changes in hemodynamics induced by endovascular treatment
PRESENTING AUTHOR FULL NAME: Laurel M. M. Marsh
INSTITUTION: Department of Mechanical Engineering and Department of Neurological Surgery, University of Washington, Seattle, WA, USA
ADDITIONAL AUTHORS NAMES, AS TO BE PUBLISHED: Michael C. Barbour, Fanette Chassagne, Venkat K. Chivukula, Cory Kelly, Sam Levy, Louis J. Kim, Michael R. Levitt, Alberto Aliseda
BACKGROUND/PURPOSE: The endovascular treatment of cerebral aneurysms, either with flow diverting stents (FDS) or coil embolization, aims to produce hemodynamic conditions leading to a stable thrombus, thus preventing the risk of rupture of the aneurysm wall. After treatment, the flow velocity in the aneurysmal sac is significantly reduced which leads to higher residence times and the formation of a stable thrombus occluding the aneurysm. However, there is a high risk of treatment failure: the embolization of the aneurysm is not complete and these treated aneurysms remain at risk of rupture. The objective of this study is to assess the changes in hemodynamics induced by endovascular treatment, with either flow diverting stents or coils, via patient-specific computational fluid dynamics simulations.
METHOD: Patient-specific CFD simulations were created from angio-CT images before endovascular treatment for 44 patients. Velocity and pressure measurements were collected in the artery around the aneurysm with a ComboWire sensor (Volcano Corp, San Diego, CA) pre and post-treatment. These measurements were used to set up the inlet and outlet boundary conditions for both pre- and post-treatment simulations. Both treatment modalities were modeled by adding a sink term to the momentum equation, on a surface for the flow diverting stents (n=23) and in a volume for the coil mass (n=21).
RESULTS: The in vivo measurements pre- and post-treatment used as boundary conditions were very similar. Aneurysm flow rate, wall shear stress on the aneurysm dome and viscous dissipation within the aneurysm sac decreased significantly in the post-treatment CFD simulation for both treatment modalities. A larger decrease of velocity in the aneurysm was observed for the aneurysms treated with FDS compared to the ones treated with coils. Also, the reduction of wall shear stress on the aneurysm dome was larger for the patients treated with coils than for FDS. Despite the common goal of producing a stable thrombus in the aneurysmal sac, the changes in hemodynamics induced by both treatments were significantly different, with larger increases in shear stress at the aneurysmal neck for the coiled than the stented cases, and much larger decreases in flow rate into the sac for the stented versus coiled aneurysms.
CONCLUSION: This in silico study performed on a large cohort showed that flow-diverting stents and coils result in fundamentally different alterations to the hemodynamic in the aneurysmal sac following treatment. Different strategies need to be followed to understand the disparate hemodynamic conditions associated with successful treatment for these two treatment techniques.