Why vascular access trials on flow surveillance failed

Since the introduction of access flow surveillance technology for routine patient screening in 1995, more than 30 clinical trials have been presented in peer reviewed journals. Despite overall positive outcomes, some trials, including randomized control trials (RCTs), failed to produce positive outcomes for access surveillance. The purpose of this study is to analyze published data related to the main component of access surveillance--adequate increase of access flow after percutaneous transluminal angioplasty (PTA).

A total of nine studies for arteriovenous grafts (AVGs) that include 350 accesses and nine studies for arteriovenous fistula (AVF) that included 503 accesses were considered for analysis from 14 publications. Practically, all reference data find high sensitivity (>90%) of access flow measurement to predict 50% stenosis. Mean access flow increase after PTA in AVGs was 319 ml/min (from 238 to 524 ml/min). Mean access flow increase in AVFs was 331 ml/min (from 195 to 402 ml/min). Relative flow increase in AVFs was 1.6 times greater than in AVGs. The authors of failed RCT for AVGs either did not select patients for PTA based on KDOQI guidelines and did not provide/analyze PTA flow results data, or reveal data that obviously show failure of PTA to adequately improve access flow.

Access flow surveillance successfully identifies patients with hemodynamically significant stenosis. PTA performed on AVFs produce better hemodynamic results than in AVGs. Inadequate flow increases during PTA and not following KDOQI guidelines are major contributing factors for failed AVG randomized tails. Radiologists should use objective means for flow evaluation during PTA.