Abstract
An abdominal aortic aneurysm (AAA) is an enlargement of the abdominal aorta that can become a life-threatening disease. The pulsatile blood flow exhibits intricate laminar patterns in the abdominal portion of the human aorta under normal resting conditions, whereas secondary flows are caused by adjacent branches and abnormal vessel geometries. If a pathological disorder (e.g., aneurysm) alters the structural composition of the artery wall, the flow dynamics become more complex. In this study, we analyzed the hemodynamics of pulsatile blood flow in three-dimensional AAA models. Computational predictions of hemodynamic changes were performed considering idealized models for four severe proximal neck angulations of symmetric aneurysms assuming conditions of laminar flow and a rigid artery wall. The predictions were based on computational fluid dynamics throughout the cardiac cycle. Postprocessing was used to visualize the numerical findings. The hemodynamic changes in factors such as velocity, flow streamline, pressure, and wall shear stress were obtained and visualized. The resulting blood flow through the severely angulated proximal neck of the abdominal aorta caused strong turbulence and asymmetric flow inside the aneurysm sac, leading to blood recirculation, especially during diastole. The simulation results showed the formation of regions with high and low wall shear stress, turbulent flow, and recirculation in the aneurysm sac depending on the angulation, which could have led to aortic wall weakness.
Highlights
An abdominal aortic aneurysm (AAA) is one of the most life-threatening cardiovascular diseases worldwide [1]
Hemodynamic parameters including blood flow velocity, pressure, wall shear stress (WSS), time-averaged WSS (TAWSS), and oscillatory shear index (OSI) for pulsatile simulations were investigated at several instants of the cardiac cycle: early systole, peak systole, late systole, early diastole, mid-diastole, and late diastole
The grid convergence index (GCI) was subject to a mesh refinement ratio ri equal to dvi/dvi+1 because the volume across simulations was similar
Summary
An abdominal aortic aneurysm (AAA) is one of the most life-threatening cardiovascular diseases worldwide [1]. In the USA, AAA fatality ranks 14th among people aged over 60 years, with a higher prevalence (8.9%) in men than in women [2,3]. The maximum diameter of an aneurysm is employed as an indicator of aortic rupture and to determine whether surgical intervention is required [7]. This indicator may be an inaccurate predictor of rupture [1,8], and new indicators such as hemodynamic parameters have been used for improved prediction of aneurysm rupture [9]
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