|Abstract:|| Objective: To describe and analyze hemodynamic modifications in patients submitted to carotid endarterectomy (CEA) with different carotid closure techniques, using a computational fluid-dynamic (CFD) strategy, in order to identify disturbed flow conditions potentially involved in the development of restenosis.
Methods: Data from 8 carotid geometries in 7 asymptomatic patients who underwent CEA were analyzed. In six cases (A-F), CEA was performed using patch graft (PG) closure, while in two cases (G and H) direct suture (DS) closure was performed. Three-dimensional carotid geometries, derived from postoperative Magnetic Resonance Angiography, were reconstructed using a level-set segmentation technique. Where PG was originally used it was virtually removed, creating a virtual DS scenario (PG vs virtual-DS) while, on the contrary, in cases submitted to DS closure, a virtual PG was inserted (DS vs virtual-PG). Modified geometries were designed using visualization-dedicated software. CFD analysis was performed using the finite elements library LifeV and velocity data obtained from Doppler Ultrasound waveforms.
To compare hemodynamic effects, wall shear stress-based quantities were considered indicators of disturbed flow and thus favorable conditions for the development of restenosis. In particular, oscillatory shear index (OSI) and relative residence time (RRT) were calculated both for original and virtual scenarios.
Results: For the six original PG cases, we measured the following: Mean of averaged-in-space OSI of 0.07 ± 0.01 for PG and 0.03 ± 0.02 for virtual-DS (difference 0.04 ± 0.01; P=.0016). Mean of the percentage of area with OSI > 0.2 (%A-OSI > 0.2) 10.08% ± 3.38% (PG) and 3.80% ± 3.22% (virtual-DS) (difference 6.28 ± 1.91; P= .008). Mean of the averaged-in-space RRT 5.48 ± 3.40 1/Pa (PG) and 2.62 ± 1.12 1/Pa (virtual-DS) (difference 2.87 ± 1.46; P =.097). Mean %A RRT > 4 1/Pa of 26.53% ± 12.98% (PG) and 9.95% ± 6.53% (virtual-DS) (difference 16.58 ± 5.93; P= .025).
For the two original DS cases we measured the following: Averaged-in-space OSI 0.02 and 0.04 (DS) and 0.03 and 0.02 (virtual-PG), %A-OSI > 0.2, 0.9% and 7.6% (DS) and 3.0% and 2.2% (virtual-PG), averaged-in-space RRT 1.8 and 2.0 1/Pa (DS) and 2.9 and 1.9 1/Pa (virtual-PG), %A-RRT > 4.0 1/Pa: 6.8% and 9.8% (DS) 9.4% and 6.2% (virtual-PG). These results revealed generally higher disturbed flows in the PG configurations with respect to the DS ones.
Conclusions: OSI and RRT values were higher in PG cases with respect to virtual-DS ones, while, in direct contrast, the virtual insertion of PG gave conflicting results that were primarily determined by the original carotid geometries.|