Initial clinical experience with a polytetrafluoroethylene vascular dialysis graft reinforced with nitinol at the venous end

Nano-embedded medical devices and delivery systems in interventional radiology

Nanomaterials research has significantly accelerated the development of the field of vascular and interventional radiology. The incorporation of nanoparticles with unique and functional properties into medical devices and delivery systems has paved the way for the creation of novel diagnostic and therapeutic procedures for various clinical disorders. In this review, we discuss the advancements in the field of interventional radiology and the role of nanotechnology in maximizing the benefits and mitigating the disadvantages of interventional radiology theranostic procedures. Several nanomaterials have been studied to improve the efficacy of interventional radiology interventions, reduce the complications associated with medical devices, improve the accuracy and efficiency of drug delivery systems, and develop innovative imaging modalities. Here, we summarize the recent progress in the development of medical devices and delivery systems that link nanotechnology in vascular and interventional radiology. This article is categorized under: Diagnostic Tools > Diagnostic Nanodevices Diagnostic Tools > In Vivo Nanodiagnostics and Imaging Therapeutic Approaches and Drug Discovery > Nanomedicine for Cardiovascular Disease.

A critical review of surgical strategies to minimise venous stenosis in arteriovenous grafts

It is inevitable that complications arising from surgical procedures are ascribed to surgical technique, and this applies to venous stenosis (VS) in arteriovenous grafts. However, despite a wide range of cellular studies, computer modelling, observational series and clinical trials, there remains uncertainty on whether surgical technique contributes to VS. This article reviews evidence from basic science, fluid dynamics and clinical data to try and rationalise the main surgical options to modify the occurrence of venous stenosis. There is sufficient data from diverse sources to make recommendations on clinical practice (size of target vein, shape of anastomosis, angle of approach, distance from venous needling, trauma to the target vein) whilst at the same time this emphasises the need to carefully report the practical aspects of surgical technique in future clinical trials.

Initial single-center experience with a new external support device for the creation of the forearm native arteriovenous fistula for hemodialysis

OBJECTIVE

To assess and compare the maturation rate of the native radiocephalic arteriovenous fistula (RC-AVF) created with and without a nitinol external support (VasQ™ Laminate Medical Technologies Ltd, Tel Aviv, Israel).

METHODS

Data of all consecutive patients who underwent the creation of native RC-AVFs at our center between October 2018 and January 2020 was prospectively collected and retrospectively analyzed.Selected patients who had a suitable vein and a radial artery with triphasic flow at preoperative duplex ultrasound exam and were selected for the creation of a radiocephalic fistula were included. Exclusion criteria were: malignant tumors, acute renal failure, previous upper limb revascularization, and septic status. Patency and maturation, vein, and artery diameter and blood flow rate were assessed at the following intervals: post-operatively, 24 h post-operatively, 1 month, 3 months, and 6 months post-operatively.

RESULTS

Forty-nine patients (31 males, mean age 65.7 years old) were included. Patients who received VasQ™ devices were 25 (VasQ group), the other 24 formed the control group. All patients underwent radio-cephalic AVF placement (21 on the wrist, 20 on the forearm, 8 on the proximal forearm). There were no perioperative complications and fatalities. At 1, 3, and 6 months, primary patency rates were 96 ± 4%, 96 ± 4%, 91 ± 6% (VasQ group) versus 87 ± 7%, 87 ± 7%, 80 ± 9% (control group, P 0.17), secondary patency rates were 96 ± 4%, 96 ± 4%, 91 ± 6% (VasQ group) versus 95 ± 4%, 90 ± 7%, 90 ± 7% (control group, P 0.79). A significantly larger vein diameter increase postoperatively (P 0.009) and a greater maturation rate (96% vs 74%, p 0.044) were found in the VasQ group compared to the control group.

CONCLUSIONS

The use of the VasQ™ device was associated with higher maturation rates and larger vein diameters postoperatively. The patency rates were slightly higher but not significantly. Further studies are needed to confirm these findings.

Hybrid arteriovenous graft for hemodialysis vascular access in a multicenter registry

OBJECTIVE

The aim of our study was to identify patients' characteristics that predicted a higher chance of arteriovenous graft patency in patients undergoing Gore Hybrid Vascular Graft (GHVG; W. L. Gore & Associates, Flagstaff, Ariz) implantation for hemodialysis access. The GHVG is a polytetrafluroethylene (PTFE) prosthesis with a nitinol-reinforced section (NRS) at the venous end.

METHODS

All consecutive patients undergoing GHVG implantation for hemodialysis access at 10 tertiary referral centers between December 2013 and January 2018 were included in the study and compared with a control group of patients undergoing standard PTFE graft implantation. Selection of patients for hybrid graft implantation was based on the impossibility of autogenous vascular access creation.

RESULTS

There were 145 patients included in the GHVG group and 218 in the PTFE group. In the GHVG and the PTFE groups, the mean age was 67 ± 13 years and 65 ± 13 years, and male patients totaled 52% and 46%, respectively. The technical success was 99%. The mean duration of the intervention was 100 minutes (median, 95 minutes; interquartile range, 80-120 minutes). The brachial-axillary configuration was used in the majority of cases (n = 78 [54%]). The 5-cm NRS length was prevalent (n = 108 [75%]). The median NRS oversize was 14% (interquartile range, 0%-21%). Mean follow-up was 13 months (range, 0-55 months). Seventy-one patients (49%) underwent at least one reintervention. Primary, assisted primary, and secondary patency estimates at 12 months were 44% ± 5%, 47% ± 5%, and 65% ± 4% for the GHVG group and 41% ± 4%, 53% ± 4%, and 75% ± 3% for the control group, respectively (P = NS). One-year survival was 90% ± 3%. On multivariable Cox regression analysis, hypotension (P < .001; hazard ratio [HR], 5.8; confidence interval [CI], 2.6-13) and diabetes (P = .024; HR, 1.9; CI, 1.1-3.2) were significant predictors of GHVG loss. A larger graft size was protective against GHVG loss (P = .042; HR, 0.73; CI, 0.54-0.99). The 10-cm-long graft showed a tendency toward improved patency but did not reach statistical significance (P = .074; HR, 0.48; CI, 0.21-1.07).

CONCLUSIONS

Diabetes and hypotension were predictors of loss of hybrid arteriovenous access. Smaller diameters of NRS were more prone to thrombosis, whereas the 10-cm length seemed to perform better than the 5-cm one.

Biodegrading highly porous elastomeric graft regenerates muscular and innervated carotid artery-Comparative study with vein graft

This study aims to investigate the superiorities of fast degrading elastomeric poly(glycerol sebacate) (PGS)/polycaprolactone (PCL) grafts over autologous vein grafts in the reconstruction of carotid artery, thus providing more suitable vascular grafts for carotid artery replacement. We fabricated small arterial grafts from microporous tubes of PGS reinforced with PCL nanofibers on the outer surface. As control, autologous jugular veins were harvested as vein grafts. Both types of grafts were interpositioned in rat carotid arteries and evaluated at 1 year postoperatively. PGS/PCL grafts remodelled into "neoarteries" (regenerated arteries) with smooth and even vessel wall approximate to native carotid arteries. In contrast, dilated vessel cavity and thickening vessel wall presented in neoarteries remoulded from vein. Histologically, neoarteries from both groups mimic arterial tissue architecture with a confluent endothelium and media and adventita-like layers, whereas PGS/PCL neoarteries presented well-organized muscular component and elastic fibres, which contributed more flexibility and elasticity. Different from vein grafts, PGS/PCL neoarteries acquired reinnervation and displayed apparent vascular function of contraction and relaxation, as was confirmed with responsiveness to various vasoactivators, which suggests that vascular cells within neoarteries express functional phenotypes and potential of autonomic reactivity that carotid arteries owned. To conclude, according to the requirement of strong flexibility, innervation from sympathetic and parasympathetic nerves which can response the carbon dioxide and blood pressure, the muscular remodelling and innervation possessed promising possibility of clinical application.

Outcomes of a Polytetrafluoroethylene Hybrid Vascular Graft with Preloaded Nitinol Stent at the Venous Outflow for Dialysis Vascular Access

BACKGROUND

To evaluate outcomes and patency of arteriovenous grafts (AVGs) created using Gore hybrid vascular grafts in hemodialysis patients with limited venous outflow or challenging anatomy.

MATERIALS AND METHODS

A retrospective review was performed in two academic centers of all patients between July 2013 and December 2016 who underwent surgical AVG creation using a Gore hybrid vascular graft in a brachial artery to axillary configuration. Patient characteristics and comorbidities as well as graft patency, function, and subsequent need for percutaneous interventions were recorded.

RESULTS

Forty-six patients including 30 females (65.2%) and 16 males (34.8%) with a mean age of 63 ± 13 years were identified. The most common indications for a hybrid vascular graft were limited surgical accessibility and/or revision of existing AVG due to severe stenotic lesions at the venous outflow in 33 patients (72%). One-year primary unassisted and assisted patency rates were 44 ± 8% and 54 ± 8%, respectively, compared with 1-year secondary patency rate of 66 ± 8%. The rate of percutaneous interventions to maintain graft function and patency was approximately one intervention per graft per year.

CONCLUSIONS

Access created with the hybrid vascular graft in a brachial-axillary (brachial artery to axillary vein) configuration is an acceptable option for patients with limited venous outflow reserve and challenging anatomy. Twelve-month primary and secondary patency rates and need for percutaneous interventions were comparable to traditional AVGs.

The formulation and characterization of 3D printed grafts as vascular access for potential use in hemodialysis

Arteriovenous graft (AVG) failure continues to be a life-threatening problem in haemodialysis. Graft failure can occur if the implanted graft is not well-matched to the vasculature of the patient. Likewise, stenosis often develops at the vein-graft anastomosis, contributing to thrombosis and early graft failure. To address this clinical need, a novel ink formulation comprised of ACMO/TMPTA/TMETA for 3D printing a AVG was developed (ACMO-AVG), in which the printed AVG was biocompatible and did not induce cytotoxicity. The ease of customizing the ACMO-AVG according to different requirements was demonstrated. Furthermore, the AVG displayed similar mechanical properties to the commercially available arteriovenous ePTFE graft (ePTFE-AVG). Unlike ePTFE-AVG, the ACMO-AVG displayed excellent anti-fouling characteristics because no plasma protein adsorption and platelet adhesion were detected on the luminal surfaces after 2 h of incubation. Similarly, exposure to human endothelial cells and human vascular smooth muscle cells did not result in any cell detection on the surfaces of the ACMO-AVG. Thus, the present study demonstrates a newly developed 3D printing ink formulation that can be successfully 3D printed into a clinically applicable vascular access used for haemodialysis.

An arteriovenous graft that was successfully 3D printed with a novel printing ink formulation that displayed excellent mechanical and anti-fouling properties.

Introduction of arteriovenous grafts with graft insertion anastomosis for hemodialysis access

OBJECTIVE

An arteriovenous bridging graft is a viable option for patients with compromised arteries or veins because of advanced age or diabetes. Arteriovenous graft with graft insertion anastomosis (AVGI) is the novel technique for graft-vein anastomosis where the prosthesis is inserted into the vein, and the anastomosis is performed on the surface of the prosthesis. This study assessed the short-term and long-term results of AVGI to clarify the efficacy of this technique.

METHODS

Between 2010 and 2015, AVGI was performed in graft-vein anastomosis of prosthetic forearm loop access. Characteristics and level of complications were assessed. To evaluate the long-term results, functional graft patency and frequency of percutaneous transluminal angioplasty were examined.

RESULTS

The study comprised 58 patients. There were no deaths related to the surgery. The time of hemostasis after AVGI was recorded at 0 seconds because no bleeding from the suture holes was seen. At 1, 2, and 3 years, primary patency were 45.1% ± 7.5%, 23.1% ± 7.5%, and 23.1% ± 7.5%, respectively, and assisted primary patency rates were 59.4% ± 7.2%, 50.8% ± 7.6%, and 50.8% ± 7.6%, respectively. Secondary patency rates at 4 and 5 years were 100% ± 0% and 94.1% ± 5.7%, respectively. The frequency of percutaneous balloon angioplasty to maintain the patency was 1.61 ± 0.53 times per year. Graft infection occurred in four patients (6.9%).

CONCLUSIONS

AVGI is an advantageous technique for graft vein anastomosis in an arteriovenous bridging graft in both the short-term and long-term.

Description and early outcomes of the hybrid graft for dialysis

Introduction

Long-term dialysis access has become more challenging as patient survival has improved in end-stage renal disease. The GORE® Hybrid Vascular Graft (GHVG) has been designed to improve dialysis access outcomes and provide additional access options for challenging patients. In this article, we will review the design of the graft, unique properties and reported outcomes.

Methods

We reviewed data available at our institution and performed a Pubmed search on GORE® Hybrid Vascular graft. We found two more studies besides the data published by our department.

Results

To date, there have been three papers showing early results of these grafts. All studies report successful placement of the grafts with no unexpected complications. Limb edema has not been a common problem, despite concerns of placing a stent graft into the axillary vein. The papers have shown 70% cumulative patency of the GHVG at 12 months. The comparative studies showed no significant benefit compared to conventional grafts. We see this as an option of continuing with arm access rather than going to more complex access creation such as a chest wall access or going to access creation in the legs.

Conclusions

The GHVG has been shown to have comparable performance to standard arteriovenous graft techniques and can expand access options for some patients with challenging anatomy.