No abstract

Numerical and experimental studies are carried out to assess the hydraulic and hemodynamic performance and the biocompatibility of a viscous impeller pump (VIP) for cavopulmonary assist in patients with a univentricular Fontan circulation. Computational fluid dynamics (CFD) predictions of impeller performance are shown to be in very good agreement with measured pressure-flow data obtained in a Fontan mock-circulation system. Additional CFD and experimental design studies intending to balance pump performance and biocompatibility with the manufacturability limitations of a percutaneous expandable impeller are also reported. The numerical models and experimental studies confirm excellent performance of the VIP with augmentation of Fontan pressure up to 35 mmHg for flow rates up to 4.5 L/min and operational speeds no higher than 5000 RPM. Scalar stress predictions on the VIP surface and laboratory hemolysis measurements both demonstrate very low hemolysis potential. The impeller designs reported offer ideal performance and can meet manufacturing tolerances of a flexible, catheter-based percutaneous expandable rotary pump.

Single ventricle heart disease is a congenital condition characterized by the inoperability of one ventricle of an infant’s heart. Those suffering from this condition face a series of palliative surgeries called the Fontan procedure, which bypasses the non-functional ventricle by creating a total cavopulmonary connection, or TCPC. This TCPC forms from the anastomosis of the superior and inferior vena cavae (SVC, IVC) to the left and right pulmonary arteries (LPA, RPA), thus allowing systemic blood flow to bypass the heart and flow passively to the lungs. The Fontan procedure creates this junction with three surgeries separated by months or years.

Cardiac single ventricle birth defects are a leading cause of death among birth defects for children under one years of age. Fontan palliation is the current clinical treatment for patients with these birth defects and result in a single working ventricle to power the entire system by forming a total cavopulmonary connection (TCPC). A significant number of patients with univentricle Fontan circulation develop Fontan failure caused by the inability of the single ventricle to power the Fontan circulation. The use of mechanical cavopulmonary assist device has been proposed as a treatment for these patients. Particularly, the application of a percutaneous, catheter driven, viscous impeller pump (VIP) has been identified to provide promising cavopulmonary support [1]. Computational Fluid Dynamics (CFD) simulations have demonstrated that this VIP pump can satisfactorily augment cavopulmonary blood flow at pressures sufficient to overcome increased downstream resistance. Experimental characterization of flow induced by the VIP in the TCPC, including detailed flow structures and hemodynamic performances, needs to be conducted for minimizing risk of hemolysis and thrombosis while maximizing the pump performance, and for validating the results from high-fidelity CFD simulations.

The Fontan procedure is used in pediatric situations in which infants have complex congenital heart disease or a single effective ventricle. This procedure by-passes right heart by connecting the left and right pulmonary arteries (LPA/RPA) to the superior and inferior vena cavae (SVC/IVC). The resulting reconstructed anatomy is called total cavopulmonary connection or TCPC. Knowledge of fluid dynamics in TCPC helps in optimizing the connection itself for reduced resistance as well as aids in designing cavopulmonary assist devices like viscous impeller pump (VIP) [1].