Computational fluid dynamics of a vascular access case for hemodialysis

Vascular accesses (VA) for hemodialysis are usually created by native arter iovenous fistulas (AVF) or synthetic grafts. Maintaining patency of VA cont inues to be a major problem for patients with end-stage renal disease, sinc e in these vessels thrombosis and intimal hyperplasia often occur. These le sions are frequently associated with disturbed flow that develops near bifu rcations or sharp curvatures. We explored the possibility of investigating blood flow dynamics in a patient-specific model of end-to-end native AVF us ing computational fluid dynamics (CFD). Using digital subtraction angiograp hies of an AVF, we generated a three-dimensional meshwork for numerical ana lysis of blood flow. As input condition, a time-dependent blood waveform in the radial artery was derived from centerline velocity obtained during ech o-color-Doppler ultrasound examination. The finite element solution was cal culated using a fluid-dynamic software package. In the straight, afferent s ide of the radial artery wall shear stress ranged between 20 and 36 dynes/c m(2). On the venous side, proximal to the anastomosis, wall shear stress wa s oscillating between negative and positive values (from -12 dynes/cm(2) to 112 dynes/cm(2)), while distal from the anastomosis, the wall shear stress returned within the physiologic range, ranging from 8 to 22 dynes/cm(2). A reas of the vessel wall with very high shear stress gradient were identifie d on the bending zone of the radial artery and on the venous side, after th e arteriovenous shunt. Secondary blood flows were also observed in these re gions. CFD gave a detailed description of blood flow field and showed that this approach can be used for patient-specific analysis of blood vessels, t o understand better the role of local hemodynamic conditions in the develop ment of vascular lesions.