COMPUTATIONAL FLUID DYNAMICS MODELS OF HEALTHY AND FAILING FONTAN CIRCULATIONS

Abstract

Failing Fontan circulation is a clinical diagnosis and can be characterized by elevated Fontan pressures and reduced cardiac output. For many of these patients, heart transplant is the only viable treatment option, and there are currently no minimally invasive medical devices available to bridge these patients to transplant. The goal of our study is to design, build, and test such a device. As a first step in the design process, we have developed representative computational models of blood flow in the total cavopulmonary connection (TCPC) in both healthy and failing Fontan cases, which are described in this abstract. Measurements made from angiograms of paediatric Fontan patients were used to develop an average three-dimensional computational model of the TCPC. Computational fluid dynamics simulations were performed in ANSYS Fluent (ANSYS, Inc., Canonsburg, PA, USA) for both healthy and failing Fontan circulations. Representative boundary conditions were defined for our model at the superior vena cava and extracardiac conduit (inlets) and the left and right pulmonary arteries (outlets) based on data from our patient cohort. At the inlets, we specified flow rates based on cardiac outputs of 1.8 L/min for the healthy case and 0.94 L/min for the failing case and a 65%/35% flow split between the extracardiac conduit and the superior vena cava. At the outlets, we specified pressures of 11 mm Hg for the healthy case and 18 mm Hg for the failing case. Results for healthy and failing Fontan circulations are presented in Figure 1 as streamlines of the blood flow through the TCPC. As expected, the velocities were higher in the healthy case than in the failing case, and the pressures (not shown) were lower in the healthy case than in the failing case. We have successfully developed a computational model to predict the blood flow in the TCPC for both healthy and failing Fontan circulations. Our calculated pressures and flow rates were consistent with expected values and fit within relevant physiological ranges. These models are a first step in the design process to develop a medical device for short-term minimally-invasive treatment for failing Fontan circulation as a bridge to heart transplant.