title: Evolving anisotropy and degree of elastolytic insult in abdominal aortic aneurysms: potential clinical relevance?
abstract: Accurately estimating patient-specific rupture risk remains a primary challenge in timing interventions for abdominal aortic aneurysms (AAAs). By re-analyzing published biaxial mechanical testing data from surgically repaired human AAAs, material anisotropy emerged as a potentially important determinant of patient-specific lesion progression. That is, based on a new classification scheme, we discovered that anisotropic aneurysmal specimens correlated with increased patient age at surgery when compared with more isotropic specimens (79.7 vs. 70.9 years, p<0.002), despite no significant difference in maximum diameter. Furthermore, using an idealized axisymmetric, finite-element growth and remodeling model of AAA progression, we found that both the initial axial extent of elastin loss and ongoing damage to elastin in the shoulder region of the AAA directly affected the degree of anisotropy as the lesion evolved, with more extensive insults increasing the anisotropy. This effect appeared to be mediated by alterations in axial loading and subsequent differences in orientation of deposited collagen fibers. While the observed increased age before surgical intervention may suggest a potential benefit of anisotropic remodeling, future biaxial tests coupled with pre-surgical data on expansion rates and detailed theoretical analyses of the biostability of a lesion as a function of anisotropy will be required to verify its clinical relevance to patient-specific rupture risk.
authors.affiliation: Department of Biomedical Engineering, Yale University, New Haven, CT 06520, USA.
authors.forename: John S
authors.initials: JS
authors.lastname: Wilson
authors.affiliation: Department of Biomedical Engineering, Yale University, New Haven, CT 06520, USA; Vascular Biology and Therapeutics Program, Yale School of Medicine, New Haven, CT 06520, USA. Electronic address: jay.humphrey@yale.edu.
authors.forename: J D
authors.initials: JD
authors.lastname: Humphrey
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D016880:Anisotropy; D001012:Aorta, Abdominal / Q000503:physiopathology; D017544:Aortic Aneurysm, Abdominal / Q000503:physiopathology*; D018450:Disease Progression; D004549:Elastin; D020342:Finite Element Analysis; D006801:Humans; D008875:Middle Aged; D008955:Models, Cardiovascular
chemical_list: D004549:Elastin
keywords: Axial stress; Computational biomechanics; Elastin damage; Growth and remodeling; Rupture risk; Stiffness
references.citation: J R Soc Interface. 2012 Dec 7;9(77):3366-77
references.pmid: 22896562
references.citation: Ann Vasc Surg. 2008 Jan;22(1):88-97
references.pmid: 18023556
references.citation: Cardiovasc Res. 2011 Nov 1;92(2):287-95
references.pmid: 21730037
references.citation: J Vasc Surg. 2003 Apr;37(4):724-32
references.pmid: 12663969
references.citation: Med Eng Phys. 2011 Jan;33(1):80-8
references.pmid: 20961796
references.citation: Eur J Vasc Endovasc Surg. 2011 Aug;42(2):207-19
references.pmid: 21440466
references.citation: Ann Biomed Eng. 2011 Jul;39(7):2010-26
references.pmid: 21373952
references.citation: J Biomech Eng. 2004 Dec;126(6):815-22
references.pmid: 15796340
references.citation: Pathobiology. 2013;80(1):11-23
references.pmid: 22797551
references.citation: J Biomech Eng. 2013 Feb;135(2):021011
references.pmid: 23445056
references.citation: Comput Methods Biomech Biomed Engin. 2011 Sep;14(9):803-17
references.pmid: 21480019
references.citation: Biomech Model Mechanobiol. 2004 Nov;3(2):98-113
references.pmid: 15452732
references.citation: J Vasc Surg. 2004 Jun;39(6):1243-52
references.pmid: 15192565
references.citation: Proc Math Phys Eng Sci. 2013 Feb 8;469(2150):20120556
references.pmid: 23633905
references.citation: J Am Coll Surg. 2004 Nov;199(5):709-15
references.pmid: 15501110
references.citation: J R Soc Interface. 2012 Sep 7;9(74):2047-58
references.pmid: 22491975
references.citation: J Vasc Surg. 1994 Jul;20(1):6-13
references.pmid: 8028090
references.citation: J Theor Biol. 2006 Jan 21;238(2):290-302
references.pmid: 16043190
references.citation: J Biomech Eng. 2006 Feb;128(1):142-9
references.pmid: 16532628
references.citation: J R Soc Interface. 2011 Mar 6;8(56):435-50
references.pmid: 20659928
references.citation: J Biomech. 2006;39(7):1324-34
references.pmid: 15885699
references.citation: J Biomech. 2007;40(10):2214-21
references.pmid: 17174959