Impact of Stents and Flow Diverters on Hemodynamics in Idealized Aneurysm Models

Abstract

Cerebral aneurysms constitute a major medical challenge as treatment options are limited and often associated with high risks. Statistically, up to 3% of patients with a brain aneurysm may suffer from bleeding for each year of life. Eight percent of all strokes are caused by ruptured aneurysms. In order to prevent this rupture, endovascular stenting using so called flow diverters is increasingly being regarded as an alternative to the established coil occlusion method in minimally invasive treatment. Covering the neck of an aneurysm with a flow diverter has the potential to alter the hemodynamics in such a way as to induce thrombosis within the aneurysm sac, stopping its further growth, preventing its rupture and possibly leading to complete resorption. In the present study the influence of different flow diverters is quantified considering idealized patient configurations, with a spherical sidewall aneurysm placed on either a straight or a curved parent vessel. All important hemodynamic parameters (exchange flow rate, velocity, and wall shear stress) are determined in a quantitative and accurate manner using computational fluid dynamics when varying the key geometrical properties of the aneurysm. All simulations are carried out using an incompressible, Newtonian fluid with steady conditions. As a whole, 72 different cases have been considered in this systematic study. In this manner, it becomes possible to compare the efficiency of different stents and flow diverters as a function of wire density and thickness. The results show that the intra-aneurysmal flow velocity, wall shear stress, mean velocity, and vortex topology can be considerably modified thanks to insertion of a suitable implant. Intra-aneurysmal residence time is found to increase rapidly with decreasing stent porosity. Of the three different implants considered in this study, the one with the highest wire density shows the highest increase of intra-aneurysmal residence time for both the straight and the curved parent vessels. The best hemodynamic modifications are always obtained for a small aneurysm diameter.

Blood Flow Clustering and Applications inVirtual Stenting of Intracranial Aneurysms

“…Streamlines are employed for comparing flow patterns. They are often seeded on the ostium and displayed side-by-side [2], [6], [16]. However, either the entire set of lines is displayed leading to visual clutter or representative lines must be selected manually.…”

Total Endovascular Repair of Thoracoabdominal Aortic Aneurysms With Non-Customized Stent Grafts

“…In a computational fluid dynamic study performed by Seshadhri and colleagues [28], the hemodynamic effects of the flow-diverting stents were analyzed, taking into account the morphologic characters of the aneurysm. The investigators found that the "dome to neck ratio (D/N ratio)" was crucial in determining the flow-modulating effect of the porous stents (Fig 5).…”

Recommendations for accurate numerical blood flow simulations of stented intracranial aneurysms

“…Additionally, the flow stasis within the aneurysm has been computed from the turnover time [22,36] and is shown in Table 2 as well. This turnover time is determined by dividing the full aneurysm volume by the inlet volume flow rate found at the aneurysm neck, defined as a straight plane placed directly above the stent.…”