A parameterized analysis of the mechanical stress for co-ronary plaque fibrous caps

Abstract

The\rfibrous cap is a protective layer of connective tissue that covers the core of an\ratherosclerotic plaque. The rupture of this layer has been commonly associated\rwith acute myocardial infarctions. The thickness of the fibrous cap, the\rpercentage of stenosed area, and the stiffness of the core were studied\r(commonly associated with vulnerable plaque characteristics) to quantify their\reffects on the cap’s mechanical stress state by performing analyses using\rcomputational fluid-structure interaction (FSI) methods. The mechanical stress\rlevels are significantly increased within the fibrous cap structure at the upstream\rside of the plaque. As expected, the highest stresses occurred for a severe\rstenosis and a thin fibrous cap. Interestingly, a weak structural support such\ras a soft lipid pool beneath the fibrous cap allowed for the hemodynamic\rpressure gradient forces to displace the fibrous cap in the direction of the\rflow, resulting in higher strains and thus higher mechanical stresses in the\rupstream portion of the plaque cap, potentially increasing the risk of cap\rrupture. The peak stress behavior of the most critical cases (thin fibrous cap\rand soft lipid core) at various degrees of stenosis was analyzed. For mid-range\rstenosis from 43% to 75%, there was a plateau region revealing that mild and\rmoderate plaques were quickly exposed to the high stress condition of severe\rplaques. In conclusion, the particular combination of a mild to severe stenosis,\ra thin fibrous cap and a soft lipid core resulted in the highest mechanical\rstresses calculated at the proximal side of the plaque. Mild and moderate plaques\rcan be subjected to stresses similar to severe plaques, possibly contributing\rto their rupture.