[Vector mapping of intravascular flows to assess wall shear stress in patients with internal carotid artery stenosis]

The purpose of this study was to evaluate the dynamics of changes in the shear stress of the internal carotid artery wall by visualizing the vector flow before and after carotid endarterectomy.

We examined 30 apparently healthy male and female volunteers (34±2.2 years), 23 patients with pathology of the internal carotid artery prior to carotid endarterectomy (65±2.9 years), and 14 patients (of the 23 surgically treated patients) on POD 4-5 after carotid endarterectomy (61.6±2.7 years). The study was carried out on an ultrasound machine Mindray Resona 7 (China) equipped with a linear transducer (3-11 MHz) and the updated V flow software. Systolic blood flow velocity (Vs) before and after stenosis is correlated with the wall shear stress (WSS) by vector analysis. The WSS was analyzed in the internal carotid artery downstream and upstream of the plaque. The change in the direction of the WSS vector during the cardiac cycle was described using the oscillatory shear index (OSI). The turbulence of the flow, the wall thickness 1 cm proximal to the bifurcation of the common carotid artery, and the percentage of stenosis at the plaque level before and after surgery were evaluated. Stenosis of the internal carotid artery was determined by longitudinal scanning using the ECST method. The intra-group correlation coefficient was calculated when measuring the stress and shear of the wall.

The average values of turbulence in stenosis were higher in systole than in diastole (p<0.001). The turbulent flow correlated with the wall shear stress before the operation (-0.5137; p<0.05). The adequacy of correction of ICA stenosis >70% was assessed by the blood flow rate and the ratio of WSS to the proximal and distal bed. The criteria for adequate correction were considered normalized values of intravascular blood flows, wall shear stress, and oscillatory shear index.

In stenosis of the internal carotid artery, the wall shear stress was significantly higher in the direction of blood flow, which is characteristic of turbulence. Movement speeds at medium and high values of deformation serve as one of the indicators for assessing pathology and identifying areas of vessel stenosis. In the postoperative period, the direction of the flow vectors corresponds to normal values, which serves as an additional criterion for the effectiveness of surgical correction. Recording of the wall shear stress using vector flow mapping in patients with cerebrovascular diseases is a new direction for evaluating the results of surgical treatment.