Prospective randomized trial of a metallic intravascular stent in hemodialysis graft maintenance

Existing and Evolving Therapies for Arteriovenous Fistula and Graft Dysfunction

A functional vascular access (VA) is of paramount importance to patients on hemodialysis therapy. While arteriovenous fistula (AVF) remains the preferred VA, their long-term patency is unpredictable. A dysfunctional VA contributes to a high morbidity rate, an increased susceptibility to major adverse cardiovascular events, recurrent hospitalization, and a poor quality of life. The recent innovations in devices and technologies have significantly expanded our options to create and prolong VA patency. Endovascular devices such as WavelinQ and Ellipsys are recent additions to creating a VA. The endovascular creation of AVF helps reduce the wait time and potentially avoids or reduces the duration of catheter use. The bioengineered graft and immediate access arteriovenous graft offer reasonable alternatives in a select group of patients. There is growing evidence that covered stents and drug-coated balloons offer options to prolong the VA patency. Finally, the role of stem cell therapy in VA is currently being explored. This article presents a comprehensive review of the conventional and current developments in the management of a dysfunctional VA.

Patency rates following treatment with the WRAPSODY™ Cell-Impermeable Endoprosthesis for recalcitrant renal access circuit dysfunction: Results from a tertiary Australian centre

OBJECTIVE

To describe clinical outcomes associated with the use of the WRAPSODY Cell-Impermeable Endoprosthesis at a tertiary center in Western Australia.

METHODS

Patients with recalcitrant occlusive disease in the venous outflow of their arteriovenous access circuits were treated with WRAPSODY. Patients were prospectively followed up to 12-month post-procedure. Study measures included 30-day adverse events, technical success, target lesion primary patency, access circuit primary patency, and assisted access circuit primary patency.

RESULTS

Twenty-seven WRAPSODY devices were used to treat 15 consecutive patients. The technical success rate was 100%. No device-related adverse events were observed during the follow-up period. Two patients did not complete the full follow up. Patency rates at 3-, 6-, and 12 months for target lesion primary patency were 100% (15/15), 100% (15/15), and 100% (13/13), respectively. Rates for access circuit primary patency at 3-, 6-, and 12 months were 73.3% (11/15), 46.7 % (7/15), and 46.2% (6/13), respectively. Edge stenosis was observed in 33.3% (5/15) of cases and accounted for 5 of the 8 patients who experienced failed access circuit primary patency on angiogram. Primary assisted functional patency was 100% at 12 months.

CONCLUSION

WRAPSODY can be utilized safely and has durable patency in real-world patients with complex anatomical renal access stenotic lesions. The therapeutic benefits associated with the device may encourage broader use in clinical practice.

SUPERA stent placement for salvaging early recurrent arteriovenous graft thrombosis after percutaneous transluminal angioplasty: A single-center study

BACKGROUND

The aim of this study was to evaluate the patency of the helical interwoven SUPERA stent for salvaging prosthetic arteriovenous (AV) grafts with rapidly recurrent thrombotic occlusion developed within a short time period after successful percutaneous transluminal angioplasty.

METHODS

From December 2019 to September 2021, the data of 20 patients with AV graft who had the SUPERA stent inserted satisfying the following conditions were consecutively collected. (1) More than 1 year has passed since the AV access operation; (2) Thrombotic re-occlusion of AV graft occurred within 3 months after previous successful endovascular treatment; (3) Residual stenosis is greater than 30% after full effacement of balloon angioplasty in the primary lesion. Post-interventional target lesion primary patency (TLPP), access circuit primary patency (ACPP), and secondary patency (SP) were calculated.

RESULTS

Primary lesions of early recurrent arteriovenous graft thrombosis were found in 13 patients with graft-vein anastomosis, six patients with intra-graft stenosis, and one patient with outflow vein complications. The lesions showed residual stenosis in 47.4% (interquartile range: 44.1%-55.3%) of patients despite full-effacement balloon angioplasty. Clinical success was achieved in all patients with full-expansion of the stents at the 1-month follow-up. The TLPP was 70.7% and 32% at 6 and 12 months, respectively, and ACPP was 47.5% and 6.8% at 6 and 12 months, respectively. The SP was 76.1% and 57.1% at 6 and 12 months, respectively. No cannulation complications occurred in the six patients with installation inside the graft. No hemodialysis or stent fracture occurred in any patient during the follow-up period.

CONCLUSIONS

The SUPERA stent may have a role in salvaging AV grafts with early recurrent thrombosis due to its greater radial force and its conformability and can be useful in treating stenosis involving the elbow or axilla, with fair patency and low complication rates.

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.

First Clinical Results of the Merit WRAPSODY™ Cell-Impermeable Endoprosthesis for Treatment of Access Circuit Stenosis in Haemodialysis Patients

PURPOSE

This prospective, observational first in human study evaluated the safety and effectiveness of WRAPSODY^TM Cell-impermeable Endoprosthesis (Merit Medical Systems, Inc.) in the treatment of arteriovenous fistula and arteriovenous graft access circuit stenosis.

MATERIALS AND METHODS

Investigators conducted a prospective analysis of 46 patients with access circuit stenosis from three centres. Treatment sites included the peripheral outflow veins (e.g. cephalic arch, basilic vein swing point; 16 fistula and 10 graft patients); the graft-vein anastomosis (9 patients); and the central veins (up to, but not including the SVC; 11 patients). Primary outcome measures included 30-day freedom from access circuit-related safety events and 30-day target lesion primary patency. Secondary outcome measures included procedural success; device- and procedure-related adverse events; target lesion primary patency; access circuit primary patency; and secondary patency. In-person follow-up was scheduled at 1, 3, 6, and 12 months. An independent data monitoring/clinical event committee adjudicated all reinterventions and device/procedure-relatedness for adverse events.

RESULTS

All initial procedures were successful. All but one patient was free from safety events through the first 30 days (97.8% (45/46)). This event was not device-related. Over the remainder of the study, one adverse event was adjudicated as possibly device-related. Six- and 12-month target lesion primary patency rates were 97.7% (42/43) and 84.6.% (33/39), respectively. Six- and 12-month access circuit primary patency rates were 84.4% (38/45) and 65.9% (29/44), respectively.

CONCLUSION

Results suggest that the study device is safe and effective for treatment of stenoses in the peripheral and central veins of arteriovenous access circuits.

LEVEL OF EVIDENCE

Level 2b, cohort study.

The challenge of stent placement within cannulation zones of Arteriovenous Fistulae

BACKGROUND

Stent placement in the cannulation zone of AVF is becoming alarmingly frequent and sometimes in cases where surgical management would be more appropriate. When complications arise repair can be particularly challenging. We present our experience and management of this problem.

METHODS

We report our experience on three patients (two females and one male, mean age 72) that were referred to our department for problems related to stents placed at the cannulation segments.

RESULTS

All patients required complex surgical interventions. In two of them maintenance of access was possible but required the use of a graft. In one complete resection of the AVF and all stents was necessary, and the patient remained on dialysis through catheter.

CONCLUSION

Stent placement at the cannulation zones may complicate access management in the future and should be avoided if possible.

Nitinol stent-assisted maturation of the dysfunctional cannulation zone in the immature arteriovenous fistula

INTRODUCTION

The native arteriovenous fistula may remain immature despite adequate arterial inflow after formation. This may occur when the puncturable vein segment (cannulation zone) is too small to be reliably punctured, occluded or too deep under the skin for needle access. We performed stenting (stent-assisted maturation) of arteriovenous fistulas with an immature cannulation zone, allowing for a large subcutaneous channel which could then be immediately punctured for dialysis.

METHODS

We performed a retrospective review of 49 patients (mean age was 58.7 ± 16.09 (12-83) years, mean arteriovenous fistula age of 162.6 ± 27.28 days) with end-stage renal failure who underwent balloon dilatation and bare-metal stent implantation (1.6 ± 0.67 (1-3) stents, median diameter and length of 8 (5-14) mm and 80 (40-150) mm, respectively) through their cannulation zone (forced maturation). Radiocephalic (35 arteriovenous fistulas), brachiocephalic (10 arteriovenous fistulas) and autogenous loop arteriovenous fistulas (4 arteriovenous fistulas) were included with 30 patients (61.2%) having an inadequate cannulation zone venous diameter, 9 patients (18.4%) having an absent cannulation zone and 10 patients (20.4%) having a patent cannulation zone deeper than 1 cm which was not reliably puncturable. The study was conducted over 9 years (January 2008-December 2016) with implantation of the SMART^® stent and Absolute Pro^® stent in 61.2% and 38.8%, respectively. Long-term outcomes including primary useable segmental and access circuit patency as well as assisted primary access circuit patency, rate of re-intervention, technical success and complications were analysed.

RESULTS

At 6 months, 12 months and 4 years, respectively, cannulation zone primary patency was 84.4%, 74.4% and 56.1% and access circuit primary patency was 62.2%, 45.3% and 23.2%; however, assisted primary access circuit patency was 95.6%, 91.1% and 83.8%, achieved with an endovascular re-intervention rate of 0.53 procedures/year with only four thrombosed circuits occurring.

DISCUSSION

Forced maturation using nitinol stents allows for long-term haemodialysis access with a low rate of re-intervention.

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.

Stent graft placement versus angioplasty for hemodialysis access failure: a meta-analysis

BACKGROUND

Hemodialysis is a common treatment for end-stage renal disease, and maintenance of access patency remains a key issue. Angioplasty is recommended as the first choice for access stenosis, but it poses a risk of a high rate of restenosis. Stent graft placement can generate a high patency rate of dialysis access. This study aimed to compare the primary patency of the treatment area and access circuit between stent grafts and angioplasty in dialysis access failure.

MATERIALS AND METHODS

Three electronic databases, namely, PubMed, Cochrane Library of Systematic Reviews, and EMBASE, were searched from the database inception to September 2017 without language restriction. Randomized controlled trials comparing the primary patency of the treatment area and access circuit between stent graft and angioplasty were included. Two independent reviewers assessed the quality of the trials and extracted relevant data.

RESULTS

Four trials satisfied our inclusion criteria. Our pooled results suggested that stent graft placement was associated with significantly higher primary patency of treatment area (hazard ratio: 0.65, 95% confidence interval: 0.55-0.77, P < 0.0001, I2 = 0) and access circuit (hazard ratio: 0.76, 95% confidence interval: 0.65-0.88, P = 0.0004, I2 = 0) in hemodialysis access compared with those of standard angioplasty.

CONCLUSIONS

The patency of hemodialysis access may be higher after stent graft placement combined with standard angioplasty than after angioplasty alone.

A prospective randomized study of stent graft placement after balloon angioplasty versus balloon angioplasty alone for the treatment of hemodialysis patients with prosthetic graft outflow stenosis

BACKGROUND

Hemodialysis graft outflow stenosis is a significant complication occurring in hemodialysis patients with prosthetic grafts for vascular access. Balloon angioplasty remains the first-line endovascular treatment of this complication, although covered stent graft implantation after balloon angioplasty also appears to be an effective and promising treatment. The aim of this study was to evaluate the efficacy and durability of stent graft placement after balloon angioplasty in comparison to balloon angioplasty alone for the treatment of graft outflow stenosis in hemodialysis patients.

METHODS

We conducted a prospective randomized study of 98 patients with clinically significant dialysis graft outflow stenosis treated in the vascular surgery section of a tertiary medical center. The patients were randomized into two groups; 49 patients were treated with stent graft placement after balloon angioplasty, and 49 patients were treated with balloon angioplasty alone. All patients underwent angiography of the graft site at 3 and 6 months after intervention, and restenosis rates were compared between the two groups. In addition, the duration of postintervention primary patency in the two groups was recorded and analyzed.

RESULTS

The postintervention restenosis rate of the stent graft placement group was superior to that seen in the balloon angioplasty alone group (9% vs 69% at 3 months [P < .0001] and 29% vs 72% at 6 months [P < .0001]). The mean postintervention primary patency duration was 380.22 ± 28.54 days for the stent graft placement group and 151.08 ± 16.79 days for the balloon angioplasty alone group (P < .0001).

CONCLUSIONS

The use of stent grafts in hemodialysis patients with graft outflow stenosis yielded superior results compared with the results seen in hemodialysis patients treated with balloon angioplasty alone. Patients treated with stent grafts after balloon angioplasty had a lower restenosis rate and a longer duration of postintervention primary patency. The placement of a stent graft after balloon angioplasty appears to be an optimal therapeutic approach for the treatment of hemodialysis patients with graft outflow stenosis.

Role of stents in hemodialysis vascular access

Stents are ubiquitously utilized in coronary and peripheral arterial disease. Interventional nephrologists, however, place stents in the venous outflow of the arteriovenous access. Stenosis is the predominant pathology that causes access dysfunction and will ultimately lead to thrombosis if uncorrected. Angioplasty and stent deployment are the current techniques available to combat stenosis. From initial bare metal stainless steel stents, the current generations of stents used are predominately covered nitinol stents. The latest randomized control trials reveal that stents decrease the number of interventions required to maintain patency but do not improve the overall access survival. Furthermore, bare metal stents have been shown to be inferior to stent grafts. This review discusses indications for stent deployment in the hemodialysis access, the current evidence for their use, and briefly touches on their complications.

Definitions and End Points for Interventional Studies for Arteriovenous Dialysis Access

This paper is part of the Clinical Trial Endpoints for Dialysis Vascular Access Project of the American Society of Nephrology Kidney Health Initiative. The purpose of this project is to promote research in vascular access by clarifying trial end points which would be best suited to inform decisions in those situations in which supportive clinical data are required. The focus of a portion of the project is directed toward arteriovenous access. There is a potential for interventional studies to be directed toward any of the events that may be associated with an arteriovenous access' evolution throughout its life cycle, which has been divided into five distinct phases. Each one of these has the potential for relatively unique problems. The first three of these correspond to three distinct stages of arteriovenous access development, each one of which has been characterized by objective direct and/or indirect criteria. These are characterized as: stage 1-patent arteriovenous access, stage 2-physiologically mature arteriovenous access, and stage 3-clinically functional arteriovenous access. Once the requirements of a stage 3-clinically functional arteriovenous access have been met, the fourth phase of its life cycle begins. This is the phase of sustained clinical use from which the arteriovenous access may move back and forth between it and the fifth phase, dysfunction. From this phase of its life cycle, the arteriovenous access requires a maintenance procedure to preserve or restore sustained clinical use. Using these definitions, clinical trial end points appropriate to the various phases that characterize the evolution of the arteriovenous access life cycle have been identified. It is anticipated that by using these definitions and potential end points, clinical trials can be designed that more closely correlate with the goals of the intervention and provide appropriate supportive data for clinical, regulatory, and coverage decisions.

Stent Graft versus Balloon Angioplasty for Failing Dialysis Access Grafts: A Long-Awaited Advance in the Treatment of Permanent Hemodialysis Access

Arteriovenous grafts (AVGs) for hemodialysis have a high failure rate, often due to the development of stenosis at the graft-to-vein anastomosis. Angioplasty (PTA) has been used for over two decades to treat AVG stenosis, with good technical success but limited AVG patency. Results of a prospective multi-center randomized trial, comparing stent graft to PTA in AVGs, has demonstrated superior access circuit patency for the stent graft group. Recent publication of this clinical study brings us into an exciting new era of dialysis access management using covered stents to improve durability of catheter-based therapy.

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.

Stent Grafts Can Convert Unusable Upper Arm Arteriovenous Fistulas into a Functioning Hemodialysis Access: A Retrospective Case Series

Introduction

Not all newly created arteriovenous fistulas (AVFs) successfully mature and develop into a functioning access for hemodialysis. Percutaneous transluminal angioplasty (PTA) and balloon-assisted maturation (BAM) have been utilized to either treat flow-limiting stenoses or to promote and accelerate maturation. We hypothesized that unusable upper arm AVFs can be rescued by conversion to a functional access using the percutaneous placement of a stent graft (SG).

Methods

Clinical data on 12 patients with an early non-usable upper arm AVF underwent percutaneous revision using SGs. There were six brachial–cephalic, three brachial–basilic, and three brachial–brachial vein transposition AVFs.

Results

All patients had either at least two or more stenoses (>2 cm) within the fistula conduit, or a long segment stenosis (>4 cm) in combination with shorter segment stenoses. Nine patients had failed PTA. Three patients had failed BAM at outside access centers. All patients were referred for failure to achieve access cannulation and concomitant hemodialysis through the AVF. SGs were placed retrograde toward the arterial anastomoses and ranged in diameter (6, 7, and 8 mm in four, seven, and one patients, respectively). The average length of the SG was 10 cm (range 5–15 cm). All SGs were post-balloon dilated at the time of placement. All AVFs were salvaged, and patients were able to maintain functional use of their access with cannulation occurring through the SG. The primary patency rate at 6 and 12 months was 91% [95% confidence interval (CI), 56–98%] and 65% (95% CI, 32–87%), respectively (n = 11 and 5 at risk, respectively). The secondary patency rate at 6 and 12 months was 100 and 72% (95% CI, 46–93%), respectively (n = 11 and 7 at risk, respectively).

Conclusion

This report outlines a successful initial experience using SGs to rescue, preserve, and convert an unusable upper arm AVF into a functioning hemodialysis access.

Transluminal Stent-Graft Repair for Pseudoaneurysm of PTFE Hemodialysis Grafts

Purpose:

To report the use of endovascular techniques to treat two cases of nonanastomotic pseudoaneurysm of a bridge graft fistula (BGF).

Methods and Results:

Two men with fully functional polytetrafluoroethylene (PTFE) BGFs both presented with an enlarging mass adjacent to their arteriovenous shunt. The false aneurysm in both instances was located by ultrasound and confirmed by shunt angiography at the time of surgery. Both fistulas were repaired by transluminally introducing a stented graft composed of a balloon-expandable Palmaz stent covered with a PTFE graft. Completion arteriography confirmed normal flow through the graft with no communication between the lumen and the aneurysmal cavity. Both patients recovered without complications and were discharged on the day of the procedure. Follow-up data reveal that both fistulas remain fully functional up to 5 and 6 months, respectively.

Conclusions:

Endovascular repair using stent-grafts can be a safe and effective method of excluding pseudoaneurysms associated with PTFE BGFs.

Advanced Stent Graft Treatment of Venous Stenosis Affecting Hemodialysis Vascular Access: Case Illustrations

Surgically placed dialysis access is an important component of dialysis replacement therapy. The vast majority of patients undergoing dialysis will have surgically placed accesses at some point in the course of their disease, and for many patients these accesses may represent their definitive renal replacement option. Most, if not all, arteriovenous fistulae and grafts will require interventions at some point in time. Percutaneous angioplasty is the typical first treatment performed for venous stenoses, with stents and stent grafts being reserved for patients in whom angioplasty and surgical options are exhausted. In some salvage situations, stent graft placement may be the only or best option for patients. This article describes, using case illustrations, placement of stent grafts in such patients; a focus will also be made on the techniques utilized in such salvage situations.

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.

Pre-emptive correction for haemodialysis arteriovenous access stenosis

BACKGROUND

Guidelines recommend routine arteriovenous (AV) graft and fistula surveillance (technology-based screening) in addition to clinical monitoring (physical examination) for early identification and pre-emptive correction of a stenosis before the access becomes dysfunctional. However, consequences on patient-relevant outcomes of pre-emptive correction of a stenosis in a functioning access as opposed to deferred correction, i.e. correction postponed to when the access becomes dysfunctional, are uncertain.

OBJECTIVES

We aimed to evaluate 1) whether pre-emptive correction of an AV access stenosis improves clinically relevant outcomes; 2) whether the effects of pre-emptive correction of an AV access stenosis differ by access type (fistula versus graft), aim (primary and secondary prophylaxis), and surveillance method for primary prophylaxis (Doppler ultrasound for the screening of functional and anatomical changes versus measurement of the flow in the access); and 3) whether other factors (dialysis duration, access location, configuration or materials, algorithm for referral for intervention, intervention strategies (surgical versus radiological or other), or study design) explain the heterogeneity that might exist in the effect estimates.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Specialised Register to 30 November 2015 using search terms relevant to this review.

SELECTION CRITERIA

We included all studies of any access surveillance method for early identification and pre-emptive treatment of an AV access stenosis.

DATA COLLECTION AND ANALYSIS

We extracted data on potentially remediable and irremediable failure of the access (i.e. thrombosis and access loss respectively); infection and mortality; and resource use (hospitalisation, diagnostic and intervention procedures). Analysis was by a random effects model and results expressed as risk ratio (RR), hazard ratio (HR) or incidence rate ratio (IRR) with 95% confidence intervals (CI).

MAIN RESULTS

We identified 14 studies (1390 participants), nine enrolled adults without a known access stenosis (primary prophylaxis; three studies including people using fistulas) and five enrolled adults with a documented stenosis in a non-dysfunctional access (secondary prophylaxis; three studies in people using fistulas). Study follow-up ranged from 6 to 38 months, and study size ranged from 58 to 189 participants. In low- to moderate-quality evidence (based on GRADE criteria) in adults treated with haemodialysis, relative to no surveillance and deferred correction, surveillance with pre-emptive correction of an AV stenosis reduced the risk of thrombosis (RR 0.79, 95% CI 0.65 to 0.97; I² = 30%; 18 study comparisons, 1212 participants), but had imprecise effect on the risk of access loss (RR 0.81, 95% CI 0.65 to 1.02; I² = 0%; 11 study comparisons, 972 participants). In analyses subgrouped by access type, pre-emptive stenosis correction did not reduce the risk of thrombosis (RR 0.95, 95% CI 0.8 to 1.12; I² = 0%; 11 study comparisons, 697 participants) or access loss in grafts (RR 0.9, 95% CI 0.71 to 1.15; I² = 0%; 7 study comparisons; 662 participants), but did reduce the risk of thrombosis (RR 0.5, 95% CI 0.35 to 0.71; I² = 0%; 7 study comparisons, 515 participants) and the risk of access loss in fistulas (RR 0.5, 95% CI 0.29 to 0.86; I² = 0%; 4 studies; 310 participants). Three of the four studies reporting access loss data in fistulas (199 participants) were conducted in the same centre. Insufficient data were available to assess whether benefits vary by prophylaxis aim in fistulas (i.e. primary and secondary prophylaxis). Although the magnitude of the effects of pre-emptive stenosis correction was considerable for patient-centred outcomes, results were either heterogeneous or imprecise. While pre-emptive stenosis correction may reduce the rates of hospitalisation (IRR 0.54, 95% CI 0.31 to 0.93; I² = 67%; 4 study comparisons, 219 participants) and use of catheters (IRR 0.58, 95% CI 0.35 to 0.98; I² = 53%; 6 study comparisons, 394 participants), it may also increase the rates of diagnostic procedures (IRR 1.78, 95% CI 1.18 to 2.67; I² = 62%; 7 study comparisons, 539 participants), infection (IRR 1.74, 95% CI 0.78 to 3.91; I² = 0%; 3 studies, 248 participants) and mortality (RR 1.38, 95% CI 0.91 to 2.11; I² = 0%; 5 studies, 386 participants).In general, risk of bias was high or unclear in most studies for many domains we assessed. Four studies were published after 2005 and only one had evidence of registration within a trial registry. No study reported information on authorship and/or involvement of the study sponsor in data collection, analysis, and interpretation.

AUTHORS' CONCLUSIONS

Pre-emptive correction of a newly identified or known stenosis in a functional AV access does not improve access longevity. Although pre-emptive stenosis correction may be promising in fistulas existing evidence is insufficient to guide clinical practice and health policy. While pre-emptive stenosis correction may reduce the risk of hospitalisation, this benefit is uncertain whereas there may be a substantial increase (i.e. 80%) in the use of access-related procedures and procedure-related adverse events (e.g. infection, mortality). The net effects of pre-emptive correction on harms and resource use are thus unclear.

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.

The Eternal Tale of Dialysis Access Vessels and Restenosis: Are Drug-Eluting Balloons the Solution?

In dialysis access fistulas and grafts, percutaneous transluminal angioplasty (PTA) is frequently followed by restenosis development, which results in repeated periodical re-interventions. The technique of drug-eluting balloon (DEB) angioplasty has shown promising results in the treatment of femoropopliteal arteriosclerotic lesions. In contrast to arteriosclerotic arteries, dialysis access vessels host unfavorable hemodynamics due to the direct conduction of high-pressure fluid into a low-pressure system. Hence, the beneficial effect of DEB angioplasty may be limited in this system. However, a first prospective randomized trial on 40 patients with arteriovenous fistula or graft stenoses exhibited a significantly higher 6-month primary patency of the treated lesions after DEB angioplasty than after uncoated balloon angioplasty. Despite such a positive reference, general recommendations regarding the value of DEBs in dialysis access vessels cannot be considered as serious unless large randomized controlled trials have been performed.

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.

Dialysis access

Although hemodialysis access procedures are considered the most common vascular procedures performed by either general or vascular surgeons, there is a paucity of level-one evidence in the literature. Randomized controlled trials are limited, and most of these studies have small sample sizes compared with other areas of vascular surgery, that is, carotid or aneurysm studies. We summarize the results of the world's literature for arteriovenous access in table format as a tool for those specialists managing patients with arteriovenous access procedures.

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.

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.

Stent graft versus balloon angioplasty for failing dialysis-access grafts

BACKGROUND

The leading cause of failure of a prosthetic arteriovenous hemodialysis-access graft is venous anastomotic stenosis. Balloon angioplasty, the first-line therapy, has a tendency to lead to subsequent recoil and restenosis; however, no other therapies have yet proved to be more effective. This study was designed to compare conventional balloon angioplasty with an expanded polytetrafluoroethylene endovascular stent graft for revision of venous anastomotic stenosis in failing hemodialysis grafts.

METHODS

We conducted a prospective, multicenter trial, randomly assigning 190 patients who were undergoing hemodialysis and who had a venous anastomotic stenosis to undergo either balloon angioplasty alone or balloon angioplasty plus placement of the stent graft. Primary end points included patency of the treatment area and patency of the entire vascular access circuit.

RESULTS

At 6 months, the incidence of patency of the treatment area was significantly greater in the stent-graft group than in the balloon-angioplasty group (51% vs. 23%, P<0.001), as was the incidence of patency of the access circuit (38% vs. 20%, P=0.008). In addition, the incidence of freedom from subsequent interventions at 6 months was significantly greater in the stent-graft group than in the balloon-angioplasty group (32% vs. 16%, P=0.03 by the log-rank test and P=0.04 by the Wilcoxon rank-sum test). The incidence of binary restenosis at 6 months was greater in the balloon-angioplasty group than in the stent-graft group (78% vs. 28%, P<0.001). The incidences of adverse events at 6 months were equivalent in the two treatment groups, with the exception of restenosis, which occurred more frequently in the balloon-angioplasty group (P<0.001).

CONCLUSIONS

In this study, percutaneous revision of venous anastomotic stenosis in patients with a prosthetic hemodialysis graft was improved with the use of a stent graft, which appears to provide longer-term and superior patency and freedom from repeat interventions than standard balloon angioplasty. (ClinicalTrials.gov number, NCT00678249.)

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.