In Vestigation Of The Mechanical Properties Of Artery And Atherosclerotic Plaque

Cardiovascular disease (CAD) is a serious threat to human health, and atherosclerosis at head or neck, coronary and perpheral vascular ateries is the very common form of cardiovascular diseases. This work aims to investigate the mechanical properties of healthy and atherosclerotic ateries. The residual stress in normal porcine aorta and the mechanical behaviors of different components of human atherosclerotic carotid artery were investigated using numerical and experimental methods, respectively.In order to determine the residual stress in arteries, first, the unloaded procine aorta in zero-stress state is cut open along the arterial axial direction. Second, if an equivalent displacement is applied to close this aorta, it can recover to the unloaded aortas state with similar geometry. In contrast, the residual stress can be calculated by equating the two processes. Based on this,5 procine aortas were selected. For each aorta,5 sets (each set has 2 samples) of samples were made from the proximal to the distal ends, and the total number were 50. Then, the cross sections of the samples were stained, and its 2D geometry was pictured by a camera. Finally, the 2D geometric data were imported into the commercial ABAQUS finite-element software, and the residual stress were analyzed. In the models, the constitutive relationship of the arterial materials, were described by the 2-order Ogden material model whose parameters were obtained by fitting the real uniaxial tensile stress-strain curves. The results shows:the circumferential residual stress shows the characteristics of compressed inner wall and tensile outer wall. Proximal end was greater than that of the distal end. Meanwhile, the residual stress was almost same for the samples cut at different positions.To examin the mechanical properties of different components of the atherosclerotic carotid plaque, we first obtained the carotid plaque by carotid endarterectomy from the affiliated hospital of XUZHOU medical college. The samples were embedded 4 hours later after collection, and stored under-40℃ condition before experiment. Then, the frozen samples were sliced, and stained with HE staining, modified oil red O staining and Masson staining respectively. With the aid of microscopy, the plaques were divided into three components: fibrous cap, lipid-rich core region and elastic fiber region. Finally, to obtain the material properties of the different components of the plaques, indentation experiments were performed by using atomic force microscopy (AFM) for the three components. The results shows that because of mechanical stimulation and probable calcification, Young’s modulus of the fibrous cap was larger but with a wide variation, lipid-rich region was the softest, and this indicates a great possibility of plaque rupture.In summary, combining experimental and numerical methods, this work investigates the mechanical properties of artery and atherosclerotic plaque. It is helpful to quantitatively understand the residual stress and mechanical properties of arterial plaques, meanwhile, it presents the relevant referential data for numerical analysis for arterial biomechanics.