Wall shear stress distribution at the carotid bifurcation: Influence of eversion carotid endarterectomy

Objectives: To test the feasibility of four-dimensional (4D) flow MRI to quantify the systolic wall shear stress (WSS_systole) and oscillatory shear index (OSI) in high-grade internal carotid artery (ICA) stenosis before and after endarterectomy (CEA). Methods: Twenty patients with ≥60 % ICA stenosis were prospectively and consequently included. Four-dimensional flow MRI was used to measure individual time-resolved 3D blood flow velocities. Segmental WSS_systole and OSI were derived at eight wall segments in analysis planes positioned along the ICA, common (CCA) and external carotid artery (ECA). Results: Regional WSS_systole of all patients decreased after CEA (P < 0.05). Changes were most prominent at the ICA bulb but remained unchanged in the CCA and ECA. OSI was significantly lower after CEA in the lateral vessel walls (P < 0.05). For analysis planes at the stenosis in- and outlet, a reduction of mean WSS_systole by 32 % and 52 % (P < 0.001) and OSI distal to the stenosis (40 %, P = 0.01) was found after CEA. Conclusions: Our findings show the potential of in vivo 4D flow MRI to quantify haemodynamic changes in wall shear stress even in patients with complex flow conditions. Key Points: • The 4D flow MRI allows in vivo measurement of individual 3D blood flow. • Regional wall shear stress can be derived from such 3D flow data. • Even complex flow in high-grade internal carotid artery stenosis can be analysed. • This technique could be valuable for future studies of carotid atherosclerosis.