Blood Flow Turbulence Measured by High-frame-rate Vector Flow Imaging Conduced to Investigating Advanced Carotid Plaque Vulnerability

Abstract

Objective: The high-frame-rate vector flow imaging (V Flow) technique is a simple, practical and feasible quantitative imaging method for detecting hemodynamic parameters of peripheral arteries in healthy people and patients with low carotid stenosis. However, whether V Flow can be used to assess hemodynamic parameters in patients with severe carotid stenosis remains to be illustrated. We sought to investigate the relationship between V Flow-evaluated hemodynamic parameters of advanced carotid stenosis and plaque composition and its value in assessing plaque vulnerability.

Methods: Patients undergoing carotid endarterectomy and ultrasound examination were collected, and plaque characteristics were graded on simple semiquantitative scales. Correlations between the turbulence index (Tur) and wall shear stress (WSS) in different parts of plaque and plaque components were analyzed. Receiver operating characteristic curves were used to analyze values of ultrasonic parameters in investigating plaque vulnerability.

Results: Tur was more severe in vulnerable plaque than in stable plaque (35.99 ± 26.17 vs 7.82 ± 8.41; p < 0.001). Plaques with severe Tur showed more intraplaque hemorrhage, thrombus, and thinner fibrous cap thickness (p < 0.05 for all). At the upstream sides of carotid stenosis, plaque with a lower mean WSS (meanWSS_upstream) was associated with decreased fibrous tissue (p = 0.022). At the peak of carotid stenosis, meanWSS (meanWSS_peak) was higher in the plaques with intraplaque hemorrhage (p = 0.028) and intraplaque neovascularization (p = 0.037). Plaques with a higher oscillatory shear index of WSS had fewer lipid core (p = 0.029) thinner fibrous cap thicknesses (p = 0.004) and more intraplaque neovascularization (p = 0.032). The areas under the curves of carotid intima-media thickness, total plaque area (TPA), Tur, MeanWSS_upstream, MaxWSS_peak, MeanWSS_peak, model 1, model 5 and model 6 for predicting plaque vulnerability were 0.804 (95% confidence interval [CI], 0.650-0.911), 0.886 (95% CI, 0.748-0.964), 0.843 (95% CI, 0.695-0.937), 0.733 (95% CI, 0.571-0.858), 0.677 (95% CI, 0.514-0.815), 0.672 (95% CI, 0.508-0.811), 0.895 (95% CI, 0.759-0.969), 0.973 (95% CI, 0.867-0.999) and 0.930 (95% CI, 0.805-0.986).

Conclusion: V Flow-detected hemodynamic parameters were related to plaque components and plaque vulnerability. V Flow has the potential to be an effective tool for investigating patients with severe carotid plaque.

Keywords: Plaque composition; Plaque vulnerability; Turbulence index (Tur); Vector flow imaging (V Flow); WSS.