Biomechanical layer-specific analysis and residual deformation of carotid arteries

The carotid arteries, including the Common Carotid (CCA) and the Internal Carotid Arteries (ICA), are of particular biomedical and clinical interest, since they are prone to atherosclerosis and frequently undergo treatments (usually angioplasty or carotid endarterectomy) to prevent stroke. Stroke is a leading cause of serious, long-term disability and the third leading cause of death, behind disease of the heart and cancer, in the United States. A standard treatment consists of removing the narrowing by surgical procedure such as carotid endarterectomy (CEA), and nowadays, more popular, carotid angioplasty with stenting (CAS) can reopen the narrowing. Both treatments endovascular and surgical are mechanical and require a thorough investigation of the mechanical behavior of the underlying tissues in the carotid arteries. The ICA is very scarcely investigated, even though plaque formation, and consequently CAS or CEA occur in the CCA, the ICA and in the carotid bifurcation. Moreover, most studies available in the literature deal with carotid arteries coming from animals. Therefore, the aim of this study is to determine the mechanical behavior of human CCA and ICA, and subsequently the adventitial and media-intima composite layers by means of extension-inflation tests at different axial stretches. Moreover, the residual stretches of the adventitia and media-intima tubes and the stress-free configuration of the intact wall, the adventitia and the media-intima composite have to be determined in order to complete the required set of data. The stress-free configuration was determined by measuring the geometries and the curvatures of stress-free specimen strips oriented in the circumferential and the axial directions. These data are used for the determination of constitutive parameters for an existing nonlinear anisotropic constitutive model for arteries and their constituent tissues. The separation of the vessel wall into major layers (adventitia and media-intima composite) is a step towards modeling the next level of hierarchy in the structure. Each layer can be described by a unique set of material parameters and an appropriate strain-energy function and used for finite element analysis.