Determining the influence of calcification on the failure properties of abdominal aortic aneurysm (AAA) tissue

Siobhan A O'Leary; John J Mulvihill; Hilary E Barrett; Eamon G Kavanagh; Michael T Walsh; Tim M McGloughlin; Barry J Doyle

doi:10.1016/j.jmbbm.2014.11.005

Determining the influence of calcification on the failure properties of abdominal aortic aneurysm (AAA) tissue

J Mech Behav Biomed Mater. 2015 Feb:42:154-67. doi: 10.1016/j.jmbbm.2014.11.005. Epub 2014 Nov 11.

Authors

Siobhan A O'Leary¹, John J Mulvihill¹, Hilary E Barrett¹, Eamon G Kavanagh², Michael T Walsh¹, Tim M McGloughlin³, Barry J Doyle⁴

Affiliations

¹ Centre for Applied Biomedical Engineering Research, Materials and Surfaces Science Institute, Mechanical, Aeronautical and Biomedical Engineering Department, University of Limerick, Limerick, Ireland.
² Department of Vascular Surgery, University Hospital Limerick, Limerick, Ireland.
³ Centre for Applied Biomedical Engineering Research, Materials and Surfaces Science Institute, Mechanical, Aeronautical and Biomedical Engineering Department, University of Limerick, Limerick, Ireland; Department of Biomedical Engineering, Khalifa University of Science, Technology & Research (KUSTAR), P.O. Box: 127788, Abu Dhabi, UAE.
⁴ Vascular Engineering, Intelligent Systems for Medicine Laboratory, School of Mechanical and Chemical Engineering, The University of Western Australia, Perth, WA 6009, Australia; Centre for Cardiovascular Science, The University of Edinburgh, Edinburgh, United Kingdom. Electronic address: barry.doyle@uwa.edu.au.

PMID: 25482218
DOI: 10.1016/j.jmbbm.2014.11.005

Abstract

Varying degrees of calcification are present in most abdominal aortic aneurysms (AAAs). However, their impact on AAA failure properties and AAA rupture risk is unclear. The aim of this work is evaluate and compare the failure properties of partially calcified and predominantly fibrous AAA tissue and investigate the potential reasons for failure. Uniaxial mechanical testing was performed on AAA samples harvested from 31 patients undergoing open surgical repair. Individual tensile samples were divided into two groups: fibrous (n=31) and partially calcified (n=38). The presence of calcification was confirmed by fourier transform infrared spectroscopy (FTIR). A total of 69 mechanical tests were performed and the failure stretch (λf), failure stress (σf) and failure tension (Tf) were recorded for each test. Following mechanical testing, the failure sites of a subset of both tissue types were examined using scanning electron microscopy (SEM)/energy dispersive X-ray spectroscopy (EDS) to investigate the potential reasons for failure. It has been shown that the failure properties of partially calcified tissue are significantly reduced compared to fibrous tissue and SEM and EDS results suggest that the junction between a calcification deposit and the fibrous matrix is highly susceptible to failure. This study implicates the presence of calcification as a key player in AAA rupture risk and provides further motivation for the development of non-invasive methods of measuring calcification.

Keywords: AAA; Abdominal aortic aneurysm; Calcification; Failure properties; Material properties; Rupture risk; Wall strength.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Aged
Aortic Aneurysm, Abdominal / pathology*
Aortic Aneurysm, Abdominal / physiopathology*
Aortic Rupture / pathology*
Aortic Rupture / physiopathology*
Biomechanical Phenomena
Calcification, Physiologic*
Female
Humans
Male
Mechanical Phenomena*