Design of a Miniature Pump for Chronic Mechanical Circulatory Support Using Computational Fluid Dynamics and Flow Visualization

Abstract

Ventricular assist devices (VADs) have become an accepted method of treating end-stage heart failure over the last few decades. In recent years, the use of rotary blood pumps (RBPs) as continuous flow VADs has surged ahead, and virtually eliminated the use of pulsatile-flow or volume-displacement pumps for implantable, chronic mechanical circulatory support (MCS). As the use of RBPs has become commonplace for the treatment of end-stage heart failure, the need for an implantable right-side MCS device for adults [1] and implantable MCS for the pediatric population has increased. Development of an implantable device specific to these populations includes unique challenges of anatomic placement and fixation. Computational Fluid Dynamics (CFD) is the use of numerical methods and algorithms to solve and analyze problems involving fluid flow. CFD has become a standard tool when designing RBPs, as it can calculate pressure-flow characteristics for a given rotary impeller speed. Additionally, through calculation of shear forces, CFD can also predict hemocompatibility by means of constitutive equations derived from empirical data. Particle image velocimetry (PIV), also known as flow visualization, is an optical measurement technique used to obtain velocity in fluids, which can be employed experimentally to verify CFD-based predictions of flow field. PIV also permits more rapid investigation of the RBP operativing range and transient conditions than can be achieved with CFD due to computational requirements. We have developed a RBP platform for chronic use with CFD to optimize hemodynamic performance. The miniaturized device includes unique inlet geometry with a rotating impeller and a vaned-diffuser in a 7mm axial hydraulic diameter. The design scheme separates the bearing and motor region from the primary flow path to further improve hemocompatibility and reduce the pump size without compromising the hydraulic capacity. Here we report CFD and PIV results of our device geometry optimized for right-sided MCS.