Measuring wall shear stress distribution in the carotid artery in an African population: Computational fluid dynamics versus ultrasound doppler velocimetry

Abstract

IntroductionComputational fluid dynamics (CFD) and ultrasound Doppler velocimetry are diagnostic tools useful for determining carotid artery segments susceptible to atheromatous plaque development. This study computes and compares the difference in Wall Shear Stress (WSS) measurements between these two methods. MethodsThe carotid artery of 204 volunteers selected using simple random sampling were scanned using standard carotid doppler protocols. Four segments of the carotid artery – the common, internal, external carotid, and the carotid bulb were sonographically assessed. The intima-media thickness, diameter, peak systolic velocity, and end-diastolic velocity were measured at a point 2 cm away from the carotid bifurcation for the three segments, while the carotid bulb was measured at the bifurcation. A 2D incompressible Navier–Stokes Equation for modelling Newtonian, pulsatile, and laminar flow in a viscoelastic pipe was applied to model velocity flow across the carotid artery using COMSOL software. WSS values were computed for experimental and CFD measurements and the results were compared. ResultsThe WSS values generated by the model had respectively peak and average values of 19.81 N/cm2 and 15.76 ± 1.81 N/cm2 for the common carotid, 10.77 N/cm2 and 7.57 ± 1.66 N/cm2 for the internal carotid, 11.51 N/cm2 and 8.05 ± 1.65 N/cm2 for the external carotid, 37.55 N/cm2 and 26.55 ± 6.62 N/cm2 for the carotid bifurcation, 1.39 N/cm2 and 3.13 ± 1.34 N/cm2 for the carotid bulb. The model measurements matched doppler velocimetry measurements with <15% variation. ConclusionModel based WSS values were higher but comparable with doppler velocimetry measurements. The carotid bulb had low WSS and is therefore the segment highly disposed to atheromatous plaque formation. Implications for practiceSubject-specific mathematical models could be incorporated during cardiovascular scan work up for accurate WSS distribution and early prediction of possible atherosclerotic sites.