Employing Fluid Structure Interaction Analyses to Reveal Insights in Atherosclerotic Progression in the Carotid Artery

Abstract

Atherosclerosis, the leading cause of death globally, has been shown to have a biomechanical link. A broad consensus exists that low levels of hemodynamic Wall Shear Stress (WSS) facilitate atherosclerotic stenoses (arterial blockages). Despite numerous studies on this phenomenon, the effects of how stenosis severity in simultaneity with its orientation relative to bulk flow may affect the rate of disease progression remain unexplored. To address these gaps, this study investigates the hemodynamic response of an anatomically realistic carotid artery using 1-way coupled Fluid Structure Interaction (FSI). We computationally analyzed blood flow in 4 stages of carotid artery stenoses (0%, 30%, 60% and 80%) at 3 levels of orientation of the stenosis with bulk flow direction. We employed a Newtonian rheology of blood, and considered the arterial walls as a Mooney-Rivlin hyperelastic solid. Low Time-Averaged Wall Shear Stress (TAWSS) below the threshold of 0.4 Pa is observed in the ICA region for the healthy (0%) and 30% stenosis cases, consistent with established studies. The 60% and 80% cases exhibit high levels of TAWSS at the stenosis throat. The interplay between the Reynolds number (Re), nondimensional WSS and nondimensional Turbulent Kinetic Energy (TKE) is investigated as a marker of disturbed shear dynamics. The 0% and 30% stenosed cases exhibited higher disturbed shear dynamics, potentially accelerating the rate of progression. In contrast, the severe stenosed cases (60% and 80%) seem to suppress disturbed shear dynamics, but may still facilitate disease progression due to high TAWSS promoting the risk of endothelial injury. Varying the stenosis orientation highlighted how geometric features affect flow disturbances. At 30% stenosis, the orientation with apex tilted towards downstream may accelerate early-stage progression relative to other orientations. In contrast, at 60% stenosis, the orientation with apex tilted upstream may also accelerate disease progression relative to other orientations, due to higher risk of endothelial injury and plaque destabilization. The study attempts to aid clinical intervention of atherosclerosis by proposing a qualitative ranking framework for the predicted rate of stenosis progression.