A comparison follow-up study on the geometric, hemodynamic and biomechanical changes in a patient-specific arteriovenous fistula

Autogenous arteriovenous fistula (AVF) remains the first choice for end-stage renal disease patients, as it is the best access for longevity and has the lowest association with morbidity and mortality. However, it suffers from... [ view full abstract ]

Autogenous arteriovenous fistula (AVF) remains the first choice for end-stage renal disease patients, as it is the best access for longevity and has the lowest association with morbidity and mortality. However, it suffers from high failure rates. The current study aims to evaluate computationally the geometric, hemodynamic and structural alterations of a brachial-cephalic fistula in a follow-up clinical case.

The follow-up study includes MR images from four post-operative time points: A(2-4wks), B(4-6wks), C(6-8wks) and D(23-25wks). Images were segmented using ITK-Snap and the morphometric analysis was based on centerlines with the use of the VMTK. Computational fluid dynamics simulations were carried out using Star-CCM+. The blood was modeled as incompressible Newtonian fluid (ρ=1050 kg/m³,μ=0.0035 kg/mˑs). Abaqus was used for finite element analysis. The artery and vein wall were assumed to have a constant thickness of 0.4mm, and modeled as a hyperelastic material following the 3^rd-order Yeoh model. A uniform systolic pressure of 120mmHg was applied for wall loading.

The anastomosis angle was 60.6^o at scan-A, increased to 68.4^o on scan-B and decreased to 63.3^o and 50.5^o, for scan-C and -D, respectively. Curvature and Tortuosity, shows a consistent decrease of approximately 40% between scan-A and D. The pressure drop increased considerably from scan-A to -D: time-averaged pressure from 22.55 to 33.45mmHg and at peak systole from 24.24 to 47.71mmHg. The maximum Principal and the von Mises stresses increased from 1.7 to 2.46 MPa and 0.28 to 0.33 MPa, respectively.

This study aimed to investigate the geometric; hemodynamic; and structural alterations of an AVF at four consecutively time-points. This analysis highlighted the morphological alterations that took place and the vascular reshaping due to changes in wall shear stress. The observed changes need further investigation to correlate them at the early stage of AVF creation for better understanding of surgery outcomes, success or failure.