Ascending aortic aneurysm haemodynamics are associated with aortic wall biomechanical properties

Davis McClarty; Maral Ouzounian; Mingyi Tang; Daniella Eliathamby; David Romero; Elsie Nguyen; Craig A Simmons; Cristina Amon; Jennifer Chia-Ying Chung

doi:10.1093/ejcts/ezab471

Ascending aortic aneurysm haemodynamics are associated with aortic wall biomechanical properties

Eur J Cardiothorac Surg. 2022 Jan 24;61(2):367-375. doi: 10.1093/ejcts/ezab471.

Authors

Affiliations

¹ Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, ON, Canada.
² Division of Cardiovascular Surgery, Department of Surgery, University Health Network, University of Toronto, Toronto, ON, Canada.
³ Department of Engineering, Institute of Biomedical Engineering, University of Toronto, Toronto, ON, Canada.
⁴ Department of Medical Imaging, University Health Network, University of Toronto, Toronto, ON, Canada.

PMID: 34718497
DOI: 10.1093/ejcts/ezab471

Abstract

Objectives: The effect of aortic haemodynamics on arterial wall properties in ascending thoracic aortic aneurysms (ATAAs) is not well understood. We aim to delineate the relationship between shear forces along the aortic wall and loco-regional biomechanical properties associated with the risk of aortic dissection.

Methods: Five patients with ATAA underwent preoperative magnetic resonance angiogram and four-dimensional magnetic resonance imaging. From these scans, haemodynamic models were constructed to estimate maximum wall shear stress (WSS), maximum time-averaged WSS, average oscillating shear index and average relative residence time. Fourteen resected aortic samples from these patients underwent bi-axial tensile testing to determine energy loss (ΔUL) and elastic modulus (E10) in the longitudinal (ΔULlong, E10long) and circumferential (ΔULcirc, E10circ) directions and the anisotropic index (AI) for each parameter. Nine resected aortic samples underwent peel testing to determine the delamination strength (Sd). Haemodynamic indices were then correlated to the biomechanical properties.

Results: A positive correlation was found between maximum WSS and ΔULlong rs=0.75, P = 0.002 and AIΔUL (rs=0.68, P=0.01). Increasing maximum time-averaged WSS was found to be associated with increasing ΔULlong (rs=0.73, P = 0.003) and AIΔUL (rs=0.62, P=0.02). Average oscillating shear index positively correlated with Sd (rs=0.73,P=0.04). No significant relationship was found between any haemodynamic index and E10, or between relative residence time and any biomechanical property.

Conclusions: Shear forces at the wall of ATAAs are associated with local degradation of arterial wall viscoelastic hysteresis (ΔUL) and delamination strength, a surrogate for aortic dissection. Haemodynamic indices may provide insights into aortic wall integrity, ultimately leading to novel metrics for assessing risks associated with ATAAs.

Keywords: Aortic biomechanics; Ascending aortic aneurysm; Computational fluid dynamics; Magnetic resonance imaging.

MeSH terms

Aorta
Aortic Aneurysm*
Aortic Aneurysm, Thoracic*
Aortic Dissection*
Biomechanical Phenomena
Hemodynamics
Humans
Stress, Mechanical