Defining a Significant Stenosis in an Autologous Radio‐Cephalic Arteriovenous Fistula for Hemodialysis

Abstract

The current definition of a significant stenosis in an autologous arteriovenous fistula (aAVF), the percentage narrowing compared with the adjacent "normal" vessel, is inaccurate. We believe a significant stenosis in the aAVF is an absolute minimal luminal diameter determined by the requirements of the hemodialysis pump. To determine what absolute diameter constitutes a hemodynamically significant stenosis in a radio-cephalic autologous arteriovenous fistula (RC aAVF), the minimal luminal diameter of dysfunctional RC aAVF was compared to that of functional RC aAVF using grayscale and color ultrasound. There were 93 fistulas in study group and 77 in control group. The mean minimum luminal diameter in study group was significantly lower than in control group (2.19 vs. 4.71 mm, p 0.001). With a cutoff value of 2.7 mm, there was 90% sensitivity and 80% specificity in distinguishing functional fistula from dysfunctional fistula. The area under the receiver-operator curve was 90% (CI 84-94%), indicating that a 2.7 mm diameter is accurate in discriminating functional from dysfunctional fistulas. An absolute minimal luminal diameter of 2.7 mm, as determined with grayscale and color ultrasound, is a useful cutoff for defining significant stenosis in a RC aAVF.

Ultrasonographic diagnosis of stenosis of native arteriovenous fistulas in haemodialysis patients

“…The small calibre of these vessels was associated with the presence of stenosis also in our study. Delayed maturation is associated with a late fistula failure, the mechanism of which might be related to a small vessel diameter; if other factors intervene it is not determined [11,12]. We found however increased prevalence of delayed maturation in stenosis patients, suggesting stenosis to be a major player in the pejorative outcome of AVF with delayed maturation.…”

“…However, recent data accentuate the importance of measurement of the minimum diameter of the stenosed area in addition to PSV in order to differentiate true, significant, stenosis from borderline stenosis [10,11]. Based on these data, we defined stenosis as a combination of both functional and morphological criteria.…”

“…The stenosis was defined as the reduction of the diameter of the vessel of more than 50% and an increase in peak systolic velocities (PSV) ratio (PSV in the stenotic area/ PSV upstream the stenotic area) >2:1 in the draining vein or >3:1 in the anastomotic area. A severe stenosis was defined by a) minimum diameter of the stenotic area < 3 mm, b) brachial artery blood flow<500 ml/min, or c) RI in the brachial artery > 0.6 [2,[7][8][9][10][11][12]. Illustration for US diagnosis of stenosis and its severity is provided in figure 1.…”

The Role of Doppler Ultrassonography in Significant and Borderline Stenosis Definition

“…According to KDOQI guidelines, a stenosis is hemodynamically significant when it exceeds 50% of the vessel’s diameter and is associated with a high pressure or a low or change in access flow [3]. However, the adjacent vessel may be smaller, larger, or even aneurysmatic and it is, therefore, not a meaningful comparator [1]. Thus, currently there is no consensual definition of significant stenosis (SS), that is, the critical point at which a stenosis is associated with the highest risk of thrombosis.…”

“…Arteriovenous fistula (AVF) is the first choice vascular access (VA) for chronic hemodialysis (HD) patients [1]. Stenosis is the most frequent AVF complication and when it is hemodynamically significant, it is the main predisposing factor for thrombosis [2].…”