Computational Fluid-Dynamic Analysis after Carotid Endarterectomy: Patch Graft versus Direct Suture Closure

Abstract

Closure technique after carotid endarterectomy (CEA) still remains an issue of debate. Routine use of patch graft (PG) has been advocated to reduce restenosis, stroke, and death, but its protective effect, particularly from late restenosis, is less evident and recent studies call into question this thesis. This study aims to compare PG and direct suture (DS) by means of computational fluid dynamics (CFD). To identify carotid regions with flow recirculation more prone to restenosis development, we analyzed time-averaged oscillatory shear index (OSI) and relative residence time (RRT), that are well-known indices correlated with plaque formation. CFD was performed in 12 patients (13 carotids) who underwent surgery for stenosis >70%, 9 with PG, and 4 with DS. Flow conditions were modeled using patient-specific boundary conditions derived from Doppler ultrasound and geometries from magnetic resonance angiography. Mean value of the spatial averaged OSI resulted 0.07 for PG group and 0.03 for DS group, the percentage of area with OSI above a threshold of 0.2 resulted 10.1% and 3.7%, respectively. The mean of averaged-in-space RRT values was 4.4 1/Pa for PG group and 1.6 1/Pa for DS group, the percentage of area with RRT values above a threshold of 4 1/Pa resulted 22.5% and 6.5%, respectively. Both OSI and RRT values resulted higher when PG was preferred to DS and also areas with disturbed flow resulted wider. The absolute higher values computed by means of CFD were observed when PG was used indiscriminately regardless of carotid diameters. DS does not seem to create negative hemodynamic conditions with potential adverse effects on long-term outcomes, in particular when CEA is performed at the common carotid artery and/or the bulb or when ICA diameter is greater than 5.0mm.