Importance of accurate geometry in the study of the total cavopulmonary connection: computational simulations and in vitro experiments.

Previous in vitro studies have shown that total cavopulmonary connection (TCPC) models incorporating offset between the vena cavae are energetically more efficient than those without offsets. In this study, the impact of reducing simplifying assumptions, thereby producing more physiologic models, was investigated by computational fluid dynamics (CFD) and particle flow visualization experiments. Two models were constructed based on angiography measurements. The first model retained planar arrangement of all vessels involved in the TCPC but incorporated physiologic vessel diameters. The second model consisted of constant-diameter vessels with non-planar vascular features. CFD and in vitro experiments were used to study flow patterns and energy losses within each model. Energy losses were determined using three methods: theoretical control volume, simplified control volume, and velocity gradient based dissipation. Results were compared to a simplified model control. Energy loss in the model with physiologically more accurate vessel diameters was 150% greater than the simplified model. The model with nonplanar features produced an asymmetric flow field with energy losses approximately 10% higher than simplified model losses. With the velocity gradient based dissipation technique, the map of energy dissipation was plotted revealing that most of the energy was dissipated near the pulmonary artery walls.