Effects of varied lipid core volume and fibrous cap thickness on stress distribution in carotid arterial plaques.

The rupture of atherosclerotic plaques is known to be associated with the stresses that act on or within the arterial wall. The extreme wall tensile stress is usually recognized as a primary trigger for the rupture of the plaque. The present study used one-way fluid-structure interaction simulation to investigate the impacts of fibrous cap thickness and lipid core volume to the wall tensile stress value and distributions on the fibrous cap. Von Mises stress was employed to represent the wall tensile stress (VWTS). A total of 13 carotid bifurcation cases were manipulated based on a base geometry in the study with varied combinations of fibrous cap thickness and lipid core volume in the plaque. Values of maximum VWTS and a stress value of VWTS_90, which represents the cut-off VWTS value of 90% in cumulative histogram of VWTS possessed at the computational nodes on the luminal surface of fibrous cap, were used to assess the risk of plaque rupture for each case. Both parameters are capable of separating the simulation cases into vulnerable and more stable plaque groups, while VWTS_90 is more robust for plaque rupture risk assessment. The results show that the stress level on the fibrous cap is much more sensitive to the changes in the fibrous cap thickness than the lipid core volume. A slight decrease of cap thickness can cause a significant increase of stress. For all simulation cases, high VWTS appears at the fibrous cap near the lipid core (plaque shoulder) regions.