Risk factors for vascular disease and arteriovenous fistula dysfunction in hemodialysis patients

Contemporary review of management techniques for cephalic arch stenosis in hemodialysis

The type of hemodialysis access and its preservation impact the quality of life and survival of patients undergoing hemodialysis. Vascular access complications are among the top causes of morbidity, hospitalization, and catheter use, with significant economic burden. Poor maturation and stenosis continue to be key impediments to upper arm arteriovenous fistula feasibility. Cephalic arch is a common location for vascular access dysfunction due to its distinctive anatomy, complex valves, and biochemical alterations attributable to renal failure. Understanding cephalic arch stenosis is critical due to its high prevalence and treatment failure. The appropriate management option is highly debatable and mostly dependent on patient characteristics and interventionist's preference. Current options include, percutaneous transluminal balloon angioplasty, stent grafts, bare metal stents, cutting balloon angioplasty, endovascular banding, and surgical procedures. This article discusses the etiologies of cephalic arch stenosis as well as currents trends in management including endovascular and surgical options.

Dual outflow upper arm arteriovenous fistula: An effective technique to prevent cephalic arch stenosis

Cephalic arch stenosis (CAS) is critical point to maintain functional arteriovenous fistula (AVF) in patients undergoing hemodialysis with brachio-cephalic AVFs. In this study, we aimed to determine the effectiveness of dual outflow (cephalic and basilic veins) as a surgical method to prevent CAS. Between July 2016 and December 2019, 369 patients underwent upper arm AVF creation. Among them the 251 patients were enrolled in this retrospective study. Two hundred seven underwent brachio-cephalic arteriovenous fistula (BCAVF) and 44 underwent brachio-cephalicbasilic arteriovenous fistula (BCBAVF). From the 251 patients, diabetes mellitus (66.7% vs 36.4%, P < .001) and hypertension (91.3% vs 75%, P = .002) were more common in the patient group who underwent BCAVF surgery; however, the difference in volume flow to the fistula did not differ between the 2 groups. CAS (30.4% vs 9.1%, P = .004) and fistula occlusion (15.9% vs 4.5%, P = .048) were likely to occur in the BCAVF group. The primary patency rates at 12 months were 74.3% and 86.4% for the BCAVFs and BCBAVFs, respectively (P = .075). The primary-assisted patency rates at 12 months were 87.0% for BCAVFs and 93.2% for BCBAVFs, respectively (P = .145). Secondary patency rates at 12 months were 92.2% for BCAVFs and 93.2% for BCBAVFs, respectively (P = .023). Compared to BCAVF, traditional upper arm AVF, upper arm AVF with cephalic and basilic vein dual drainage can be optimal surgical method to preventing CAS.

ACR Appropriateness Criteria® Dialysis Fistula Malfunction

The creation and maintenance of a dialysis access is vital for the reduction of morbidity, mortality, and cost of treatment for end stage renal disease patients. One's longevity on dialysis is directly dependent upon the quality of dialysis. This quality hinges on the integrity and reliability of the access to the patient's vascular system. All methods of dialysis access will eventually result in dialysis dysfunction and failure. Arteriovenous access dysfunction includes 3 distinct classes of events, namely thrombotic flow-related complications or dysfunction, nonthrombotic flow-related complications or dysfunction, and infectious complications. The restoration of any form of arteriovenous access dysfunction may be supported by diagnostic imaging, clinical consultation, percutaneous interventional procedures, surgical management, or a combination of these methods. This document provides a rigorous evaluation of how variants of each form of dysfunction may be appraised and approached systematically. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

Oxidative stress: An essential factor in the process of arteriovenous fistula failure

For more than half a century, arteriovenous fistula (AVFs) has been recognized as a lifeline for patients requiring hemodialysis (HD). With its higher long-term patency rate and lower probability of complications, AVF is strongly recommended by guidelines in different areas as the first choice for vascular access for HD patients, and its proportion of application is gradually increasing. Despite technological improvements and advances in the standards of postoperative care, many deficiencies are still encountered in the use of AVF related to its high incidence of failure due to unsuccessful maturation to adequately support HD and the development of neointimal hyperplasia (NIH), which narrows the AVF lumen. AVF failure is linked to the activation and migration of vascular cells and the remodeling of the extracellular matrix, where complex interactions between cytokines, adhesion molecules, and inflammatory mediators lead to poor adaptive remodeling. Oxidative stress also plays a vital role in AVF failure, and a growing amount of data suggest a link between AVF failure and oxidative stress. In this review, we summarize the present understanding of the pathophysiology of AVF failure. Furthermore, we focus on the relation between oxidative stress and AVF dysfunction. Finally, we discuss potential therapies for addressing AVF failure based on targeting oxidative stress.

Vascular access for lipid apheresis: a challenge in young children with homozygous familial hypercholesterolemia

Background

Homozygous familial hypercholesterolemia (hoFH) is a rare genetic disorder leading to extremely increased LDL-cholesterol (LDL-C), resulting in high cardiovascular risk in early childhood. Lipid apheresis (LA) is an effective treatment and should be started as early as possible to prevent premature cardiovascular events. As peripheral punctures in children can be challenging due to small vessels and anxiety, this study aimed to evaluate feasibility and safety of central venous catheters (CVCs) as vascular access for LA in young children with hoFH.

Methods

Retrospective analysis (2016-2019) on four children with hoFH aged 3-5 years, performing weekly or biweekly LA with a CVC.

Results

LDL-C decreased by> 60%. In three children, the use of a permanent CVC for 698, 595, and 411 days, respectively, avoided difficult peripheral access, without the occurrence of occlusion or thrombosis. Unfortunately, one child had recurrent CVC-related infections and needed an arteriovenous fistula from the age of 5. Although the mean dwell time per catheter was 212 days, there were, as expected, severe side effects of early catheter infections with sepsis and accidental self-removal. Starting LA at an early age improved or stabilized carotid intima-media thickness (IMT) in three children. However, IMT did increase in one child caused by intolerance to peripheral punctures and LA interruption.

Conclusions

Permanent CVCs are a viable temporary access choice for LA in young children with hoFH until peripheral venipuncture is practicable. The risk of CVC-related infections needs to be taken into account.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12887-022-03192-7.

The association of erythropoietin-stimulating agents and increased risk for AV-fistula dysfunction in hemodialysis patients. A retrospective analysis

BACKGROUND

Patients in maintenance hemodialysis (HD) need a patent vascular access for optimal treatment. The recommended first choice is a native arteriovenous fistula (AVF). Complications of AVF are frequent and include thrombosis, stenosis and infections leading to worsening of dialysis efficacy. Some known risk factors are age, gender and the presence of diabetes mellitus. The aim was to investigate if further risk variables are associated with dysfunctional AVF.

METHODS

This retrospective observational study included 153 chronic HD patients (Cases) referred to a total of 473 radiological investigations due to clinically suspected complications of their native AVF. Another group of chronic HD patients (n = 52) who had a native AVF but were without history of previous complications for at least 2 years were controls. Statistical analyses included ANOVA, logistic regression, parametric and non-parametric methods such as Student's T-test and Mann-Whitney test.

RESULTS

Among Cases, at least one significant stenosis (> 50% of the lumen) was detected in 348 occasions. Subsequent PTA was performed in 248 (71%). Median erythropoiesis-stimulating agent (ESA) weekly doses were higher in Cases than in Controls (8000 vs 5000 IU, p < 0.001). Cases received higher doses of intravenous iron/week than the Controls before the investigation (median 50 mg vs 25 mg, p = 0.004) and low molecular weight heparin (LMWH, p = 0.028). Compared to Controls, Cases had a lower level of parathyroid hormone (median 25 vs 20 ρmol/L, p = 0.009). In patients with diabetes mellitus, HbA1c was higher among Cases than Controls (50 vs 38 mmol/mol, p < 0.001). Multiple regression analysis revealed significant associations between Cases and female gender, prescription of doxazocin, and doses of ESA and LMWH. There was no difference between the groups regarding hemoglobin, CRP or ferritin.

CONCLUSION

In conclusion, the present study indicated that the factors associated with AVF problems were high doses of ESA, iron administration, and tendency of thromboembolism (indicated by high LMWH doses); the use of doxazocin prescription, however, requires further investigation.

Experimental murine arteriovenous fistula model to study restenosis after transluminal angioplasty

Percutaneous transluminal angioplasty (PTA) is a very common interventional treatment for treating stenosis in arteriovenous fistula (AVF) used for hemodialysis vascular access. Restenosis occurs after PTA, resulting in vascular lumen loss and a decrease in blood flow. Experimental animal models have been developed to study the pathogenesis of stenosis, but there is no restenosis model after PTA of stenotic AVF in mice. Here, we describe the creation of a murine model of restenosis after angioplasty of a stenosis in an AVF. The murine restenosis model has several advantages, including the rapid development of restenotic lesions in the vessel after angioplasty and the potential to evaluate endovascular and perivascular therapeutics for treating restenosis. The protocol includes a detailed description of the partial nephrectomy procedure to induce chronic kidney disease, the AVF procedure for development of de novo stenosis and the angioplasty treatment associated with progression of restenosis. We monitored the angioplasty-treated vessel for vascular patency and hemodynamic changes for a period of 28 d using ultrasound. Vessels were collected at different time points and processed for histological analysis and immunostaining. This angioplasty model, which can be performed with basic microvascular surgery skills, could be used to identify potential endovascular and perivascular therapies to reduce restenosis after angioplasty procedures.

Mean Platelet Volume Predicts Vascular Access Events in Hemodialysis Patients

Arteriovenous fistula (AVF) and arteriovenous graft (AVG) is the vascular access (VA) of 78% of hemodialysis patients (HD) in France. VA dysfunction corresponding to either stenosis requiring angioplasty or acute thrombosis is responsible for 30% of hospitalizations. Mean platelet volume (MPV) is a biological marker of cardiovascular events. We studied MPV in a cohort of HD patients as a predictive marker of VA dysfunction. We conducted a prospective monocentric cohort study that included patients with AVF or AVG on chronic HD (n = 153). The primary outcome was the incidence of VA dysfunction regarding MPV value. The median MPV was 10.8 fL (7.8-13.5), and four groups were designed according to MPV quartiles. Fifty-four patients experienced the first event of VA dysfunction. The incidence of VA dysfunction was higher in patients with the highest MPV: 59% (23 events), 34% (14 events), 27% (11 events), and 18% (6 events), respectively, for the fourth, third, second, and first quartiles (p = 0.001). Multivariate analysis confirmed an independent association between MPV and VA dysfunction-OR 1.52 (1.13-2.07), p < 0.001. VA dysfunction is predicted by MPV level. Patients with the highest MPV have the highest risk of VA events.

Antiplatelet agents maintain arteriovenous fistula and graft function in patients receiving hemodialysis: A nationwide case-control study

Background

In this study, we evaluated the effects of various medications on the patency of vascular access (VA) for hemodialysis.

Methods

We analyzed data from the Longitudinal Health Insurance Database of Taiwan. We adopted a case–control study design within a cohort of patients who had received regular hemodialysis between 2002 and 2012; 34,354 patients with first VA failure were identified, and the duration from VA creation date to the first VA failure date was calculated. We then classified these patients into two groups, namely arteriovenous fistula (AVF, n = 25,933) and arteriovenous graft (AVG, n = 8,421). Each group was further divided into two subgroups, namely short-term (<1 year) and long-term (≥1 year) patency.

Results

The risk factors for early VA failure were age ≥65 years, diabetes mellitus, hyperlipidemia, cerebral vascular disease, congestive heart failure, peripheral artery disease, and sepsis. Male sex, hypertension, cancer, and peptic ulcer were associated with early AVF failure. Antiplatelet therapy increased the AVF and AVG patency times with adjusted odds ratios of 0.748 (95% confidence interval [CI]: 0.703–0.796, p < 0.0001) and 0.810 (95% CI: 0.728–0.901, p = 0.0001), respectively. A significant decrease in the VA failure risk was observed with an increase in the cumulative defined daily dose of antiplatelet agents.

Conclusion

This nationwide study demonstrated that some risk factors were associated with early VA failure and that the use of antiplatelet agents prevented the loss of VA patency in a dose–response manner. Thus, antiplatelet drugs should be routinely administered to high-risk patients receiving dialysis.

Significant association of anti-platelet factor 4/heparin antibody with cardiovascular disease in hemodialysis patients: a longitudinal 7-year study

BACKGROUND

Hemodialysis patients have a high incidence of anti-platelet factor 4/heparin antibody (PF4-H Ab) and are at a high risk of cardiovascular disease. This study determines the association between PF4-H Ab and cardiovascular events including coronary artery disease (CAD), ischemic stroke (IS), and native arteriovenous fistula thrombosis (AVFT), in a longitudinal 7-year follow-up.

PATIENTS AND METHODS

84 hemodialysis patients were enrolled. Data collection included chart reviews and assessments of laboratory records. PF4-H Ab was evaluated by ELISA and a titer ≥ 0.4 was defined to have PF4-H Ab.

RESULTS

30 patients were PF4-H Ab positive, 30 patients had CAD, 29 patients had IS, and 43 patients had AVFT. In Cox proportional hazard regression analysis, PF4-H Ab (HR 2.72, p = 0.01) was a significant risk factor for CAD. Age (HR 1.06, p = 0.003), PF4-H Ab (HR 4.53, p < 0.001), 7-year averaged serum phosphate levels (HR 0.53, p = 0.012), and 7-year averaged blood platelet count (HR 1.01, p = 0.029) were risk factors for IS. Age (HR 1.03, p = 0.047), PF4-H Ab (HR 3.57, p < 0.001), and 7-year averaged serum triglyceride levels (HR 1.01, p = 0.005) were risk factors for AVFT. In PF4-H Ab-positive groups, thrombocytopenia was not associated with CAD, IS, and AVFT by Fisher's test analysis.

CONCLUSION

This study reveals that PF4-H Ab is a risk factor for developing CAD, IS, and AVFT among hemodialysis patients.

Factors Influencing Arteriovenous Fistula Dysfunction in Japanese Patients on Chronic Hemodialysis

Arteriovenous fistula dysfunction is a constant problem in chronic hemodialysis patients. We investigated the factors influencing fistula dysfunction in 184 patients on chronic hemodialysis. Stepwise regression analysis and Cox proportional hazards model were used to assess the relationship between fistula dysfunction and age, sex, duration of hemodialysis, diabetes mellitus, hematocrit, serum creatinine, blood urea nitrogen, KW, prothrombin time, blood pressure, anticoagulant therapy, dose of erythropoietin, calcium channel blocker therapy, and angiotensin-converting enzyme inhibitor therapy. Fistula dysfunction showed a significant relationship with a low systolic blood pressure, a low hematocrit, the presence of diabetes mellitus, and angiotensin-converting enzyme inhibitor therapy. These results suggested that treatment with angiotensin-converting enzyme inhibitors may help to prevent fistula dysfunction.

Local Adipose-Associated Mediators and Adaptations Following Arteriovenous Fistula Creation

Introduction

Local inflammation is an important regulator of vascular remodeling. We hypothesized that adipose tissue adjacent to hemodialysis arteriovenous fistulae modulates maturation.

Methods

During fistula creation, perivenous adipose was collected from 111 participants in the Hemodialysis Fistula Maturation Study. Nine adipose-associated mediators were measured. Duplex ultrasound was performed at 4 time points postoperatively from 1 day to first cannulation (10–26 weeks). Associations between logarithmically transformed biomarker levels and fistula remodeling were evaluated using mixed effects regression.

Results

Elevated interleukin (IL)-6 and monocyte chemoattractant protein (MCP)-1 were associated with a reduction in the fractional vein diameter during the early time frame of 1 day to 2 weeks (diameter change of 26.6% and 20.4% at the 25th and 75th percentile for IL-6, P = 0.01; 27.8% and 21.1% at the 25th and 75th percentile for MCP-1, P = 0.02), but not in later stages of remodeling. Local leptin levels showed a significant negative correlation with fractional venous flow increase between 2 and 6 weeks (percent flow change 31.4% and 11.3% at the 25th and 75th percentile for leptin, P = 0.03).

Conclusion

Thus, impaired fistula vein dilation and reduced capacity for flow augmentation associate with specific local adipose phenotypic signatures in a time-dependent manner. In view of adipose tissue plasticity, these findings raise the possibility of novel adipose-based strategies to facilitate fistula maturation.

Arteriovenous Fistulas for Hemodialysis Created using a Long-Term Absorbable Suture: A Safe Solution and a Measure to Minimize Myointimal Hyperplasia

Background/aims

The goal of the therapeutic management of patients affected by end-stage renal disease (ESRD) is to maintain the vascular access (VA) as long as possible. Myointimal hyperplasia development in the vascular walls of arteriovenous fistulas (AVFs) is considered one of the most important factors responsible for procedure failure. These alterations could be linked to hemodynamic changes in the anastomosis and to the presence of the surgical suture itself. We report our preliminary experience, discussing the use and the possible benefits of an absorbable suture in polyglycolide trimethylene carbonate (PTC) in AVF creation.

Methods

Seventy-four AVFs were created as primary access for hemodialysis (HD), using PTC, over 4 years. Age, gender, ESRD etiology, artery and vein preoperative diameters, AVF survival outcome, and the number of AVFs created per year were recorded. The Kaplan-Meier method was used to analyze AVF survival rates.

Results

No dehiscences, pseudoaneurysms, or failures in the “critical” period related to PTC absorption were recorded. Kaplan-Meier analysis was used to evaluate AVF survival; 12-month primary AVF survival (74.33%) and AVF failure (25.67%) rates, 9 “early” (8.22%) and 10 “late” failures (13.51%), and a 360-day mean survival were found.

Conclusions

Our data indicate that PTC, a well known and widely used material for sutures in vascular surgery, is safe and effective in AVF creation. Potential advantages of PTC sutures are represented by a reduced myointimal hyperplasia formation in the AVF vascular walls, prolonging the AVF lifespan and avoiding re-interventions.

Maturation of arteriovenous fistula: Analysis of key factors

The growing proportion of individuals suffering from chronic kidney disease has considerable repercussions for both kidney specialists and primary care. Progressive and permanent renal failure is most frequently treated with hemodialysis. The efficiency of hemodialysis treatment relies on the functional status of vascular access. Determining the type of vascular access has prime significance for maximizing successful maturation of a fistula and avoiding surgical revision. Despite the frequency of arteriovenous fistula procedures, there are no consistent criteria applied before creation of arteriovenous fistulae. Increased prevalence and use of arteriovenous fistulae would result if there were reliable criteria to assess which arteriovenous fistulae are more likely to reach maturity without additional procedures. Published studies assessing the predictive markers of fistula maturation vary to a great extent with regard to definitions, design, study size, patient sample, and clinical factors. As a result, surgeons and specialists must decide which possible risk factors are most likely to occur, as well as which parameters to employ when evaluating the success rate of fistula development in patients awaiting the creation of permanent access. The purpose of this literature review is to discuss the role of patient factors and blood markers in the development of arteriovenous fistulae.

Vascular access in lipoprotein apheresis: a retrospective analysis from the UK's largest lipoprotein apheresis centre

INTRODUCTION

Lipoprotein apheresis (LA) has proven to be an effective, safe and life-saving therapy. Vascular access is needed to facilitate this treatment but has recognised complications. Despite consistency in treatment indication and duration there are no guidelines in place. The aim of this study is to characterise vascular access practice at the UK's largest LA centre and forward suggestions for future approaches.

METHODS

A retrospective analysis of vascular access strategies was undertaken in all patients who received LA treatment in the low-density lipoprotein (LDL) Apheresis Unit at Harefield Hospital (Middlesex, UK) from November 2000 to March 2016.

RESULTS

Fifty-three former and current patients underwent 4260 LA treatments. Peripheral vein cannulation represented 79% of initial vascular access strategies with arteriovenous (AV) fistula use accounting for 15%. Last used method of vascular access was peripheral vein cannulation in 57% versus AV fistula in 32%. Total AV fistula failure rate was 37%.

CONCLUSIONS

Peripheral vein cannulation remains the most common method to facilitate LA. Practice trends indicate a move towards AV fistula creation; the favoured approach receiving support from the expert body in this area. AV fistula failure rate is high and of great concern, therefore we suggest the implementation of upper limb ultrasound vascular mapping in all patients who meet treatment eligibility criteria. We encourage close ties between apheresis units and specialist surgical centres to facilitate patient counselling and monitoring. Further prospective data regarding fistula failure is needed in this expanding treatment field.

Clinical Course of Hemodialysis Access After Initial Endovascular Intervention for Stenosis in Asian Renal Failure Patients

BACKGROUND

Arteriovenous fistula (AVF) and arteriovenous fistula graft (AVG) access for hemodialysis can develop stenosis, eventually leading to thrombosis and access failure. Prompt endovascular intervention can salvage the access but restenosis does occur. Clinical course, restenosis pattern, and risk factors associated with initial stenosis of AVFs/AVGs in Asian hemodialysis patients were studied.

METHOD

A retrospective study was conducted (January 2009-June 2012) on consecutive patients with renal failure who developed the first-time stenosis in the vascular access and were managed with endovascular intervention. One hundred fourteen patients (54 AVFs and 60 AVGs) were studied, and all clinical outcomes were recorded until October 2013.

RESULTS

The mean time from access creation to endovascular intervention for the first-time stenosis for patients with AVF and AVG was 23.5 (32.7 standard deviation [SD]) months and 12.5 (11.0) months, respectively. An average of 1.7 (range, 1-5) interventions were performed for AVFs, whereas 2.4 (range, 1-11) for AVGs ( P = .008). Upon conclusion of the study, 23 patients with AVF survived with functional index access, whereas 10 passed away with a functional original access. The remaining 21 patients with AVFs failed, requiring new access, tunneled catheter, or peritoneal dialysis. Of the 60 patients with AVG, 6 survived and 8 died with functional index access; 46 required new access or other forms of dialysis ( P = .000). Kaplan-Meier estimated that access patency and survival with functional access were significantly lower for AVGs than for AVFs after the first salvage intervention. Female patients had an increased risk of restenosis with both univariate ( P = .016) and multivariate ( P = .013) analysis. With univariate analysis ( P = .039), patients with hyperlipidemia had a higher risk of developing restenosis in the vascular access.

CONCLUSION

The clinical course and prognosis of failing AVFs and AVGs are distinct. The information on access prognosis and stenosis recurrence patterns will be helpful for patient counseling and planning of follow-up intervals, after the first-time intervention for access stenosis.

Comparison of Post-Creation Procedures and Costs between Surgical and an Endovascular Approach to Arteriovenous Fistula Creation

Introduction

Due to early and late failures that may occur with surgically created hemodialysis arteriovenous fistulas (SAVF), post-creation procedures are commonly required to facilitate AVF maturation and maintain patency. This study compared AVF post-creation procedures and their associated costs in patients with SAVF to patients with a new endovascularly created AVF (endoAVF).

Methods

A 5% random sample from Medicare Standard Analytical Files was abstracted to determine post- creation procedures and associated costs for SAVF created from 2011 to 2013. Medicare enrollment during the 6 months prior to and after the AVF creation was required. Patients’ follow-up inpatient, outpatient, and physician claims were used to identify post-creation procedures and to estimate average procedure costs. Comparative procedural information on endoAVF was obtained from the Novel Endovascular Access Trial (NEAT).

Results

Of 3764 Medicare SAVF patients, 60 successfully matched to endoAVF patients using 1:1 propensity score matching of baseline demographic and clinical characteristics. The total post-creation procedural event rate within 1 year was lower for endoAVF patients (0.59 per patient-year) compared to the matched SAVF cohort (3.43 per patient-year; p<0.05). In the endoAVF cohort, event rates of angioplasty, thrombectomy, revision, catheter placement, subsequent arteriovenous graft (AVG), new SAVF, and vascular access-related infection were all significantly lower than in the SAVF cohort. The average first year cost per patient-year associated with post-creation procedures was estimated at US$11,240 USD lower for endoAVF than for SAVF.

Conclusions

Compared to patients with SAVF, patients with endoAVF required fewer post-creation procedures and had lower associated mean costs within the first year.

Monocyte Chemoattractant Protein-1 Levels and Postangioplasty Restenosis of Arteriovenous Fistulas

BACKGROUND AND OBJECTIVES

Inflammation is relevant in restenosis of atherosclerotic vascular diseases, but its role in dialysis arteriovenous fistula remains unknown. In animal studies, upregulation of monocyte chemoattractant protein-1 has been shown in venous segments of arteriovenous fistula. We, therefore, aimed to investigate serial changes in circulating monocyte chemoattractant protein-1 after percutaneous transluminal angioplasty of dialysis arteriovenous fistulas and its relation to restenosis.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Fifty-nine patients with dysfunctional arteriovenous fistulas that were referred for percutaneous transluminal angioplasty were enrolled prospectively between January of 2010 and July of 2012. Three of them were excluded due to percutaneous transluminal angioplasty failure or acute infection. Blood was sampled from arteriovenous fistulas at baseline, 2 days, 2 weeks, and 3 months after percutaneous transluminal angioplasty. Clinical follow-up was continued monthly for 3 months. Angiographic follow-up was arranged at the end of 3 months. Seventeen patients without significant stenosis were enrolled as the control group.

RESULTS

Fifty-six patients completed clinical follow-up. Significant increases in monocyte chemoattractant protein-1 were observed at 2 days and 2 weeks (both P<0.001) after percutaneous transluminal angioplasty. Twenty-three (41%) patients had symptomatic restenosis. The restenosis group had a higher percentage change in monocyte chemoattractant protein-1 levels at 2 days (median =47%; interquartile range, 27%-65% versus median =17%; interquartile range, 10%-25%; P<0.001) after percutaneous transluminal angioplasty compared with the patent group. Fifty-two patients completed angiographic follow-up. A positive correlation between relative luminal loss and monocyte chemoattractant protein-1 increase at 2 days after percutaneous transluminal angioplasty was found (r=0.53; P<0.001). In multivariate analysis, postangioplasty monocyte chemoattractant protein-1 increase at 2 days was an independent predictor of restenosis. Using receiver operator characteristic analysis, >25% postangioplasty increase of monocyte chemoattractant protein-1 was significantly associated with restenosis after percutaneous transluminal angioplasty (hazard ratio, 5.36; 95% confidence interval, 1.81 to 15.8).

CONCLUSIONS

Circulating monocyte chemoattractant protein-1 levels were elevated 2 days and 2 weeks after percutaneous transluminal angioplasty. Early postangioplasty increase of monocyte chemoattractant protein-1 level was associated with restenosis of arteriovenous fistulas.

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.

Tracking and Therapeutic Value of Human Adipose Tissue-derived Mesenchymal Stem Cell Transplantation in Reducing Venous Neointimal Hyperplasia Associated with Arteriovenous Fistula

PURPOSE

To determine if adventitial transplantation of human adipose tissue-derived mesenchymal stem cells (MSCs) to the outflow vein of B6.Cg-Foxn1(nu)/J mice with arteriovenous fistula (AVF) at the time of creation would reduce monocyte chemoattractant protein-1 (Mcp-1) gene expression and venous neointimal hyperplasia. The second aim was to track transplanted zirconium 89 ((89)Zr)-labeled MSCs serially with positron emission tomography (PET) for 21 days.

MATERIALS AND METHODS

All animal experiments were performed according to protocols approved by the institutional animal care and use committee. Fifty B6.Cg-Foxn1(nu)/J mice were used to accomplish the study aims. Green fluorescent protein was used to stably label 2.5 × 10(5) MSCs, which were injected into the adventitia of the outflow vein at the time of AVF creation in the MSC group. Eleven mice died after AVF placement. Animals were sacrificed on day 7 after AVF placement for real-time polymerase chain reaction (n = 6 for MSC and control groups) and histomorphometric (n = 6 for MSC and control groups) analyses and on day 21 for histomorphometric analysis only (n = 6 for MSC and control groups). In a separate group of experiments (n = 3), animals with transplanted (89)Zr-labeled MSCs were serially imaged with PET for 3 weeks. Multiple comparisons were performed with two-way analysis of variance, followed by the Student t test with post hoc Bonferroni correction.

RESULTS

In vessels with transplanted MSCs compared with control vessels, there was a significant decrease in Mcp-1 gene expression (day 7: mean reduction, 62%; P = .029), with a significant increase in the mean lumen vessel area (day 7: mean increase, 176% [P = .013]; day 21: mean increase, 415% [P = .011]). Moreover, this was accompanied by a significant decrease in Ki-67 index (proliferation on day 7: mean reduction, 81% [P = .0003]; proliferation on day 21: mean reduction, 60%, [P = .016]). Prolonged retention of MSCs at the adventitia was evidenced by serial PET images of (89)Zr-labeled cells.

CONCLUSION

Adventitial transplantation of MSCs decreases Mcp-1 gene expression, accompanied by a reduction in venous neointimal hyperplasia.

Obesity-related decrease in intraoperative blood flow is associated with maturation failure of radiocephalic arteriovenous fistula

OBJECTIVE

Successful arteriovenous fistula (AVF) maturation is often challenging in obese patients. Optimal initial intraoperative blood flow (IOBF) is essential for adequate AVF maturation. This study was conducted to elucidate the effect of obesity on IOBF and radiocephalic AVF maturation.

METHODS

Patients with a newly created radiocephalic AVF were included (N = 252). Obesity was defined as a baseline body mass index (BMI) ≥25 kg/m(2), and primary maturation failure was defined as failure to use the AVF successfully by 3 months after its creation. IOBF was measured immediately after construction of the AVF with a VeriQ system (MediStim, Oslo, Norway).

RESULTS

The mean BMI was 24.1 ± 3.9 kg/m(2), and the prevalence of obesity was 31.3%. Particularly, 8.3% (21 patients) had a BMI ≥30 kg/m(2). Primary maturation failure occurred in 100 patients (39.7%), and an IOBF <190 mL/min was closely associated with the risk of maturation failure (relative risk, 3.05; 95% confidence interval, 1.52-6.11). Compared with nonobese patients, obese subjects had a significantly higher prevalence of diabetes and elevated high-sensitivity C-reactive protein levels, whereas diameters of vessels were similar. When the patients were further divided into three groups as BMI <25, 25 to 29.9, and ≥30 kg/m(2), patients in the higher BMI group showed significantly lower IOBF and higher maturation failure rate. According to multivariate analysis, the statistically significant variables that determined maturation failure were obesity, previous vascular disease, increased high-sensitivity C-reactive protein levels, and IOBF <190 mL/min.

CONCLUSIONS

Obese patients had a significantly lower IOBF, and both obesity and low IOBF contributed to the primary maturation failure of AVF. Obesity-associated inflammation and atherosclerosis might play roles in this association.

Adipose phenotype predicts early human autogenous arteriovenous hemodialysis remodeling

OBJECTIVE

Substantial proportions of autogenous arteriovenous fistulas (AVFs) for hemodialysis access fail to mature for unclear reasons. AVFs develop in a large mass of surrounding adipose tissue that is increasingly recognized as an active participant in the vascular response to injury via paracrine and endocrine mechanisms. We thus hypothesized that baseline phenotypic characteristics of the adipose tissue juxtaposed to the developing AVF associate with subsequent inward or outward vein wall remodeling.

METHODS

Clinical data and subcutaneous adipose tissue were collected from 22 consented patients undergoing AVF creation. Tissue was assayed (protein levels) for interleukin (IL)-6, IL-8, leptin, tumor necrosis factor-α, monocyte chemoattractant protein-1 (MCP-1), resistin, and adiponectin. Vein dimensions were acquired by duplex ultrasound imaging, preoperatively and at 4 to 6 weeks postoperatively, 1 cm cephalad to the arteriovenous anastomosis, which is the most common location of AVF stenosis).

RESULTS

The vein at the assayed location outwardly remodeled 55.7% on average (median before, 3.7 mm; median after, 4.7 mm; P = .005). The preoperative vein diameter failed to correlate with postoperative size at the point of assay (R = 0.31; P = .155) unless two outliers were excluded (R = 0.64; P = .002). After removal of the same outliers, the correlation coefficient between venous diameter change (preoperative vs postoperative) and IL-8, tumor necrosis factor-α, MCP-1, resistin, and adiponectin was -0.49, -0.79, -0.66, -0.64, and -0.69, respectively (P < .05). Postoperative AVF flow volume correlated with MCP-1 (R = -0.53; P < .05) and adiponectin (R = -0.47; P < .05).

CONCLUSIONS

These data reveal a novel relationship between local adipose phenotype and the eventual venous wall response to hemodynamic perturbation in humans. The predictive value of these mediators generally equaled or exceeded that of preoperative vein size. Beyond providing mechanistic insights into vascular wall adaptations due to flow perturbations, this discovery suggests that strategies focused on altering adipose tissue biology may improve AVF maturation.

Red blood cell distribution width is associated with early failure of arteriovenous fistula for haemodialysis access

This study aimed to investigate the predictive value of red blood cell distribution width (RDW) for early failure of arteriovenous fistula (AVF) for haemodialysis access. The hospital records of those patients who underwent primary AVF creation procedures for haemodialysis between December 2010 and September 2013 were included for retrospective analysis. Of 313 patients, 195 (62%) were male and 118 (38%) were female. Mean age was 60 (range 17-90) years. Of the 313 AVF procedures performed, 229 (73%) were created at forearm (radial artery-cephalic vein), and 84 (27%) were created upperarm (antecubital, brachiocephalic, or brachiobasilic procedures). Early AVF failure was found in 61 (19%) patients. According to chi-square test, the incidence of early AVF failure was higher in patients with heart failure and peripheral artery disease (P < 0.001). According to Mann-Whitney U test, the RDW (P = 0.001) and C-reactive protein (P = 0.024) values were higher in patients with early AVF. Our data showed that preoperative RDW is a reliable parameter that can be useful in predicting the early failure of AVF.

Vein graft adaptation and fistula maturation in the arterial environment

Veins are exposed to the arterial environment during two common surgical procedures, creation of vein grafts and arteriovenous fistulae (AVF). In both cases, veins adapt to the arterial environment that is characterized by different hemodynamic conditions and increased oxygen tension compared with the venous environment. Successful venous adaptation to the arterial environment is critical for long-term success of the vein graft or AVF and, in both cases, is generally characterized by venous dilation and wall thickening. However, AVF are exposed to a high flow, high shear stress, low-pressure arterial environment and adapt mainly via outward dilation with less intimal thickening. Vein grafts are exposed to a moderate flow, moderate shear stress, high-pressure arterial environment and adapt mainly via increased wall thickening with less outward dilation. We review the data that describe these differences, as well as the underlying molecular mechanisms that mediate these processes. Despite extensive research, there are few differences in the molecular pathways that regulate cell proliferation and migration or matrix synthesis, secretion, or degradation currently identified between vein graft adaptation and AVF maturation that account for the different types of venous adaptation to arterial environments.

Features of atherosclerosis in hemodialysis patients

Background

Cardiovascular disease is the main cause of mortality in dialysis patients. Carotid intima–media thickness (CIMT) is used as a surrogate marker of early atherosclerosis. Atherosclerosis can cause vascular access failure. The purpose of this study was to define the clinical features of atherosclerosis in hemodialysis patients based on CIMT and to define the relationship between CIMT and access failure.

Methods

In this cross-sectional study, the CIMT of 60 patients on hemodialysis was examined using B-mode Doppler ultrasonography between May 2012 and November 2012. Carotid atherosclerosis was defined as a CIMT≥0.9 mm or the incidence of atherosclerotic plaques.

Results

The patients’ mean age was 54.5±10.6 years, and 60% of the patients were male. The CIMT was 0.81±0.47 mm (range, 0.35–2.50 mm). The group with atherosclerosis was characterized by older age compared with those without atherosclerosis. Patients with atherosclerosis showed much shorter durations of access patency than their counterparts in the nonatherosclerosis group (hazard ratio, 2.822; 95% confidence interval, 1.113–7.156; P=0.029). Moreover, being overweight was associated with a 2.47-fold (95% confidence interval, 1.101–5.548) increased primary access failure.

Conclusion

This study shows that atherosclerosis is associated with older age. Patients who are overweight and have atherosclerosis may have shortened access patency.

The effect of buttonhole cannulation vs. rope-ladder technique on hemodialysis access patency

The rope-ladder (RL) technique is the most common technique used for cannulation of arteriovenous fistulae (AVF). Buttonhole cannulation (BHC), or constant-site technique, is recommended by the National Kidney Foundation's Kidney Disease Outcome Quality Initiative (NKF/KDOQI) vascular access guidelines. We compared outcomes of primary patency, episodes of bacteremia, access blood flow (Qa), and quality of life (QoL) scores between RL and BHC patients. Using a prospectively collected, vascular access database, a total of 45 prevalent dialysis patients using BHC were compared with 38 patients using the RL technique over a median of 12 months (inter-quartile range: 4-27 months). The two groups did not differ significantly in demographics except that diabetes was more common in those using BHC as compared to rope-ladder (69% vs. 34%; p = 0.002). Risk factors associated with lack of primary patency were age (hazards ratio [HR] = 1.02 per decade; 95% CI: 1.00-1.03; p = 0.04) and female gender (HR = 1.92; 95% CI: 1.08-3.40; p = 0.03). Use of the buttonhole technique was not associated with improved primary patency (HR = 1.22, 95% CI: 0.65-2.28; p = 0.53). Episodes of bacteremia and mean scores from KDQOL-36 did not differ significantly between the groups. This study demonstrates for the first time that BHC use is not associated with improved access patency.

Thrombin-anti-thrombin levels and patency of arterio-venous fistula in patients undergoing haemodialysis compared to healthy volunteers: a prospective analysis

Background

Patients on haemodialysis (HD) are at an increased risk of sustaining thrombotic events especially to their vascular access which is essential for maintenance of HD.

Objectives

To assess whether 1) markers of coagulation, fibrinolysis or endothelial activation are increased in patients on HD compared to controls and 2) if measurement of any of these factors could help to identify patients at increased risk of arteriovenous (AVF) access occlusion.

Patients/Methods

Venous blood samples were taken from 70 patients immediately before a session of HD and from 78 resting healthy volunteers. Thrombin-antithrombin (TAT), D-dimer, von Willebrand factor (vWF), plasminogen activator inhibitor-1 antigen (PAI-1) and soluble p-selectin were measured by ELISA. C-reactive protein (hsCRP) was measured by an immunonephelometric kinetic assay. Determination of the patency of the AVF was based upon international standards and was prospectively followed up for a minimum of four years or until the AVF was non-functioning.

Results

A total of 70 patients were studied with a median follow-up of 740 days (range 72-1788 days). TAT, D-dimer, vWF, p-selectin and hsCRP were elevated in patients on HD compared with controls. At one year follow-up, primary patency was 66% (46 patients). In multivariate analysis TAT was inversely associated with primary assisted patency (r= -0.250, p= 0.044) and secondary patency (r = -0.267, p= 0.031).

Conclusions

The novel finding of this study is that in patients on haemodialysis, TAT levels were increased and inversely correlated with primary assisted patency and secondary patency. Further evaluation is required into the possible role of TAT as a biomarker of AVF occlusion.

The influence of metabolic syndrome on hemodialysis access patency

OBJECTIVE

The natural history of patients with metabolic syndrome (MetS) undergoing hemodialysis access placement is unknown. MetS has previously been found as a risk factor for poor outcomes for vascular surgery patients undergoing other interventions. The aim of this is study is to describe the outcomes of MetS patients undergoing primary hemodialysis access placement.

METHODS

The medical records of the 187 patients who underwent hemodialysis access placement between 1999 and 2009 at the Veterans Administration Connecticut Healthcare System were reviewed. Survival, primary patency, and secondary patency were evaluated using the Gehan-Breslow test for survival. MetS was defined as the presence of three or more of the following: blood pressure≥130/90 mm Hg; triglycerides≥150 mg/dL; high-density lipoprotein≤50 mg/dL for women and ≤40 mg/dL for men; body mass index≥30 kg/m2; or fasting blood glucose≥110 mg/dL.

RESULTS

Of the 187 patients who underwent hemodialysis access placement, 115 (61%) were identified to have MetS. The distribution of MetS factors among all patients was hypertension in 98%, diabetes in 58%, elevated triclyceride in 39%, decreased high-density lipoprotein in 60%, elevated body mass index in 36%, and 39% were currently receiving hemodialysis. Patients were a mean age of 66 years. The median length of follow-up was 4.2 years. The forearm was site of fistula placement in 53%; no difference existed between groups (MetS, 57%; no MetS, 50%; P=.388). The median time to primary failure was 0.46 years for all patients (MetS, 0.555 years; no MetS, 0.436 years; P=.255). Secondary patency was 50% at 1.18 years for all patients (no MetS, 1.94 years; MetS, 0.72 years; P=.024). Median survival duration for all patients was 4.15 years (no MetS, 5.07 years; MetS, 3.63 years; P=.019).

CONCLUSIONS

MetS is prevalent among patients undergoing hemodialysis access placement. Patients with MetS have equivalent primary patency rates; however, their survival and cumulative patency rates are significantly lower than in patients without MetS. Patients with MetS form a high-risk group that needs intensive surveillance protocols.

Interleukin-6 -634 C/G and -174 G/C polymorphisms in Korean patients undergoing hemodialysis

BACKGROUND/AIMS

Chronic inflammatory status is a possible risk factor for vascular access dysfunction in hemodialysis (HD) patients, but susceptibility differences appear among individuals. Interleukin (IL)-6 is a well-known inflammatory cytokine with various polymorphisms. We examined whether IL-6 polymorphisms are associated with vascular access dysfunction in HD patients.

METHODS

A total of 80 HD patients (including 42 diabetic patients) were enrolled. Polymorphisms in the IL-6 gene promoter (-634 C/G and -174 G/C) were studied using restriction length polymorphism polymerase chain reaction analysis. Vascular access patency was compared between the patient groups with respect to IL-6 polymorphisms. An additional 89 healthy individuals were enrolled in the control group. Plasma IL-6 levels were determined by enzyme-linked immunosorbent assay.

RESULTS

The GG genotype and G allele at position -634 in the IL-6 promoter were more frequently observed in HD patients than in controls. Furthermore, the distribution of the -634 polymorphism differed according to vascular access patency in non-diabetic HD patients. However, the G allele was not a significant risk factor for early access failure. No significant association appeared between the IL-6 -634 C/G polymorphism and plasma IL-6 levels. The C allele of the IL-6 -174 G/C polymorphism was not detected in our study population.

CONCLUSIONS

The IL-6 -634 G allele appears with greater frequently in patients with end-stage renal disease and may be associated with vascular access dysfunction in non-diabetic HD patients.

A high red blood cell distribution width predicts failure of arteriovenous fistula

In hemodialysis patients, a native arteriovenous fistula (AVF) is the preferred form of permanent vascular access. Despite recent improvements, vascular access dysfunction remains an important cause of morbidity in these patients. In this prospective observational cohort study, we evaluated potential risk factors for native AVF dysfunction. We included 68 patients with chronic renal disease stage 5 eligible for AVF construction at the Department of General and Vascular Surgery, Central Clinical Hospital Ministry of Internal Affairs, Warsaw, Poland. Patient characteristics and biochemical parameters associated with increased risk for AVF failure were identified using Cox proportional hazards models. Vessel biopsies were analyzed for inflammatory cells and potential associations with biochemical parameters. In multivariable analysis, independent predictors of AVF dysfunction were the number of white blood cells (hazard ratio [HR] 1.67; 95% confidence interval [CI] 1.24 to 2.25; p<0.001), monocyte number (HR 0.02; 95% CI 0.00 to 0.21; p = 0.001), and red blood cell distribution width (RDW) (HR 1.44; 95% CI 1.17 to 1.78; p<0.001). RDW was the only significant factor in receiver operating characteristic curve analysis (area under the curve 0.644; CI 0.51 to 0.76; p = 0.046). RDW>16.2% was associated with a significantly reduced AVF patency frequency 24 months after surgery. Immunohistochemical analysis revealed CD45-positive cells in the artery/vein of 39% of patients and CD68-positive cells in 37%. Patients with CD68-positive cells in the vessels had significantly higher white blood cell count. We conclude that RDW, a readily available laboratory value, is a novel prognostic marker for AVF failure. Further studies are warranted to establish the mechanistic link between high RDW and AVF failure.

Increased plasma chymase concentration and mast cell chymase expression in venous neointimal lesions of patients with CKD and ESRD

The underlying inflammatory component of chronic kidney disease may predispose blood vessels to intimal hyperplasia (IH), which is the primary cause of dialysis access failure. We hypothesize that vascular pathology and markers of IH formation are antecedent to arteriovenous (AV) fistula creation. Blood, cephalic, and basilic vein segments were collected from predialysis chronic kidney disease (CKD) patients with no previous AV access and patients with end-stage renal disease (ESRD). Immunohistochemistry was performed with antibodies against mast cell chymase, transforming growth factor-beta (TGF-β) and interleukin-6 (IL-6), which cause IH. Plasma chymase was measured by ELISA. IH was present in 91% of CKD and 75% of ESRD vein segments. Chymase was abundant in vessels with IH, with the greatest expression in intima and medial layers, and virtually absent in the controls. Chymase colocalized with TGF-β1 and IL-6. Plasma chymase concentration was elevated up to 33-fold in patients with CKD versus controls and was associated with increased chymase in vessels with IH. We show that chymase expression in vessels with IH corresponds with plasma chymase concentrations. As chymase inhibition attenuates IH in animal models, and we find chymase is highly expressed in IH lesions of patients with CKD and ESRD, we speculate that chymase inhibition could have therapeutic value in humans.

Upregulation of surrogate markers of inflammation and thrombogenesis in patients with ESRD: pathophysiologic and therapeutic implications

Patients with end-stage renal disease (ESRD) undergoing regular hemodialysis have high annual mortality rate of around 15%. The most predominant cause of death is cardiovascular, which is not entirely explainable with conventional cardiac risk factors present in these patients. It has been postulated that ESRD is a chronic inflammatory and hypercoagulable condition with marked elevation of several markers that may explain this high mortality. In the current study, patients with ESRD on a stable regimen of hemodialysis were studied for the inflammatory and thrombogenesis markers to explain this phenomenon. The parameters studied were of thrombogenesis-thrombin-antithrombin III complex (TAT), prothrombin fragment (F1.2), D-dimer, and fibrinopeptide A (FPA) and inflammation-CD40 ligand, myeloperoxidase (MPO), tumor necrosis factor α (TNF-α), monocyte chemotactic protein-1 (MCP-1), and nitric oxide (NO), and compared to control group comprised of 100 healthy volunteers. Our study shows that ESRD patients exhibit activation of the coagulation and inflammatory processes.

MCP-1 contributes to arteriovenous fistula failure

Vascular access dysfunction compromises the care of patients on chronic hemodialysis. Elucidating the mechanisms of such dysfunction and devising strategies that may interrupt neointimal hyperplasia and relevant pathogenetic pathways are essential. Here, we show that, in the venous segment of a murine model of an arteriovenous fistula, monocyte chemoattractant protein-1 (MCP-1) mRNA and protein increase, accompanied by increased activity of the transcription factors NF-κB and AP-1. Genetic deficiency of MCP-1 proved markedly protective in this murine model, reflected by increased fistula patency 6 weeks after its formation, decreased venous wall thickness, and increased luminal area. An early effect of MCP-1 deficiency was the attenuation of the marked induction of CCL5 (RANTES) that occurred in this model, a chemokine recently recognized as a critical participant in vascular injury. Finally, in a rat model of an arteriovenous fistula, we localized expression of MCP-1 to the endothelium, proliferating smooth muscle cells and infiltrating leukocytes. In summary, marked upregulation of MCP-1 occurs in the venous segment of an arteriovenous fistula in rodents, and this vasculopathic chemokine contributes to failure of the fistula.

"Venopathy" at work: recasting neointimal hyperplasia in a new light

Hemodialysis vascular access is a unique form of vascular anastomosis. Although it is created in a unique disease state, it has much to offer in terms of insights into venous endothelial and anastomotic biology. The development of neointimal hyperplasia (NH) has been identified as a pathologic entity, decreasing the lifespan and effectiveness of hemodialysis vascular access. Subtle hints and new data suggest a contrary idea-that NH, to some extent an expected response, if controlled properly, may play a beneficial role in the promotion of maturation to a functional access. This review attempts to recast our understanding of NH and redefine research goals for an evolving discipline that focuses on a life-sustaining connection between an artery and vein.

Clinical Outcome of Overlapping Stents in Hemodialysis Access

Purpose

Endovascular stents have recently been shown to extend access patency in thrombosed and stenotic arteriovenous grafts. Given this improved patency, stent placement has outpaced balloon angioplasty in hemodialysis (HD) access interventions. However, concern remains over localized corrosion and increased neointimal hyperplasia of overlapping stents in the access circuit and whether this promotes premature stent failure.

Methods

This is a retrospective analysis of HD patients referred for access dysfunction during a 2-yr period. Using a prospectively collected, vascular access database, we identified 76 patients seen for follow-up angiography due to access dysfunction after stent placement. We compared the outcomes of overlapping vs. non-overlapping stents in measured primary assisted patency and mean percent luminal diameter as a marker of lesion severity.

Results

The two groups did not differ significantly in demographics or comorbid conditions. Only gender had a significant discrepancy between the two groups, with 65.5% vs. 42.9% male (p=0.01) in the overlapping vs. non-overlapping stent groups, respectively. The mean percent luminal stenosis was found to be 83.7 ± 17.3 and 85.5 ± 12.6 (p=0.55) for the overlapping vs. non-overlapping stent groups, respectively. For overlapping and non-overlapping stents, 30-day primary patency was 94% and 89%, respectively, 60-day primary patency was 77% and 63%, respectively, and 90-day primary patency was 68% and 50%, respectively. Using multiple regression analysis, no risk factors were identified to be associated with the severity of luminal stenosis. No identifiable risk factors were found to be associated with improved primary patency. In particular, overlapping vs. non-overlapping stents were not identified as a statistically significant factor influencing primary (assisted) patency (hazards ratio 0.60; 95% cI 0.34 to 1.06; p>0.05).

Conclusions

This study provides evidence that the theoretical concern of metal on metal corrosion and increased neointimal hyperplasia that can be seen with overlapping stents does not play a significant clinical role.

Characterization of a model of an arteriovenous fistula in the rat: the effect of L-NAME

Vascular access dysfunction contributes to the mortality of patients undergoing chronic hemodialysis. The present study analyzed the changes that evolve in a femoral arteriovenous fistula in the rat. The venous segment of this model exhibited, at 1 week, activation of pro-inflammatory transcription factors and up-regulation of pro-inflammatory, proliferative, procoagulant, and profibrotic genes; and at 4 weeks, the venous segment displayed neointimal hyperplasia, smooth muscle proliferation, and thrombus formation. These changes were accompanied by endothelial (e) nitric oxide synthase (NOS) and inducible (i) NOS up-regulation. The administration of NG-nitro-L-arginine methyl ester, an inhibitor of NOS activity, increased venous neointimal hyperplasia and pro-inflammatory gene expression (monocyte chemoattractant protein-1 and cytokine-induced neutrophil chemoattractant-1), increased systolic blood pressure, and decreased blood flow through the fistula. In another hypertensive model, the rat subtotal nephrectomy model, venous neointimal hyperplasia in the arteriovenous fistula was also exacerbated. We conclude that this arteriovenous fistula model recapitulates the salient features observed in dysfunctional, hemodialysis arteriovenous fistulas, and that venous neointimal hyperplasia is exacerbated when this model is superimposed in two different models of systemic hypertension. Since the uremic milieu contains increased amounts of asymmetric dimethylarginine, we speculate that such accumulation of this endogenous inhibitor of NOS, by virtue of its pressor or nitric oxide-depleting effects, or a combination thereof, may contribute to the limited longevity of arteriovenous fistulas used for hemodialysis.

Endovascular stents for dialysis access: under what circumstances do the data support their use?

Despite strict K/DOQI clinical practice guidelines regarding the deployment of stents in the hemodialysis vascular circuit, their use has increased exponentially over the last 10 years in both arteriovenous fistulas and grafts. The literature is very scant regarding outcomes, with most studies suffering from design flaws. Some authors have advocated the use of stents for specific clinical scenarios, such as patients with thrombosed arteriovenous grafts or ones with a severe stenosis at the venous anastomosis. Others have advocated a more liberal strategy to deploy stents at a variety of sites if the stenotic lesion remains greater than 30% after angioplasty. Although not approved for the treatment of pseudoaneurysms in the AV grafts, stent use in this setting is emerging to be an important strategy. The use of stents as a treatment for rupture of a vessel while performing a percutaneous angioplasty is well described and performed routinely. It is important to recognize the clinical scenarios when stent placement may present a distinct disadvantage (eg, loss of a potential secondary fistula creation in the same extremity). Finally, well-designed studies need to address all these issues to clarify indications and to provide stronger scientific guidelines for stent use.

Characteristic differences in cephalic arch geometry for diabetic and non-diabetic ESRD patients

BACKGROUND

Fistula access in chronic haemodialysis patients is recommended. The first and second choice for location of fistula placement is radial-cephalic followed by the brachiocephalic fistula. Fistula access using the cephalic vein often results in cephalic arch stenosis that is less common in diabetics for unclear reasons. The objective of the current study is to determine if geometry of the cephalic arch differs between diabetics and non-diabetics.

METHODS

In a retrospective design, 57 patients with brachiocephalic fistula access had radiology films of the cephalic arch reviewed for geometric analysis. Twelve patients were excluded from final analysis because of stent placement in the cephalic arch. Measurements made included diameter of the cephalic vein, minimum radius of curvature and angle of the arch. Demographics were statistically analysed to determine the association with the geometric measurements.

RESULTS

Global and local measurements showed evidence of two arch types. Wider arch angles and larger R/d were associated with diabetes by univariate (P < 0.05) and multivariate analyses (P < 0.05). A wider arch angle was also associated with a history of right permcath access by multivariable analysis (P = 0.042).

CONCLUSIONS

Based on this study, it was found that there are two distinct types of cephalic arch geometries. Patients having diabetes mellitus show a significant probability of having a larger R/d ratio and wider arch angle. This study has given insight into structural alterations in geometry of the cephalic arch of diabetics with brachiocephalic fistula access.

Polymorphism in the promoter region of the klotho gene (G-395A) is associated with early dysfunction in vascular access in hemodialysis patients

BACKGROUND/AIMS

Vascular access dysfunction is an important cause of morbidity and mortality in hemodialysis (HD) patients. Recent studies have shown that a klotho gene mutation is related to endothelial dysfunction, thrombosis, and arteriosclerosis, which are regarded as causes of vascular access dysfunction. We investigated the relationship between the klotho G-395A polymorphism and early dysfunction in vascular access in HD patients.

METHODS

Patients who underwent vascular access operations between 1999 and 2002 were enrolled (n=126). Genotyping was performed by allelic discrimination using a 5'-nuclease polymerase chain reaction assay. Clinical data that could be relevant to access dysfunction were obtained from medical records. Early dysfunction of vascular access was defined as the need for any angioplastic or surgical intervention to correct or replace a poorly or nonfunctioning vascular access within 1 year and at least 8 weeks after initial access placement.

RESULTS

Of the 126 patients, the genotype frequency of G-395A was 72.2% for GG (n=91), 24.6% for GA (n=31), and 3.2% for AA (n=4), and the frequency of minor allele was 0.155. Clinical data were similar between the two groups, divided according to the status of the A allele. Early dysfunction occurred in 34 (27.0%) of patients, but it occurred at a significantly higher rate in A allele carriers (45.7%, 16/35) than in noncarriers (19.8%, 18/91; p=0.003).

CONCLUSIONS

Our results suggest that the klotho G-395A polymorphism could be a risk factor for early dysfunction of vascular access in HD patients.