2-week post-operative sonographic blood flow and vein calibre in predicting primary radio-cephalic arteriovenous fistula non-assisted maturation and prolonged longterm outcomes

 Kidney Disease Outcomes Quality Initiative (KDOQI) guideline recommends fore-arm radio-cephalic autogenous arteriovenous fistulas (RCAVF) over upper-arm fistulas (AVF) as first line vascular access (VA) in hemodialysis end stage renal disease (ESRD) patients. However, RCAVFs have inferior outcomes with regards to maturation and patency rates predicated by higher rate of juxta-anastomotic stenosis, poorer feeding arterial blood flow (BF) and outflow vein calibre (VC). Whilst demographic and morbidity factors have proven inconsistent predictive factors in the literature, a few studies have consistently singled out both immediate and 2-week post-operative BF and VC. However, these studies are limited by their focus on early outcomes (<1 year), heterogeneity of VAs studied and use of non-standardised outcome definitions. Our aim, therefore, was to establish the 2-week post-operative BF and VC that permit optimal maturation and longterm outcomes in a homogenous cohort of primary RCAVFs using standardised outcome measures mandated by prevalent VA guidelines.

This was a prospective study conducted in multi-ethnic Asian ESRD patients who had their primary RCAVFs created between October 2013 and October 2014 under regional anaesthesia at a single centre and followed up for 10 years. All AVFs were assessed 2-week post-operatively for brachial artery BF and outflow VC using doppler ultrasound. A 10MHz linear probe and GE Logic e R7 machine were used exclusively by a single operator. Receiver operating characteristic (ROC) curves were generated to determine the optimal BF and VC cut-off for AVF maturation. Maturation was based on KDOQI definition ( BF>600mL/min, VC>6mm and vein depth <6mm at 6 weeks post-op). An area under the curve (AUC)> 0.7 was considered clinically significant. Kaplan–Meier (KM) analysis was used to evaluate 1, 5 and 10-year primary and secondary patency rates  on best BF and VC cut-offs. Cox regression statistics was used to determine factors favouring AVF longterm outcomes.

Fifty-seven primary RCAVFs were included in the study. Males comprised 68.4%, diabetes 73.7%, smokers 70.2% and preripheral artery disease (PAD) 20% of the cohort. Median age and BMI  were 58 (IQR 52-65) years and 25 (IQR 23-27)kg/m2 respectively. Sonography- based non-assisted maturation at 6 weeks was 56%. ROC identified 500 mL/min and 5mm as the best BF and VC cut-off respectively to most accurately predict 6-week maturation. The sensitivity, specificity, positive predictive value and negative predictive value were 85, 68, 77% and 74% for BF and 80, 60, 70 and 74% for VC respectively. Survival (KM) analysis showed that AVFs with 2-week VC >5mm versus <5mm had significantly greater 1, 5 and 10-year primary patency rates of 50, 46 and 30 versus  24, 10 and 10 % respectively (p<0.05). Secondary patency rates were also significantly better at 100, 90, 80 versus 85 , 80 and 65% respectively  (p<0.05). There was no significant difference in patency rates between AVFs with BF>500 and <500mL/min. Multivariate cox proportional regression hazard analysis showed that VC<5mm (HR 2.30, CI 1.27-4.99, p= 0.03) and PAD (HR 1.64, 95% CI 1.27-10.06, p=0.02) significantly contributed to the variability of primary patency. Only VC (HR 0.28, 95% CI 0.13-0.063, p=0.002) impacted significantly on secondary patency.

A 2-week post-op BF of 500mL/min and VC 5mm  predict RCAVF non-assisted maturation, but only 2- week VC accurately impacts on prolonged longterm AVF survival. Therefore VA surveillance efforts should target RCAVFs as early as 2-week so that those with VC <5mm can be subject to timely enhanced surveillance and intervention for maintenance of prolonged longterm patency.