Screening for subclinical stenosis in native vessel arteriovenous fistulae

Guidelines recommend the use of ultrasound dilution techniques (UDT), inclu ding measurement of access recirculation (AR) and access blood flow (Q(a)), to screen for subclinical vascular access dysfunction. Although these tech niques are efficacious in polytetrafluoroethylene grafts, data in native ve ssel arteriovenous fistulae (AVF) are lacking. A prospective observational study was conducted to evaluate the utility of UDT screening in AVF, Q(a) a nd AR were measured bimonthly. Positive studies required fistulograms and w ere defined by Q(a) < 500 ml/min, <Delta>Q(a) > 20% from baseline or AR > 5 %. Accesses with stenosis underwent percutaneous angioplasty. After 1 yr, t here were 1355 mo of follow-up in 177 patients. There were 44 positive stud ies in 40 patients. Q(a) was <500 ml/min in 36 (82%), <Delta>Q(a) was >20% in 5 (11%), and AR was >5% in 6 (14%). Of patients with Q(a) < 500 ml/min, 29 (81%) had stenosis. Only two patients (40%) with <Delta>Q(a) > 20% but Q (a) > 500 ml/min had stenosis. No patient with AR > 5% had stenosis unless Q(a) was also <500 ml/min. immediate patency rate was 93% post-PTA. Mean Q( a) increased from 303<plus/minus>154 ml/min to 602 +/- 220 ml/min (P < 0.00 01), and mean urea reduction ratio increased from 70.4<plus/minus>8.4% to 7 4.6 +/-6.5% (P = 0.003) post-PTA. The results demonstrate that UDT could de tect subclinical stenoses in AVF, and most lesions were amenable to angiopl asty. AVF that underwent PTA delivered higher Q(a) and urea reduction ratio , and immediate patency rates were acceptable. Access failure after negativ e UDT was unusual. Measuring AR increases the time required to perform UDT but does not improve utility. Serial measurements of Q(a) alone may be the best strategy for screening AVF.