High Wall Shear Stress can Predict Wall Degradation in Ascending Aortic Aneurysms: An Integrated Biomechanics Study

M Yousuf Salmasi; Selene Pirola; Sumesh Sasidharan; Serena M Fisichella; Alberto Redaelli; Omar A Jarral; Declan P O'Regan; Aung Ye Oo; James E Moore Jr; Xiao Yun Xu; Thanos Athanasiou

doi:10.3389/fbioe.2021.750656

High Wall Shear Stress can Predict Wall Degradation in Ascending Aortic Aneurysms: An Integrated Biomechanics Study

Front Bioeng Biotechnol. 2021 Oct 18:9:750656. doi: 10.3389/fbioe.2021.750656. eCollection 2021.

Authors

Affiliations

¹ Department of Surgery and Cancer, Imperial College London, London, United Kingdom.
² Department of Chemical Engineering, Imperial College London, London, United Kingdom.
³ Department of Bioengineering, Imperial College London, London, United Kingdom.
⁴ Politecnico di Milano, Milan, Italy.
⁵ MRC London Institute of Medical Sciences, Imperial College London, London, United Kingdom.
⁶ Barts Heart Centre, London, United Kingdom.

Abstract

Background: Blood flow patterns can alter material properties of ascending thoracic aortic aneurysms (ATAA) via vascular wall remodeling. This study examines the relationship between wall shear stress (WSS) obtained from image-based computational modelling with tissue-derived mechanical and microstructural properties of the ATAA wall using segmental analysis. Methods: Ten patients undergoing surgery for ATAA were recruited. Exclusions: bicuspid aortopathy, connective tissue disease. All patients had pre-operative 4-dimensional flow magnetic resonance imaging (4D-MRI), allowing for patient-specific computational fluid dynamics (CFD) analysis and anatomically precise WSS mapping of ATAA regions (6-12 segments per patient). ATAA samples were obtained from surgery and subjected to region-specific tensile and peel testing (matched to WSS segments). Computational pathology was used to characterize elastin/collagen abundance and smooth muscle cell (SMC) count. Results: Elevated values of WSS were predictive of: reduced wall thickness [coef -0.0489, 95% CI (-0.0905, -0.00727), p = 0.022] and dissection energy function (longitudinal) [-15,0, 95% CI (-33.00, -2.98), p = 0.048]. High WSS values also predicted higher ultimate tensile strength [coef 0.136, 95% CI (0 0.001, 0.270), p = 0.048]. Additionally, elevated WSS also predicted a reduction in elastin levels [coef -0.276, 95% (CI -0.531, -0.020), p = 0.035] and lower SMC count ([oef -6.19, 95% CI (-11.41, -0.98), p = 0.021]. WSS was found to have no effect on collagen abundance or circumferential mechanical properties. Conclusions: Our study suggests an association between elevated WSS values and aortic wall degradation in ATAA disease. Further studies might help identify threshold values to predict acute aortic events.

Keywords: CFD; aneurysm; aortic surgery; computational fluid dynamics; computational pathology; magnetic resonance imaging; vascular biomechanics; wall shear stress.

Abstract

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