OPTIMIZED DESIGN OF AN AXIAL FLOW VAD FOR INFANTS AND CHILDREN

Abstract

Purpose: Since donor organ waiting periods may he as long as 5 months, pediatric cardiac failure patients could benefit tremendously from the availability of a mechanical circulatory support device for longer-term, bridge-to-transplant (BTT). We have designed an implantable axial flow pediatric VAD (PVAD) for longer-term support of these patients. This PVAD has an impeller that is fully suspended in magnetic bearings and is designed for 1.5 μm to produce 72 mmHg at 8000 RPM. This design has been refined and optimized with consideration for rapid prototype manufacturing and magnetic / motor component placement. Methods: A computational model of the PVAD was created to include an inducer, impeller, diffuser, and flow straightener. Using computational fluid dynamics (CFD), this model was analyzed for rotational speeds of 7000 to 9000 RPM under steady state flow conditions. A transient flow calculation with a time varying inflow condition and rotor / stator dynamics was also completed. Results: CFD analysis of the PVAD, which measures 65 mm in length by 35 mm in diameter, demonstrates that the pump will deliver 0.5 to 3 μm over physiologic pressures. Fluid forces exerted on the rotor under steady state conditions were estimated to he approximately 1 N, and the fluid efficiency was calculated to range from 20% to 30%, typical values for blood pumps. Conclusions: This optimized design illustrated excellent performance and will be the basis for prototype manufacturing and extensive experimental testing.