Predicting Thrombus Formation in Patients with Internal Carotid Artery Webs

Introduction A 42 year-old male presented with a left middle cerebral artery stroke associated with an ICA web and only moderate stenosis. Although initially treated with medications, he later presented with recurrent strokes... [ view full abstract ]

Introduction
A 42 year-old male presented with a left middle cerebral artery stroke associated with an ICA web and only moderate stenosis. Although initially treated with medications, he later presented with recurrent strokes due to thrombus formation distal to the stenosis. To gain insight from this occurrence, patient-specific imaging information was combined with CFD analysis for predicting thrombus formation in the setting of carotid webs.

Goals
1.Conduct comparative analysis of unhealthy and healthy carotid artery.
2. Identify flow dynamics that could be used to predict future thrombus formation in settings of carotid webs,to avoid recurrent strokes.

Method
3D volume rendering models were constructed for both ipsilateral and contralateral carotid artery using Scan IP(Simpleware Inc,V 7.0), exported to Fluent(Ansys Inc, V15.0). A mesh sensitivity analysis was conducted to achieve stabilization of WSS. Unsteady simulations were conducted with flow division ratio boundary conditions.

Results
Low time-averaged wall shear stress(TAWSS) values, which can be associated with wall thickening, were found in the unhealthy(left)carotid arising from sudden flow expansion behind the web(Fig.1).Elevated oscillatory shear index values were found at the site of the web confirming instantaneous WSS deviation from primary flow direction(Fig. 2).The same location showed high values of relative residence time(RRT),which is directly proportional to chances of thrombus formation(Fig. 3).

Conclusions
We found altered hemodynamic parameters in the unhealthy carotid that have been previously associated with thrombus formation and stroke(1,2).Study is being conducted on additional patients to validate these findings.

References
1.Arab-Ghanbari. American Journal of Applied Sciences.2009;6(2):337.
2.Rayz VL. Annals of biomedical engineering.2010;38(10):3058-69.