Abstract 418: Low Plaque Tensile Stress May be a Driving Force to Plaque Regression: Contrast Enhanced MRI Study in a Porcine Model of Atherosclerosis
Low and oscillatory flow shear stress (SS) is thought to promote the initialization and progression of early atherosclerosis. However, the flow SS appears to have no effect on plaque regression from lipid lowering therapy. We hypothesized that plaque tensile stress (TS) may be one of determinants to the plaque regression. Atherosclerotic plaques were induced in the left carotid arteries of 3 Yucatan pigs by repeated balloon-overstretch injury and 8 months hypercholesterolemic diet (progression: PRO), followed by one month of normal chow diet (regression: REG). Gadofluorine M enhanced MRI was performed at different time points to obtain morphology of the plaque and vessel wall during PRO and REG. After the last MRI scan, both normal right and injured left carotid artery segments were dissected for histopathology and mechanical testing for the plaque material properties. A 3D fluid-structure-interaction computation model that combines the MRI and material properties measurements was applied to calculate the plaque TS and flow SS during PRO and REG. Induced plaque structure resembled early plaque with thickened intima. Data analysis shows a strong correlation of flow SS with the growth of plaque during PRO (R = 0.84), but moderate correlation during REG (R = 0.64). In contrast, TS strongly correlated with REG of plaque (R = 0.96) (in Figure⇓). Tensile stress appears to be one of important hemodynamic forces involved in plaque regression. Comprehensive assessment of plaque TS and flow SS may help in a clinical setting to stratify the risk associated with the plaque, as well as to elucidate the mechanism of the plaque response to therapy.