Biomechanics and Modeling in Mechanobiology

, Volume 16, Issue 2, pp 705–720

Biomechanical Characterization of Ascending Aortic Aneurysms

  • Marija Smoljkić
  • Heleen Fehervary
  • Philip Van den Bergh
  • Alvaro Jorge-Peñas
  • Louis Kluyskens
  • Steven Dymarkowski
  • Peter Verbrugghe
  • Bart Meuris
  • Jos Vander Sloten
  • Nele Famaey
Original Paper

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.

Keywords

Ascending aortic aneurysm Material properties Planar biaxial testing In vivo pressure–diameter measurements Rupture risk 

Copyright information

© Springer-Verlag Berlin Heidelberg 2016

Authors and Affiliations

  • Marija Smoljkić
    • 1
  • Heleen Fehervary
    • 1
  • Philip Van den Bergh
    • 1
  • Alvaro Jorge-Peñas
    • 1
  • Louis Kluyskens
    • 2
  • Steven Dymarkowski
    • 3
  • Peter Verbrugghe
    • 2
  • Bart Meuris
    • 2
  • Jos Vander Sloten
    • 1
  • Nele Famaey
    • 1
  1. 1.Biomechanics Section Department of Mechanical EngineeringKU LeuvenLeuvenBelgium
  2. 2.Clinical Cardiac Surgery, Department of Cardiovascular SciencesKU LeuvenLeuvenBelgium
  3. 3.Translational MRI, Department of Imaging and PathologyKU LeuvenLeuvenBelgium

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