STRESS CONCENTRATIONS OF VULNERABLE PLAQUES WITH A COMPOSITE VARIABLE CORE

摘要

Vulnerable plaques are inflamed, active, and growing lesions which are prone to complications such as rupture, luminal and mural thrombosis, intraplaque hemorrhage, and rapid progression to stenosis. It remains difficult to assess what factors influence the biomechanical stability of vulnerable plaques and promote some of them to rupture while others remain intact. The rupture of thin fibrous cap overlying the necrotic core of a vulnerable plaque is the principal cause of acute coronary syndrome. The mechanism or mechanisms responsible for the sudden conversion of a stable atherosclerotic plaque to a life threatening athero-thrombotic lesion are not fully understood. It has been widely assumed that plaque morphology is the major determinant of clinical outcome [1, 2]. Thin-cap fibroatheroma with a large necrotic core and a fibrous cap of <65μm was describes as a more specific precursor of plaque rupture due to tissue stress. The importance of stress/strain distribution is now well recognized in vascular pathophysiology, specifically in the mechanisms of plaque rupture. Investigating the mechanobiological behavior of arteries is crucial to understand the mechanisms of coronary angioplasty and the efficacy of vascular implants such as stents and grafts. Finite element modeling (FEM) and advanced fluid structure interaction (FSI) studies can better characterize coronary stenosis coupling constitutive equations. Mechanical factors such as stress concentrations within a plaque (material fatigue), lesion characteristic (location, size, and composition), and flow patterns are involved in rupture of plaques. Although permanent load and repetitive stress may not cause immediate rupture, it does weaken the cap and might lead to unexpected rupture of the lesion. Assessment of local mechanical characteristics caused by plaque structure is important for identifying vulnerable plaques and may improve final estimation of the risk for coronary syndrome.