Novel Magnetically Levitated Right Ventricular Assist Device for Pediatric and Adult Patients with Acquired or Congenital Heart Disease

Abstract

Thousands of pediatric and adult patients in the U.S. are diagnosed with congestive heart failure (CHF) secondary to acquired or congenital heart disease. Symptoms of CHF include left-sided heart dysfunction, fluid retention and swelling in lower extremities, weakness, and shortness of breath. A substantial number of these patients also develop right-sided heart failure secondary to the left-sided failure or dysfunction. Strategies to address right ventricular heart failure include pharmacological treatments, which only slow the progression of heart disease, or complete heart transplants. With a lack of donor organs available, mechanical circulatory assist devices are alternative therapeutic options; however, there are few such devices for right ventricular failure in pediatric patients. To address this unmet clinical need, we are developing a new right ventricular assist device (RVAD) or blood pump as a novel treatment strategy for these patients. The axial flow RVAD utilizes third-generation drive technology by incorporating a magnetic suspension to levitate the axial impeller within the pump housing. This magnetically suspended configuration enables the pump to have clearances between rotating and stationary components that are much wider than afforded by conventional mechanical and fluid bearings, thus lowering shear stresses and risk of blood cell damage and clotting. The RVAD consists of five internal fluid domains and bladed regions: inducer, impeller, diffuser and flow straightener. It spans 30 mm in diameter by 60 mm in length. Acting to improve blood flow to the lungs, this RVAD is designed to achieve cardiovascular requirements by generating desired blood flow rates and increased pressures. Numerical simulations of the design were performed using ANSYS computer software to estimate the hydraulic performance of the RVAD. Pressure generation was analyzed over a physiologic blood flow range and varying rotational speeds. In addition to pressure generation, the fluid stress levels, axial and radial fluid forces on the impeller of the RVAD, and power consumption were evaluated. Sufficient pressure rises of 2-142 mmHg were attained for flow rates of 2-6 L/min at rotational speeds 7000-15000 RPM. It was observed that higher flow rates generate lower pressure rises for all speeds, and higher speeds generate increased pressure rises, which follows expected pump trends. For these operating conditions, axial forces were found to be less than 3 N and radial forces less than 1 N. Scalar stresses were less than 425 Pa with residence times less than 600 ms for operating speeds under 12000 RPM. Rotational speeds of 12000 RPM and higher generated high scalar stress values at the trailing edges of the impeller blades. Due to the strong computational data, a prototype of the RVAD was constructed and hydraulically tested. The prototype delivered sufficient pressure rises of 1-126 mmHg for flow rates of 0.1-5 L/min at rotational speeds 6000-14000 RPM with an average deviation of 48% from computational data. These results demonstrated strong pump performance for right ventricular assistance, thus supporting the continued development of this RVAD for pediatric patients with right-sided heart failure.M.S., Biomedical Engineering -- Drexel University, 201