The significance of non-Newtonian behavior in the Fontan circulation: a computational fluid dynamics study on pediatric patient-specific models

For univentricular heart patients, Fontan circulation presents a unique challenge due to its passive blood flow through the lungs, resulting in chronic non-pulsatile low-shear-rate pulmonary blood flow where non-Newtonian effects might be substantial. This study evaluates the influence of non-Newtonian behavior on fluid dynamics and energetic efficiency in pediatric patient-specific models with Fontan circulation. We employed Lattice Boltzmann Method-Immersed Boundary based computational fluid dynamics simulations on patient-specific Fontan pulmonary vascular geometries and compared Newtonian and non-Newtonian fluid models. The study involved twenty patients exhibiting a low cardiac output state. The flow and shear stress distribution are assessed with both local and total non-Newtonian importance factors evaluated. Several metrics of indexed flow energy loss are quantified. Results show significant differences in flow structure between Newtonian and non-Newtonian models. Specifically, the non-Newtonian simulations demonstrate significantly higher viscosity, corresponding to a high non-Newtonian importance factor and larger energy loss. These findings suggest that non-Newtonian behavior contributes to flow structure and energetic inefficiency in the low cardiac output state of Fontan circulation. Further investigation is needed to determine the extent of correlation between these and clinical outcomes.