engleski

Numerical Modeling of Abdominal Aortic Aneurysm Expansion

Abdominal aortic aneurysm (AAA) is a dilatation of aorta characterized by loss of functional elastin and smooth muscle cells, as well as enhanced production of collagen. The majority of AAAs includes an intraluminal thrombus (ILT) that decreases peak wall stress ; however, it also degrades aortic wall, thus reducing its strength. Aneurysm rupture has a high mortality rate. To help clinicians predict rupture, growth and remodeling models have been developed. Nevertheless, in hitherto conducted studies effect of ILT has been neglected. The doctoral thesis includes detailed biochemomechanical overview of the thrombus-laden aneurysms. Based on this review a new comprehensive growth and remodeling ILT model interconnected with kinematics of the aneurysmal aortic wall has been developed. The majority of parameters were chosen to fit experimental results and showed a great potential to predict behavior of AAAs. The remaining parameters were studied parametrically, describing most common rupture or stabilization risk factors. Changes in dilatation rates were compared to clinical observations, and insight into their influences on aneurysmal changes was given. The results also emphasize the necessity to include biochemical and biomechanical influences of ILT on the wall when predicting AAA outcome (rupture, continuous growth or stabilization). Finally, the 3-D growth and remodeling theory of aortic wall was implemented into finite element analysis program (FEAP), which enables simulation of more realistic aneurysm geometries – axially symmetric (fusiform) and non-symmetric (intracranial aneurysm). Results for fusiform aneurysms obtained by 3-D finite elements were compared to membrane element results available in literature. A great potential to model saccular aneurysms, and advantage of 3-D to 2-D elements was shown. The aim of AAA growth modeling is to increase understanding of aneurysm pathophysiology (e.g., "staccato” expansion), and to determine reliable rupture risk and stabilization factors.

abdominal aortic aneurysm, intraluminal thrombus, growth and remodeling, proteolytic activity, rupture risk factors

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