Hemodynamic assessments of the ascending thoracic aortic aneurysm using fluid-structure interaction approach

Abstract

Current assessment and management of ascending thoracic aortic aneurysm (ATAA) rely heavily on the diameter of the ATAA and blood pressure rather than biomechanical and hemodynamic parameters such as arterial wall deformation or wall shear stress. The objective of the current study was to develop an accurate computational method for modeling the mechanical responses of the ATAA to provide additional information in patient evaluations. Fully coupled fluid structure interaction simulations were conducted using data from cases with ATAA with measured geometrical parameters in order to evaluate and analyze the change in biomechanical responses under normotensive and hypertensive conditions. Anisotropic hyperelastic material property estimates were applied to the ATAA data which represented three different geometrical configurations of ATAAs. The resulting analysis showed significant variations in maximum wall shear stress despite minimal differences in flow velocity between two blood pressure conditions. Additionally, the three different ATAA conditions identified different aortic expansions that were not uniform under pulsatile pressure. The elevated wall stress with hypertension was also geometry-dependent. The developed models suggest that ATTA cases have unique characteristic in biomechanical and hemodynamic evaluations that can be useful in risk management.

Recent Advances in Biomechanical Characterization of Thoracic Aortic Aneurysms

“…Therefore, combining 4DUS with ex vivo testing could help improve study significance and lead to an important clinical tool for improving patient stratification (18). In addition, data collected from 4DUS may be used to improve computational modeling as more hemodynamic models incorporate deformable walls (72,79).…”

“…FSI studies are often used to improve the assessment of WSS in image-based geometries, by incorporating pulsatile motion of deformable vessel walls and the aortic valve using various mechanical models (95,122,(130)(131)(132). Yeh et al studied WSS distributions in three patients by creating FSI models of ascending TAAs with anisotropic hyperelastic material properties (79). Although only a limited section of an idealized ascending TAA was modeled, the authors suggest that changing blood pressure levels caused varying maximum WSS between patients despite minimal differences in velocity, suggesting that the changes in WSS were geometry-dependent (79).…”

Bio-chemo-mechanics of thoracic aortic aneurysms

“…Current TAA computational models focus on at most two of the factors discussed in this review. Examples include microstructurally-based models that incorporate collagen or elastin fiber structure in the solid mechanics predictions [19, 65], FSI simulations that include geometry, solid mechanical properties, and hemodynamics specific to TAA [66], and growth and remodeling models that predict solid mechanics based on changes in matrix parameters and SMC contractility [64]. Solid mechanics with growth and remodeling has been coupled to fluid dynamics simulations [67] or to an agent based model with biological and chemical responses to various signaling molecules [68], but these multifactorial models have not been applied to TAAs.…”

NO-HYPE: a novel hydrodynamic phantom for the evaluation of MRI flow measurements

“…The hemodynamic information from rapid PC-MRI scans is valuable in different clinical scenarios [13], but the accuracy of PC-MRI measurements is often unknown, thus limiting its actual incorporation in clinical practice. PC-MRI has been extensively studied in vivo in the aortic arch and carotid arteries [14][15][16], as well as in small structures such as cerebral arteries and intracranial aneurysms [17].…”