The effect of respiration, exercise, and pulsatility on in vitro Fontan hemodynamics

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Tree, Michael
Yoganathan, Ajit P.
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The Fontan procedure is the current intervention for single ventricle congenital heart defect patients. Eventually, all Fontan patients suffer long-term complications. These comorbidities are associated with blood fluid dynamics (hemodynamics) within the Fontan surgical connection. Numerous in vitro studies explore the effects of different patient conditions (breath-held, free-breathing, exercise, etc.) on Fontan hemodynamics. However, none of these studies are conducted with a flexible wall Fontan connection model. The purpose of this study was to develop a flexible Fontan connection model and examine the effect of patient condition on Fontan connection hemodynamics. The study employed model verification, bulk hemodynamic measurement, particle image velocimetry, and computational methods to explore the effects of respiration, exercise, and pulsatility on Fontan hemodynamics. Development resulted in a patient-specific compliance-verified in vitro Fontan circulation model. The model was then used to find the apparent power loss, viscous dissipation, and hepatic flow distribution of the Fontan connection under both physiological and derived experimental conditions. The study found respiration consistently increased apparent power loss. Increasing exercise intensity also increased apparent power loss; the indexed viscous dissipation term also increased with increasing exercise intensity. Increasing pulsatility increased apparent power loss monotonically, but viscous dissipation showed a consistent non-monotonic relationship. This relationship is explained using the Womersley parameter. Power loss and viscous dissipation are further compared, concluding that viscous dissipation is a superior hemodynamic metric. Hepatic flow distribution showed no consistent trends due to respiration, exercise, or pulsatility effects. The time-resolved three-dimensional velocity fields acquired to compute the metrics are useful for computational fluid dynamics simulation verification.
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