• Miriam Nightingale, Michael Baran Scott, Taisiya Sigaeva, David Guzzardi, Julio Garcia, S Chris Malaisrie, Patrick McCarthy, Michael Markl, FedakPaul W MPWMLibin Cardiovascular Institute of Alberta, University of Calgary, Calgary, Alberta, Canada; Department of Cardiac Sciences, Cummings School of Medicine, University of Calgary, Calgary, Alberta, Canada., Elena S Di Martino, and Alex J Barker.
• Department of Biomedical Engineering, Schulich School of Engineering, University of Calgary, Calgary, Alberta, Canada; Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, Alberta, Canada.
• J. Thorac. Cardiovasc. Surg. 2024 Aug 1; 168 (2): 465476.e5465-476.e5.

ObjectiveIn this study we aimed to conclusively determine whether altered aortic biomechanics are associated with wall shear stress (WSS) independent of region of tissue collection. Elevated WSS in the ascending aorta of patients with bicuspid aortic valve has been shown to contribute to local maladaptive aortic remodeling and might alter biomechanics.MethodsPreoperative 4-dimensional flow magnetic resonance imaging was performed on 22 patients who underwent prophylactic aortic root and/or ascending aorta replacement. Localized elevated WSS was identified in patients using age-matched healthy atlases (n = 60 controls). Tissue samples (n = 78) were collected and categorized according to WSS (elevated vs normal) and region. Samples were subjected to planar biaxial testing. To fully quantify the nonlinear biomechanical response, the tangential modulus (local stiffness) at a low-stretch (LTM) and high-stretch (HTM) linear region and the onset (TZo) and end stress of the nonlinear transition zone were measured. A linear mixed effect models was implemented to determine statistical relationships.ResultsA higher LTM in the circumferential and axial direction was associated with elevated WSS (P = .007 and P = .018 respectively) independent of collection region. Circumferential TZo and HTM were higher with elevated WSS (P = .024 and P = .003); whereas the collection region was associated with variations in axial TZo (P = .013), circumferential HTM (P = .015), and axial HTM (P = .001).ConclusionsThis study shows strong evidence that biomechanical changes in the aorta are strongly associated with hemodynamics, and not region of tissue collection for bicuspid valve aortopathy patients. Elevated WSS is associated with tissue behavior at low stretch ranges (ie, LTM and TZo).Copyright © 2023 The American Association for Thoracic Surgery. Published by Elsevier Inc. All rights reserved.

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