Stent placement versus angioplasty improves patency of arteriovenous grafts and blood flow of arteriovenous fistulae

Endovascular tools for vascular access stenosis: Flow-chart proposal

Stenosis represents the most relevant arteriovenous fistula (AVF) pathology and can affects the entire conduit forming the fistula, from afferent artery to central venous vessels. Correction of vascular access stenosis significantly affects the survival and quality of life for end stage renal disease patients (ESRD) dependent on hemodialysis. Guidelines consider the procedure of percutaneous transluminal angioplasty (PTA) relevant for the primary treatment of these lesions with excellent results in restoring AVF immediately at the end of the procedure. From first AVF angioplasty in 1981 to now, wide scientific innovation has led to development of new devices, composed by different materials and technologies, specific for the site and the type of stenosis to be treated, able to manage resistant stenotic lesion and to reduce stenosis recurrences. International guidelines do not clearly specify all treatment possibilities in the individual case. In this review the authors want to provide specific information on most used devices for stenosis treatment based on literature evidence, showing when and where to use the various tools available with flow-chart treatment proposal.

Outcomes of early cannulation arteriovenous graft versus PTFE arteriovenous graft in hemodialysis patients: A meta-analysis and systematic review

Arteriovenous graft (AVG) is an alternative for hemodialysis (HD) patients with end-stage renal disease when their permanent vascular accesses fail. Since the last decades, the most widely used materials in these patients have been polytetrafluoroethylene (PTFE)-AVGs. Recently, several studies have reported that early cannulation (EC)-AVG can be an alternative to PTFE-AVG. This systematic review and meta-analysis aimed to compare the outcomes of EC-AVG and PTFE-AVG in HD patients. We searched the Ovid Embase, Ovid MEDLINE, and Cochrane Central Register of Controlled Trials for the relevant studies published from 01.01.2000 to 19.12.2022 by keywords and free words. All randomized controlled trials (RCTs) and observational cohort studies comparing EC-AVG with PTFE-AVG were included. Ten studies were included in analysis: one RCT, six retrospective cohort studies, and three prospective cohort studies. The results showed shorter cannulation intervals (four studies, 1116 participants: mean difference -23.62 days, 95% CI [-32.03, -15.21], p < 0.05) and less central venous catheter (CVC) usage (four studies, 733 participants: OR 0.20, 95% CI [0.04, 0.92], p < 0.05) for EC-AVG compared with PTFE-AVG, while comparable outcomes of primary patency (eight studies, 1712 participants: HR 0.89, 95% CI [0.70, 1.12]), primary assisted patency (five studies, 1355 participants: HR 1.13, 95% CI [0.70, 1.84]), secondary patency (nine studies, 1920 participants: HR 0.93, 95% CI [0.66, 1.31]), and infection risk (four studies, 640 participants: HR 1.12, 95% CI [0.48, 2.58]). When compared to PTFE-AVG in HD patients, EC-AVG seems to exhibit shorter cannulation intervals, less CVC usage, and comparable outcomes of graft patency, and infection risk.

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.

Bare-Metal Stent in Dysfunctional Hemodialysis Access: An Assessment of Circuit Patency according to Access Type and Stent Location

Purpose

To evaluate the circuit patency after nitinol bare-metal stent (BMS) placement according to the type of access and location of the stent in dysfunctional hemodialysis access.

Materials and Methods

Between January 2017 and December 2019, 159 patients (mean age, 64.1 ± 13.2 years) underwent nitinol BMS placement for dysfunctional access. The location of stents was as follows: 18 brachiocephalic vein, 51 cephalic arch, 40 upper arm vein, 10 juxta-anastomotic vein, 7 arteriovenous (AV) anastomosis, and 33 graft-vein (GV) anastomosis. Circuit patency was evaluated by the Kaplan-Meier method, and cox regression model.

Results

A total of 159 stents were successfully deployed in 103 AV fistula (AVF) and 56 AV graft (AVG). AVG showed lower primary and secondary patency at 12-months compared with AVF (primary patency; 25.0% vs. 44.7%; p = 0.005, secondary patency; 76.8% vs. 92.2%; p = 0.014). Cox regression model demonstrated poorer primary patency at 12 months after stenting in the cephalic arch and GV anastomosis compared with the other sites.

Conclusion

AVF showed better primary and secondary circuit patency at 12 months following the placement of BMS compared with AVG. Stents in the cephalic arch and GV anastomosis were associated with poorer primary patency at 12 months compared to those in other locations.

Arteriovenous fistulas for hemodialysis: Brief review and current problems

The number of people worldwide living with end-stage renal disease is increasing. Arteriovenous fistulas are the preferred method of vascular access in patients who will require hemodialysis. As the number of patients with arteriovenous fistulas grows, the role of physicians who intervene who maintain and salvage these fistulas will grow in importance. This review aims to familiarize practitioners with the rationale for arteriovenous fistula creation, the detection of fistula dysfunction, and the state of the art on fistula maintenance and preservation. Current controversies are briefly reviewed.

Results of the endovascular treatment system for occluded native arteriovenous fistula

BACKGROUND

Arteriovenous fistula is the definitive vascular access for patients on long-term haemodialysis. The aim of this study is to present the techniques and results of the Endovascular Treatment System that we have developed for managing the occluded native arteriovenous fistula.

METHODS

The current study is a retrospective chart review on all patients who presented with an occluded native arteriovenous fistula and underwent attempted recanalization between 1 January 2005 and 31 December 2014.

RESULTS

A total of 130 patients were included in the study. Post-intervention primary access patency was 83.8% at 6 months, 78.7% at 12 months, 64.6% at 2 years and 59.6% at 3 years. Post-intervention assisted access patency in fistulas-in-use was 86.5% at 6 months, 81% at 12 months, 66.8% at 2 years and 61.2% at 3 years. Post-intervention secondary patency for all cases was 84.7% at 6 months, 80.2% at 12 months, 66.1% at 2 years and 62% at 3 years. Post-intervention secondary patency in fistula-in-use was 91.1% at 6 months, 90% at 12 months, 85% at 2 years and 74.6% at 3 years. Access survival nor patency differed significantly when incisional thrombectomy was compared to angioplasty with or without stenting with access survival of 91.2% and 92.5% at 12 months and access patency of 82.9% and 89.7% at 12 months (P = 0.834 and P = 0.898, respectively).

CONCLUSIONS

In autologous arteriovenous thrombosed fistulae, the use of endovascular techniques to revive the access is a viable and safe technique to employ in most cases.

Site of service influence on stent use for hemodialysis access interventions

OBJECTIVE

With rising health care spending in the United States, the Centers for Medicare and Medicaid Services (CMS) in recent years attempted to use reimbursement rates to influence use of less expensive care sites for covered patients, such as ambulatory surgery centers (ASCs) and office-based laboratories (OBLs), in lieu of hospital service sites. It has been suggested that cost savings have not been realized because of more procedures being performed by physicians with ownership interests in nonhospital facilities. CMS adopted massive reimbursement changes for 2019 OBL and ASC-based procedures, which reduced dialysis access angioplasty reimbursement in the ASC setting by 50%, whereas facility reimbursement for stenting increased by 33% above prior levels. The clinical utility of adjunctive stenting in treating dialysis access stenosis remains controversial and highly discretionary. As a vascular group performing such procedures in both a hospital and nonhospital facility in which we have equity interest, we reviewed our use of stents in dialysis access procedures both in the hospital and in the ASC/OBL to determine whether site of service affected stent use.

METHODS

A retrospective review of a prospectively maintained database was performed from 2014 to 2018. All patients undergoing dialysis access angiography with angioplasty and adjunctive stent placement at our OBL (later ASC) and our primary hospital were included in the study.

RESULTS

There were 961 angioplasty or stent procedures performed for dialysis accesses between the two sites, 564 (58.7%) in the hospital setting and 397 (41.3%) at the OBL/ASC. There was a significant difference in race and age between the two sites, with younger, minority patients more frequently being treated in the hospital and older, white patients more likely to be treated in the ambulatory setting; 153 (27.1%) underwent adjunctive stent placement in the hospital and 127 (32.0%) in the ambulatory setting (P = .09).

CONCLUSIONS

Whereas financial incentives have not yet had an appreciable influence on stent use for dialysis access within previous reimbursement paradigms, the dramatic changes recently adopted by CMS may well alter this dynamic and could lead to substantially higher overall costs without proven clinical advantage. Interventionalists may be incentivized to add stents when performing balloon angioplasty in ASCs. With high failure and reintervention rates and increasingly expensive adjuncts (drug-coated balloons and stents, covered stents), the cost implications of attempts to incentivize interventionalists toward a specific type of procedure or site of care are substantial, and unintended negative consequences are likely to occur.

Treatment of failing arterio-venous dialysis graft by angioplasty, stent, and stent graft: Two-years analysis of patency rates and cost-effectiveness

The objective of this prospective randomized single-center study was to compare primary and secondary patency rates, number of percutaneous transluminal angioplasty (PTA) interventions and cost-effectiveness among PTA, deployment of a stent, or a stent graft in the treatment of failing arteriovenous dialysis grafts (AVG) due to restenosis in the venous anastomosis or the outflow vein. Altogether 60 patients with failing AVG and restenosis in the venous anastomosis or the outflow vein were randomly assigned to either PTA, placement of a stent (E-Luminexx^®) or stent graft (Fluency Plus^®). After the procedure, patients with stent or stent graft received dual antiplatelet therapy for the next three months. Follow-up angiography was scheduled at 3, 6, and 12 months unless requested earlier due to suspected stenosis or malfunction of the access. Subsequently, angiography was performed only if requested by the clinician. During a median follow-up of 22.4 (IQR=5.7) months patients with PTA, stent, or stent graft required 3.1±1.7, 2.5±1.7, or 1.7±2.1 (P=0.031) secondary PTA interventions. The primary patency rates were 0, 18 and 65% at 12 months and 0, 18 and 37% at 24 months in the PTA, stent, and stent graft group respectively (P<0.0001). The cost of the procedures in the first two years was €7,900±€3,300 in the PTA group, €8,500±€4,500 in the stent group, and €7,500±€6,200 in the stent graft group (P=0.45). We conclude that the treatment of failing dialysis vascular access by the deployment of a stent graft significantly improves its primary patency rates and decreases the number of secondary PTA interventions; however, the reduction in costs for maintaining AVG patency is not significant.

An Economic Analysis of Stent Grafts for Treatment of Vascular Access Stenosis: Point-of-Care and Medicare Perspectives in the United States

PURPOSE

To conduct an economic analysis on the impact of increased stent graft (SG) use for treatment of arteriovenous graft (AVG) anastomotic stenosis or arteriovenous fistula (AVF)/AVG in-stent restenosis (ISR) from United States point-of-care (POC) and Medicare perspectives.

MATERIALS AND METHODS

The analyses compared initial device and reintervention costs over 2 years between current and projected treatment mixes, including percutaneous transluminal angioplasty (PTA), bare metal stents (BMSs), and SGs. In projected scenarios, the absolute increase in SG use was approximately 3%. Costs included procedure reimbursement rates (Medicare) and device list prices (POC) for index procedures and reinterventions. Reintervention rates and types were informed by the RENOVA and RESCUE randomized trials. Reinterventions were primarily PTA only; however, stent use occurred a proportion of the time. BMS reintervention rates were assumed to be identical to PTA based on observational data. A population size of 1,000 patients was assumed.

RESULTS

To the POC (n = 1,000), increased SG use was predicted to result in cost savings ranging from $4,106 to $34,420 for AVG anastomotic stenosis. For AVF/AVG ISR, increased SG use was predicted to result in either a cost increase of $17,187 or a cost savings of $13,159. To Medicare (n = 1,000), increased SG use was predicted to save costs for both populations, with savings ranging from $57,401 to $169,544.

CONCLUSIONS

The use of SG for treatment of AVG anastomotic stenosis and AVF/AVG ISR appears to be economically favorable for POC providers and Medicare. Further data on reintervention rates are required from other SG trials to validate findings.

Balloon Angioplasty Versus Stenting for the Treatment of Failing Arteriovenous Grafts: A Meta-Analysis

PURPOSE

To assess the outcomes of plain balloon angioplasty versus stenting for the treatment of failed or malfunctioning chronic haemodialysis arteriovenous grafts (AVGs).

METHODS

A systematic search of the literature was undertaken using the PUBMED, EMBASE, and Cochrane databases from January 2000 to September 2016 for articles comparing balloon angioplasty versus stenting in the management of failed or malfunctioning chronic haemodialysis AVGs. Results are reported as OR and 95% CI.

RESULTS

The search identified eight studies (1051 patients). Balloon angioplasty alone was used in 521 patients (49.6%) and stenting in 530 patients (50.4%). At the time of the endovascular re-intervention, the mean life of AVGs was 807.7±115.4 days for the balloon angioplasty and 714.2±96.3 days for the stenting group (p=.92). All AVGs were located in the arm. Most procedures (98.1%) were performed across the venous anastomosis, while 88% of the patients in the stenting group received a stent graft. The technical success rate was significantly higher in the stenting group (OR 0.16, 95% CI 0.08-0.31, p<.001). At 12 months, loss of primary and secondary patency was significantly higher in patients undergoing plain balloon angioplasty compared with stenting (OR 3.54, 95% CI 2.18-5.74, p<.001, and OR 1.82, 95% 1.17-2.82, p=.008, respectively).

CONCLUSION

Stenting is associated with better technical success and patency rates compared with plain angioplasty in treating failed or malfunctioning chronic haemodialysis AVGs, and thus it should be considered as the first line therapeutic option.

Viabahn stent for hemodialysis shunt: efficacy, long segment recanalization and prognostic factors for reintervention

INTRODUCTION

The study evaluated the Heparin Bioactive Surface (HBS) Viabahn Stent (W.L. Gore & Associates, Flagstaff, Arizona) efficacy in the maintenance or re-establishment of hemodialysis.

MATERIALS AND METHODS

Fifty HBS Viabahn stents deployed in 37 consecutive patients with hemodialysis dysfunction from January 2008 to May 2016 were evaluated in a single-institution retrospective review. Outcomes were stent patency intended as primary circuit patency (PP), assisted primary patency (APP), target lesion primary patency (TLPP) and secondary patency (SP). Moreover, the risk factor analysis for hemodialysis dysfunction that required reintervention was performed. A subgroup analysis was conducted to assess patency of Viabahn stent to treat peripheral venous long segment obstruction (LSO).

RESULTS

Overall Kaplan-Meyer PPs were 60% at 12 months and 42% at 24 months. Overall TLPP estimated rates were 68% and 49% at 12 and 24 months, respectively. The corresponding SP rates were 85% and 78% at the same period. Estimated PP rates at 12 and 24 months for stent placement after peripheral venous long segment recanalization procedure were 53% and 31%, respectively. Corresponding SP rates were 82% and 68%, respectively. The APP rates were 79% at 12 months and 61% at 24 months. Female sex, access age and thrombosis were associated with reduced primary patency.

CONCLUSIONS

Considering the high rates of PP, TLPP, APP and SP, Viabahn stents have been proven effective in maintaining or re-establishing the hemodialysis access. Moreover, stent placement after recanalization of LSO of venous out-flow represented a valid approach to rescue a dysfunctional fistula that would otherwise be abandoned.

Angioplasty and stenting for the proximal anastomotic stenosis of a brachio-axillary bypass graft using a helical interwoven nitinol stent: A case report

RATIONALE

Thrombosis due to anastomotic site stenosis is the most common complication in patients with brachio-axillary arteriovenous graft (AVG). Intravascular stent placement may play a special role in the salvage of dialysis grafts that have been previously performed percutaneous angioplasty or surgical procedure on the graft. Herein, we applied a novel stent named Supera which has a high degree of flexibility and resistance to external compression for treating a patient with recurrent venous anastomotic stenosis of brachio-axillary AVG.

PATIENTS CONCERNS AND DIAGNOSES

We report a case of the patient with end-stage renal disease who presented with brachio-axillary AVG malfunction.

INTERVENTIONS

The patient underwent repeated percutaneous angioplasty with thrombectomy for total graft occlusion, and we placed the Supera stent to salvage the graft.

OUTCOMES

Postprocedural Doppler ultrasonography did not show any restenosis on the 1- and 3-month follow-up periods, and average flow volume in the stent was >1000 mL/min. And he has been on dialysis for 6 months without any problems after stent placement.

LESSONS

The Supera stent is a useful treatment option of interventional procedure for recurrent venous anastomotic stenosis of brachio-axillary AVG in the clinical practice.

Arteriovenous Access Failure, Stenosis, and Thrombosis

Vascular access–related complications can lead to patient morbidity and reduced patient quality of life. Some of the common arteriovenous access complications include failure to mature, stenosis formation, and thrombosis.

Stent and Stent-Graft Use in Arteriovenous Dialysis Access

Dialysis access failure is a major cause of mortality and morbidity among dialysis patients. Preservation of access is critical to maintaining hemostasis, avoiding uremia, and managing the complications of kidney failure. While angioplasty remains the most common method of managing arteriovenous (AV) access stenoses, the use of stents and stent grafts to manage venous stenoses associated with AV access has become more prominent. There have been several prospective randomized trials that have demonstrated the benefit of these devices in maintaining the target lesion patency of the treated areas. In this article, the author reviews the data relating to stent and stent-graft use at the venous anastomosis and outflow veins for pseudoaneurysms of grafts, at the cephalic arch, and for central venous stenoses.

Influence of drugs on arteriovenous vascular access dysfunction

Vascular access dysfunction, due to venous stenosis at the vein-artery anastomosis in arteriovenous fistulas and vein-graft anastomosis in synthetic arteriovenous grafts, is a major cause of morbidity and mortality in dialysis patients. The two overarching approaches to prevent and treat vascular access dysfunction are from systemic or local (including endovascular and perivascular) routes. However, there are currently very few effective therapies to treat vascular access dysfunction. This article will review major studies evaluating systemic, endovascular, and perivascular therapies for vascular access dysfunction. Ongoing research to evaluate novel innovations to prevent and/or manage vascular access dysfunction appears promising.

Comparison of two Endovascular Treatments of a Stenosed Arteriovenous Fistula: Balloon-Angioplasty with and without Stenting

Purpose

Arteriovenous fistulas (AVFs) are created in patients to enable a permanent vascular access for hemodialysis. The AVF causes changes in the hemodynamic conditions leading to possible complications, stenoses being the most common one. Our objective was to compare the effect of treating the stenosed AVF by balloon-angioplasty, whether followed or not with stenting.

Methods

We considered an AVF presenting an 60% arterial stenosis and simulated the two endovascular treatments using an implicit approach. We then simulated the fluid-structure interactions (FSI) within (i) the patient-specific stenosed AVF, (ii) the AVF after angioplasty, and (iii) the AVF after angioplasty plus stenting with ANSYS Workbench.

Results

We show that a self-expandable stent does not modify the curvature of the vessel after angioplasty; it only increases the local Young modulus of the stented wall by an order of magnitude. The results of the FSI simulations indicate that the two treatments induce the same hemodynamic conditions: they both reduce the pressure difference across the stenosis, while maintaining the flow distribution downstream of the stenosis. The venous flow rate that has to be guaranteed for hemodialysis is unaltered. Thanks to its large axial flexibility, the self-expandable stent causes at maximum a three-fold increase in the internal wall stresses at peak systole as compared to angioplasty alone.

Conclusions

By maintaining the vessel lumen shape over time, the stent is likely to reduce the risk of restenosis that can otherwise occur after balloon-angioplasty because of the viscoelastic recoil of the vessel.

Why Vascular Access Trials on Flow Surveillance Failed

Introduction

Since the introduction of access flow surveillance technology for routine patient screening in 1995, more than 30 clinical trials have been presented in peer reviewed journals. Despite overall positive outcomes, some trials, including randomized control trials (RCTs), failed to produce positive outcomes for access surveillance. The purpose of this study is to analyze published data related to the main component of access surveillance–-adequate increase of access flow after percutaneous transluminal angioplasty (PTA).

Results

A total of nine studies for arteriovenous grafts (AVGs) that include 350 accesses and nine studies for arteriovenous fistula (AVF) that included 503 accesses were considered for analysis from 14 publications. Practically, all reference data find high sensitivity (>90%) of access flow measurement to predict 50% stenosis. Mean access flow increase after PTA in AVGs was 319 ml/min (from 238 to 524 ml/min). Mean access flow increase in AVFs was 331 ml/min (from 195 to 402 ml/min). Relative flow increase in AVFs was 1.6 times greater than in AVGs. The authors of failed RCT for AVGs either did not select patients for PTA based on KDOQI guidelines and did not provide/analyze PTA flow results data, or reveal data that obviously show failure of PTA to adequately improve access flow.

Summary

Access flow surveillance successfully identifies patients with hemodynamically significant stenosis. PTA performed on AVFs produce better hemodynamic results than in AVGs. Inadequate flow increases during PTA and not following KDOQI guidelines are major contributing factors for failed AVG randomized tails. Radiologists should use objective means for flow evaluation during PTA.

Novel therapies for hemodialysis vascular access dysfunction: myth or reality?

Hemodialysis vascular access dysfunction is a major source of morbidity for patients with ESRD. Development of effective approaches to prevent and treat vascular access failure requires an understanding of the underlying mechanisms, suitable models for preclinical testing, systems for targeted delivery of interventions to maximize efficacy and minimize toxicity, and rigorous clinical trials that use appropriate outcome measures. This article reviews the substantial progress and ongoing challenges in developing novel treatments for arteriovenous vascular access failure and focuses on localized rather than systemic interventions.

Acesso vascular para hemodialise: o que ha de novo?

O aumento da expectativa de vida dos portadores de doenças crônicas, entre as quais a insuficiência renal crônica, faz com que métodos de tratamentos estejam em constante aperfeiçoamento. O uso em longo prazo da hemodiálise torna necessário confeccionar e manter acessos vasculares de utilização duradoura. Tanto as fístulas arteriovenosas - primeira opção de acesso para os pacientes hemodialíticos - como os cateteres vêm sendo objeto de estudos na literatura, na tentativa de prolongar sua vida útil. Esta revisão tem como objetivo relatar as alternativas e soluções atuais para os acessos vasculares para hemodiálise.

Challenges and management of high-flow arteriovenous fistulae

The Kidney Dialysis Outcomes Quality Initiative and Fistula First Initiative have embraced the arteriovenous fistula as the gold standard for hemodialysis accesses. Despite this status, fistulae are fraught with complex issues ranging from a high primary failure rate to high flow resulting in increased cardiovascular morbidity. It is important not to overlook the insidious peril of a hyperfunctioning access that may actively promote cardiac overload, cardiopulmonary recirculation, rapid access growth with aneurysm enlargement, recurrent venous stenosis resulting in access failure, and inflow/outflow mismatch. Once recognized, flow can and should be reduced to mitigate these and other negative effects.

Balloon angioplasty vs nitinol stent placement in the treatment of venous anastomotic stenoses of hemodialysis grafts after surgical thrombectomy

OBJECTIVE

Most arteriovenous hemodialysis grafts fail ≤18 months after implantation, most commonly due to intimal hyperplasia at the venous anastomosis. This open prospective study compared balloon angioplasty vs nitinol stent placement in the treatment of venous anastomotic stenosis after thrombectomy of prosthetic brachial-axillary accesses.

METHODS

Between February 2007 and December 2010, 61 patients with an initial thrombosis of a prosthetic brachial-axillary access were admitted to our hospital. Of these patients, 28 (46%), treated before June 2008, underwent thrombectomy plus balloon angioplasty of the venous anastomosis (group A), whereas the remaining 33 (54%) patients, who were treated after July 2008, underwent graft thrombectomy plus angioplasty with self-expanding nitinol stent placement (group B). Primary, primary-assisted, and secondary patency rates were calculated using Kaplan-Meier analysis and compared between the two groups with the log-rank test.

RESULTS

Primary patency was 32% at 3 months, 24% at 6 months, and 14% at 12 months in group A, and the respective values were 85%, 63% and 49% in group B. Primary patency was significantly better in group B than in group A (P < .001; log-rank test). Cumulative median patency was 60 days in group A and 260 days in group B. Patient age, sex, comorbidities, graft material, and graft age did not have prognostic significance. Primary-assisted and secondary patency rates were significantly higher in group B.

CONCLUSIONS

Graft thrombectomy plus angioplasty with self-expanding nitinol stent placement provides significantly higher patency rates compared with thrombectomy plus plain balloon angioplasty of the venous anastomosis.

Efficacy of SMART Stent Placement for Salvage Angioplasty in Hemodialysis Patients with Recurrent Vascular Access Stenosis

Vascular access stenosis is a major complication in hemodialysis patients. We prospectively observed 50 patients in whom 50 nitinol shape-memory alloy-recoverable technology (SMART) stents were used as salvage therapy for recurrent peripheral venous stenosis. Twenty-five stents each were deployed in native arteriovenous fistula (AVF) and synthetic arteriovenous polyurethane graft (AVG) cases. Vascular access patency rates were calculated by Kaplan-Meier analysis. The primary patency rates in AVF versus AVG at 3, 6, and 12 months were 80.3% versus 75.6%, 64.9% versus 28.3%, and 32.3% versus 18.9%, respectively. The secondary patency rates in AVF versus AVG at 3, 6, and 12 months were 88.5% versus 75.5%, 82.6% versus 61.8%, and 74.4% versus 61.8%, respectively. Although there were no statistically significant difference in patency between AVF and AVG, AVG showed poor tendency in primary and secondary patency. The usefulness of SMART stents was limited in a short period of time in hemodialysis patients with recurrent vascular access stenosis.

Outcomes of endovascular intervention for salvage of failing hemodialysis access

OBJECTIVE

To investigate the effectiveness of endovascular balloon angioplasty to preserve the patency of failing hemodialysis arteriovenous fistulas (AVF) and prosthetic arteriovenous grafts (AVG).

METHODS

Patients on hemodialysis who received endovascular intervention for access problems were retrospectively analyzed. Fistulography was performed on patients who were suspected to have access stenosis and balloon angioplasty performed in the same setting if a stenosis of ≥50% is detected. Patients were followed up for post-operative complications and access restenosis or failure.

RESULTS

42 hemodialysis patients with 44 access sites (29 AVFs, 15 AVGs) required endovascular balloon angioplasty. There were no perioperative complications. Technical success rate was 100%. Median time from initial access creation to first balloon angioplasty was 13 months (2-146 months) for AVFs and 8 months (2-71 months) for AVGs. 19 of 44 patients subsequently developed restenosis. Median time for restenosis or access failure was 11 months (1-18 months) for AVFs and 5 months (1-10 months) for AVGs. Kaplan-Meier analysis for access patency after endovascular intervention showed 72% patency at 6 months and 32% at 12 months.

CONCLUSIONS

Endovascular balloon angioplasty is effective in restoring patency of failing hemodialysis accesses. Recurrence is common, and repeat interventions are required.

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.

Surgical aspects and biological considerations of arteriovenous fistula placement

Since the Fistula First Initiative was formulated in 2003, providers and payers have increasingly emphasized the need to create more arteriovenous fistulae. To maximize the chances of successful fistula maturation, a thorough understanding of the biology and surgical aspects of fistula placement are essential. A functional endothelium in the target vessels is the prerequisite for the adaptive remodeling of the vessel wall, which has to take place after fistula formation. Mechanoreceptors of the endothelium sense the increase in shear stress and, through a variety of activated signaling cascades, induce the necessary changes and vasodilation of the respective vessels. The successful fistula placement starts with a thorough preoperative evaluation, which focuses on protecting the target vessels and avoiding intravenous catheters and devices. Intraoperatively, the risk of endothelial dysfunction and hyperplasia is further minimized through an atraumatic dissection with minimal manipulation of the vein and artery. The surgical technique should also focus on decreasing the vessel compliance mismatch and avoiding an inflammatory response secondary to hematoma formation. Postoperatively, the fistula must be diligently monitored for the complications of thrombosis, postoperative steal syndrome, neuropathy, aneurysm formation, infection, and high-output cardiac failure. Early recognition of a problem is the key to saving an otherwise doomed fistula. An armamentarium of percutaneous techniques is available to the access surgeon to treat the most common causes of failed access formation. However, in some cases a surgical revision of the access site through patch angioplasty, a jump graft, and graft interposition is necessary to create a fistula which can be successfully 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.

The history of interventional nephrology

Visionary nephrologists in the early 1960s invented the dialysis machine, constructed arteriovenous shunts and fistulas, and designed vascular and peritoneal catheters to provide their patients with long-term dialysis. As the number of dialysis patients grew, the construction and care of vascular access was abandoned by nephrologists to surgeons and radiologists. There was a decline in the number of fistulas and an increase in grafts in the United States. Vascular access was not the first priority for the nonnephrologists, and this set the stage for the emergence of diagnostic and interventional nephrologists. These self-taught nephrologists trained others, resulting in a critical mass of subspecialists who founded the Society of Diagnostic and Interventional Nephrology. This review traces the origin of this exciting field from its pioneers to the society as it exists today. The future of this society depends on academic nephrology fellowship programs fostering training and research in this field.

Hemodialysis vascular access monitoring: current concepts

Most arteriovenous grafts fail due to irreversible thrombosis, and most clotted grafts have an underlying stenotic lesion. These observations raise the plausible hypothesis that early detection of graft stenosis with preemptive angioplasty will reduce the likelihood of graft thrombosis. A number of noninvasive methods can be used to detect hemodynamically significant graft stenosis with a high positive predictive value. These tests include clinical monitoring, as well as surveillance by static dialysis venous pressures, flow monitoring, or duplex ultrasound. However, these surveillance tests have a much lower positive predictive value for graft thrombosis in the absence of preemptive angioplasty. In other words, none of the currently available surveillance tests can reliably distinguish between stenosed grafts destined to clot, and those that will remain patent without intervention. As a consequence, any program of graft surveillance necessarily results in a substantial proportion of unnecessary angioplasties. Moreover, a substantial proportion of grafts thrombose despite a normal antecedent surveillance test. Numerous observational studies have found an impressive reduction of graft thrombosis after implementation of a stenosis surveillance program. In contrast, 5 of 6 randomized clinical trials failed to show a reduction of graft thrombosis in patients undergoing graft surveillance, as compared with those receiving only clinical monitoring. The lack of benefit of surveillance is largely attributable to the rapid recurrence of stenosis after angioplasty. Thus, routine surveillance for graft stenosis, with preemptive angioplasty, cannot be recommended for reduction of graft thrombosis. Future research should be directed at pharmacologic interventions to prevent graft stenosis.

Stent placement in hemodialysis access: historical lessons, the state of the art and future directions

Vascular access stenosis in patients undergoing chronic hemodialysis is a major issue that is associated with increased morbidity, mortality, and cost of medical care. Recent data have emphasized that endovascular stents could be used in the treatment of central as well as peripheral stenotic lesions. In general, a peripheral or central vein lesion that is elastic or recurs within a three-month period after an initially successful balloon angioplasty or a stenosis where surgical revision is not possible are some indications for intravascular stent placement. Recent reports have expanded the role of stents in the management of pseudoaneurysms associated with dialysis access. In this context, the utilization of these devices must take into account a fair comparison with the traditional (surgical) approaches regarding effectiveness as well as costs. This report describes the role of stents in arteriovenous dialysis access. In addition, some of the recent advances in the structure and complicating issues such as stent fracture, migration, and infection, as well cannulation through the stent, are discussed.

Stent migration and folding in the subclavian vein during subclavian hemodialysis catheter placement

The role of stent placement in hemodialysis (HD) access intervention continues to evolve. As more stents are placed, new and unusual complications are coming to light. We describe a case in which an unsuccessful attempt to place a left subclavian dialysis catheter resulted in the inadvertent migration and folding of a previously deployed subclavian stent. Attempts to remove the stent with a snare were unsuccessful. Patency was restored to the access circuit by placing a new stent through the struts of the folded one. Clinical vascular practice guidelines for vascular access on the use of fluoroscopy for temporary HD catheter placement may need to be re-evaluated with the reported increase in stent placement in the US HD population.

How I do it: endovascular stent deployment using a novel technique that obviates the need for introducer-sheath upsizing

A case is presented and a novel technique is described by which an endovascular stent is deployed in the venous outflow system of an arteriovenous fistula without the traditional exchange to a larger diameter introducer sheath.