INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING Int. J. Numer. Meth. Biomed. Engng. (2013) Published online in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/cnm.2595 Numerical simulation of the f luid structure interactions in a compliant patient-specif ic arteriovenous fistula Iolanda Decorato 1 , Zaher Kharboutly 1 , Tommaso Vassallo 1 , Justin Penrose 2 , Cécile Legallais 1 and Anne-Virginie Salsac 1, * ,† 1 Biomechanics and Bioengineering Laboratory (UMR CNRS 7338), Université de Technologie de Compiègne, 60203 Compiègne, France 2 ANSYS UK Limited, 97 Milton Park, OX14 4RY, United Kingdom SUMMARY The objective of the study is to investigate numerically the fluid-structure interactions (FSI) in a patient- specific arteriovenous fistula (AVF) and analyze the degree of complexity that such a numerical simulation requires to provide clinically relevant information. The reference FSI simulation takes into account the non- Newtonian behavior of blood, as well as the variation in mechanical properties of the vascular walls along the AVF. We have explored whether less comprehensive versions of the simulation could still provide rele- vant results. The non-Newtonian blood model is necessary to predict the hemodynamics in the AVF because of the predominance of low shear rates in the vein. An uncoupled fluid simulation provides informative qualitative maps of the hemodynamic conditions in the AVF; quantitatively, the hemodynamic parameters are accurate within 20% maximum. Conversely, an uncoupled structural simulation with non-uniform wall properties along the vasculature provides the accurate distribution of internal wall stresses, but only at one instant of time within the cardiac cycle. The FSI simulation advantageously provides the time-evolution of both the hemodynamic and structural stresses. However, the higher computational cost renders a clinical use still difficult in routine. Copyright © 2013 John Wiley & Sons, Ltd. Received 14 November 2012; Revised 24 July 2013; Accepted 14 August 2013 KEY WORDS: arteriovenous fistula; fluid-structure interactions; hemodynamics vessel wall internal stresses 1. INTRODUCTION Hemodialysis is conducted in patients with end-stage renal disease in order to filter blood waste products and compensate for the ill-functioning kidneys. To enable hemodialysis, a partial extracor- poreal circulation needs to be set up toward the artificial kidney. It requires a permanent vascular access that is easily available for a repeated use and that provides a blood flow larger than 500 mlmin 1 [1,2]. The most standard technique is to create in the arm an arteriovenous fistula (AVF) by connecting a vein onto an artery (e.g., the cephalic vein onto the radial artery in the case of an end-to-side AVF) [3]. Subjected to arterial pressure, the vein gets arterialized after 3 to 6 months [4]. Once mature, the fistula behaves as a low resistance, high compliance pathway between the high pressure arterial system and the low pressure venous system [3]. The lifespan of an AVF is limited from a few days to about 10 years because of the onset of com- plications [3]. Some complications may affect directly the AVF, such as atherosclerotic plaques, stenoses, or aneurysms [3,5]. In practice, the AVF failure is caused by an insufficient or excessive blood flow inside the vein, compromising either the hemodialysis procedure [6] or the cardiac load. *Correspondence to: Anne-Virginie Salsac, Université de Technologie de Compiègne, CS 60319, 60203 Compiègne, France. † E-mail: anne-virginie.salsac@utc.fr Copyright © 2013 John Wiley & Sons, Ltd.