Non-Kolmogorov turbulence in carotid artery stenosis and the impact of carotid stenting on near-wall turbulence

Abstract

Endovascular stents have become a standard management procedure for carotid artery stenosis. Recent discoveries related to the complex turbulence dynamics in blood flow necessitate revisiting the pathology of carotid stenosis itself and the impact of stenting on blood hemodynamics. In the present work, and for the first time, the therapeutic hemodynamic changes after carotid artery stenting are explored via high-resolution large eddy simulation of non-Newtonian multiharmonic pulsatile flow in realistic patient-specific geometries. The focus of the present study is the transition to turbulence before and after stent deployment. Transition to turbulence was characterized in space, time, and frequency domains. The multiharmonic flow had generalized a time-dependent Reynolds number of 115 ± 26 at the inlet plane of the computational domain. The inlet boundary condition was defined as a multiharmonic waveform represented by six harmonics that are responsible for transferring at least 94% of the mass flow rate in the common carotid artery. Multiharmonic non-Newtonian pulsatile flow exhibited non-Kolmogorov turbulence characteristics. The stent was found to cause a significant reduction in the velocity oscillations downstream the stenosis throat and restore the inverse kinetic energy cascade. It also stabilized hemorheological fluctuations downstream the stenosis throat. Finally, the stent had a significant effect on the kinetic energy cascade at a distance of 10 µm from the artery wall at the carotid bifurcation and stenosis throat. These findings are important to guide the design and optimization of carotid stents and have significant value in understanding the mechanisms of vascular remodeling and carotid stenosis pathophysiology and symptomatology.