Lumen Irregularity Dominates the Relationship Between Mechanical Stress Condition, Fibrous-Cap Thickness, and Lumen Curvature in Carotid Atherosclerotic Plaque

摘要

High mechanical stress condition over the fibrous cap (FC) has been widely accepted as a contributor to plaque rupture. The relationships between the stress, lumen curvature, and FC thickness have not been explored in detail. In this study, we investigate lumen irregularity-dependent relationships between mechanical stress conditions, local FC thickness (LT_(FC)), and lumen curvature (LC_(lumen)). Magnetic resonance imaging slices of carotid plaque from 100 patients with delineated atherosclerotic components were used. Two-dimensional structure-only finite element simulations were performed for the mechanical analysis, and maximum principal stress (stress-P_1) at all integral nodes along the lumen was obtained. LT_(FC) and LC_(lumen) were computed using the segmented contour. The lumen irregularity (L-δir) was defined as the difference between the largest and the smallest lumen curvature. The results indicated that the relationship between stress-P_1, LT_(FC), and LC_(lumen) is largely dependent on L-δir. When L-δir ≥ 1.31 (irregular lumen), stress-P_1 strongly correlated with lumen curvature and had a weako correlation with local FC thickness, and in 73.4% of magnetic resonance (MR) slices, the critical stress (maximum of stress-P_1 over the diseased region) was found at the site where the lumen curvature was large. When L-δir ≤ 0.28 (relatively round lumen), stress-P_1 showed a strong correlation with local FC thickness but weako correlation with lumen curvature, and in 71.7% of MR slices, the critical stress was located at the site of minimum FC thickness. Using lumen irregularity as a method of identifying vulnerable plaque sites by referring to the lumen shape is a novel and simple method, which can be used for mechanics-based plaque vulnerability assessment.