The Effects of Protrusion into the Outflow Vein on Outcomes of Stent Grafts Used to Treat Cephalic Arch Stenoses in Dysfunctional Brachiocephalic Fistulae.

PURPOSE: To assess long-term patency rates of cephalic arch stent grafts in brachiocephalic fistulae and the importance of device position. MATERIALS AND METHODS: This retrospective study reviewed 152 patients with dysfunctional brachiocephalic fistulae and cephalic arch stenosis treated with stent grafts (Viabahn; W. L. Gore) at a single tertiary center between 2012 and 2021. The median age was 67.5 years (range, 25-91 years), and the median follow-up period was 637 days (range, 3-3,368 days). A grading system of protrusion was applied: (a) Grade 0, no protrusion; (b) Grade 1, perpendicular; and (c) Grade 2, in-line protrusion. Subsequent fistulograms were available in 133 (88%) of the 152 patients and were assessed for central vein stenosis within 10 mm of the stent graft. Clinical records were assessed for sequelae of stent graft protrusion. Stent graft primary and cumulative circuit patencies were calculated using the Kaplan-Meier method. RESULTS: Protrusion was documented in 106 (70%) stent grafts-56 Grade 1 and 50 Grade 2. Central vein stenosis was seen in 1 (2%) case of no protrusion (Grade 0) and 38 (40%) cases of protrusion (P < .0001). There was no significant difference in stenosis between Grade 1 and 2 protrusion (P = .15). No adverse clinical sequelae occurred in 147 (97%) patients. Eight patients had a new access subsequently formed in the same arm, and 3 of these 8 patients developed symptoms due to the previous stent graft protrusion (all Grade 2). The primary patency rates of the stent-grafts at 6 and 12 months were 73% and 50%, respectively. The cumulative access circuit patency rates at 1, 2, and 5 years were 84%, 72%, and 54%, respectively. CONCLUSIONS: This study demonstrated that protrusion of a cephalic arch stent graft into the central vein is safe and only clinically relevant when a subsequent ipsilateral access is created.

Order, disorder, and metalation of tetraphenylporphyrin (2H-TPP) on Au(111).

A thermally induced order-disorder transition of tetraphenylporphyrin (2H-TPP) on Au(111) is characterised by scanning probe microscopy and X-ray photoelectron spectroscopy-based techniques. We observed that a transition from an ordered close-packed phase to a disordered diffuse phase is correlated with an on-surface cyclodehydrogenation reaction, and that additional heating of this diffuse phase gives rise to a single distinct nitrogen environment indicative of the formation of a Au-TPP species.

Use of a VBX balloon expandable stent-graft for management of right brachiocephalic vein stenosis.

Here we describe the use of a VBX balloon expandable stent-graft (WL Gore, Flagstaff, AZ, USA) to treat a right brachiocephalic vein stenosis in a haemodialysis patient prior to ipsilateral upper limb arterio-venous (AV) fistula formation. Balloon expandable stent-grafts are unsuitable for treating peripheral fistula stenoses due to their susceptibility of being crushed. The right brachiocephalic vein is both relatively short in comparison to the left and is less susceptible to extrinsic compression and the use of such a device to treat stenosis here allows for very accurate placement and restoration of luminal diameter. The advantages and disadvantages of using these devices in haemodialysis access circuits are also discussed herein, in what we believe to be the first report of the application of a dedicated commercially available balloon expandable stent graft in a haemodialysis patient.

Evolution of adsorption heights in the on-surface synthesis and decoupling of covalent organic networks on Ag(111) by normal-incidence X-ray standing wave.

Structural characterization in on-surface synthesis is primarily carried out by Scanning Probe Microscopy (SPM) which provides high lateral resolution. Yet, important fresh perspectives on surface interactions and molecular conformations are gained from adsorption heights that remain largely inaccessible to SPM, but can be precisely measured with both elemental and chemical sensitivity by Normal-Incidence X-ray Standing Wave (NIXSW) analysis. Here, we study the evolution of adsorption heights in the on-surface synthesis and post-synthetic decoupling of porous covalent triazine-phenylene networks obtained from 2,4,6-tris(4-bromophenyl)-1,3,5-triazine (TBPT) precursors on Ag(111). Room temperature deposition of TBPT and mild annealing to ∼150 °C result in full debromination and formation of organometallic intermediates, where the monomers are linked into reticulated networks by C-Ag-C bonds. Topologically identical covalent networks comprised of triazine vertices that are interconnected by biphenyl units are obtained by a thermally activated chemical transformation of the organometallic intermediates. Exposure to iodine vapor facilitates decoupling by intercalation of an iodine monolayer between the covalent networks and the Ag(111) surface. Accordingly, Scanning Tunneling Microscopy (STM), X-ray Photoelectron Spectroscopy (XPS) and NIXSW experiments are carried out for three successive sample stages: organometallic intermediates, covalent networks directly on Ag(111) and after decoupling. NIXSW analysis facilitates the determination of adsorption heights of chemically distinct carbon species, i.e. in the phenyl and triazine rings, and also for the organometallic carbon atoms. Thereby, molecular conformations are assessed for each sample stage. The interpretation of experimental results is informed by Density Functional Theory (DFT) calculations, providing a consistent picture of adsorption heights and molecular deformations in the networks that result from the interplay between steric hindrance and surface interactions. Quantitative adsorption heights, i.e. vertical distances between adsorbates and surface, provide detailed insight into surface interactions, but are underexplored in on-surface synthesis. In particular, the direct comparison with an in situ prepared decoupled state unveils the surface influence on the network structure, and shows that iodine intercalation is a powerful decoupling strategy.

Erratum: Preoperative assessment for percutaneous and open surgical arteriovenous fistula creation in patients for haemodialysis.

[This corrects the article DOI: 10.1093/ckj/sfz121.][This corrects the article DOI: 10.1093/ckj/sfz121.].

Preoperative assessment for percutaneous and open surgical arteriovenous fistula creation in patients for haemodialysis.

Preoperative assessment prior to surgical arteriovenous fistulas (AVFs) including ultrasound-guided mapping has been shown to have beneficial effects on their immediate success as well as early outcomes. This has led to their wide acceptance and adoption however clinical practice criteria is variable and is reflected in variabilities in practice. When transposing this to percutaneously created endovascular AVFs (endoAVFs), variable preoperative assessment criteria could equally result in variable practice and potentially subsequent and expectant outcomes. We aimed to review literature on reported validated methodologies and workflows of preoperative assessment for surgical AVF creation as reported in highest levels of available evidence, specifically randomized controlled trials. Published practice recommendations and guidelines on best clinical practice as well as systematic reviews and meta-analyses of published studies were also reviewed. Data on practice methodology from identified trial publications and protocols was collated and a summative narrative synthesis was carried out which compared these methodologies to additional assessments that may be required when targeting assessment for percutaneous endoAVF formation, based on our units experience as part of an international multicentre trial. In this review we present a brief overview of published literature and guidelines and propose a unified and uniform workflow for preoperative assessment for surgical AVFs and endoAVFs to aide clinical and imaging practice.

Chemical shielding of H2O and HF encapsulated inside a C60 cage.

Molecular surgery provides the opportunity to study relatively large molecules encapsulated within a fullerene cage. Here we determine the location of an H2O molecule isolated within an adsorbed buckminsterfullerene cage, and compare this to the intrafullerene position of HF. Using normal incidence X-ray standing wave (NIXSW) analysis, coupled with density functional theory and molecular dynamics simulations, we show that both H2O and HF are located at an off-centre position within the fullerene cage, caused by substantial intra-cage electrostatic fields generated by surface adsorption of the fullerene. The atomistic and electronic structure simulations also reveal significant internal rotational motion consistent with the NIXSW data. Despite this substantial intra-cage interaction, we find that neither HF or H2O contribute to the endofullerene frontier orbitals, confirming the chemical isolation of the encapsulated molecules. We also show that our experimental NIXSW measurements and theoretical data are best described by a mixed adsorption site model.

Structural characterisation of molecular conformation and the incorporation of adatoms in an on-surface Ullmann-type reaction.

The on-surface synthesis of covalently bonded materials differs from solution-phase synthesis in several respects. The transition from a three-dimensional reaction volume to quasi-two-dimensional confinement, as is the case for on-surface synthesis, has the potential to facilitate alternative reaction pathways to those available in solution. Ullmann-type reactions, where the surface plays a role in the coupling of aryl-halide functionalised species, has been shown to facilitate extended one- and two-dimensional structures. Here we employ a combination of scanning tunnelling microscopy (STM), X-ray photoelectron spectroscopy (XPS) and X-ray standing wave (XSW) analysis to perform a chemical and structural characterisation of the Ullmann-type coupling of two iodine functionalised species on a Ag(111) surface held under ultra-high vacuum (UHV) conditions. Our results allow characterisation of molecular conformations and adsorption geometries within an on-surface reaction and provide insight into the incorporation of metal adatoms within the intermediate structures of the reaction.

Management of acute and chronic iliofemoral venous outflow obstruction: a multidisciplinary team consensus.

The aim of this manuscript was to establish a consensus for the management of acute and chronic venous obstruction among specialists in the UK. Specialist physicians representing vascular surgery, interventional radiology and hematology were invited to 3 meetings to discuss management of acute and chronic iliofemoral obstruction. The meetings outlined controversial areas, included a topic-by-topic review; and on completion reached a consensus when greater than 80% agreement was reached on each topic. Physicians from 19 UK hospitals agreed on treatment protocols and highlighted areas that need development. Potential standard treatment algorithms were created. It was decided to establish a national registry of venous patients led by representatives from the treating multidisciplinary teams. Technical improvements have facilitated invasive treatment of patients with acute and chronic venous obstruction; however, the evidence guiding treatment is weak. Treatment should be conducted in centers with multi-disciplinary input; robust, coordinated data collection; and regular outcome analysis to ensure safe and effective treatment and a basis for future evolvement.

Early experience and observations in endovascular dialysis fistula re-intervention.

In recent years, new emerging technology has allowed the endovascular creation of dialysis fistulas in the proximal forearm without the need for open surgery. Two such systems currently exist, and evidence to date has demonstrated high rates of technical success in fistula creation, high rates of dialysis functionality, and low rates of re-intervention using both systems. Whilst early trial data has demonstrated lower rates of re-intervention to maintain patency compared to surgical fistulas, endovascular re-interventions are still required to maintain functionality. The endovascular fistula (endoAVF) typically exhibits a shared drainage pattern and is morphologically distinct from the surgical fistula and patterns of failure observed often differ to what has been traditionally encountered. A fresh approach and understanding is therefore required and here we share our observations and experience of endovascular re-intervention in endoAVF created with the Wavelinq system.

A Review of the Current Status of Percutaneous Endovascular Arteriovenous Fistula Creation for Haemodialysis Access.

Surgical fistulas were first described over 50 years ago and have revolutionized the outlook for millions of dialysis-dependent patients. Despite many developments, results remain sub-optimal with high rates of primary failure and re-intervention to maintain patency. Surgical fistulas are known to fail in part due to intimal hyperplasia leading to stenosis, and vessel manipulation during anastomosis creation can be contributory. New technology is emerging that allows the endovascular creation of fistulas with minimal vessel trauma and the initial results demonstrate encouraging outcomes with high technical success rates, low re-intervention, and failure rates and good usability for hemodialysis. Two such device systems are currently available, and here, we provide an overview of the current global status of endoAVF, patient selection criteria, trial results, technical aspects, re-interventions, and outlook for the future.

Interactions and stabilisation of acetone, sulfur dioxide and water with 1-octyl-3-methylimidazolium tetrafluoroborate [OMIM][BF4] at low temperatures.

The interactions between three small molecules, water (H2O), sulfur dioxide (SO2) and acetone ((CH3)2CO), with the ionic liquid (IL) 1-octyl-3-methylimidazolium tetrafluoroborate, [OMIM][BF4], have been determined using line of sight temperature programmed desorption (LOSTPD) from a gold surface. Multilayers of the IL were deposited by physical vapour deposition with multilayers of the small molecular species (adsorbed from the gas phase) at 90 K. LOSTPD was then carried out with the small molecular species desorbing first from the mixed multilayer, followed at higher temperatures by desorption of the IL from the gold surface. The IL had a high activation energy for desorption of 126(6) kJ mol-1. Pure acetone showed a desorption activation energy of 38(2) kJ mol-1, which increased to 45-61 kJ mol-1 when it was pre-adsorbed below an overlying porous layer of the ionic liquid at 90 K. The stabilised acetone is thought to be associated with pores containing ionic moieties. Destabilised acetone was also observed and thought to originate from pores containing octyl chains. The quantity of stabilised acetone scaled with the amount of IL, being ≈1.1 molecules per IL ion pair. SO2 and H2O were co-adsorbed with the IL at 90 K leading to an intimate mixture of the two. For pure SO2 the desorption energy was 32(2) kJ mol-1, which increased to 40-52 kJ mol-1 for relative concentrations up to 6 SO2 molecules per IL ion pair. For pure water the activation energies were 49(5) kJ mol-1 and 43(1) kJ mol-1 for amorphous and crystalline ice respectively. When co-adsorbed with the IL the stabilisation energies were 42-49 kJ mol-1, but up to 505 water molecules per IL ion pair could be stabilised to some degree. The desorption mechanisms and the reasons for these interactions are discussed.

Electroanalysis of Neutral Precursors in Protic Ionic Liquids and Synthesis of High-Ionicity Ionic Liquids.

Protic ionic liquids (PILs) are ionic liquids that are formed by transferring protons from Brønsted acids to Brønsted bases. While they nominally consist entirely of ions, PILs can often behave as though they contain a significant amount of neutral species (either molecules or ion clusters), and there is currently a lot of interest in determining the degree of "ionicity" of PILs. In this contribution, we describe a simple electroanalytical method for detecting and quantifying residual excess acids in a series of ammonium-based PILs (diethylmethylammonium triflate [dema][TfO], dimethylethylammonium triflate [dmea][TfO], triethylammonium trifluoroacetate [tea][TfAc], and dimethylbutylammonium triflate [dmba][TfO]). Ultra-microelectrode voltammetry reveals that some of the accepted methods for synthesizing PILs can readily result in the formation of nonstoichiometric PILs containing up to 230 mM excess acid. In addition, vacuum purification of PILs is of limited use in cases where nonstoichiometric PILs are formed. Although excess bases can be readily removed from PILs under ambient conditions, excess acids cannot be removed, even under high vacuum. The effects of excess acid on the electrocatalytic oxygen reduction reaction (ORR) in PILs have been studied, and the onset potential of the ORR in [dema][TfO] increases by 0.8 V upon addition of acid to PIL. On the basis of the results of our analyses, we provide some recommendations for the synthesis of highly ionic PILs.

Results of Stent Graft Placement to Treat Cephalic Arch Stenosis in Hemodialysis Patients with Dysfunctional Brachiocephalic Arteriovenous Fistulas.

PURPOSE: To determine effectiveness of the VIABAHN (W.L. Gore & Associates, Flagstaff, Arizona) stent graft to treat cephalic arch stenosis in patients with dysfunctional brachiocephalic arteriovenous fistulas after inadequate venoplasty response. MATERIALS AND METHODS: Between 2012 and 2015, patients with failed venoplasty of symptomatic cephalic arch stenosis received a VIABAHN stent graft. Follow-up venography was performed at approximately 3, 6, and 12 months. Data were retrospectively analyzed with patency estimated using Kaplan-Meier and log-rank methodology. There were 39 patients included. RESULTS: Technical and clinical success was 100%. Primary target lesion patency was 85% (95% confidence interval [CI], 69%-93%), 67% (95% CI, 50%-80%), and 42% (95% CI, 25%-57%) at 3, 6, and 12 months. There was no significant difference in patency with regard to sex or age (P = .8 and P = .6, respectively). Primary assisted patency was 95% (95% CI, 82%-99%) at 3, 6, and 12 months. Access circuit primary patency was 85% (95% CI, 69%-93%), 67% (95% CI, 50%-80%), and 42% (95% CI, 25%-57%) at 3, 6, and 12 months. There was no significant difference in patency between patients with the stent graft as the first treatment episode in the cephalic arch and those that had previous intervention at this site (P = .98). There were 48 repeat venoplasty procedures performed in the cephalic arch to maintain patency, including 7 repeat VIABAHN insertions. No complications were encountered. CONCLUSIONS: The VIABAHN stent graft is a safe, effective, and durable device for treating cephalic arch stenosis when venoplasty fails.

Imaging in Vascular Access.

This review examines four imaging modalities; ultrasound (US), digital subtraction angiography (DSA), magnetic resonance imaging (MRI) and computed tomography (CT), that have common or potential applications in vascular access (VA). The four modalities are reviewed under their primary uses, techniques, advantages and disadvantages, and future directions that are specific to VA. Currently, US is the most commonly used modality in VA because it is cheaper (relative to other modalities), accessible, non-ionising, and does not require the use of contrast agents. DSA is predominantly only performed when an intervention is indicated. MRI is limited by its cost and the time required for image acquisition that mainly confines it to the realm of research where high resolution is required. CT's short acquisition times and high resolution make it useful as a problem-solving tool in complex cases, although accessibility can be an issue. All four imaging modalities have advantages and disadvantages that limit their use in this particular patient cohort. Current imaging in VA comprises an integrated approach with each modality providing particular uses dependent on their capabilities. MRI and CT, which currently have limited use, may have increasingly important future roles in complex cases where detailed analysis is required.

Systematic review of drug eluting balloon angioplasty for arteriovenous haemodialysis access stenosis.

BACKGROUND: Native or prosthetic arteriovenous (AV) fistulas are preferred for permanent haemodialysis (HD) access. These are marked with circuit steno-occlusive disease leading to dysfunction or even failure. Late failure rates have been reported as high as 50%. Standard angioplasty balloons are an established percutaneous intervention for HD access stenosis. Reported restenosis rates remain high and practice guidelines recommend a wide 6-month primary patency (PP) of at least 50% for any intervention. Neointimal hyperplasia is one of the main causes for access circuit stenosis. Drug eluting balloon (DeB) angioplasty has been proposed as an alternative intervention to reduce restenosis by local drug delivery and possible inhibition of this process. PURPOSE: To systematically assess the reported efficacy and safety of DeB angioplasty in percutaneous management of prosthetic and autologous HD access stenosis. METHODS: Protocol for the review was developed following the PRISMA-P 2015 statement. An electronic database (Medline, EMBASE, Clinical Trials.gov and Cochrane CENTRAL) search was conducted to identify articles reporting on the use of DeB intervention in HD AV access. Backward and forward citation search as well as grey literature search was performed. The MOOSE statement and PRISMA 2009 statement were followed for the reporting of results. Data from the included studies comparing DeBs with non-DeBs were pooled using a random effects meta-analysis model and reported separately on randomised and non-randomised studies. RESULTS: Six studies reported on 254 interventions in 162 participants (mean 27 ± 10 SD). The pooled mean and median duration of follow-up was 12 and 13 months (range 6-24 months). These comprised two randomised control trials (RCTs) and four cohort studies. Participant's mean age was 64 ± 5 years and 61% were male. Target lesions (TLs) ranged from under 2 mm to 5.9 mm and 51 were reported as de novo stenosis. Device failure described as wasting of the DeB was reported in two studies (55% and 92.8%). At 6 months TL PP was reported between 70% to 97% for DeBs in the RCTs and cohort studies, and 0% to 26% for non-DeBs. TLs treated with DeBs were associated with a higher primary patency at 6 months as compared to non-DeB balloons (RCTs: odds ratio [OR] 0.25, 95% CI 0.08 to 0.77 and I2 = 19%, cohort studies: OR 0.10, 95% CI 0.03 to 0.31 and an I2 = 20%). No procedure-related major or minor complications were reported. CONCLUSIONS: Current literature reports DeBs as being safe and may convey some benefit in terms of improved rate of restenosis when used to treat AV access disease. However, this body of evidence is small and clinically heterogeneous. A large multicentre RCT may help to clarify the role of DeBs in the percutaneous treatment of AV HD access stenosis.

Cost analysis of the Hemodialysis Reliable Outflow (HeRO) Graft compared to the tunneled dialysis catheter.

BACKGROUND: In end-stage renal disease patients with central venous obstruction, who have limited vascular access options, the Hemodialysis Reliable Outflow (HeRO) Graft is a new alternative with a lower incidence of complications and longer effective device life compared to tunneled dialysis catheters (TDCs). We undertook an economic analysis of introducing the HeRO Graft in the UK. METHODS: A 1-year cost-consequence decision analytic model was developed comparing management with the HeRO Graft to TDCs from the perspective of the National Health Service in England. The model comprises four 3-month cycles during which the vascular access option either remains functional for hemodialysis or fails, patients can experience access-related infection and device thrombosis, and they can also accrue associated costs. Clinical input data were sourced from published studies and unit cost data from National Health Service 2014-15 Reference Costs. RESULTS: In the base case, a 100-patient cohort managed with the HeRO Graft experienced 6 fewer failed devices, 53 fewer access-related infections, and 67 fewer device thromboses compared to patients managed with TDCs. Although the initial device and placement costs for the HeRO Graft are greater than those for TDCs, savings from the lower incidence of device complications and longer effective device patency reduces these costs. Overall net annual costs are £2600 for each HeRO Graft-managed patient compared to TDC-managed patients. If the National Health Service were to reimburse hemodialysis at a uniform rate regardless of the type of vascular access, net 1-year savings of £1200 per patient are estimated for individuals managed with the HeRO Graft. CONCLUSIONS: The base case results showed a marginal net positive cost associated with vascular access with the HeRO Graft compared with TDCs for the incremental clinical benefit of reductions in patency failures, device-related thrombosis, and access-related infection events in a patient population with limited options for dialysis vascular access.