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.
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
IntroductionDecisions 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 analysisThe 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 disseminationEthical 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.
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