Quality assurance in surgical trials of arteriovenous grafts for haemodialysis: A systematic review, a narrative exploration and expert recommendations.

BACKGROUND: Introducing new procedures and challenging established paradigms requires well-designed randomised controlled trials (RCT). However, RCT in surgery present unique challenges with much of treatment tailored to the individual patient circumstances, refined by experience and limited by organisational factors. There has been considerable debate over the outcomes of arteriovenous grafts (AVG) compared to AVF, but any differences may reflect differing practice and potential variability. It is essential, therefore, when considering an RCT of a novel surgical procedure or device that quality assurance (QA) is defined for both the new approach and the comparator. The aim of this systematic review was to evaluate the QA standards performed in RCT of AVG using a multi-national, multi-disciplinary approach and propose an approach for future RCT. METHOD: The methods of this have been previously registered (PROSPERO: CRD420234284280) and published. In summary, a four-stage review was performed: identification of RCT of AVG, initial review, multidisciplinary appraisal of QA methods and reconciliation. QA measures were sought in four areas - generic, credentialing, standardisation and monitoring, with data abstracted by a multi-national, multi-speciality review body. RESULTS: QA in RCT involving AVG in all four domains is highly variable, often sub-optimally described and has not improved over the past three decades. Few RCT established or defined a pre-RCT level of experience, none documented a pre-trial education programme, or had minimal standards of peri-operative management, no study had a defined pre-trial monitoring programme, and none assessed technical performance. CONCLUSION: QA in RCT is a relatively new area that is expanding to ensure evidence is reliable and reproducible. This review demonstrates that QA has not previously been detailed, but can be measured in surgical RCT of vascular access, and that a four-domain approach can easily be implemented into future RCT.

What are the observed procedural costs of vascular access surgery? Protocol for a systematic review.

INTRODUCTION: A central component in the introduction of a novel surgical procedure or technique is an evaluation of its cost efficiency when compared with a benchmark standard of care. Accurate assessment of costs is thus essential in ensuring appropriate allocation of resources within a healthcare system. The treatment of kidney failure requires a significant volume of resources, and vascular access provision is the main modifiable cost. The costs of providing this service are obscured by generic NHS reference costs, which lack adequate granularity to allow meaningful comparisons between treatments. The aim of this systematic review will be to assess the reporting of procedural costs in all published economic analyses of vascular access surgery and perform a comparison of the reported procedural costs involved in arteriovenous fistula (AVF) and arteriovenous graft (AVG) creation. This will provide an estimate as to the accuracy of the NHS reference costs in this field. METHODS AND ANALYSIS: The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines will be followed. A systematic search will be performed of the MEDLINE, Embase and Cochrane databases to identify full-text economic analyses of vascular access for haemodialysis in which the procedural cost of AVF or AVG creation is reported. Publications in English from 1 January 2000 to 30 August 2023, will be eligible for inclusion. Studies will be selected by title and abstract review, followed by a full-text review using inclusion and exclusion criteria. Studies not reporting the procedural costs of surgery will be excluded. Data collected will pertain to procedural costs of AVF and AVG creation. Costs will be adjusted to a common currency using a gross domestic product (GDP) deflator index and conversion rates based on purchasing power parities for GDP. Comparison with NHS reference costs will indicate their reliability for use in future economic analyses in this field. ETHICS AND DISSEMINATION: Ethical approval is not required for this systematic review. Findings will be disseminated through peer-reviewed publications and conference presentations. PROSPERO REGISTRATION NUMBER: CRD42023458779.

Cephalic arch stenosis: an analysis of outcome by type of first intervention.

BACKGROUND: Cephalic arch stenoses (CAS) occur in near 70% of elbow arteriovenous fistulas. Percutaneous transluminal angioplasty (PTA) remains first-line treatment despite documented stent-grafts (SG) efficacy. The study aim is to report long-term outcomes based on initial treatment of CAS. METHODS: Retrospective review of 12-year data in single tertiary centre. Outcomes included technical success, rupture rate, primary patency (PP), dialysis performance; categorical variables assessed via χ2 or Fisher's; nonparametric tests used for skewed data. Kaplan-Meier analysis used for PP and cumulative patency. Cox proportional hazard regression model to assess explanatory variables in PP. RESULTS: One hundred one brachio- and radiocephalic fistulas with CAS were included. SG as first intervention had higher success than PTA (85% vs 61%, p = 0.003). Rupture occurred in 9/85 (10.6%) PTA vs 0% in SG (p = 0.046). In a subgroup with poor urea reduction rate (URR), both PTA and SG improved dialysis performance post-intervention (p = 0.002). SG demonstrated better PP than PTA (79,73,60% patency at 3, 6, 9 months; versus 71,51,47%; p = 0.195) and cumulative patency (73,61,61% at 1, 2, 3 years; versus 60,34,26%; p < 0.001). Of the variables analyzed, technical success of PTA was the only discriminating factor (coeff.-1.01; RR 35%, p = 0.035). Accesses that underwent secondary stenting performed better than primarily stented CAS (p = 0.01). CONCLUSIONS: SG superiority is confirmed in CAS, particularly when angioplasty is unsuccessful. While PTA has short-lived benefits, it can improve dialysis performance. Other than higher success rate, primary CAS stenting did not have advantages compared to post-PTA stenting in our study. Other factors related to inflow, outflow, conduit characteristics are presumed to be involved in access longevity.

Early-cannulation arteriovenous grafts: Multidisciplinary learning is essential to optimize outcomes.

BACKGROUND: It is likely that there will be an increasing role for early-cannulation arteriovenous grafts (ecAVG) with a wider recognition of the need to tailor vascular access to avoid futile procedures and unnecessary TCVC. However, experience of these products is not common and limited to early surgical adopters, with little information on the systemic changes and multi-disciplinary care needed to optimize outcomes. The aim of this study was to report the impact of a multi-disciplinary approach on quantifiable outcomes. METHODS: A retrospective analysis of a prospectively maintained database of 295 ecAVG implanted over an 8-year time-period was performed. Indicative outcomes were chosen to reflect nephrology (patient selection), nursing care (cannulation complications of infection and pseudoaneurysm) and radiology (thrombosis) on cumulative impact (functional patency) over three distinct time periods. RESULTS: The incidence of ecAVG increased 10-fold over the three time periods. The use of ecAVG changed significantly from salvage tertiary access to TCVC avoidance and salvage of existing AVF. Nursing complications reduced markedly with significantly fewer over-cannulation episodes and pseudo-aneurysms. With an improved pro-active surveillance programme, the time to first thrombosis doubled and the risk of thrombosis halved. Ultimately this resulted in significantly improved functional patency with a risk of ecAVG loss less than one-third by the last time-period. CONCLUSIONS: All aspects of ecAVG use require scrutiny and critical appraisal. Failure or success is not simply achieved by performing good technical surgery with an efficacious product, but by the care taken across a wide range of elements spanning case selection, implantation, use and maintenance.

Quality assurance in surgical trials of arteriovenous grafts for haemodialysis: protocol for a systematic review.

INTRODUCTION: Decisions regarding the optimal vascular access for haemodialysis patients are becoming increasingly complex, and the provision of vascular access is open to variations in systems of care as well as surgical experience and practice. Two main surgical options are recognised: arteriovenous fistula and arteriovenous graft (AVG). All recommendations regarding AVG are based on a limited number of randomised controlled trials (RCTs). It is essential that when considering an RCT of a surgical procedure, an appropriate definition of quality assurance (QA) is made for both the new approach and the comparator, otherwise replication of results or implementation into clinical practice may differ from published results. The aim of this systematic review will be to assess the methodological quality of RCT involving AVG, and the QA measures implemented in delivering interventions in these trials. METHODS AND ANALYSIS: The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines will be followed. A systematic search will be performed of the MEDLINE, Embase and Cochrane databases to identify relevant literature. Studies will be selected by title and abstract review, followed by a full-text review using inclusion and exclusion criteria. Data collected will pertain to generic measures of QA, credentialing of investigators, procedural standardisation and performance monitoring. Trial methodology will be compared against a standardised template developed by a multinational, multispecialty review body with experience in vascular access. A narrative approach will be taken to synthesise and report data. ETHICS AND DISSEMINATION: Ethical approval is not required as it is a protocol for a systematic review. Findings will be disseminated through peer-reviewed publications and conference presentations, with the ultimate aim of providing recommendations for future RCT of AVG design.

Recruitment into randomised trials of arteriovenous grafts: A systematic review.

Although randomised controlled trials (RCT) are considered the optimal form of evidence, there are relatively few in surgery. Surgical RCT are particularly likely to be discontinued with poor recruitment cited as a leading reason. Surgical RCT present challenges over and above those seen in drug trials as the treatment under study may vary between procedures, between surgeons in one unit, and between units in multi-centred RCT. The most contentious and debated area of vascular access remains the role of arteriovenous grafts, and thus the quality of the data that is used to support opinions, guidelines and recommendations is critical. The aim of this review was to determine the extent of variation in the planning and recruitment in all RCT involving AVG. The findings of this are stark: there have been only 31 RCT performed in 31 years, the vast majority of which exhibited major limitations severe enough to undermine the results. This underlines the need for better quality RCT and data, and further inform the design of future studies. Perhaps most fundamental is the planning for a RCT that accounts for the intended population, the uptake of a RCT and the attrition for the significant co-morbidity in this population.

The impact of renal artery stenting on therapeutic aims.

Renal artery stenosis manifests as poorly-controlled hypertension, impaired renal function or pulmonary oedema, therefore the success of treatment is dependent on indication. This study aims to determine the outcomes of patients undergoing renal artery stenting (RASt) based on therapeutic aim compared to criteria used in the largest randomised trial. Retrospective case-note review of patients undergoing RASt between 2008-2021 (n = 74). The cohort was stratified by indication for intervention (renal dysfunction, hypertension, pulmonary oedema) and criteria employed in the CORAL trial, with outcomes and adverse consequences reported. Intervention for hypertension achieved significant reduction in systolic blood pressure and antihypertensive agents at 1 year (median 43 mmHg, 1 drug), without detrimental impact on renal function. Intervention for renal dysfunction reduced serum creatinine by a median 124 µmol/L, sustained after 6 months. Intervention for pulmonary oedema was universally successful with significant reduction in SBP and serum creatinine sustained at 1 year. Patients who would have been excluded from the CORAL trial achieved greater reduction in serum creatinine than patients meeting the inclusion criteria, with equivalent blood pressure reduction. There were 2 procedure-related mortalities and 5 procedural complications requiring further intervention. 5 patients had reduction in renal function following intervention and 7 failed to achieve the intended therapeutic benefit. Renal artery stenting is effective in treating the indication for which it has been performed. Previous trials may have underestimated the clinical benefits by analysis of a heterogenous population undergoing a procedure rather than considering the indication, and excluding patients who would maximally benefit.

Pre-emptive or reactive treatment, angioplasty or stent-graft? The outcome for interventions for venous stenosis in early-cannulation arteriovenous grafts.

BACKGROUND: Early-cannulation arteriovenous grafts (ecAVG) have good initial patency, but frequent episodes of reintervention for venous stenosis (VS) and thrombosis limit their use. Stent grafts (SG) have shown promise in reducing re-interventions and improving functional patency for dysfunctional ecAVG and recurrent VS. There is little data on the impact of stent grafts as the first elective procedure for VS. The aim of this study was to determine firstly, if treating VS whilst asymptomatic has a better outcome than treating after presentation with thrombosis; and secondly, to determine the best initial treatment for asymptomatic VS: SG or angioplasty. METHODS: A retrospective study was performed of 259 ecAVG with a sutured anastomosis. The case-mix and outcomes of 153 who presented with VS was analysed by presentation (elective at surveillance or emergency following thrombosis), and then for only elective patients, by treatment (SG vs angioplasty). RESULTS: There was no significant difference in case-mix and time to presentation by mode of presentation (100 elective and 53 with thrombosis) other than a higher rate of pro-thrombotic disorders in thrombosed ecAVG. Thrombosed ecAVG had poorer outcomes with increased re-intervention rates and thrombosis in the following year, and reduced long-term functional patency. In patients presenting electively, primary SG rather than angioplasty led to significantly reduced thrombosis rates, a longer time to re-intervention in the following year, and superior long-term functional patency. The use of SG was the same in both groups. Both the mode of presentation and the type of intervention performed were independently predictive of a poorer subsequent functional patency. CONCLUSIONS: Primary elective stent-grafting may be the optimal strategy to reducing maintenance costs with ecAVG.

The impact of stent-graft sizing on venous stenosis re-intervention and arteriovenous graft patency: Free-floating stent outflow is associated with improved outcomes.

BACKGROUND: Early cannulation arteriovenous grafts (ecAVG) for dialysis access are limited by reintervention for venous stenosis (VS) despite their good initial patency. Whilst stent-grafts (SG) have shown promise, the optimal sizing is unclear. Therefore, this study aims to determine if outflow vein diameter, SG diameter or these relative to each other (V:Sr) alters outcomes, and if so, which is more important. METHODS: Retrospective analysis was performed of Gore® Acuseal® ecAVGs with VS treated with Gore® Viabahn® SG over a 7-year period. Primary patency (PP), time to thrombosis and functional patency were analysed by SG length/diameter, vein diameter and V:Sr. RESULTS: We identified 114 ecAVGs with median follow-up 492 days (IQR 189-770). SG length and diameter did not correlate with PP, however, there was a significant relationship between vein diameter and PP (RR = 0.901 (0.832-0.975), p = 0.01) and between V:Sr and PP (RR = 0.462 (0.255-0.838), x2 = 5.866, p = 0.0015). The optimal V:Sr was ⩾1.4 (i.e. vein diameter at least 40% greater than the stent-graft; or 'free-floating' stent outflow) (RR = 2.759 (1.670-4.558), p < 0.001), translating to a difference in median PP of 252 versus 496 days (IQR: 188-316; 322-670). On multivariate analysis, absolute vein diameter lost significance, whilst V:Sr remained an independently significant predictor of PP (RR = 3.247 (1.560-6.759), p = 0.02). CONCLUSIONS: Placement of the SG outflow into a relatively larger segment of vein was associated with a significant increase in PP independent of the absolute vein diameter. This suggests that larger calibre SG which are apposed to the vein wall are not required for optimal primary patency, and indeed should be actively avoided. Instead, a 'free-floating' stent outflow which is undersized relative to the recipient vein (whilst maintaining a minimum anchoring calibre) is recommended where possible. This should be considered during intervention and may require selection of longer devices, where practical, to bring the stent outflow into a larger vein segment. LEVEL OF EVIDENCE: Level 3a, Non-randomised controlled cohort/follow-up study.

Interrogating the haemodynamic effects of haemodialysis arteriovenous fistula on cardiac structure and function.

Arteriovenous fistula (AVF) is the preferred type of vascular access for maintenance haemodialysis but it may contribute to maladaptive cardiovascular remodelling. We studied the effect of AVF creation on cardiac structure and function in patients with chronic kidney disease (CKD). In this prospective cohort study patients with CKD listed for first AVF creation underwent cardiac magnetic resonance (CMR) imaging at baseline and at 6 weeks. All participants had ultrasound measurements of fistula blood flow at 6 weeks. The primary outcome was the change in left ventricular (LV) mass. Secondary outcomes included changes in LV volumes, LV ejection fraction, cardiac output, LV global longitudinal strain and N-terminal-pro B-type natriuretic peptide (NT-proBNP). A total of 55 participants were enrolled, of whom 40 (mean age 59 years) had AVF creation and completed both scans. On the second CMR scan, a mean increase of 7.4 g (95% CI 1.1-13.7, p = 0.02) was observed in LV mass. Significant increases in LV end-diastolic volumes (p = 0.04) and cardiac output (p = 0.02) were also seen after AVF creation. No significant changes were observed in LV end-systolic volumes, LV ejection fraction, NT-proBNP and LV global longitudinal strain. In participants with fistula blood flows ≥ 600 mL/min (n = 22) the mean increase in LV mass was 15.5 g (95% CI 7.3-23.8) compared with a small decrease of 2.5 g (95% CI - 10.6 to 5.6) in participants with blood flows < 600 mL/min (n = 18). Creation of AVF for haemodialysis resulted in a significant increase of LV myocardial mass within weeks after surgery, which was proportional to the fistula flow.

Patient characteristics predict patency of early-cannulation arteriovenous grafts.

There is a new emphasis on tailoring appropriate vascular access for hemodialysis to patients and their life-plans, but there is little known about the optimal use of newer devices such as early-cannulation arteriovenous grafts (ecAVG), with studies utilising them in a wide variety of situations. The aim of this study was to determine if the outcome of ecAVG can be predicted by patient characteristics known pre-operatively. This retrospective analysis of 278 consecutive ecAVG with minimum one-year follow-up correlated functional patency with demographic data, renal history, renal replacement and vascular access history. On univariate analysis, aetiology of renal disease, indication for an ecAVG, the number of previous tunnelled central venous catheters (TCVC) prior to insertion of an ecAVG, peripheral vascular disease, and BMI were significant associates with functional patency. On multivariate analysis the number of previous TCVC, the presence of peripheral vascular disease and indication were independently associated with outcome after allowing for age, sex and BMI. When selecting for vascular access, understanding the clinical circumstances such as indication and previous vascular access can identify patients with differing outcomes. Importantly, strategies that result in TCVC exposure have an independent and cumulative association with decreasing long-term patency for subsequent ecAVG. As such, TCVC exposure is best avoided or minimised particularly when ecAVG can be considered.

Ferumoxytol MR Angiography versus Duplex US for Vascular Mapping before Arteriovenous Fistula Surgery for Hemodialysis.

Background Duplex US is performed routinely for vascular mapping prior to arteriovenous fistula (AVF) creation for hemodialysis but cannot demonstrate the central vasculature. Ferumoxytol, an iron oxide nanoparticle, provides an alternative to gadolinium contrast material for MR angiography for safe use in chronic kidney disease (CKD). Purpose To assess the clinical utility of ferumoxytol-enhanced MR angiography compared with duplex US for vascular mapping before upper limb AVF creation in participants with CKD. Materials and Methods In a prospective comparative study (ClinicalTrials.gov: NCT02997046) from December 2016 to August 2018, participants with CKD underwent ferumoxytol-enhanced MR angiography and duplex US. Two independent readers evaluated vessels for diameter, stenosis or occlusion, arterial disease, and central stenosis. Intraclass correlation coefficients (ICCs) and Bland-Altman plots were used to assess intra- and interreader variability. On the basis of accepted standards for AVF creation, an algorithm was developed to predict AVF outcome based on imaging findings. Multivariable regression models used AVF success as the dependent variable and age, sex, and duplex US or ferumoxytol-enhanced MR angiography findings as independent variables. Results Fifty-nine participants with CKD (mean age, 59 years ± 13 [standard deviation]; 30 women) were evaluated. A total of 51 fistulas were created, of which 24 (47%) were successful. Ferumoxytol-enhanced MR angiography showed excellent inter- and intrareader repeatability (ICC, 0.84-0.99) for all variables assessed. In addition to revealing 15 central vasculature stenoses, ferumoxytol-enhanced MR angiography resulted in characterization of 88 of 236 (37%) of the arterial sections examined as unsuitable for AVF creation compared with 61 of 236 (26%) sections with duplex US (P = .01). Ferumoxytol-enhanced MR angiography independently predicted AVF success in models including (odds ratio, 6.5; 95% confidence interval: 1.7, 25; P = .006) and those excluding (odds ratio, 4.6; 95% confidence interval: 1.3, 17; P = .02) the central vasculature. Conclusion In addition to enabling identification of central vessel pathologic features, ferumoxytol-enhanced MR angiography revealed peripheral arterial disease not recognized with duplex US and was more predictive than duplex US of the outcome of arteriovenous fistula surgery. © RSNA, 2020 Online supplemental material is available for this article. See also the editorial by Finn in this issue.

Randomised clinical trial: standard of care versus early-transjugular intrahepatic porto-systemic shunt (TIPSS) in patients with cirrhosis and oesophageal variceal bleeding.

BACKGROUND: Early-transjugular intrahepatic porto-systemic shunt (TIPSS) has been recommended in international guidelines for high-risk patients with oesophageal variceal bleeding. AIM: To validate the results of a previous randomised control trial which supports use of early-TIPSS. METHODS: In a two-centre open-label parallel-group randomised control trial, patients with cirrhosis and acute variceal bleeding were recruited following haemostasis with vaso-active drugs and endoscopic band ligation. Participants were randomised to standard of care or early-TIPSS. The primary outcome was 1-year survival, secondary outcomes included early and late rebleeding, and complications of portal hypertension. RESULTS: Fifty-eight patients (58 ± 11.12 years; 32.7% female) were randomised. After one year, seven patients died in the standard of care group and six in the early-TIPSS group, a 1-year survival of 75.9% vs 79.3% respectively (P = 0.79). Variceal rebleeding occurred in eight patients in the standard of care group compared with three patients in the early-TIPSS group (P = 0.09). Not all participants randomised to early-TIPSS received the intervention in time. For those receiving TIPSS per-protocol, variceal rebleeding rates were reduced (0% vs 27.6%, P = 0.04) but this had no effect on survival (76.9% vs 75.9%, P = 0.91). Serious adverse events were similar in both treatment groups, except that rates of hepatic encephalopathy were higher in patients receiving TIPSS (46.1% vs 20.7%, P < 0.05). CONCLUSIONS: Early-TIPSS reduced variceal rebleeding, increased encephalopathy but had no effect on survival in high-risk patients with oesophageal variceal bleeding. Early-TIPSS may not be feasible in many centres however, larger studies are needed. ClinicalTrials.gov reference: NCT02377141.

Direct venous pressure assessment pre-renal transplantation to optimise graft venous drainage.

BACKGROUND: Renal transplantation is the modality of choice in the treatment of end-stage kidney disease. Surgically challenging aspects of renal transplantation may include creation of vascular anastomoses where there is complex vascular anatomy. We present a paediatric case of living-related donor (LRD) renal transplantation in whom direct intravenous pressure measurement guided the management of the vascular anastomoses in the context of inferior vena cava (IVC) obstruction. CASE-DIAGNOSIS/TREATMENT: During venography for transplant assessment, 150 mL of 0.9% sodium chloride was infused for over 20 s into well-developed collateral paravertebral veins to simulate the anticipated high-volume venous return from an implanted kidney. Direct venous pressure measurements were 20 mmHg in the right paravertebral vein and 19 mmHg in the left paravertebral vein. We were reassured by this result that the collateralised venous system could sustain the high venous drainage and maintain the arteriovenous (AV) gradient required for adequate graft perfusion. Intra-operative measurement at the time of transplantation, following release of venous clamps, of 22 mmHg supported the validity of this approach. CONCLUSIONS: In children with complex venous anatomy pre-transplant, direct intravenous pressure measurement may provide a useful adjunct in deciding which vessel is most suitable for transplant anastomosis.

Early Cannulation ePTFE Arteriovenous Access Grafts are Associated with a Low Incidence of Pseudoaneurysm Formation.

BACKGROUND: Pseudoaneurysm formation is common in standard thin-walled polytetrafluoroethylene (sPTFE) grafts, occurring in up to 10% of grafts, and is reported as the most common cause of graft loss for grafts more than 2 years old. The Gore® Acuseal™ graft is an early cannulation graft, needled before incorporation, and thus may be especially prone to pseudoaneurysm formation. In addition, as this is a relatively new product, there are limited data on long-term outcomes such as pseudoaneurysm. We report one center's experience of the incidence and etiological factors associated with pseudoaneurysm formation over 5 years and 265 grafts. METHODS: A total of 265 Acuseal grafts were placed in the last 5 years. All patients had prospective data entered into an electronic searchable patient record. Surveillance was performed with 3 monthly imaging (digital subtraction angiography or ultrasound), clinical examination, and hemodynamic performance. Data examined included the incidence, causative factors, and outcomes of pseudoaneurysm. RESULTS: Eleven grafts (4.15%) developed a pseudoaneurysm, with 2 patients developing significant hemorrhage. The median time to development of a pseudoaneurysm was 25 months interquartile range (IQR, 20-28 months). Several common etiological factors were identified. All but one patient had overuse of needling sites (n = 10; 90.9%). Other factors associated with pseudoaneurysm formation were inadequate surveillance (n = 9; 81.8%), venous outflow stenosis (n = 9; 81.8%), and anticoagulation/dual antiplatelet therapy (n = 7; 63.6%). Management included observation and needle rotation (n = 5; 45.5%), stent grafting (n = 3; 27.3%), or excision (n = 1; 9.1%) of the pseudoaneurysm. Surgical or endovascular augmentation of the venous outflow was required in 9 patients (81.8%). Graft ligation and explantation were required in 5 patients (45.5%) with graft preservation achieved in 6/11 patients (54.5%). CONCLUSIONS: Pseudoaneurysm formation occurs less frequently in Acuseal grafts compared with historical data for standard PTFE grafts. Pseudoaneurysm formation did not occur in any graft within the first 13 months after implantation, suggesting early cannulation before incorporation is not by itself a risk factor for pseudoaneurysm development. Poor needling, venous stenosis, inadequate surveillance, and anticoagulation/dual antiplatelet therapy are remediable factors, and graft preservation is possible. Acuseal is a robust graft with lower rates of pseudoaneurysm formation on long-term follow-up than standard PTFE grafts.

Ferumoxytol magnetic resonance angiography: a dose-finding study in patients with chronic kidney disease.

OBJECTIVES: Ferumoxytol is an alternative to gadolinium-based compounds as a vascular contrast agent for magnetic resonance angiography (MRA), particularly for patients with chronic kidney disease (CKD). However, dose-related efficacy data are lacking. We aimed to determine the optimal (minimum effective) dose of ferumoxytol for MRA in patients with CKD. METHODS: Ferumoxytol-enhanced MRA (FeMRA) was performed at 3.0 T in patients with CKD after dose increments up to a total of 4 mg/kg. Image quality was assessed by contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR) in the abdominal aorta and inferior vena cava. Quadratic regression analyses were performed to estimate the effects of dose increments on CNR and SNR. RESULTS: Twenty-three patients underwent FeMRA (mean age 60 [SD 13] years, 87% men, 48% had diabetic nephropathy) with cumulative doses of 0, 1, 2, 3 and 4 mg/kg of ferumoxytol. On regression analyses, a parabolic relationship was observed between ferumoxytol dose and signal with progressive signal loss using doses exceeding 4 mg/kg. A dose of 3 mg/kg achieved ≥ 75% of predicted peak CNR and SNR and images were deemed of excellent diagnostic quality. CONCLUSIONS: In patients with CKD undergoing FeMRA, a dose of 3 mg/kg provides excellent arterial and venous enhancement. The benefits of increasing the dose to a theoretically optimal value of 4 mg/kg appear to be negligible and likely of minimal, if any, diagnostic value. KEY POINTS: • Ferumoxytol is used off-label as an MRI contrast agent but dose-related data are lacking. • In patients with CKD requiring MR angiography, a dose of 3 mg/kg provides excellent vascular enhancement.

A national study of autogenous arteriovenous access use and patency in a contemporary hemodialysis population.

OBJECTIVE: The predicted outcomes of autogenous arteriovenous (AV) hemodialysis access creation are predominantly based on historical data; however, both the hemodialysis population and clinical practices have changed significantly during the last decade. This study examined contemporary AV access clinical use and patencies. METHODS: A multicenter observational cohort study was performed of all new AV accesses created in Scotland in 2015. The primary end point was efficacy assessed by successful AV access use for a minimum of 30 days and primary, primary assisted, and secondary patency at 1 year. Data obtained included all interventions to maintain or to restore patency. Predictors of patency loss including demographics, comorbid conditions, dialysis status, AV access location, duplex ultrasound surveillance, procedures, prior access, and antiplatelets were assessed. Kaplan-Meier and competing risks analyses were performed to estimate the probability of AV access failure. All patients were followed up for at least 1 year or had a censoring event. RESULTS: A total of 582 AV accesses were created in 537 patients (mean age, 60 [standard deviation, 14] years; 60% men; 42% with diabetes) in nine adult renal centers. Mean follow-up was 11.8 (standard deviation, 7.6) months. By the end of the follow-up, 322 (55.3%) AV accesses were successfully used for dialysis. At 1 year, 48% (95% confidence interval [CI], 44-52) of AV accesses had primary patency, (95% CI, 63-71) had primary assisted patency, and 69% (95% CI, 65-73) had secondary patency. The leading cause of primary patency loss was primary failure (30%). An average of 0.48 intervention per patient-year was required to maintain patency. On multivariable analysis, patency was better for an upper arm than for a forearm AV access (1-year secondary patency of upper arm vs forearm AV accesses, 74% vs 58%). The cumulative hazard and incident functions for AV access failure were 31% (95% CI, 27-35) and 23% (95% CI, 20-27) at 1 year, respectively. CONCLUSIONS: Despite advances in recent years with preoperative vessel assessment and surveillance, patency rates have not improved, with primary failure remaining the major obstacle. Competing events should be taken into consideration; otherwise, biases may occur with overestimation of the probability of AV access failure.