Abdominal aortic aneurysm (AAA) is a focal enlargement of the infrarenal aorta. If left untreated, AAA will gradually expand until rupture; an event that carries a mortality rate of 90 percent and which is ranked as the 13th most common cause of death in the US. Associated with surgical repair of AAA are significant costs and risks to the patient. Thus, it is important to determine when the risk of rupture justifies the risks associated with surgery. The ability to reliably evaluate the susceptibility of a particular AAA to rupture could vastly improve the clinical management of these patients, as there presently exists no such reliable evaluation criterion. AAA rupture occurs when the mechanical stress (i.e., internal forces) acting on the aneurysm wall exceeds its ability to withstand these stresses (i.e., the wall's failure strength). The greater the wall stress to wall strength ratio for a particular AAA, the greater the likelihood of rupture. They therefore believe that a """"""""biomechanics-based approach"""""""" would lead to an improved assessment of the propensity for rupture of AAA on a patient-specific basis. Before the decision is made for surgical intervention for an individual patient, the investigators believe that the surgeon should know two things: the mechanical stress acting on that aneurysm and the strength of the AAA wall. They have recently made great strides toward these ends. However, to improve their AAA wall stress estimates the biomechanical behavior of the AAA wall needs to be more carefully and rigorously defined. Therefore, Specific Aim #1 is to refine their current methodology to account for the more realistic, anisotropic biomechanical behavior of AAA. They previously showed that there occurs a significant, 50 percent decrease in strength of the AAA wall versus nonaneurysmal aorta. However, they did not determine spatial variation of AAA wall strength.
Specific Aim #2 is to develop a statistically based, multifactorial model to noninvasively estimate spatial variation of AAA wall strength.
Specific Aim #3 is to generate the spatial variation of the rupture potential index (RPI) for individual AAA. The RPI is defined as the locally acting wall stress divided by the local wall strength. As the RPI nears a value of 1.0, AAA rupture is imminent. The clinician may therefore inspect the RPI distribution in order to make an evaluation for a particular AAA. This novel, innovative, computer-based noninvasive method would be an important and reliable diagnostic tool to guide the surgeon in decisions for elective repair of AAA, greatly improving the clinical management for those afflicted with this disease.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL060670-03
Application #
6629003
Study Section
Surgery and Bioengineering Study Section (SB)
Program Officer
Wassef, Momtaz K
Project Start
2001-02-15
Project End
2005-01-31
Budget Start
2003-02-01
Budget End
2004-01-31
Support Year
3
Fiscal Year
2003
Total Cost
$335,458
Indirect Cost
Name
University of Pittsburgh
Department
Surgery
Type
Schools of Medicine
DUNS #
004514360
City
Pittsburgh
State
PA
Country
United States
Zip Code
15213
Pichamuthu, Joseph E; Phillippi, Julie A; Cleary, Deborah A et al. (2013) Differential tensile strength and collagen composition in ascending aortic aneurysms by aortic valve phenotype. Ann Thorac Surg 96:2147-54
Doyle, Barry J; Killion, John; Callanan, Anthony (2012) Use of the photoelastic method and finite element analysis in the assessment of wall strain in abdominal aortic aneurysm models. J Biomech 45:1759-68
McGloughlin, Timothy M; Doyle, Barry J (2010) New approaches to abdominal aortic aneurysm rupture risk assessment: engineering insights with clinical gain. Arterioscler Thromb Vasc Biol 30:1687-94
Corbett, T J; Doyle, B J; Callanan, A et al. (2010) Engineering silicone rubbers for in vitro studies: creating AAA models and ILT analogues with physiological properties. J Biomech Eng 132:011008
Doyle, Barry J; Cloonan, Aidan J; Walsh, Michael T et al. (2010) Identification of rupture locations in patient-specific abdominal aortic aneurysms using experimental and computational techniques. J Biomech 43:1408-16
Doyle, B J; Grace, P A; Kavanagh, E G et al. (2009) Improved assessment and treatment of abdominal aortic aneurysms: the use of 3D reconstructions as a surgical guidance tool in endovascular repair. Ir J Med Sci 178:321-8
Doyle, Barry J; Corbett, Timothy J; Callanan, Anthony et al. (2009) An experimental and numerical comparison of the rupture locations of an abdominal aortic aneurysm. J Endovasc Ther 16:322-35
Doyle, Barry J; Callanan, Anthony; Burke, Paul E et al. (2009) Vessel asymmetry as an additional diagnostic tool in the assessment of abdominal aortic aneurysms. J Vasc Surg 49:443-54
Doyle, Barry J; Corbett, Timothy J; Cloonan, Aidan J et al. (2009) Experimental modelling of aortic aneurysms: novel applications of silicone rubbers. Med Eng Phys 31:1002-12
Doyle, B J; Morris, L G; Callanan, A et al. (2008) 3D reconstruction and manufacture of real abdominal aortic aneurysms: from CT scan to silicone model. J Biomech Eng 130:034501

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