Biomechanical structural stresses of atherosclerotic plaques

Atherosclerotic plaques may rupture without warning, causing fatal clinical events such as myocardial infarction and stroke. Degree of stenosis, which is the current criterion for assessment of atherosclerotic disease severity, has been observed to have poor correlation with plaque vulnerability. Under physiological conditions, plaque undertakes mechanical loadings due to blood pressure and flow. From the material view point, rupture possibly occurs when the extra loading exceeds the material strength of the plaque. Therefore, morphological and mechanical features should be considered in an integrated way for a more accurate assessment of plaque vulnerability and for identification of the at-risk patient. Biomechanical stress analysis is a technique that allows such comprehensive assessment. This article focuses on the mechanical stresses in the plaque structure, which are believed to be of greater magnitude than the associated wall shear stress and are thought to be more closely associated with plaque rupture. We discuss the basic mechanics that govern plaque behavior, the material properties of atherosclerotic tissues and the studies investigating the association between high biomechanical stresses and plaque rupture. Parameter studies investigating the effect of morphologic factors on the critical biomechanical stresses and limitations of current simulation models are also reviewed.