Comparison of Power Losses in Intra-atrial and Extra-cardiac Total Cavo- Pulmonary Connections using Computational Fluid Dynamic Techniques

According to the National Heart Lung and Blood Institute, more than 30,000 newborns in the United States are born with Congenital Heart Defects (CHDs) every year. The Total Cavo-pulmonary Connection (TCPC) or the Fontan operation is a widely employed procedure to palliate CHD conditions. Two variants of this procedure are currently in use namely the intra-atrial TCPC and the extra-cardiac TCPC. Determining which of these procedures is hemodynamically favorable has been elusive clinically. One characteristic which may distinguish the two is power loss, estimated using computational fluid dynamic (CFD) analysis. It is our hypothesis that the extra-cardiac Fontan is more hemodynamically favorable compared to the lateral tunnel Fontan, due to decreased vortex formation, decreased flow collision, less eccentric flow and thus lower viscous dissipation. We performed steady flow CFD simulations on 3-D anatomical reconstructions of total cavo-pulmonary connections (TCPC) from 11 Fontan patients using cardiac magnetic resonance imaging (CMR) data, 5 with extracardiac and 6 with lateral tunnel intra-atrial Fontans. Caval flows were determined using CMR velocimetry and outlet pressures were tuned for both the left and right pulmonary arteries in order to yield three different flow splits: equal flow to each lung, equal lung resistance of 2 Woods units, and CMR-measured.