The effect of angulation in abdominal aortic aneurysms: fluid–structure interaction simulations of idealized geometries

Abstract

Abdominal aortic aneurysm (AAA) represents a degenerative disease process of the abdominal aorta that results in dilation and permanent remodeling of the arterial wall. A fluid structure interaction (FSI) parametric study was conducted to evaluate the progression of aneurysmal disease and its possible implications on risk of rupture. Two parametric studies were conducted using (i) the iliac bifurcation angle and (ii) the AAA neck angulation. Idealized streamlined AAA geometries were employed. The simulations were carried out using both isotropic and anisotropic wall material models. The parameters were based on CT scans measurements obtained from a population of patients. The results indicate that the peak wall stresses increased with increasing iliac and neck inlet angles. Wall shear stress (WSS) and fluid pressure were analyzed and correlated with the wall stresses for both sets of studies. An adaptation response of a temporary reduction of the peak wall stresses seem to correlate to a certain extent with increasing iliac angles. For the neck angulation studies it appears that a breakdown from symmetric vortices at the AAA inlet into a single larger vortex significantly increases the wall stress. Our parametric FSI study demonstrates the adaptation response during aneurysmal disease progression and its possible effects on the AAA risk of rupture. This dependence on geometric parameters of the AAA can be used as an additional diagnostic tool to help clinicians reach informed decisions in establishing whether a risky surgical intervention is warranted.

Strategy of endovascular versus open repair for patients with clinical diagnosis of ruptured abdominal aortic aneurysm: the IMPROVE RCT

“…Previously, it has been indicated that AAA wall stress increased with both iliac bifurcation angle and aortic neck angle, whereas AAA WSS remained almost constant. 110 This might suggest that AAAs with higher proximal neck angles and iliac bifurcation angles are at a higher risk of rupture. However, the recent comparisons of the morphology of ruptured AAAs and intact AAAs (see The comparative aortic morphology of intact and ruptured abdominal aortic aneurysms) have questioned these suggestions and hinted that AAAs with wider iliac bifurcations might be less prone to rupture, despite other morphological factors.…”

Microcalcifications Increase Coronary Vulnerable Plaque Rupture Potential: A Patient-Based Micro-CT Fluid–Structure Interaction Study

“…43,44 Briefly, the fluid was assumed to be Newtonian with a density of q = 1.050 g/cm 3 and dynamic viscosity of l = 0.035 g/(cm s), representing human blood properties at 37°C. The fluid domain is governed by the Navier-Stokes and the continuity equations.…”

“…Large strains and large deformations were considered as described before. 43,44 Boundary Conditions and Phase Lag Physiological pressure conditions were applied at the outlet of the vessel utilizing pressure waveform. Velocity waveforms for the complete cardiac cycle were assigned at the inlet.…”

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

“…The AAA arises in the infrarenal aorta with a diameter greater than 3 cm and can be up to 9 cm in length [1,2]. Most of the studies on aneurysms have focused on already existing realistic or idealized aneurysms [33][34][35][36][37][38][39][40][41][42][43] with the aim of defining a relevant rupture criterion [4,7,10,19,20,24]. The ratio of the vessel stress to vessel strength is regarded as an alternative tool to conventional diameter criteria, which may be insufficient in small aneurysms.…”