The Biaxial Biomechanical Behavior of Abdominal Aortic Aneurysm Tissue
Rupture of the abdominal aortic aneurysm (AAA) occurs when the local wall stress exceeds the local wall strength. Knowledge of AAA wall mechanics plays a fundamental role in the development and advancement of AAA rupture risk assessment tools. Therefore, the aim of this study is to evaluate the biaxial mechanical properties of AAA tissue. Multiple biaxial test protocols were performed on AAA samples harvested from 28 patients undergoing open surgical repair. Both the Tangential Modulus (TM) and stretch ratio (λ) were recorded and compared in both the circumferential (ϴ) and longitudinal (L) directions at physiologically relevant stress levels, the influence of patient specific factors such as sex, age AAA diameter and status were examined. The biomechanical response was also fit to a hyperplastic material model. The AAA tissue was found to be anisotropic with a greater tendency to stiffen in the circumferential direction compared to the longitudinal direction. An anisotropic hyperelastic constitutive model represented the data well and the properties were not influenced by the investigated patient specific factors however, a future study utilizing a larger cohort of patients is warranted to confirm these findings. This work provides further insights on the biomechanical behavior of AAA and may be useful in the development of more reliable rupture risk assessment tools.
KeywordsMechanical properties AAA Anisotropy
The authors would like to thank the Irish Research Council ‘EMBARK Initiative’ (Grant No. IDRS/2010/2941) for funding this study. BJD would like to acknowledge The University of Western Australia Research Fellowship and NHMRC Project Grant APP1063986. This work was supported by the Irish Government’s Programme for Research in Third Level Institutions Cycle 5, with the assistance of the European Regional Development Fund. The authors would also like to thank the Department of Vascular Surgery, University Hospital Limerick, Ireland, in particular Dr. Peter Coyle, for their help in harvesting and collecting the AAA tissue and also Caleb Horst for providing technical support for the Cellscale Biotester.
Conflict of interest
There are no conflicts of interest.
- 2.Buijs, R., T. Willems, R. Tio, H. Boersma, I. Tielliu, R. Slart, et al. Calcification as a risk factor for rupture of abdominal aortic aneurysm. Eur. J. Vasc. Endovasc. Surg. 6:542–548, 2013.Google Scholar
- 7.Darling, R., C. Messina, and D. Brewster. Autospsy of unoperated aortic aneurysms. The case of early resection. Circulation 56:164, 1977.Google Scholar
- 12.Kamenskiy A., Y. Dzenis, S. J. Kazmi, M. Pemberton, I. Pipinos, N. Phillips, et al. Biaxial mechanical properties of the human thoracic and abdominal aorta, common carotid, subclavian, renal and common iliac arteries. Biomech Model Mechanobiol. 2014. doi: 10.1007/s10237-014-0576-6.
- 19.O’Leary S., B. Doyle, and T. McGloughlin. The impact of long term freezing on the mechanical properties of porcine aortic tissue. J. Mech. Behav. Biomed. 37:165–173, 2014.Google Scholar
- 31.Tavares Monteiro J., E. Simão da Silva, M. Raghavan, P. Puech-Leão, M. Higuchi, and J. Otoch. Histologic, histochemical, and biomechanical properties of fragments isolated from the anterior wall of abdominal aortic aneurysms. J. Vasc. Surg. 59:1393–1401, 2013.Google Scholar
- 33.Thompson, S. G., L. C. Brown, M. J. Sweeting, M. J. Bown, L. G. Kim, M. J. Glover, et al. Systematic review and meta-analysis of the growth and rupture rates of small abdominal aortic aneurysms: implications for surveillance intervals and their cost-effectiveness. Health Technol. Assess. 17:1–118, 2013.PubMedCrossRefGoogle Scholar
- 35.Tong, J., T. Cohnert, P. Regitnig, and G. Holzapfel. Effects of age on the elastic properties of the intraluminal thrombus and the thrombus-covered wall in abdominal aortic aneurysms: biaxial extension behaviour and material modelling. Eur. J. Vasc. Endovasc. Surg. 42:207–219, 2011.PubMedCrossRefGoogle Scholar