A Rule-Based Computational Study on the Early Progression of Intracranial Aneurysms Using Fluid-Structure Interaction: Comparison between Straight Model and Curved Model

Abstract

Study of the development of aneurysm is a difficult task due to lack of experimental and clinical data. The current study takes advantage of fluid-structure interaction (FSI) to simulate the formation and growth of aneurysms by focusing on the interplay between the wall shear stress, degeneration of the vessel wall, and the wall deformation. We construct numerical aneurysm models arisen from both straight and curved arteries, under the hypothesis that high local wall shear stress larger than a certain threshold value will lead to a linear decrease in the wall mechanical properties. In the straight model, the growth of aneurysm is small and only at the distal neck region, and the aneurysm stops growing after several steps. In contrast, in the curved model, the aneurysm continues to grow in height and width. Our computer simulation study shows that even if the wall shear stress inside an aneurysm is low, aneurysm development can occur due to degeneration of the wall distal and proximal to the aneurysm. Our study demonstrates the potential utility of rule-based numerical methods in the investigation of developmental biology of cardiovascular diseases.

Investigation of material modeling in fluid–structure interaction analysis of an idealized three-layered abdominal aorta: aneurysm initiation and fully developed aneurysms

“…The Young's modulus ratio for intima/media/adventitia was assumed to be 1/3/2 [40,59]. Degeneration was applied on the media layer by decreasing its modulus of elasticity or the coefficients of the strain energy function by 1/20 [51]. The degenerated regions of four different sizes are shown in Fig.…”

“…They modeled the initiation of an aneurysm by decreasing Young's modulus of elasticity at a local region where hypothetical SMC relaxation was considered. Feng et al [50,51] made a similar assumption considering that high wall shear stress (WSS) causes wall weakening. They decreased the modulus of elasticity at the regions of high WSS in curved and straight idealized intracranial arterial geometries.…”

Modelling evolution and the evolving mechanical environment of saccular cerebral aneurysms

“…One criticism of the above models is that whilst they simulated the structural adaption of the tissue, they did not relate this to the evolving haemodynamic environment. Feng et al 2004Feng et al , 2008 appear to be the first to couple evolution to haemodynamic stimuli and Chatziprodromou et al 2007 also highlight the need to consider the role of the haemodynamics, e.g. WSS, on the influence on aneurysm evolution.…”

A realistic simulation of saccular cerebral aneurysm formation: focussing on a novel haemodynamic index, the gradient oscillatory number

“…For example, our group proposed a simulation model by hypothesising the existence of a threshold in the WSS above which Young's modulus of the arterial wall would decrease by a constant ratio (Feng et al 2008). Although the result of this study was suggestive, the resultant aneurysms were fusiform, while most cerebral aneurysms are saccular.…”