Computational study on hemodynamic changes in patient-specific proximal neck angulation of abdominal aortic aneurysm with time-varying velocity

Abstract

Aneurysms are considered as a critical cardiovascular disease worldwide when they rupture. The clinical understanding of geometrical impact on the flow behaviour and biomechanics of abdominal aortic aneurysm (AAA) is progressively developing. Proximal neck angulations of AAAs are believed to influence the hemodynamic changes and wall shear stress (WSS) within AAAs. Our aim was to perform pulsatile simulations using computational fluid dynamics (CFD) for patient-specific geometry to investigate the influence of severe angular (≥ 60) neck on AAA's hemodynamic and wall shear stress. The patient's geometrical characteristics were obtained from a computed tomography images database of AAA patients. The AAA geometry was reconstructed using Mimics software. In computational method, blood was assumed Newtonian fluid and an inlet varying velocity waveform in a cardiac cycle was assigned. The CFD study was performed with ANSYS software. The results of flow behaviours indicated that the blood flow through severe bending of angular neck leads to high turbulence and asymmetry of flows within the aneurysm sac resulting in blood recirculation. The high wall shear stress (WSS) occurred near the AAA neck and on surface of aneurysm sac. This study explained and showed flow behaviours and WSS progression within high angular neck AAA and risk prediction of abdominal aorta rupture. We expect that the visualization of blood flow and hemodynamic changes resulted from CFD simulation could be as an extra tool to assist clinicians during a decision making when estimation the risks of interventional procedures.

Biomechanical Assessment of Bicuspid Aortic Valve Phenotypes: A Fluid–Structure Interaction Modelling Approach

“…(data in supplementary material: [80]). In addition, a previous study employing laminar flow to study aortic valve calcification did not find a laminar flow model to limit the predicted results [26].…”

Computational Study of Abdominal Aortic Aneurysms with Severely Angulated Neck Based on Transient Hemodynamics Using an Idealized Model

“…Blood was assumed to be a Newtonian fluid with a constant dynamic viscosity of 0.0035 Pa•s and a density of 1060 kg/m 3 [16,32]. The Newtonian fluid assumption is reasonable in larger arteries because non-Newtonian effects mostly occur in small vessels [23,33]. Moreover, because the blood flow within blood vessels is pulsatile [34], a user-defined function for a time-dependent velocity waveform was applied at the inlet throughout a cardiac cycle with a velocity ranging between −0.05 and 0.3 m/s, as shown in Figure 3.…”

Computational analysis to predict the effect of pre-bifurcation stenosis on the hemodynamics of the internal and external carotid arteries

“…The assumption of a supine position was used, so that the body force term was omitted from the Navier-Stokes equations [37], and the κ-ɛ turbulence model was used as the peak Reynolds numbers were above that anticipated for laminar flow. The effect of laminar versus turbulent flow predictions in CFD models reconstructed from clinical scans has been presented elsewhere [13].…”

“…Therefore, there has been much focus on understanding vascular plaque formation and predicting the effects of stenosis on hemodynamics [10][11][12]. One such approach is to use numerical models to calculate blood flow [13]. As blood flow through the circulatory system is pulsatile, computational studies use transient models [8,14,15].…”