Patient-Specific CT-Based Fluid-Structure-Interaction Aorta Model to Quantify Mechanical Conditions for the Investigation of Ascending Aortic Dilation in TOF Patients

Abstract

Background. Some adult patients with Tetralogy of Fallot (TOF) were found to simultaneously develop ascending aortic dilation. Severe aortic dilation would lead to several aortic diseases, including aortic aneurysm and dissection, which seriously affect patients’ living quality and even cause patients’ death. Current practice guidelines of aortic-dilation-related diseases mainly focus on aortic diameter, which has been found not always a good indicator. Therefore, it may be clinically useful to identify some other factors that can potentially better predict aortic response to dilation. Methods. 20 TOF patients scheduled for TOF repair surgery were recruited in this study and were divided into dilated and nondilated groups according to the Z scores of ascending aorta diameters. Patient-specific aortic CT images, pressure, and flow rates were used in the construction of computational biomechanical models. Results. Simulation results demonstrated a good coincidence between numerical mean flow rate at inlet and the one obtained from color Doppler ultrasonography, which implied that computational models were able to simulate the movement of the aorta and blood inside accurately. Our results indicated that aortic stress can effectively differentiate patients of the dilated group from the ones of the nondilated group. Mean ascending aortic stress-P1 (maximal principal stress) from the dilated group was 54% higher than that from the nondilated group (97.97 kPa vs. 63.47 kPa, p value = 0.044) under systolic pressure. Velocity magnitude in the aorta and aortic wall displacement of the dilated group were also greater than those of the nondilated group with p value < 0.1. Conclusion. Computational modeling and ascending aortic biomechanical factors may be used as a potential tool to identify and analyze aortic response to dilation. Large-scale clinical studies are needed to validate these preliminary findings.

Fluid–structure interaction study for biomechanics and risk factors in Stanford type A aortic dissection

“…Compared with fluid‐only models with a rigid wall assumption, FSI significantly reduces the predicted wall shear stress due to wall adaptation 53 . Yet, very few valuable FSI studies have been established for type A aortic dissection, and they are subjected to significant modelling assumptions regarding patient‐specific parameters and the mechanical properties of the vessel 43,49,53–57 . Fibre‐reinforced biological tissues, including the aortic wall, however, need to be addressed with the directional preference in mathematical modelling 58,59 .…”

“…53 Yet, very few valuable FSI studies have been established for type A aortic dissection, and they are subjected to significant modelling assumptions regarding patient-specific parameters and the mechanical properties of the vessel. 43,49,[53][54][55][56][57] Fibre-reinforced biological tissues, including the aortic wall, however, need to be addressed with the directional preference in mathematical modelling. 58,59 In addition, many previous studies assumed blood to be a Newtonian fluid, despite evidence that it exhibits shear-thinning behaviour.…”