Ahmad Tabatabaeishoorijeh

Introduction: Aortic dissection is the number one disease affecting the human aorta. Computational modeling has recently been utilized to better understand the hemodynamics parameters associated with aortic dissection. However, more accurate risk prediction models are needed to better understand the prognosis of the disease in aortic dissection patients. In this study, we aim to understand the differences between rigid-wall computational fluid dynamics (CFD) and dynamic fluid structure interactions (FSI). We hypothesize that FSI models are better predictors of hemodynamic parameters such as pressures, wall shear stresses (WSS), and velocities when compared to rigid-wall CFD models.

Methods: A review of the literature was conducted using MEDLINE and PubMed databases until June 2022, and the articles were selected based on their comparison of FSI to rigid-wall CFD simulations in the modeling of aortic dissection. Eligible studies evaluated comparisons of aortic dissection in patient-specific, idealized, or animal models. In addition, one study of in-vivo 4D-MRI measurements was included for comparison purposes. Studies utilizing simulations in aortic aneurysm and purely mathematical models were excluded.

Results: A total of 4 articles met the criteria and were included in this analysis. In the simulation studies, two used patient-specific models (3 patients total) and one used idealized dissection models. The in-vivo 4D-MRI study included 224 patient-specific aortic measurements. Among the studies that compared non-rigid FSI models to traditional rigid wall models, all found that FSI models were better predictors of hemodynamic parameters such as wall shear stress (WSS), flow, and pressure gradients. In fact, Zhu et al¹ found that FSI models established lower blood velocities and wall shear stresses (WSS) along the dissected aorta. In another study, Chong et al² established the significant effect of a dynamic dissection flap, which can be modeled to move up to 4.45 mm in FSI non-rigid models, on the thrombus formation in the false lumen (FL). Baumler et al³ also found a decrease in the WSS by a factor of 2.3, and a decrease of mean pressure by a factor of 0.63 between true lumen (TL) and FL. Ultimately, the in-vivo WSS value of 2.23 ± 1.04 Pa found by Callaghan et al⁴ was closer to the WSS values extracted from FSI models compared to rigid CFD models.

Conclusion: This study demonstrates the differences between non-rigid FSI modeling and rigid-wall CFD simulations. More accurate calculations of hemodynamic parameters through FSI models can better inform patient-specific prognosis where otherwise not possible.

Works Cited:

1. Zhu Y, Mirsadraee S, Rosendahl U, Pepper J, Xu XY. Fluid-Structure Interaction Simulations of Repaired Type A Aortic Dissection: a Comprehensive Comparison With Rigid Wall Models. Front Physiol. 2022;13:913457. Published 2022 Jun 14. doi:10.3389/fphys.2022.913457
2. Chong MY, Gu B, Chan BT, Ong ZC, Xu XY, Lim E. Effect of intimal flap motion on flow in acute type B aortic dissection by using fluid-structure interaction. Int J Numer Method Biomed Eng. 2020;36(12):e3399. doi:10.1002/cnm.3399
3. Baumler K, Vedula V, Sailer AM, et al. Fluid-structure interaction simulations of patient-specific aortic dissection. Biomech Model Mechanobiol. 2020;19(5):1607-1628. doi:10.1007/s10237-020-01294-8
4. Callaghan FM, Grieve SM. Normal patterns of thoracic aortic wall shear stress measured using four-dimensional flow MRI in a large population. Am J Physiol Heart Circ Physiol. 2018;315(5):H1174-H1181. doi:10.1152/ajpheart.00017.2018