Biomechanics of Abdominal Aortic Aneurysms
نویسندگان
چکیده
An abdominal aortic aneurysm (AAA) is a complex vascular pathology which leads to a localized and asymmetric dilation of the abdominal aorta. Ruptures of untreated AAAs are common and catastrophic events which may account for high mortality rates, particularly in elder males. It is well known that biomechanical factors play fundamental roles in AAA lesion growth, remodeling and rupture. Compared to tremendous advances during the past decade in our understanding of the biomechanics of diseased aneurysmal tissue and healthy aorta, it is more important to explore changes in the biomechanical properties of aneurysmal tissue in the AAA pathological progression. This provides us a basis to better understand AAA degeneration and the associated rupture mechanism, from a mechanical point of view. This PhD thesis mainly focuses on experimental investigations of the biomechanical properties of two major types of tissues within the AAA, i.e. intraluminal thrombus (ILT) and thrombus-covered wall. By performing biaxial extension and peeling tests, we systematically explore biaxial mechanical responses and quantitatively determine dissection properties of ILTs and the thrombus-covered walls, and further develop a more appropriate 3D material model to characterize the biaxial mechanical behaviors of both tissue types. Another key contribution of this thesis is to determine the relative thrombus age within the AAA by characterizing the microstructure of ILT samples using histology and by investigating changes in the biomechanical properties of thrombotic tissues. As a novel factor in the AAA research, the relative thrombus age is critically important to show the initiation and progression of the ILT and its potential effects on AAA wall mechanics. Further, we find that ILT aging relates to wall weakening in the AAAs. Mass fraction analysis is aiming to quantify dry weight percentages of two protein components elastin and collagen within the AAA wall, which, in turn, determine mechanical properties at the tissue level. Moreover, gender differences in biomechanical properties of AAA are also discussed.
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