetes 36 (46.8%) and hypertension 20 (26.0%) was significantly higher in the failure group than in the successful group, respectively 235 (31.7%) and 145 (19.5%). The patients with blood pressure below 120/70 mm Hg had a higher risk of failed surgery (36.4%) than those with blood pressure above 120/70 mm Hg (9.16%). The cephalic vein and radial artery diameters were significantly smaller in the failure group (1.35 ± 0.64 mm, 2.13 ± 0.81 mm) than in the successful group (1.98 ± 0.47 mm, 2.47 ± 0.74 mm); the PTH levels in the failure group were significantly higher (782.39 ± 423.85) than in the successful group (378.83 ± 352.21).

Conclusions

The autogenous arteriovenous fistula surgery failure highly correlated with the patient's age, blood pressure, the primary disease and the vessel diameter. In addition, the PTH levels had a certain correlation with the failure of the fistula surgery.

Serum Indoxyl Sulfate Associates with Postangioplasty Thrombosis of Dialysis Grafts

Hemodialysis vascular accesses are prone to recurrent stenosis and thrombosis after endovascular interventions.In vitro data suggest that indoxyl sulfate, a protein-bound uremic toxin, may induce vascular dysfunction and thrombosis. However, there is no clinical evidence regarding the role of indoxyl sulfate in hemodialysis vascular access. From January 2010 to June 2013, we prospectively enrolled patients undergoing angioplasty for dialysis access dysfunction. Patients were stratified into tertiles by baseline serum indoxyl sulfate levels. Study participants received clinical follow-up at 6-month intervals until June 2014. Primary end points were restenosis, thrombosis, and failure of vascular access. Median follow-up duration was 32 months. Of the 306 patients enrolled, 262 (86%) had symptomatic restenosis, 153 (50%) had access thrombosis, and 25 (8%) had access failure. In patients with graft access, free indoxyl sulfate tertiles showed a negative association with thrombosis-free patency (thrombosis-free patency rates of 54%, 38%, and 26% for low, middle, and high tertiles, respectively;P=0.001). Patients with graft thrombosis had higher free and total indoxyl sulfate levels. Using multivariate Cox regression analysis, graft thrombosis was independently predicted by absolute levels of free indoxyl sulfate (hazard ratio=1.14;P=0.01) and free indoxyl sulfate tertiles (high versus low, hazard ratio=2.41;P=0.001). Results of this study provide translational evidence that serum indoxyl sulfate is a novel risk factor for dialysis graft thrombosis after endovascular interventions.

Activated Protein C-Resistance Determination and Vascular Access Thrombosis in Populations with High Prevalence of Factor V Leiden

BACKGROUND/AIMS

Factor V Leiden heterozygosity occurs in 3-8% of the general European and US populations. Activated protein C resistance (APC-R)--a non-molecular laboratory test--can efficiently demonstrate the presence of this mutation and can be performed on most coagulation analyzers. On the other hand, fistula or graft thrombosis is a common and costly complication in hemodialysis patients. Our aim was to establish the value of APC-R determination in hemodialysis patients by assessing the risk of access thrombosis in patients with increased APC-R.

METHODS

A total of 133 patients (81 men, mean age 64.5 ± 14.9 years and 52 women, mean age 63.6 ± 15 years) were selected. Participants were divided into 2 groups: those with access thrombosis (54 patients, 40.6%) and those with no access thrombosis (79 patients, 59.4%), and they were tested for the most common congenital or acquired thrombophilia risk factors.

RESULTS

Overall, 12 patients (9%) had an increased APC-R and 10 of them had at least 1 episode of access thrombosis (83.3%). Univariate analysis to estimate crude odds ratio (OR) showed an OR of 8.8 (95% CI 1.8-41.8) times higher risk for access thrombosis in these patients. No significant differences were found after adjusting for age, hypertension, diabetes mellitus, coronary artery disease, cerebrovascular disease, peripheral arterial disease and malignancy. Sex was also a factor influencing thrombosis, presenting a higher OR for women (OR 2.2, 95% CI 1.1-4.4).

CONCLUSION

This study revealed a significant association between access thrombosis and increased APC-R in hemodialysis patients. This indicates that the determination of APC-R should be considered--especially, in populations with a high prevalence of Factor V Leiden--as proper anticoagulant therapy in these patients may reduce the risk of access thrombosis.

Upper Limb Grafts for Hemodialysis Access

Arteriovenous (AV) grafts are required for hemodialysis access when options for native fistulas have been fully exhausted, where they continue to play an important role in hemodialysis patients, offering a better alternative to central vein catheters. When planning autogenous accesses using Doppler ultrasound, adequate arterial inflow and venous outflow must be consciously preserved for future access creation with grafts. Efforts to improve graft patency include changing graft configuration, graft biology and hemodynamics. Industry offers early cannulation grafts to reduce central catheter use and a bioengineered graft is undergoing clinical studies. Although the outcome of AV grafts is inferior to fistulas, grafts can provide long-term hemodialysis access that is a better alternative to central venous catheters. AV grafts have significant drawbacks, mainly poor patency, infection and cost but also have some advantages: early maturation, ease of creation and needling and widespread availability. The outcome of AV graft surgery is variable from center to center. The primary patency rate for AV grafts is 58% at 6 months and the secondary patency rate is 76% at 6 months and 55% at 18 months. There are centers of excellence that report a 1 year secondary patency rate of up to 91%. In this review of the use of AV grafts for hemodialysis access in the upper extremities, technical issues involved in planning the access and performing the surgery in its different configurations are discussed and the role of surveillance and maintenance with their attendant surgical and radiological interventions is described.

Association Between Vascular Access Dysfunction and Subsequent Major Adverse Cardiovascular Events in Patients on Hemodialysis: A Population-Based Nested Case-Control Study

The association between dialysis vascular access dysfunction and the risk of developing major adverse cardiovascular events (MACE) in hemodialysis patients is unclear and has not yet been investigated. We analyzed data from the National Health Insurance Research Database of Taiwan to quantify this association. Adopting a case-control design nested within a cohort of patients who received hemodialysis from 2001 to 2010, we identified 9711 incident cases of MACE during the stage of stable maintenance dialysis and 19,422 randomly selected controls matched to cases on age, gender, and duration of dialysis. Events of vascular access dysfunction in the 6-month period before the date of MACE onset (ie, index date) for cases and before index dates for controls were evaluated retrospectively. The presence of vascular access dysfunction was associated with a 1.385-fold higher odds of developing MACE as estimated from the logistic regression analysis. This represents a significantly increased adjusted odds ratio (OR) at 1.268 (95% confidence interval [CI] = 1.186-1.355) after adjustment for comorbidities and calendar years of initiating dialysis. We also noted a significant exposure-response trend (P < 0.001) between the frequency of vascular access dysfunction and MACE, with the greatest risk (adjusted OR = 1.840, 95% CI = 1.549-2.186) noted in patients with ≥3 vascular access events. We concluded that dialysis vascular access dysfunction was significantly associated with an increased risk of MACE. Hence, vascular access failure can be an early sign for MACE in patients receiving maintenance hemodialysis. Active monitoring and treatment of cardiovascular risk factors and related diseases, not merely managing vascular access dysfunction, would be required to reduce the risk of MACE.

A Patient with Recurrent Arteriovenous Graft Thrombosis

Arteriovenous grafts (AVGs) are prone to frequent thrombosis that is superimposed on underlying hemodynamically significant stenosis, most commonly at the graft-vein anastomosis. There has been great interest in detecting AVG stenosis in a timely fashion and performing preemptive angioplasty, in the belief that this will prevent AVG thrombosis. Three surveillance methods (static dialysis venous pressure, flow monitoring, and duplex ultrasound) can detect AVG stenosis. Whereas observational studies have reported that surveillance with preemptive angioplasty substantially reduces AVG thrombosis, randomized clinical trials have failed to confirm such a benefit. There is a high frequency of early AVG restenosis after angioplasty caused by aggressive neointimal hyperplasia resulting from vascular injury. Stent grafts prevent AVG restenosis better than balloon angioplasty, but they do not prevent AVG thrombosis. Several pharmacologic interventions to prevent AVG failure have been evaluated in randomized clinical trials. Anticoagulation or aspirin plus clopidogrel do not prevent AVG thrombosis, but increase hemorrhagic events. Treatment of hyperhomocysteinemia does not prevent AVG thrombosis. Dipyridamole plus aspirin modestly decreases AVG stenosis or thrombosis. Fish oil substantially decreases the frequency of AVG stenosis and thrombosis. In patients who have exhausted all options for vascular access in the upper extremities, thigh AVGs are a superior option to tunneled internal jugular vein central vein catheters (CVCs). An immediate-use AVG is a reasonable option in patients with recurrent CVC dysfunction or infection. Tunneled femoral CVCs have much worse survival than internal jugular CVCs.

Catheter-related atrial thrombus: tip of the iceberg?

Although guidelines recommend catheters as a last resort for establishing a vascular access in patients undergoing dialysis, they continue to be used widely for this purpose. Catheter-related atrial thrombus (CRAT) is rarely reported in this group of patients, and it can lead to serious complications. The aim of this study was to determine the incidence of CRAT in patients undergoing hemodialysis with permanent-tunneled catheters. A total of 50 patients undergoing hemodialysis with permanent catheters were included in this study. The diagnosis of CRAT was based on transthoracic echocardiography findings. Thrombus was present in nine patients (18%) and related to the tip of the catheter in all cases. Except for one patient with two foci of thrombus, all patients had a single focus. There were no significant associations between the development of thrombus and the duration of catheter use or the location of the catheter. Furthermore, catheter-related atrial thrombus did not appear to have a significant effect on mortality. The asymptomatic character of CRAT can be responsible for the low reporting rates, and its exact role in increased mortality and morbidity related with catheter use remains unknown. While planning management strategies, information on different options for vascular access routes and possible catheter-related complications should be provided to all patients who will undergo dialysis, together with a discussion involving other replacement alternatives for end-stage renal disease.

End-stage renal disease and thrombophilia

Chronic kidney disease is an established risk factor for arterial and venous thromboembolism (TE). Whereas the overall risk of TE in moderately decreased kidney function is approximately 2.5-fold higher compared to patients with normal renal function, the risk increase is 5.5-fold in patients with severe renal dysfunction. In patients with renal dysfunction and arterial thrombosis (OR: 4.9), malignancy (OR: 5.8) surgery (OR: 14.0) or thrombophilia (OR: 4.3) the risk to suffer from venous TE is higher compared to the risk associated to the baseline renal dysfunction alone. The treatment options for end-stage renal diseases include hemodialysis, peritoneal dialysis and kidney transplantation. During all treatment modalities thrombotic complications have been described, namely catheter malfunction and shunt thrombosis in patients undergoing hemodialysis in up to 25% of patients, and TE, pulmonary embolism or graft vessel thrombosis in approximately 8% of patients. The reported incidence of reno-vascular thrombosis following renal transplantation leading to hemorrhagic infarction with organ rejection or organ loss varied between 2-12%. Keeping in mind the multifactorial etiology of TE in patients with kidney dysfunction a general screening for thrombophilia in this patient group is not indicated. Selected screening on an individual patient basis should be discussed if the family history for TE is positive or the patient itself had suffered one thrombosis before the onset of the renal disease or multiple TEs during hemodialysis or post kidney transplantation in patients waiting for living donor kidney transplantation.

Exhausting multiple hemodialysis access failures

INTRODUCTION

Vascular access is often considered the Achilles heel the of hemodialysis because of its impact on morbidity, all cause mortality and finally costs of these patients. The most common complication of permanent hemodialysis (HD) vascular access is thrombosis, with some cases being related to hypercoagulability states. Antiphospholipid antibody syndrome (APAS) is a cause of increased thrombotic tendency, and this may complicate the management of such patients on HD.

CASE REPORT

We describe a 41-year-old woman with end stage renal disease (ESRD) from Adult Polycystic Kidney Disease who was referred to our tertiary care center for treatment and selection of renal replacement therapy form. It was thought to initiate with peritoneal dialysis considering her actual conditions. She was putted on hemodialysis for several sessions, and a subclavian cathether was her first vascular access. The surgeon created an arterio-venous fistula which did not mature. After the implantation of the peritoneal cathether she started peritoneal dialysis and continued living with that for 2 years. She felt exhausted and because of a grave peritonitis episode accompanied with procedure failure and a long hospitalization she was transferred to hemodialysis. Renal transplantation was not possible because she didn't have a kidney donation. She was maintained on regular HD, but her dialysis care was complicated by recurrent vascular access failures. She had multiple interventions for arterio-venous fistulas and grafts but almost all of them failed due to thrombosis to the extent that only one access site was available for her routine renal replacement treatment. A thorough thrombophilia screen confirmed the presence of antiphospholipid antibodies. A diagnosis of APAS was made and she was anticoagulated with warfarin. The AVG made in this last available site is still working from 18 months. If it fails we have no answers and solutions for her.

CONCLUSION

The presence of APAS can complicate HD management by causing recurrent vascular access thrombosis and failure, and nephrologist must remain alert to this possibility. Checking and treating as soon as possible it's our future challenge.

Role of the VEGF 936 gene polymorphism and VEGF-A levels in the late-term arteriovenous fistula thrombosis in patients undergoing hemodialysis

PURPOSE

Vascular access is vital for hemodialysis patients. A major factor that facilitates arteriovenous (AV) fistula failure is stenosis and thrombosis due to intimal hyperplasia developing in the venous segment of AV fistula. It has been reported that VEGF accelerated re-endothelialization, reduction in intimal thickening, and/or mural thrombus formed in the injured vascular structures. In this study, we aimed to identify the effect of the VEGF 936 gene polymorphism and vascular endothelial growth factor-A (VEGF-A) levels in the late period of AV fistula loss in hemodialysis patients.

METHODS

The study was carried out with a patient group of 42 individuals who experienced two or more fistula thrombosis in the late period after the AV fistula operation and also a control group of 38 patients who have not had any AV fistula thrombosis history for 3 years or more. All participants were assessed for VEGF-936C/T gene polymorphism and VEGF-A levels.

RESULTS

VEGF-936C/T genotypes were determined in the large proportion in the control group (31.6 %), while VEGF-936C/C genotypes were determined in a large proportion in the patient group (90.5 %). Individuals carrying the VEGF-936C/C genotype had an increased risk of 5.54 for getting AV fistula thrombosis. The VEGF-A levels of patient group (27.3 ± 43.5 pg/ml) were significantly lower than those of the control group (70.7 ± 53.1 pg/ml).

CONCLUSION

There is an increased risk of AV fistula thrombosis in individuals carrying the VEGF-936C/C genotype. The other renal replacement modalities should be considered in patients with this genotype. As a result, it will be possible to prevent the morbidity and mortality due to fistula failure.

Single nucleotide variants in the protein C pathway and mortality in dialysis patients

BACKGROUND

The protein C pathway plays an important role in the maintenance of endothelial barrier function and in the inflammatory and coagulant processes that are characteristic of patients on dialysis. We investigated whether common single nucleotide variants (SNV) in genes encoding protein C pathway components were associated with all-cause 5 years mortality risk in dialysis patients.

METHODS

Single nucleotides variants in the factor V gene (F5 rs6025; factor V Leiden), the thrombomodulin gene (THBD rs1042580), the protein C gene (PROC rs1799808 and 1799809) and the endothelial protein C receptor gene (PROCR rs867186, rs2069951, and rs2069952) were genotyped in 1070 dialysis patients from the NEtherlands COoperative Study on the Adequacy of Dialysis (NECOSAD) cohort) and in 1243 dialysis patients from the German 4D cohort.

RESULTS

Factor V Leiden was associated with a 1.5-fold (95% CI 1.1-1.9) increased 5-year all-cause mortality risk and carriers of the AG/GG genotypes of the PROC rs1799809 had a 1.2-fold (95% CI 1.0-1.4) increased 5-year all-cause mortality risk. The other SNVs in THBD, PROC, and PROCR were not associated with 5-years mortality.

CONCLUSION

Our study suggests that factor V Leiden and PROC rs1799809 contributes to an increased mortality risk in dialysis patients.

The dialysis scenario in patients with systemic lupus erythematosus

Although prognosis of lupus nephritis has improved over time, a substantial amount of lupus patients still reach end-stage renal disease and require dialysis. Treatment of these patients can be challenging, since the disease poses a number of problems that can portend a poor prognosis, such as infections, lupus reactivations, vascular access thrombosis and cardiovascular complications. Consensus is lacking among investigators about the real incidence of these complications and related diagnosis and treatment. Moreover, the choice of the type of dialysis treatment and the overall prognosis are still a matter of debate. In this paper, we have reviewed the currently available literature in an attempt to answer the most controversial issues about the topic.

Candidate gene analysis of arteriovenous fistula failure in hemodialysis patients

BACKGROUND AND OBJECTIVES

Arteriovenous fistula (AVF) failure remains an important cause of morbidity in hemodialysis patients. The exact underlying mechanisms responsible for AVF failure are unknown but processes like proliferation, inflammation, vascular remodeling, and thrombosis are thought to be involved. The current objective was to investigate the association between AVF failure and single nucleotide polymorphisms (SNPs) in genes related to these pathophysiologic processes in a large population of incident hemodialysis patients.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A total of 479 incident hemodialysis patients were included between January 1997 and April 2004. Follow-up lasted 2 years or until AVF failure, defined as surgery, percutaneous endovascular intervention, or abandonment of the vascular access. Forty-three SNPs in 26 genes, related to proliferation, inflammation, endothelial function, vascular remodeling, coagulation, and calcium/phosphate metabolism, were genotyped. Relations were analyzed using Cox regression analysis.

RESULTS

In total, 207 (43.2%) patients developed AVF failure. After adjustment, two SNPs were significantly associated with an increased risk of AVF failure. The hazard ratio (95% confidence interval) of LRP1 rs1466535 was 1.75 (1.15 to 2.66) and patients with factor V Leiden had a hazard ratio of 2.54 (1.41 to 4.56) to develop AVF failure. The other SNPs were not associated with AVF failure.

CONCLUSIONS

In this large cohort of hemodialysis patients, only 2 of the 43 candidate SNPs were associated with an increased risk of AVF failure. Whether other factors, like local hemodynamic circumstances, are more important or other SNPs play a role in AVF failure remains to be elucidated.

Aspects of platelet disturbances in haemodialysis patients

Patients with mild-to-chronic kidney disease (CKD) exhibit a variety of haemostatic disorders, ranging from an increased clotting tendency and reductions in the levels of natural inhibitors of coagulation to defective fibrinolysis. In addition, platelet (PLT) abnormalities are common. In this minireview, we report on aspects of haemodialysis (HD)-induced PLT activation. It is demonstrated that PLTs from HD patients are exhausted due to repeated stimulation of HD treatment and recurrent release of PLT degranulation products. During HD, additional aberrations of the haemostatic process occur. Besides deviations of coagulation and fibrinolysis, PLT activation and a reduction in their granule content have been observed during HD treatment. As HD treatment is carried out three times per week, month after month, chronic HD patients may suffer persistently from coagulation defects and PLT disorders on top of the alterations induced by the uraemic state itself. PLT activation occurs together with thrombin and fibrin generation. However, macro fibrin depositions in clot devices are not demonstrated, microaggregates occur not only in the extracorporeal circuit (ECC) but are also present in the blood circulation. As vascular access thrombosis is a frequent complication in patients with HD treatment, it is believed that hypercoagulability could result from vascular changes combined with PLTs and activation of coagulation factors.

Indications for vascular grafts as hemodialysis access: consensus from experience in Italy

INTRODUCTION

In Italy, the use of arteriovenous grafts (AVG) is limited (1-5 %) due to different approaches to vascular access (VA) management as compared to other countries, where guidelines (which may not apply to the Italian setting) have been produced. Therefore, the Study Group (GdS) on VA of the Italian Society of Nephrology produced this position paper, providing a list of 8 recommendations built upon current guidelines.

METHODS

The most controversial and innovative issues of existing guidelines have been summed up in 12 different statements. We selected 60 Italian dialysis graft experts, nephrologists and vascular surgeons (PP1SIN Study Investigators). They were asked to express their agreement/disagreement on each issue, thus creating a new method to share and exchange information.

RESULTS

Most of them agreed (consensus > 90%) on specific criteria set to choose AVG over native AVF (nAVF) and tunnelled venous catheter (tVC) and on the necessary conditions to implant them. They did not fully agree on the use of AVG in obese patients, in patients at risk of developing ischemia, on the priority of AVG as an alternative to brachial-basilic fistula with vein transposition, and in case of a poorly organized setting regarding graft maintenance. Keeping in mind that the nAVF should be preferred whenever is feasible, AVGs are indicated when superficial veins are unavailable or to repair a nAVF (bridge graft). An AVG is an alternative to tVC if the expected patient survival is long enough to guarantee its clinical benefits.

Thrombophilia and arteriovenous fistula survival in ESRD

BACKGROUND AND OBJECTIVES

The role of thrombophilia in failing arteriovenous fistula (AVF) among patients with ESRD undergoing hemodialysis is not established. This study aimed to assess whether AVF primary patency is associated with thrombophilia and coagulation abnormalities.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This observational study screened 219 patients between 2002 and 2004 for thrombophilia before AVF surgery. Thrombophilia included factor V Leiden and prothrombin G20210A mutations, protein C and antithrombin activities, and protein S. Coagulation abnormalities included high factor VIII:C, homocysteine, fibrinogen, and d-dimer levels; presence of antiphospholipid antibodies; and short thrombin time. We reviewed patient charts for comorbid conditions, AVF maturation and interventions, kidney transplantation, and patient survival (mean follow-up duration, 3.6 [range, 2.3-5.8] years). Primary patency from the AVF placement and functional primary patency from the first AVF cannulation were analyzed with Kaplan-Meier and Cox proportional hazards models.

RESULTS

Thrombophilia was present in 9% of the patients, and coagulation abnormalities occurred in 77%. One-year primary patency was 68%; 46% of the AVF failures occurred before the initiation of hemodialysis. Female sex (hazard ratio [HR], 2.6; 95% confidence interval [CI], 1.7-4.1) and thrombophilia (HR, 2.2; 95% CI, 1.2-4.2) were independent risk factors for loss of primary patency. Thrombophilia mutations or low antithrombin level (HR, 3.8), female sex (HR, 2.5), and diabetes (HR, 1.9) were associated with shortened functional primary patency of AVF.

CONCLUSIONS

Against the background of frequent coagulation abnormalities, thrombophilia and female sex predispose patients with ESRD to access failure, mostly due to thrombosis or stenosis.

Association of factor V gene polymorphism with arteriovenous graft failure

BACKGROUND

Dialysis grafts fail due to recurrent stenosis and thrombosis. Vasoactive and prothrombotic substances affecting intimal hyperplasia or thrombosis may modify graft outcomes.

STUDY DESIGN

Genetic polymorphisms association study of patients enrolled in a multicenter randomized clinical trial.

SETTING & PARTICIPANTS

354 Dialysis Access Consortium (DAC) Study patients receiving a new graft with DNA samples obtained. Participants were randomly assigned to treatment with aspirin plus dipyridamole versus placebo.

PREDICTOR

DNA sequence polymorphisms for the following candidate genes and their interaction with the study intervention: methylenetetrahydrofolate reductase (MTHFR), heme oxygenase 1 (HO-1), factor V (F5), transforming growth factor β1 (TGFβ1), klotho, nitric oxide synthase (NOS), and angiotensin-converting enzyme (ACE).

OUTCOME

Graft failure (>50% stenosis, angioplasty, thrombosis, surgical intervention, or permanent loss of function).

RESULTS

During a median patient follow-up of 34.3 months, 304 grafts failed. After adjusting for clinical factors (patient age, sex, access location, diabetes, cardiovascular disease, baseline aspirin use, body mass index, timing of graft placement, and study treatment) and genetic ancestral background, single-nucleotide polymorphism rs6019 of the factor V gene was associated significantly with graft failure in a dominant model (HR of 1.70 [95% CI, 1.32-2.19; P < 0.001] for G/C and G/G genotypes vs C/C genotypes). There was no significant association between graft failure and polymorphisms of MTHFR, HO-1, TGFβ1, klotho, NOS, or ACE.

LIMITATIONS

Small sample size.

CONCLUSION

The rs6019 genotype of Factor V is associated with increased risk of graft failure. Anticoagulation may reduce graft failure in patients with the G/C or G/G genotypes.

Inherited protein S deficiency due to a novel nonsense mutation in the PROS1 gene in the patient with recurrent vascular access thrombosis: A case report

Vascular access thrombosis is one of the major causes of morbidity in patients maintained on chronic hemodialysis. Thrombophilia has been recognized as a risk factor of vascular access thrombosis. The authors report a case of inherited protein S deficiency associated with vascular access thrombotic events. DNA sequence analysis of the PROS1 gene identified a novel heterozygous nonsense mutation in exon 10 by transition of AAG (lysine) to TAG (stop codon) at codon 473 (c.1417A>T, p.K473X). Results from the study suggest that the inherited protein S deficiency due to a PROS1 gene mutation may cause vascular access thrombosis in hemodialysis patients.

Role of thrombophilia in vascular access thrombosis among chronic hemodialysis patients in Tunisia

Vascular access thrombosis represents a serious and common problem in hemodialysis patients. Therefore, identification of relevant thrombotic risk factors could lead to an improved antithrombotic therapy. This case control study was performed to evaluate the relationship between some thrombophilias and vascular access thrombosis in hemodialysis patients. Seventy-eight patients undergoing dialysis (between May 2007 and September 2009) were selected as subjects. This sample was divided into two groups; a case group of 28 patients who had sustained one or more thrombotic events that resulted in vascular access failure and a control group of 50 patients, who had never had a thrombotic occlusion of a functioning permanent dialysis access. Antithrombin, protein C and protein S levels were measured. Also, both groups were tested for the factor V Leiden mutation, the prothrombin G20210A mutation, the methylene tetrahydrofolate reductase C677T and A1298C mutations. Among genetic mutations of factor V Leiden, prothrombin G20210A and methylene tetrahydrofolate reductase genes, the C677T methylene tetrahydrofolate reductase mutation was the only significant genetic cause of vascular access thrombosis (P=0.005). Our data demonstrated a significantly increased risk of vascular access thrombosis in carriers of the C677T methylene tetrahydrofolate reductase mutation.