Haemodynamics and the Site Specificity of Aneurysmal Disease in the Iliac Arteries
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An aneurysm is a localised dilation of an artery wall that is life threatening when ruptured. Iliac artery aneurysms (IAA) may occur in isolation, but often accompany other large artery aneurysms, such as abdominal aortic aneurysms (AAA). For people over 65 years, the prevalence of AAA is high, at approximately 5–6% for men and 1–2% for women. Of the iliac arteries, aneurysms often occur in the common and internal iliac arteries, but are rarely found in the external iliac arteries. These three arteries are in close proximity to each another, and there is no obvious explanation as to why aneurysms form in certain arteries and not others. The aim of this investigation is to examine the site specificity of aneurysmal disease in the iliac arteries using computational fluid dynamic (CFD) models. The commercial CFD solver, STAR-CCM+ was used to calculate the three-dimensional, unsteady numerical solutions to the Navier-Stokes equations for laminar, pulsatile blood flow through both a healthy and a diseased patient arterial geometry. The modelling methodology focused on commonly-used and recommended practices associated with large artery CFD. The TimeAveraged Wall Shear Stress (TAWSS), maximal wall shear stress and Oscillatory Shear Index (OSI) were investigated and compared with the physical stresses and flow phenomena commonly associated with aneurysmal disease. The results support the low-flow, or low wall shear stress theory for the site specificity of aneurysmal progression. Only aneurysmal-prone regions are afflicted with areas of TAWSS low enough for the onset of monocyte adhesion; associated with a local inflammatory response and the degradation of the extracellular matrix. Also, the aneurysmal-prone regions show no focal increases in wall shear stress values (that is, there is no indication of ‘high-flow’ aneurysmal progression). While there are some improvements that should be made to the models, the results provide a strong foundation for future CFD investigations into aneurysmal disease within the iliac arteries.

The University of Western Australia
Friday, May 16, 2014
Author Name: 
Lachlan J. Kelsey