The influence of stenosis severity and geometric orientation on atherosclerotic progression: A fluid-structure interaction study in the carotid artery

Atherosclerosis remains the leading global cause of mortality, and its progression is strongly influenced by the local hemodynamic environment. Low Wall Shear Stress (WSS) is widely recognized as a promoter of atherosclerosis, yet the combined influence of stenosis severity and its geometric orientation on disease progression in anatomically realistic geometries has not been systematically examined. This study assesses the risk of atherosclerotic progression in a carotid artery using one-way Fluid-Structure Interaction (FSI). Four stenosis levels were simulated (0, 30, 60, and 80%), along with three angular orientations of the stenotic apex relative to the ICA wall. Blood flow was modeled using the [Formula: see text] SST turbulence model, and arterial walls were represented using a Mooney-Rivlin hyperelastic formulation. For 0% and 30% stenosed cases, regions of low Time-Averaged WSS (TAWSS <= 0.4 Pa) appeared in the ICA. In contrast, the 60% and 80% stenoses produced markedly elevated TAWSS at the stenosis throat, ranging from 20-60 Pa. Arterial wall deformation of the 0% and 30% cases was observed around 0.8 mm, while the 60% and 80% stenoses exhibited prominent foci of high deformation upto 2.1 mm. The presence of disturbed flow dynamics and their resulting atheroprogression risk was assessed through the interplay of Reynolds number, nondimensional WSS, nondimensional Turbulent Kinetic Energy (TKE) and the Oscillatory Shear Index (OSI). At 30% severity, the upstream-tilted stenosis intensified early-stage progression indicators, whereas at 60% severity, the downstream-tilted orientation increased plaque vulnerability. The study demonstrates a comparative framework to rank relative risk of atheroprogression using the disturbed flow signatures and wall mechanics observed across the 8 geometries.