title: Biomechanical Characterization of Ascending Aortic Aneurysms.
abstract: Ascending thoracic aortic aneurysms (ATAAs) are a silent disease, ultimately leading to dissection or rupture of the arterial wall. There is a growing consensus that diameter information is insufficient to assess rupture risk, whereas wall stress and strength provide a more reliable estimate. The latter parameters cannot be measured directly and must be inferred through biomechanical assessment, requiring a thorough knowledge of the mechanical behaviour of the tissue. However, for healthy and aneurysmal ascending aortic tissues, this knowledge remains scarce. This study provides the geometrical and mechanical properties of the ATAA of six patients with unprecedented detail. Prior to their ATAA repair, pressure and diameter were acquired non-invasively, from which the distensibility coefficient, pressure-strain modulus and wall stress were calculated. Uniaxial tensile tests on the resected tissue yielded ultimate stress and stretch values. Parameters for the Holzapfel-Gasser-Ogden material model were estimated based on the pre-operative pressure-diameter data and the post-operative stress-stretch curves from planar biaxial tensile tests. Our results confirmed that mechanical or geometrical information alone cannot provide sufficient rupture risk estimation. The ratio of physiological to ultimate wall stress seems a more promising parameter. However, wall stress estimation suffers from uncertainties in wall thickness measurement, for which our results show large variability, between patients but also between measurement methods. Our results also show a large strength variability, a value which cannot be measured non-invasively. Future work should therefore be directed towards improved accuracy of wall thickness estimation, but also towards the large-scale collection of ATAA wall strength data.
authors.affiliation: Biomechanics Section Department of Mechanical Engineering, KU Leuven, Celestijnenlaan 300, 2419, Leuven, Belgium.
authors.forename: Marija
authors.identifier: 0000-0003-3736-2358
authors.initials: M
authors.lastname: Smoljkić
authors.affiliation: Biomechanics Section Department of Mechanical Engineering, KU Leuven, Celestijnenlaan 300, 2419, Leuven, Belgium.
authors.forename: Heleen
authors.initials: H
authors.lastname: Fehervary
authors.affiliation: Biomechanics Section Department of Mechanical Engineering, KU Leuven, Celestijnenlaan 300, 2419, Leuven, Belgium.
authors.forename: Philip
authors.initials: P
authors.lastname: Van den Bergh
authors.affiliation: Biomechanics Section Department of Mechanical Engineering, KU Leuven, Celestijnenlaan 300, 2419, Leuven, Belgium.
authors.forename: Alvaro
authors.initials: A
authors.lastname: Jorge-Peñas
authors.affiliation: Clinical Cardiac Surgery, Department of Cardiovascular Sciences, KU Leuven, Leuven, Belgium.
authors.forename: Louis
authors.initials: L
authors.lastname: Kluyskens
authors.affiliation: Translational MRI, Department of Imaging and Pathology, KU Leuven, Leuven, Belgium.
authors.forename: Steven
authors.initials: S
authors.lastname: Dymarkowski
authors.affiliation: Clinical Cardiac Surgery, Department of Cardiovascular Sciences, KU Leuven, Leuven, Belgium.
authors.forename: Peter
authors.initials: P
authors.lastname: Verbrugghe
authors.affiliation: Clinical Cardiac Surgery, Department of Cardiovascular Sciences, KU Leuven, Leuven, Belgium.
authors.forename: Bart
authors.initials: B
authors.lastname: Meuris
authors.affiliation: Biomechanics Section Department of Mechanical Engineering, KU Leuven, Celestijnenlaan 300, 2419, Leuven, Belgium.
authors.forename: Jos
authors.initials: J
authors.lastname: Vander Sloten
authors.affiliation: Biomechanics Section Department of Mechanical Engineering, KU Leuven, Celestijnenlaan 300, 2419, Leuven, Belgium. nele.famaey@kuleuven.be.
authors.forename: Nele
authors.initials: N
authors.lastname: Famaey
mesh_terms: D001011:Aorta / Q000033:anatomy & histology / Q000502:physiology; D017545:Aortic Aneurysm, Thoracic / Q000503:physiopathology*; D001696:Biomechanical Phenomena; D006801:Humans; D008954:Models, Biological; D011312:Pressure; D013314:Stress, Mechanical
keywords: Ascending aortic aneurysm; In vivo pressure–diameter measurements; Material properties; Planar biaxial testing; Rupture risk