Master's Thesis Defense - Comparison of Power Losses in Intra-atrial and Extra-cardiac Total Cavo-Pulmonary Connections using Computational Fluid Dynamic Techniques
Date: December 4, 2008
Time: 11:30 AM
Location: Bossone Research Enterprise Center, Room: 709
Advisors: Dov Jaron, Ph.D., and Kevin Whitehead, M.D., Ph.D.
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 extra-cardiac 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.
Power loss calculations using control volume analysis were performed for each TCPC and each flow condition studied. Power losses were normalized to cardiac output and the two groups compared using the Student t-test for two independent groups. The lowest power losses were seen in the equal lung resistance condition, where power loss in the EC TCPC was 0.91±0.70 mW/l/min, compared to 3.3±1.3 mW/l/min for the IC TCPC. Power losses were similar for the other flow conditions. This difference between EC and IC TCPC was statistically significant for each flow split studied (p<0.01 for all splits studied). CFD modeling of 3-D anatomical reconstructions demonstrates differences in power loss between EC and IC TCPC, indicating that the EC Fontan may be more energetically favorable. More studies are required to determine whether these differences are universal. These differences may be important in the long-term survival and quality of life of patients with TCPC.
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