Introduction: A 42 year-old male presented with a left middle cerebral artery stroke associated with an internal carotid artery web and only moderate stenosis. Although initially treated with medications, he later presented with recurrent strokes due to thrombus formation distal to the stenosis. In order to learn from this experience, patient-specific imaging information was combined with computational fluid dynamics (CFD) with the goal of predicting thrombus formation in the setting of carotid webs.
Methods: 3D volume rendering models were constructed for both the unhealthy ipsilateral and healthy contralateral carotid artery using source images from the CT angiogram. Models were meshed with Scan IP (Simpleware Inc,V 7.0) then exported to Fluent (Ansys Inc.) for CFD simulations. A mesh sensitivity analysis was conducted, then simulations were carried out with the appropriate mesh and time step for 4 cardiac cycles to dampen the transient effects. Recirculation patterns were obtained, as well as output parameters including wall shear stress (WSS) and residence time (RT), which have been previously associated with thrombus formation and stroke (1,2).
Results: Preliminary results reveal that a mesh with 1,500,000 tetrahedral elements is sufficient for this CFD simulation along with a time step of 0.0025 sec (Figure 1). A recirculation region just distal to the carotid web was observed (Figure 2). We expect our calculations to reveal areas of low wall shear stress and increased residence time at the site of the carotid web. Both of these findings are strongly predictive of thrombus formation.
Conclusions: CFD is a useful method for predicting thrombus formation in patients with carotid webs. Additional patients are required to determine a clinically relevant parameter, such as WSS or RT, which may be helpful in determining the best course of management in these patients who are at particularly high risk of recurrent stroke despite only mild or moderate stenosis.
Patient Care: This research can help determine the best course of management in patients with carotid webs, using output parameters from CFD studies and patient-specific information.
Learning Objectives: By the conclusion of this session, participants should be able to:
1.Understand the natural history of the carotid artery web phenomenon.
2.Identify the importance of CFD modeling for predicting future thrombus formation in order to avoid recurrent strokes.
References: 1.Arab-Ghanbari M, Khani M, Arefmanesh A, Tabatabai-Ghomshe F. Analysis of Blood Turbulent Flow in Carotid Artery Including the Effects of Mural Thrombosis Using Finite Element Modeling. American Journal of Applied Sciences. 2009;6(2):337.
2.Rayz VL, Boussel L, Ge L, Leach JR, Martin AJ, Lawton MT, et al. Flow residence time and regions of intraluminal thrombus deposition in intracranial aneurysms. Annals of biomedical engineering. 2010;38(10):3058-69.