Characterization of Blood Flow Patterns in Patients after Carotid Endarterectomy using ultrasound-based Velocity Vector Imaging

Objective Carotid endarterectomy (CEA) with patch angioplasty creates local bulb widening that might alter post-operative hemodynamics and contribute to restenosis. Detailed insight in flow complexity might gain insight in restenosis risk. Ultrasound-based velocity vector imaging (US-VVI) was used to characterize blood flow patterns in the carotid bifurcation after CEA. Methods In this prospective, multicenter study, seventy patients with ≥50% carotid stenosis scheduled for CEA were enrolled. All patients underwent conventional and ultrafast ultrasound examinations 6-8 weeks post-operatively. After US-VVI reconstruction, three experienced researchers visually evaluated blood flow patterns and examined how these patterns coincided with atheroprone regions, defined by relative low and oscillatory wall shear stress (WSS). Qualitative evaluation was supported by quantitative analysis, including vector complexity, vortex presence, WSS, and lumen diameter. Results Sixteen patients were excluded, resulting in a final cohort of 54 patients (70.4% male, median age 72.0 [66.3-76.8] years). Three distinct flow phenotypes were identified: two high flow complexity conditions, arising from vortical flow (31.5%), or unstructured multi-directional flow (48.1%), and a low flow complexity condition (20.4%). Significantly lower time-averaged WSS and elevated oscillatory WSS were observed in vortical flow (0.19 [0.13-0.22] Pa and 0.32 [0.30-0.38], respectively) and unstructured flow (0.21 [0.16-0.29] Pa, 0.40 [0.32-0.46]) compared with the low flow condition (0.35 [0.27-0.45] Pa and 0.07 [0.04-0.07]). Vector complexity was significantly elevated for both high complexity conditions compared with the low complexity condition. High flow complexity conditions were further characterized by prolonged vortex presence and were linked with enlarged post-operative lumen diameters despite normalized velocities. Conclusions US-VVI was shown to be feasible after recent CEA with patch angioplasty and enabled the identification of complex flow patterns associated with atheroprone conditions. Vector complexity and vortex characterization provided complementary insights into the underlying flow complexity. This study suggests that surgery-induced lumen widening exhibits atheroprone flow conditions that may contribute to future restenosis.