For univentricular heart patients, the Fontan operation creates a unique non-physiologic circulation where the pulmonary arteries are directly supplied from the systemic venous blood return, leading to chronic non-pulsatile low-shear-rate pulmonary blood flow. Computational fluid dynamic (CFD) simulations are widely used in cardiovascular biofluid studies and a Newtonian fluid assumption is common since blood acts as a Newtonian fluid in large arteries. Although blood viscosity increases exponentially in low-shear-rate flow environments, a Newtonian assumption is still conventionally used in both experimental and CFD studies of the low-shear-rate Fontan circulation. The error introduced by a Newtonian assumption in this setting has not been thoroughly evaluated. Recent in vitro studies have demonstrated that non-Newtonian effects are substantial in the Fontan circulation. However, no previous studies have used CFD to systemically investigate non-Newtonian effects in Fontan simulations. Thus the role of shear-rate-dependent non-Newtonian blood viscosity in this pathophysiology is still unclear. In this study we used a computational approach to compare flow behavior between a non-Newtonian fluid and a Newtonian fluid in a simplified model of the Fontan circulation over a wide range of experimental conditions. We examined important clinical metrics in Fontan hemodynamics: shear stress, power loss, pulmonary flow distribution, viscous dissipation, and non-Newtonian importance factors. Our results suggest that the Newtonian fluid assumption for blood introduces considerable error into the simulations of the Fontan circulation, where the fluid environment is predominated by low-shear-rate flow.

对于单心室心脏病患者，Fontan手术可形成独特的非生理循环，其中系统性静脉血液回流直接供应肺动脉，从而导致慢性非搏动性低剪切率肺血流。计算流体动力学（CFD）模拟在心血管生物流体研究中被广泛使用，由于血液在大动脉中起牛顿流体的作用，因此牛顿流体的假设很普遍。尽管在低剪切速率的流动环境中血液粘度呈指数增加，但是在低剪切速率的Fontan循环的实验研究和CFD研究中，传统上仍采用牛顿假设。牛顿假设在这种情况下引入的误差尚未得到彻底评估。最近的体外研究表明，在Fontan循环中非牛顿效应是很重要的。但是，以前没有研究使用CFD来系统地研究Fontan模拟中的非牛顿效应。因此，剪切速率依赖性非牛顿血液粘度在这种病理生理中的作用仍不清楚。在这项研究中，我们使用一种计算方法来比较在广泛的实验条件下，在Fontan循环简化模型中非牛顿流体和牛顿流体之间的流动行为。我们研究了Fontan血液动力学的重要临床指标：剪切应力，功率损失，肺血流分布，粘性耗散和非牛顿重要因素。