Blood Flow Characteristics in Patients with Asymptomatic Carotid Artery Stenosis Using Ultrasound-based Velocity Vector Imaging

OBJECTIVE: Disturbed blood flow patterns alter local shear stress that contributes to plaque progression and vulnerability. Longitudinal studies linking blood flow patterns to carotid plaque progression using ultrasound-based velocity vector imaging (US-VVI) are currently lacking. The objective of the study was to identify atheroprone or rupture-prone flow characteristics in asymptomatic carotid artery stenosis using US-VVI. METHODS: Eighty-five asymptomatic carotid stenoses (30%-70%) were examined using conventional and ultrafast ultrasound at baseline and one-year follow-up. After US-VVI reconstruction, three experienced investigators visually evaluated blood flow patterns and identified atheroprone and rupture-prone flow features. Flow-derived parameters, including vector complexity, vortex presence, time-averaged wall shear stress (TA-WSS) and oscillatory shear index, were quantified in four sub-regions (pre-stenosis, upstream, downstream and post-stenosis). RESULTS: After one-year follow-up, nine patients dropped out and six datasets were excluded due to poor image quality, yielding 68 US-VVI acquisitions from 66 patients (77% men, age 75.0 [66.8-79.3] y). Visual assessment revealed three predominant flow conditions: a straight jet (61.8%), a bending jet directed toward the plaque (11.8%) and a bending jet directed away from the plaque (26.5%). Bending jet conditions showed more atheroprone characteristics in downstream and post-stenotic regions, characterized by higher vector complexity, more and longer vortices, lower TA-WSS and elevated oscillatory shear index. Elevated TA-WSS at peak stenosis, considered a rupture-prone characteristic, occurred more often in bending jet (33.3%-62.5%) than in straight jet conditions (23.8%). CONCLUSION: US-VVI identified local flow patterns associated with plaque progression and vulnerability in asymptomatic carotid stenosis. These features were more common in bending jet conditions, in which the jet direction appears to influence the location of atheroprone regions. GOV ID: NCT05270005.