AUTHOR=Salmasi M. Yousuf , Pirola Selene , Sasidharan Sumesh , Fisichella Serena M. , Redaelli Alberto , Jarral Omar A. , O’Regan Declan P. , Oo Aung Ye , Moore James E. , Xu Xiao Yun , Athanasiou Thanos 

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

JOURNAL=Frontiers in Bioengineering and Biotechnology

VOLUME=9

YEAR=2021

URL=https://www.frontiersin.org/journals/bioengineering-and-biotechnology/articles/10.3389/fbioe.2021.750656

DOI=10.3389/fbioe.2021.750656

ISSN=2296-4185

ABSTRACT=<p><bold>Background:</bold> 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.</p><p><bold>Methods:</bold> 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.</p><p><bold>Results:</bold> Elevated values of WSS were predictive of: reduced wall thickness [coef −0.0489, 95% CI (−0.0905, −0.00727), <italic>p</italic> = 0.022] and dissection energy function (longitudinal) [−15,0, 95% CI (−33.00, −2.98), <italic>p</italic> = 0.048]. High WSS values also predicted higher ultimate tensile strength [coef 0.136, 95% CI (0 0.001, 0.270), <italic>p</italic> = 0.048]. Additionally, elevated WSS also predicted a reduction in elastin levels [coef −0.276, 95% (CI −0.531, −0.020), <italic>p</italic> = 0.035] and lower SMC count ([oef −6.19, 95% CI (−11.41, −0.98), <italic>p</italic> = 0.021]. WSS was found to have no effect on collagen abundance or circumferential mechanical properties.</p><p><bold>Conclusions:</bold> 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.</p>