Computational fluid-dynamic analysis of carotid bifurcations after endarterectomy: closure with patch graft versus direct suture

Objectives This study aims at comparing by means of computational fluid-dynamics (CFD) the hemodynamics before and after carotid endarterectomy (CEA), and, after CEA, between patch graft (PG) and direct suture (DS) closures. Design We analyzed wall shear stress (WSS), velocities, and vorticity before and after CEA, to highlight the effect of surgery on hemodynamics, and time averaged WSS (TAWSS), oscillatory shear index (OSI) and relative residence time (RTT) after CEA to highlight the differences in terms of risk of restenosis between PG and DS. Methods Thirteen cases underwent CEA for stenosis > 70% and were closed with 9 PG and 4 DS. For each of them we measured the flow with Doppler Ultrasound (DUS) and reconstructed geometries from Magnetic Resonance Angiography (MRA). Results The mean value of the spatial averaged TAWSS was 1.0 Pa for PG and 1.5 Pa for DS, whereas it was 0.03 for PG and 0.07 for DS in the case of OSI. The percentage areas with low TAWSS and high OSI resulted wider for PG in comparison to DS (TAWSS: 66.2% for PG and 37.2% for DS; OSI: 10.1% for PG and 3.7% for OSI). RRT values resulted higher in the PG group. In particular, the mean of the averaged-in-space values was 4.4 1/Pa for PG and 1.6 1/Pa for DS, whereas the PA with high RRT were 22.5% and 6.5%, respectively. Conclusions The carotid regions with percentage area of low TAWSS, high OSI and high RRT were wider in the PG group when compared with DS. Thus, hemodynamic conditions more prone to restenosis were observed for PG. The increase of the cross-section area created by PG could induce flow disturbances with potential consequences on long term outcomes. Selective use of PG should consider specific conditions of the patients.