A computational study on the biomechanical factors related to stent-graft models in the thoracic aorta

Abstract

Endovascular aortic stent-graft is a new, minimally invasive procedure for treating thoracic aortic diseases, and has quickly evolved to be one of the standard treatments subject to anatomic constraints. This procedure involves the placement of a self-expanding stent-graft system in a high-flow thoracic aorta. Stent-graft deployment in the thoracic aorta, especially close to the aortic arch, normally experiences a significant drag force which might lead to the risk of stent-graft failure. A comprehensive investigation on the biomechanical factors affecting the drag force on a stent-graft in the thoracic aorta is thus in order, and the goal is to perform an in-depth study on the contributing biomechanical factors. Three factors affecting the deployed stent-graft are considered, namely, the internal diameter of the vessel, the starting position of the graft and the diameter of curvature of the aortic arch. Computational fluid dynamic techniques are applied to model the blood flow. The inlet velocity and outlet pressure are assumed to be pulsatile. The three-dimensional continuity equation and the time-dependent Navier-Stokes equations for an incompressible fluid were solved numerically. The drag force due to the change of momentum within the stent-graft and the shear stress were calculated and analyzed. The drag force on a stent-graft will depend critically on the internal diameter and the starting position of stent-graft deployment. Larger internal diameter leads to larger drag force and the stent-graft deployed at the more distal position may be associated with significantly diminished drag force. Smaller diameter of curvature of the aortic arch probably results in a decline of the drag force on the stent-graft, even though this factor merely causes only a modest difference. These findings may have important implications for the choice and design of stent-grafts in the future.

A Liquid-Solid Coupling Hemodynamic Model with Microcirculation Load

“…The inlet condition was velocity inlet, which was used for simulating the process of cardiac impulse. Systole was 0-0.2 s, and the maximum systolic velocity was 0.8 m/s [17]. Diastole ranged from 0.2 s to the end of a cardiac cycle.…”

Pulsatile spiral blood flow through arterial stenosis

“…In large arteries such as the one under investigation in this model, blood can be assumed to behave as a Newtonian fluid (Lam, Fung, Cheng, & Chow, 2008) and hence the continuity equation and the Reynolds averaged Navier-Stokes equations can be written in tensor form as;…”

Personalised imaging and biomechanical modelling of large vessels

“…Two other papers [1, 2] describe methods to develop a cascade of methods to start from an image and end with a wall stress or shear stress field in either the carotid artery [1] and aortas [2]. These methods are essential for obtaining patient specific information in the clinical environment.In the next series of papers, the pathophysiology of diseases is deepened by showing that haemodynamics contributes factors to the formation of brain aneurysm [3], aneurysm expansion [4] and stent-graft vessel wall interaction [5]. Chien et al [3] show that in ruptured aneurysm the flow field is different compared to flow fields in aneurysm without rupture.…”

“…In the next series of papers, the pathophysiology of diseases is deepened by showing that haemodynamics contributes factors to the formation of brain aneurysm [3], aneurysm expansion [4] and stent-graft vessel wall interaction [5]. Chien et al [3] show that in ruptured aneurysm the flow field is different compared to flow fields in aneurysm without rupture.…”

“…The question is whether this difference could have been detected before rupture occurred. Helderman et al [4] develop a general method to predict aneurysm expansion, while Lam et al [5] describe the parameters that will help to better design stents.…”