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The Quasi-Static Failure Properties of the Abdominal Aortic Aneurysm Wall Estimated by a Mixed Experimental-Numerical Approach
KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Biomechanics.
KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Biomechanics.
2012 (English)In: Annals of Biomedical Engineering, ISSN 0090-6964, E-ISSN 1573-9686, Vol. 41, no 7, 1554-1566 p.Article in journal (Refereed) Published
Abstract [en]

Assessing the risk for abdominal aortic aneurysm (AAA) rupture is critical in the management of aneurysm patients and an individual assessment is possible with the biomechanical rupture risk assessment. Such an assessment could potentially be improved by a constitutive AAA wall model that accounts for irreversible damage-related deformations. Because of that the present study estimated the elastic and inelastic properties of the AAA wall through a mixed experimental-numerical approach. Specifically, finite element (FE) models of bone-shaped tensile specimens were used to merge data from failure testing of the AAA wall with their measured collagen orientation distribution. A histo-mechanical constitutive model for collagen fibers was employed, where plastic fibril sliding determined not only remaining deformations but also weakening of the fiber. The developed FE models were able to replicate the experimentally recorded load-displacement property of all 16 AAA wall specimens that were investigated in the study. Tensile testing in longitudinal direction of the AAA defined a Cauchy strength of 569(SD 411) kPa that was reached at a stretch of 1.436(SD 0.118). The stiffness and strength of specimens decreased with the wall thickness and were elevated (p = 0.018; p = 0.030) in patients with chronic obstructive pulmonary disease (COPD). Smoking affected the tissue parameters that were related to the irreversible deformation response, and no correlation with gender and age was found. The observed effects on the biomechanical properties of the AAA wall could have long-term consequences for the management of aneurysm patients, i.e., specifically they might influence future AAA rupture risk assessments. However, in order to design appropriate clinical validation studies our findings should firstly be verified in a larger patient cohort.

Place, publisher, year, edition, pages
Springer-Verlag New York, 2012. Vol. 41, no 7, 1554-1566 p.
Keyword [en]
Aneurysm rupture, Collagen, Constitutive modeling, Damage, Plasticity
National Category
Medical Biotechnology
Identifiers
URN: urn:nbn:se:kth:diva-122848DOI: 10.1007/s10439-012-0711-4ISI: 000320329200018Scopus ID: 2-s2.0-84879422869OAI: oai:DiVA.org:kth-122848DiVA: diva2:623594
Funder
Swedish Research Council, 2007-4514EU, FP7, Seventh Framework Programme, FAD-200647
Note

QC 20130719

Available from: 2013-05-28 Created: 2013-05-28 Last updated: 2017-12-06Bibliographically approved
In thesis
1. Failure of vascular tissue with applications to the aneurysm wall, carotid plaque and myocardial tissue
Open this publication in new window or tab >>Failure of vascular tissue with applications to the aneurysm wall, carotid plaque and myocardial tissue
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Cardiovascular disease is the leading cause of death in the modern world. Examples are thoracic aortic aneurysm (TAA), abdominal aortic aneurysm (AAA) and stroke due to plaque rupture. Failure in soft tissues caused by medical devices is also a medical challenge. In all these cardiovascular events a better prediction of failure of the tissue and a better understanding about the tissue properties will help in predicament and treatment. For example the diameter-based indication for surgical repair of AAA and TAAs is not sufficient and refined methods are needed. In this thesis failures of some soft vascular tissues, was studied. Experiments have been combined with numerical modeling to understand the elastic and failure properties of AAA, TAA and plaque tissue as well as the ventricular wall. Vascular tissue is anisotropic, time-dependent, nonlinear and shows large deformations. Among others this thesis showed the importance of viscoelasticity which motivates to develop a new continuum mechanical framework. In addition a large part of this thesis dealt with anisotropy of vascular tissue. For the first time the collagen orientation distribution in the AAA wall has been identified. Collagen and its distribution orientation is also an important feature of this tissue. There was a correlation between the strength and stiffness of the AAA samples with the decreasing wall thickness. Increased stiffness was found in the aortic wall of patients with chronic obstructive pulmonary disease (COPD) compared to patients that did not have COPD. As well as difference in stiffness of TAA tissue, in patients with non-pathologic and pathologic aortic valves. Some of the findings in this thesis could have a long-term consequence for management of risk of rupture in AAA, TAA and plaque.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. x, 30 p.
Series
Trita-HFL, ISSN 1104-6813 ; 0545
National Category
Other Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-122840 (URN)978-91-7501-798-3 (ISBN)
Public defence
2013-06-07, Sal D2, Lindstedtsvägen 5, KTH, Stockholm, 09:00 (English)
Opponent
Supervisors
Note

QC 20130528

Available from: 2013-05-28 Created: 2013-05-28 Last updated: 2013-05-29Bibliographically approved

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