Failing dialysis access accounts for approximately 20% of end-stage renal disease patient admission in the US and remains a major source of morbidity and mortality [1]. Although native arteriovenous fistula is the vascular access of choice (fistula first), the use of synthetic arteriovenous grafts (AVGs) remain a valid and frequent solution for dialysis worldwide. AVG failure is mainly caused by thrombosis which most of the time is attributed to significant stenosis within the arteriovenous circuit. Stenosis is also the main cause of AVG dysfunction leading to inadequate dialysis [2].
In their article ‘Arteriovenous grafts: early ultrasonography tells their fortune', Kudlicka et al. [3] investigated the efficacy of early surveillance using Doppler ultrasonography (DUS), following AVG creation, to aid in identifying predictors related to decreased vascular access survival. Interestingly, the authors correlated early significant stenosis detected by DUS with a substantial higher risk of access loss (hazards ratio 14.73; 95% CI 5.10-42.58). Moreover, the combination of DUS risk factors, such as initial AVG flow volume <600 ml/min, mediocalcinosis of the feeding artery and early intimal hyperplasia in the venous anastomosis, were also correlated with decreased access survival. As a result, the authors introduced the very interesting concept of personalized surveillance, stratified to high, medium and low risk patients according to DUS findings, proposing pre-emptive angioplasty for those at high risk. However, several issues should be taken into consideration prior to applying this strategy in every day clinical practice, as the study presents significant limitations.
First of all, although the authors included a substantial number of AVGs (340 cases) and all procedures were performed in an experienced center, this was a retrospective, single-center study. Furthermore, the authors performed pre-emptive angioplasty in patients in whom DUS-defined significant stenosis was detected, driven by their previous publication of a randomized controlled trial (RCT) indicating that pre-emptive angioplasty improved AVG patency [4]. This posed an important bias, as it was not possible to know whether pre-emptive angioplasty positively or negatively affected survival, by inducing a more aggressive hyperplastic process. The discussion about surveillance and pre-emptive angioplasty has interested investigators for many years, but until today, although DUS surveillance has been proven to be effective in detecting stenosis within AVGs, the benefit from pre-emptive angioplasty in prolonging access survival has been disputed by 5 RCTs [5].
As a result, currently available evidence indicates that surveillance-guided pre-emptive angioplasty may decrease thrombosis rate, but does not increase the rate of overall AVG survival [6]. Failure of pre-emptive angioplasty to improve access survival could be attributed, among other factors, to its poor mid-term benefit, as 6-month patency rates following AVG angioplasty remains disappointingly low, no more than 50-60% at best, a fact that led various authors to investigate new endovascular technologies, such as covered stents and drug-coated balloons, in RCTs, demonstrating their efficacy in improving patency compared to plain balloon angioplasty [7]. Nevertheless, recognizing early DUS surveillance criteria for AVG failure is certainly a significant step forward in the management of patients who were dialyzed using an AVG, and further well-designed, multicenter RCTs trials are required to provide level I evidence as to improve vascular access survival.
