In a monopivot centrifugal blood pump, reducing stagnation areas especially around the bearing is very important. In this study, three models of impellers with different number of washout holes were proposed; the model with four flow paths and four washout holes, the model with six flow paths and six washout holes, the model with six flow paths and three washout holes. These impellers were made by 3D printing, and hydrodynamic performance, and impeller rotating position were compared among their assembled pumps. Next, their shear stress distribution inside the pump, which is closely related to the antithrombogenicity of the pump, was analyzed using computational fluid dynamics (CFD). As a result, the model with six flow paths and three washout holes was found to have high hydrodynamic performance, no lift-off problem, and high antithrombogenicity that had a small flow stagnation area.
