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

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.

The Correlation of Aortic Neck Angle and Length in Abdominal Aortic Aneurysm with Severe Neck Angulation for Prediction of Intraoperative Neck Complications and Postoperative Outcomes after Endovascular Aneurysm Repair

“…EVAR within a hostile neck anatomy, particularly in short and severe neck angulation, is associated with poor early and late outcomes [ 3 , 5 ]. One study of AAA with severely angulated necks revealed significant changes in velocity, flow streamline, pressure, and wall shear stress inside the aneurysm sac [ 16 ]. These findings provide valuable insights that can help predict the occurrence of ruptured AAA.…”

The Correlation of Aortic Neck Angle and Length in Abdominal Aortic Aneurysm with Severe Neck Angulation for Prediction of Intraoperative Neck Complications and Postoperative Outcomes after Endovascular Aneurysm Repair

“…EVAR within a hostile neck anatomy, particularly in short severe neck angulation, is associated with poor early and late outcomes [3,5]. One study of AAA with severely angulated necks revealed significant changes in velocity, flow streamline, pressure, and wall shear stress inside the aneurysm sac [16]. These findings provide valuable insights that can help predict the occurrence of ruptured AAA.…”

Intraluminal Thrombus Characteristics in AAA Patients: Non-Invasive Diagnosis Using CFD

“…In our study, this PC-MRI-based volumetric flow was converted to a corresponding velocity waveform and applied as an inlet boundary condition for each patient (an example shown for P1 in Figure 3). A zero-reference pressure was imposed at the outlet boundaries [14,[39][40][41]. The temporal variations of the physiological velocity inlet condition were reproduced by Fourier series and implemented through a "user_defined_function" (UDF) script.…”