CARD3: Wall Shear Stress Signature of the Axial B-impeller Design with Superior Hemodynamics

Abstract

Purpose: Ventricular assist devices (VADs) present great promise as both bridge-to-transplant and destination therapies for patients with end-stage heart failure. However, complications—such as hemolysis, gastrointestinal bleeding, and degradation of the von Willebrand factor—stand in the way of their widespread application. High levels of wall shear stress resulting from poor hemodynamics within the bladed flow domain are primarily responsible. Computational fluid dynamics (CFD) software was used to map the hemodynamic performance of the B-impeller—a biologically-inspired, helicoid VAD impeller design—and provide detailed insight into the internal flow structures, leading to the shear stress levels within. Methods: The B-impeller with casing was parametrically modeled using a computer aided design software. The geometry was exported to a CFD software and simulations were subsequently run to assess the impeller hemodynamics with respect to the wall shear stress parameter. Results: The B-impeller was found to have a very low shear stress signature versus typical VAD designs, which exhibit much higher signatures than the defined hemolytic threshold of 400 Pascals. The peak and area-averaged values of shear stress were found to be 304.512 Pa (at a flow rate of 9 L/min) and 39.949 Pa (averaged over multiple input flow rate simulations), respectively. Conclusion: The B-impeller concept shows great potential to reduce the adverse hemolytic events associated with most other turbo VADs, in addition to its ability to generate high rates of flow in a minimally intrusive diameter of 8 mm. This biologically inspired, rim-driven impeller design was found to reduce shear stress levels over competitive designs by virtue of its radical, open architecture. This low shear stress signature translates to lowering rates of hemolysis, bleeding, and von Willebrand factor degradation, thereby improving post-implantation outcomes of patients.