Patency of ePTFE Arteriovenous Graft Placements in Hemodialysis Patients: Systematic Literature Review and Meta-Analysis

Hemodialysis nurses' knowledge, attitude, and practices in managing vascular access: A cross-sectional study in Saudi Arabia

Hemodialysis continues to be the primary approach for renal replacement therapy. Vascular access (VA), particularly arteriovenous fistula or arteriovenous graft, is the preferred technique for establishing hemodialysis access due to its lower risk of infection and central venous stenosis compared to catheters. The aim of this cross-sectional investigation was to examine hemodialysis nurses' knowledge, confidence, and practices in managing VA in Saudi Arabia. This is an online cross-sectional survey study that was conducted in Saudi Arabia between June and August 2023. This study utilized a previously validated questionnaire. Examined dialysis nurses' knowledge, attitude, practice, and self-efficacy pertaining to VA cannulation and evaluation. Binary logistic regression analysis was used to identify predictors of better knowledge of dialysis VA. A total of 197 participants were involved in this study. Around one-third of the study participants (37.0%) reported that they have received specialized training in managing VA. Participants agreement (answered agree or strongly agree) on statements that examined attitudes toward dialysis VA cannulation and management was high and ranged between 75.0% and 93.0%. The majority of participants (97.5%) reported that they perform this assessment. Most nurses (65%) preferred the rope-ladder technique. Participants agreement on statements that examined self-efficacy on dialysis VA cannulation and management was high and ranged between 72.1% and 98.0%. The most commonly agreed upon statement was that "they have confident in performing hemodialysis access (arteriovenous fistula and arteriovenous graft) assessment before cannulation." With 98.0% (answered agree and strongly agree). The mean knowledge score for our study sample was 6.4 (SD: 2.0) out of 12 (53.3%); which reflects marginal-level of knowledge on dialysis VA. Binary logistic regression analysis identified that nurses who have undergraduate degree are 92% more likely to be knowledgeable on dialysis VA compared to others (P < .05). Concerning VA, the level of knowledge among hemodialysis nurses working in Saudi Arabia was inadequate. Nurses who hold an undergraduate degree are presumed to have a more extensive understanding of dialysis VA. Further education programs are necessary for HD nurses to enhance their knowledge of VA, thereby optimizing their professional practices and enhancing the outcomes for their patients.

Off-the-Shelf Synthetic Biodegradable Grafts Transform In Situ into a Living Arteriovenous Fistula in a Large Animal Model

Current vascular access options require frequent interventions. In situ tissue engineering (TE) may overcome these limitations by combining the initial success of synthetic grafts with long-term advantages of autologous vessels by using biodegradable grafts that transform into autologous vascular tissue at the site of implantation. Scaffolds (6 mm-Ø) made of supramolecular polycarbonate-bisurea (PC-BU), with a polycaprolactone (PCL) anti-kinking-coil, are implanted between the carotid artery and jugular vein in goats. A subset is bio-functionalized using bisurea-modified-Stromal cell-derived factor-1α (SDF1α) derived peptides and ePTFE grafts as controls. Grafts are explanted after 1 and 3 months, and evaluated for material degradation, tissue formation, compliance, and patency. At 3 months, the scaffold is resorbed and replaced by vascular neo-tissue, including elastin, contractile markers, and endothelial lining. No dilations, ruptures, or aneurysms are observed and grafts are successfully cannulated at termination. SDF-1α-peptide-biofunctionalization does not influence outcomes. Patency is lower in TE grafts (50%) compared to controls (100% patency), predominantly caused by intimal hyperplasia. Rapid remodeling of a synthetic, biodegradable vascular scaffold into a living, compliant arteriovenous fistula is demonstrated in a large animal model. Despite lower patency compared to ePTFE, transformation into autologous and compliant living tissue with self-healing capacity may have long-term advantages.

Experimental comparative study of a novel drug-eluting arteriovenous graft in a sheep model

Background

Arteriovenous (AV) grafts often develop severe complications of stenosis due to neointimal proliferation that occurs either at the venous anastomosis site or at the outflow receiving vein. This study compares primary patency during 12 months of follow up for a new experimental Biomodics© interpenetrating polymer network (IPN) drug-eluting graft prototype with state-of-the-art GORE® ACUSEAL (ACUSEAL) in an AV graft model in sheep.

Methods and results

An end-to-end bypass from the common carotid artery to the jugularis vein was performed bilaterally in 12 sheep. The usage of ACUSEAL or the IPN, both 6.0 mm in diameter, was determined via randomization. The sheep were followed up every 4 weeks with ultrasonic duplex scanning to determine patency; the experienced observer was blinded to the randomization. One sheep died after 11 days, and the final sample accordingly consisted of 11 animals. When comparing neointimal hyperplasia after 12 months in the two grafts, Fisher's exact test showed a significant difference with none out of 11 in the IPN grafts and 9 out of 11 in the ACUSEAL graft (p < 0.001). However, the Biomodics© IPN exhibited severe deterioration over time.

Conclusions

Almost all of the grafts occluded during the 12 months of follow up. Although the zwitterion-bounded interpenetrating drug eluting polymer network showed signs to impair neointimal hyperplasia and thrombosis, age-related degeneration hindered demonstrating a potential improvement in patency.

First-in-human feasibility study of the aXess graft (aXess-FIH): 6-Month results

OBJECTIVE

The creation of an arteriovenous fistula (AVF) is considered the most effective hemodialysis (HD) vascular access. For patients who are not suitable for AVF, arteriovenous grafts (AVGs) are the best access option for chronic HD. However, conventional AVGs are prone to intimal hyperplasia, stenosis, thrombosis, and infection. Xeltis has developed an AVG as a potential alternative to currently available AVGs based on the concept of endogenous tissue restoration. The results of the first 6-month follow-up are presented here.

METHODS

The aXess first-in-human (FIH) study [NCT04898153] is a prospective, single-arm, multicenter feasibility study that evaluates the early safety and performance of the aXess Hemodialysis Graft. A total of 20 patients with end-stage renal disease were enrolled across six European investigational sites.

RESULTS

At 6-months follow-up, all grafts were patent with primary and secondary patency rates were 80% and 100%, respectively. Three patients required a re-intervention to maintain graft patency, while one re-intervention was required to restore patency. One graft thrombosis and zero infections were reported.

CONCLUSION

The expected advantages of the novel aXess Hemodialysis Graft over conventional AVGs would be evaluated by the analysis on long-term safety and effectiveness during the 5-year follow-up of the currently ongoing trial.

Enhanced hemocompatibility and rapid magnetic anastomosis of electrospun small-diameter artificial vascular grafts

Background: Small-diameter (<6 mm) artificial vascular grafts (AVGs) are urgently required in vessel reconstructive surgery but constrained by suboptimal hemocompatibility and the complexity of anastomotic procedures. This study introduces coaxial electrospinning and magnetic anastomosis techniques to improve graft performance. Methods: Bilayer poly(lactide-co-caprolactone) (PLCL) grafts were fabricated by coaxial electrospinning to encapsulate heparin in the inner layer for anticoagulation. Magnetic rings were embedded at both ends of the nanofiber conduit to construct a magnetic anastomosis small-diameter AVG. Material properties were characterized by micromorphology, fourier transform infrared (FTIR) spectra, mechanical tests, in vitro heparin release and hemocompatibility. In vivo performance was evaluated in a rabbit model of inferior vena cava replacement. Results: Coaxial electrospinning produced PLCL/heparin grafts with sustained heparin release, lower platelet adhesion, prolonged clotting times, higher Young's modulus and tensile strength versus PLCL grafts. Magnetic anastomosis was significantly faster than suturing (3.65 ± 0.83 vs. 20.32 ± 3.45 min, p < 0.001) and with higher success rate (100% vs. 80%). Furthermore, magnetic AVG had higher short-term patency (2 days: 100% vs. 60%; 7 days: 40% vs. 0%) but similar long-term occlusion as sutured grafts. Conclusion: Coaxial electrospinning improved hemocompatibility and magnetic anastomosis enhanced implantability of small-diameter AVG. Short-term patency was excellent, but further optimization of anticoagulation is needed for long-term patency. This combinatorial approach holds promise for vascular graft engineering.

Sirolimus-coated balloon angioplasty in maintaining the patency of thrombosed arteriovenous graft: 1-year results of a prospective study

BACKGROUND

A prospective, pilot study was designed to test the feasibility of using sirolimus-coated balloon (SCB) to treat graft vein junction of thrombosed arteriovenous graft (AVG) following successful pharmacomechanical thrombectomy. The present report provides the 1-year results of this study.

METHODS

This is a 1-year follow-up of a single, prospective, single-arm study that was conducted from 2018 to 2019 in 20 patients who presented to a tertiary institution with thrombosed AVG. The recruited patients received SCB angioplasty at the graft-vein junction following successful endovascular thrombectomy of a thrombosed AVG. One year after recruitment, there were three deaths, one AVG revision, and one AVG explantation among the participants recruited. The outcomes of 15 subjects at 1-year following the index procedure obtained from electronic medical records were re-examined.

RESULTS

The 1-year access circuit primary patency rate was 40%, while assisted primary and secondary patency rates were 46.7% and 73.3%, respectively. A total of 16 interventions (4 angioplasties, 12 thrombectomies) were performed in 9 patients over the 12 months. Four AVGs were abandoned. The median number of interventions per patient was 1 (0-3) per year. Using Kaplan-Meier analysis, the mean estimated post-intervention access circuit primary patency was 230 (95% CI: 162-300) days, while access circuit assisted primary patency was 253 (95% CI: 187-320) days, and access circuit secondary patency was 292 (95% CI: 230-356) days. Sub-group analysis did not show a significant difference in the mean estimated primary patency between AVG with de novo and recurrent stenosis (245 days, 95% CI: 151-339 vs 210 days, 95% CI: 113-307; p = 0.29).

CONCLUSIONS

SCB may help sustain the patency of thrombosed AVG following successful thrombectomy.

Expanded Utility of Human Acellular Vessel in Hemodialysis Access Surgery and Arterial Aneurysm Repair

Vascular access is essential for hemodialysis (HD) in patients with end-stage renal disease (ESRD). When the standard of care arteriovenous fistula (AVF) is limited, secondary to aneurysmal degeneration, trauma, and thrombus, interposition grafting is a reasonable reconstruction approach. As these grafts and comorbidities place ESRD patients at sustained risk of complications, reconstructions with regenerative medicine biologic conduits hold promise in improving safety and efficacy. Here, a biocompatible human acellular vessel (HAV) is our conduit of interest. With United States Food and Drug Administration use authorization under the Expanded Access Program, we report three cases of complex vascular access surgery with four aneurysm repairs using HAV. Patient selection focused on meeting unmet needs for those without adequate care alternatives, including active access and endoprosthetic stent graft infections, right heart failure due to high-output AVF, and arterial and access outflow aneurysms. In this high-risk expanded access population, operative technical success and interval success for patients given their inherent comorbidities, offer potential expanded utility of HAV in HD access surgery and arterial aneurysm repair.

Polyester urethane urea (PEUU) functionalization for enhanced anti-thrombotic performance: advancing regenerative cardiovascular devices through innovative surface modifications

Introduction: Thrombogenesis, a major cause of implantable cardiovascular device failure, can be addressed through the use of biodegradable polymers modified with anticoagulating moieties. This study introduces a novel polyester urethane urea (PEUU) functionalized with various anti-platelet deposition molecules for enhanced antiplatelet performance in regenerative cardiovascular devices. Methods: PEUU, synthesized from poly-caprolactone, 1,4-diisocyanatobutane, and putrescine, was chemically oxidized to introduce carboxyl groups, creating PEUU-COOH. This polymer was functionalized in situ with polyethyleneimine, 4-arm polyethylene glycol, seleno-L-cystine, heparin sodium, and fondaparinux. Functionalization was confirmed using Fourier-transformed infrared spectroscopy and X-ray photoelectron spectroscopy. Bio-compatibility and hemocompatibility were validated through metabolic activity and hemolysis assays. The anti-thrombotic activity was assessed using platelet aggregation, lactate dehydrogenase activation assays, and scanning electron microscopy surface imaging. The whole-blood clotting time quantification assay was employed to evaluate anticoagulation properties. Results: Results demonstrated high biocompatibility and hemocompatibility, with the most potent anti-thrombotic activity observed on pegylated surfaces. However, seleno-L-cystine and fondaparinux exhibited no anti-platelet activity. Discussion: The findings highlight the importance of balancing various factors and addressing challenges associated with different approaches when developing innovative surface modifications for cardiovascular devices.

Biological mechanisms of infection resistance in tissue engineered blood vessels compared to synthetic expanded polytetrafluoroethylene grafts

Objective

Synthetic expanded polytetrafluoroethylene (ePTFE) grafts are known to be susceptible to bacterial infection. Results from preclinical and clinical studies of bioengineered human acellular vessels (HAVs) have shown relatively low rates of infection. This study evaluates the interactions of human neutrophils and bacteria with ePTFE and HAV vascular conduits to determine whether there is a correlation between neutrophil-conduit interactions and observed differences of their infectivity in vivo.

Methods

A phase III comparative clinical study between investigational HAVs (n = 177) and commercial ePTFE grafts (n = 178) used for hemodialysis access (ClinicalTrials.gov Identifier: NCT02644941) was evaluated for conduit infection rates followed by histological analyses of HAV and ePTFE tissue explants. The clinical histopathology of HAV and ePTFE conduits reported to be infected was compared with immunohistochemistry of explanted materials from a preclinical model of bacterial contamination. Mechanistic in vitro studies were then conducted using isolated human neutrophils seeded directly onto HAV and ePTFE materials to analyze neutrophil viability, morphology, and function.

Results

Clinical trial results showed that the HAV had a significantly lower (0.93%; P = .0413) infection rate than that of ePTFE (4.54%). Histological analysis of sections from infected grafts explanted approximately 1 year after implantation revealed gram-positive bacteria near cannulation sites. Immunohistochemistry of HAV and ePTFE implanted in a well-controlled rodent infection model suggested that the ePTFE matrix permitted bacterial infiltration and colonization but may be inaccessible to neutrophils. In the same model, the HAV showed host recellularization and lacked detectable bacteria at the 2-week explant. In vitro results demonstrated that the viability of human neutrophils decreased significantly upon exposure to ePTFE, which was associated with neutrophil elastase release in the absence of bacteria. In contrast, neutrophils exposed to the HAV material retained high viability and native morphology. Cocultures of neutrophils and Staphylococcus aureus on the conduit materials demonstrated that neutrophils were more effective at ensnaring and degrading bacteria on the HAV than on ePTFE.

Conclusions

The HAV material seems to demonstrate a resistance to bacterial infection. This infection resistance is likely due to the HAV's native-like material composition, which may be more biocompatible with host neutrophils than synthetic vascular graft material.

Mid-term cumulative patency of fistula and PTFE grafts among hemodialysis patients: A retrospective, single-center study from Palestine

BACKGROUND

Due to the long waiting time for kidney transplantation, most End-Stage renal disease patients are commenced on either hemodialysis or peritoneal dialysis. Reusable fistulas have the lowest risk for death, cardiovascular events, and infections among all vascular accesses. This study aims to report the outcomes of the arteriovenous fistulas and PTFE grafts and the related predictive clinical and demographic variables.

METHODS

This retrospective study reviewed the charts of all hemodialysis patients between January 2017 and January 2021 at the Dialysis Center of An-Najah National University Hospital, Nablus, Palestine. Our outcomes were a primary failure, primary and secondary patency, and the related factors. Survival analysis using the Kaplan-Meier method was conducted, and the log-rank test was used to compare patency rates. The Cox proportional hazards regression model tested factors relevant to primary and secondary patency rates in univariate and multivariate analyses.

RESULTS

A total of 312 procedures were performed during the study period. Primary failure was 7.1% for AVF, 13.9% for arterio-venous graft (AVG) procedures. Peripheral arterial disease and left-sided AVF were associated with more primary failure rates. AVF, primary patency rates at 1, 2, and 3 years were 82%, 69%, and 59%, respectively, while secondary patency rates at 1, 2, and 3 years were 85%, 72%, and 63%, respectively. Factors associated with increased AVF patency in a proportional hazard model were younger age and dual antiplatelet administration.

CONCLUSION

Our study adds further evidence that autogenous AVF has better results than prosthetic AVG in both primary and secondary patency rates as well as less primary failure rates. Therefore, we encourage further longitudinal studies that assess the benefits of using antiplatelet on AVF outcome versus risks of bleeding, especially with dual agents.

Development of a universal, oriented antibody immobilization method to functionalize vascular prostheses for enhanced endothelialization for potential clinical application

BACKGROUND

Thrombosis is a common cause of vascular prosthesis failure. Antibody coating of prostheses to capture circulating endothelial progenitor cells to aid endothelialization on the device surface appears a promising solution to prevent thrombus formation. Compared with random antibody immobilization, oriented antibody coating (OAC) increases antibody-antigen binding capacity and reduces antibody immunogenicity in vivo. Currently, few OAC methods have been documented, with none possessing clinical application potential.

RESULTS

Dopamine and the linker amino-PEG8-hydrazide-t-boc were successfully deposited on the surface of cobalt chromium (CC) discs, CC stents and expanded polytetrafluoroethylene (ePTFE) grafts under a slightly basic condition. CD34 antibodies were immobilized through the reaction between aldehydes in the Fc region created by oxidation and hydrazides in the linker after t-boc removal. CD34 antibody-coated surfaces were integral and smooth as shown by scanning electron microscopy (SEM), had significantly reduced or no substrate-specific signals as revealed by X-ray photoelectron spectroscopy, were hospitable for HUVEC growth as demonstrated by cell proliferation assay, and specifically bound CD34 + cells as shown by cell binding testing. CD34 antibody coating turned hydrophobic property of ePTFE grafts to hydrophilic. In a porcine carotid artery interposition model, a confluent monolayer of cobblestone-shaped CD31 + endothelial cells on the luminal surface of the CD34 antibody coated ePTFE graft were observed. In contrast, thrombi and fibrin fibers on the bare graft, and sporadic cells on the graft coated by chemicals without antibodies were seen.

CONCLUSION

A universal, OAC method was developed. Our in vitro and in vivo data suggest that the method can be potentially translated into clinical application, e.g., modifying ePTFE grafts to mitigate their thrombotic propensity and possibly provide for improved long-term patency for small-diameter grafts.

Dialysis nurses’ knowledge, attitude, practice and self-efficacy regarding vascular access: A cross-sectional study in Singapore

Introduction:

Dialysis nurses play a paramount role in vascular access (VA) management. The aim of this study is to evaluate dialysis nurses’ knowledge, attitude, practice and self-efficacy (KACP-SE) pertaining to VA cannulation and evaluation.

Method:

An anonymous self-administered survey was administered to dialysis nurses from two tertiary hospitals (four dialysis units) and two community dialysis centres from April to May 2022. The 37-items survey consists of four dimensions of questions relating to VA cannulation and management: knowledge, attitude, practice and self-efficacy. The content validity and face validity of the survey was reviewed by three experienced VA professionals and five dialysis nurses respectively. The internal consistency and construct validity of the survey have been assessed with psychometric tests.

Results:

There were 23 and 47 nurses, working in the participated community and tertiary hospital dialysis centres respectively, responded to the survey. The internal consistency coefficients indicated acceptable reliability of the instrument (KR-20 coefficient was 0.55 and 0.76 for knowledge and practice domains; Cronbach’s α was 0.85 and 0.64 for self-efficacy and attitude domains). In the exploratory factor analysis for attitude and self-efficacy, the instrument could account for 64.0% and 53.0% of the total variance respectively. In the knowledge domain, five out of eight single-select multiple-choice questions were correctly answered by >70% of the participants. Overall, the mean (±SD) of participants’ total self-efficacy score was 24.3 (±3.1) over total score of 30. The majority of the participants (82.4%) either agreed or strongly agreed that ultrasound guidance is useful for cannulation.

Conclusion:

This KAP-SE instrument can be used to evaluate knowledge, attitude, practice and self-efficacy of dialysis nurses toward VA management. The participants demonstrated acceptable knowledge level, but with some knowledge gaps identified. It also revealed nurses’ good self-efficacy level and welcoming attitude towards adopting ultrasound in VA cannulation among the participants.

Strategies to counteract adverse remodeling of vascular graft: A 3D view of current graft innovations

Vascular grafts are widely used for vascular surgeries, to bypass a diseased artery or function as a vascular access for hemodialysis. Bioengineered or tissue-engineered vascular grafts have long been envisioned to take the place of bioinert synthetic grafts and even vein grafts under certain clinical circumstances. However, host responses to a graft device induce adverse remodeling, to varied degrees depending on the graft property and host's developmental and health conditions. This in turn leads to invention or failure. Herein, we have mapped out the relationship between the design constraints and outcomes for vascular grafts, by analyzing impairment factors involved in the adverse graft remodeling. Strategies to tackle these impairment factors and counteract adverse healing are then summarized by outlining the research landscape of graft innovations in three dimensions-cell technology, scaffold technology and graft translation. Such a comprehensive view of cell and scaffold technological innovations in the translational context may benefit the future advancements in vascular grafts. From this perspective, we conclude the review with recommendations for future design endeavors.

A Single-Center Experience with Forearm Arteriovenous Loop Grafts for Hemodialysis

BACKGROUND

Autogenous arteriovenous fistula (AVF) remains the standard of hemodialysis (HD) access; however, it cannot be reasonably obtained in all patients. For patients with contraindications to AVFs, prosthetic arteriovenous graft (AVG) remains an alternative. AVGs are plagued by high failure rates; however, there is a paucity of literature examining this. This study aims to examine a single-center review of outcomes of forearm loop AVGs in patients requiring HD access.

METHODS

A single institution, retrospective chart review was completed from 2012 to 2019, including demographics, end-stage renal disease etiology, brachial vessel diameters, and comorbidities. Logistic regression and Cox proportional hazard models were evaluated. Outcomes were defined as primary patency (time elapsed from graft creation until it was utilized as the patient's primary access), primary-assisted patency (time from primary access to intervention to maintain patency), and functional patency (time from graft placement until graft failure). Additionally, multinomial regression models were used to evaluate associations with categorical number of required interventions.

RESULTS

Ninety-eight patients [mean age 61.8 (13.9) years, 42.9% female] were identified as having brachial artery to brachial vein AVG creation during the study period, of which 75% achieved primary patency. Primary-assisted patency was 0.36 [standard error (SE) 0.07] at 6 months and 0.12 (SE 0.05) at 1 year. Functional patency was 0.75 (SE 0.07) at 6 months and 0.43 (SE 0.09) at 1 year. No association between preoperative vessel diameters and primary-assisted or functional patency was observed. Interestingly, there was a significant negative association between previous ipsilateral access and achievement of primary patency with a 60% decrease in odds of achieving primary patency in patients with previous ipsilateral access [odds ratio 0.4, 95% confidence interval (CI) 0.1-0.9, P = 0.03]. There was also noted to be a significant association between the presence of an ipsilateral catheter and increased risk of subsequent abandonment of the AVG (hazard ratio 2.6, 95% CI 1.1-5.8, P = 0.02).

CONCLUSIONS

Prosthetic forearm loop AVGs remain hindered in their utility as they show high rates of graft failure within a year of creation. A significant patient-specific factor leading to this was not clearly demonstrated. As guidelines change regarding the nature of dialysis access for patients on HD, these results draw into question the utility of prosthetic forearm loop grafts in patients requiring long-term HD access.

Single-Institution Learning Curve for Management of Mega-Fistulae Revision

Mega-fistulae are generalized aneurysmal dilations of a high flow (1500-4000 mL/min) autogenous arteriovenous (AV) access which may result in hemorrhage and/or high-output cardiac failure. Current treatment options for mega-fistula include ligation with and without prosthetic jump graft, aneurysmorrhaphy, aneurysmectomy with vein transposition, and imbrication. These options may not be suitable for advanced disease; may leave the patient without working AV access, poor cosmetic results, and possible recurrence. We describe our early experience with a technique of complete mega-fistula resection and replacement with an early use prosthetic graft that both maintains existing AV access and eliminates the need for long-term catheter placement; including lessons learned.