The role of surveillance in mature arteriovenous fistula management.
The existing guidelines recommend arteriovenous fistulae (AVF) surveillance by access blood flow (Qa) measurement and the correction of hemodynamically significant stenoses to prolong access survival. Unfortunately, many studies supporting these recommendations are inadequate methodologically; therefore, both the optimal criteria for surveillance and the value of preventive stenosis repair in AVF remain controversial. Recent literature confirms that Qa measurement allows an accurate identification of both stenosis (area under the curve (AUC) ranging from 0.80-0.93) and access at risk of failure (AUC ranging from 0.82-0.98) in AVFs and suggests a Qa <700-1000 ml/min and/or a reduction in Qa >25% as optimal predictors for stenosis and a Qa <400 ml/min for incipient thrombosis. Recent prospective studies evaluated whether Qa surveillance could improve AVF patency rates compared to monitoring based on clinical and dialysis-related criteria alone. The majority of studies have historical, rather than concurrent, control groups and provide conflicting results, some showing a reduction and some showing no change in thrombosis rates by Qa monitoring. On the other hand, the few randomized controlled studies available show that Qa surveillance, when coupled with preemptive intervention, reduces the already low thrombosis rate in AVF and suggest that the functional access life can be prolonged. However, there is still the need for additional methodologically adequate studies to understand fully the role of surveillance in AVF management.