Predicting haemodialysis arteriovenous fistula outcomes using computational fluid dynamics (CFD) and ferumoxytol-enhanced MRI (Fe-MRI)

Objective: Arteriovenous fistulas (AVF) are the preferred vascular access for maintenance haemodialysis. However, AVF non-maturation occurs in up to 60% of patients, frequently caused by inadequate vascular remodelling or stenosis development. This study explores the relationships between AVF anatomy, haemodynamics and AVF outcomes by combining, uniquely, high-fidelity numerical simulations and state-of-the-art ferumoxytol-enhanced magnetic resonance imaging (Fe-MRI) in patients. Methods: Patients underwent Fe-MRI 6 weeks after AVF creation. A novel computational fluid dynamics (CFD) methodology was employed to rigorously investigate haemodynamic metrics, including wall shear stress (WSS) and oscillatory shear index (OSI), and quantify changes in the AVF lumen at 1 cm intervals along the proximal artery, anastomosis and AVF vein. The primary outcome was AVF success, defined as AVF usage (assisted or unassisted) for dialysis for at least 3 months. ROC analysis was conducted to assess anatomical predictors of AVF flows of ⩾1000 ml/min. Results: The analysis included 17 AVFs (13 successful, 4 failed). Compared to failed fistulas, successful AVFs had higher mean WSS and OSI. Failed AVFs exhibited different haemodynamics, including lower flow rates with less helical flow. On ROC analysis, the three metrics associated with the highest area under the curve (AUC) values were the feeding artery curvature (0.82) and diameter (0.76), and draining vein diameter (0.74), with a combined AUC value of 0.83. Conclusion: These data suggest that high WSS, OSI, larger feeding artery and draining vein diameters and lower feeding artery curvature are associated with successful AVF outcomes. Whilst venous parameters are important, this study highlights the critical role of feeding artery characteristics, particularly diameter and curvature. These findings provide significant insights into the role of haemodynamics and geometry in modulating AVF maturation, suggesting that incorporation of arterial metrics into preoperative assessments could enhance surgical decision-making for more reliable AVF maturation and better long-term outcomes in haemodialysis patients.