Creating patient-specific vein models to characterize wall shear stress in hemodialysis population

Abstract

End-Stage Renal Disease (ESRD) patients require arteriovenous fistulas (AVF) that allow a mature vein to withstand hemodialysis. Unfortunately, venous thrombosis and stenosis in the cephalic vein arch after AVF placement is common and heavily influenced by hemodynamics. To better assess forces and flow behavior in the cephalic arch, we have built patient-specific millifluidic models that allow us to explore the complex interplay between patient-specific vein geometry and fluctuating hemodynamics. These 3D models were created from patient-specific intravascular ultrasound and venogram images obtained three- and twelve-months post AVF creation and fabricated into soft elastomer-based millifluidic devices. Geometric validation of fabricated phantom millifluidic device shows successful replication of original computational 3D model. Millifluidic devices were perfused with a blood-mimicking fluid containing fluorescent tracer beads under steady-state physiologic cephalic vein flow conditions (20 mL/min). Particle image velocimetry was employed to calculate wall shear stress (WSS) across the cephalic arches. Experimental WSS profile evaluation reveals that the physiologic cephalic arch model yields WSS values within physiologic range [76–760 mPa]. Moreover, upon comparing WSS profiles across all models, it is noticeable that WSS values increase as vein diameter decreases, which further supports employed experimental and analysis strategy. The presented millifluidic devices show promise for experimental WSS characterization under pathologic flow conditions to contrast from calculated physiologic hemodynamics and better understand WSS influence on thrombosis and stenosis in hemodialysis patients.