Heat and low-density lipoprotein transfer in healthy aorta using fluid-structure interaction method

The abnormal accumulation of low-density lipoprotein (LDL) can lead to aortic atherosclerosis. However, the aortic LDL transfer and its relationship with hemodynamics are still not fully explored. This study aims to reveal the mechanism of heat and LDL transfer in healthy aortas, leveraging a fluid-structure interaction (FSI) model. Two healthy aortic geometry models were reconstructed based on clinical computed tomography angiography images. The flow rate used as the inlet boundary condition was taken from another previous publication, and non-invasive blood pressure measurement data were exploited to determine the parameters of the three-element Windkessel model for boundary conditions of the aortic outlets. The aortic wall was assumed to be uniform in thickness, and the hyperelastic material was simulated by Yeoh second-order model. Our two-way FSI method was further developed to predict the heat and LDL transfer. Results show that the correlation coefficients of time-averaged LDL, temperature, and wall shear stress (WSS)-related indices between the rigid and hyperelastic aortic wall are high (> 0.914) except for the topological shear variation index (TSVI). The interaction between the blood flow and the aortic wall is suggested to be considered to accurately capture the distribution of oscillatory shear index, relative residual time (RRT), and TSVI. Besides, we find that there is a positive correlation (> 0.596) between the concentration of LDL and aortic wall temperature. The long RRT region also coincides with the high LDL area, which negatively correlates with WSS and TSVI. This study demonstrates the heat and LDL transfer in healthy aortas using the FSI model, and the findings would inform novel strategies to measure LDL concentration and regulate its accumulation.