So far there is no study to measure the Poisson's ratio of the human coronary arteries in order to verify their incompressibility regardless of being healthy or atherosclerosis. It has been reported that atherosclerosis alters the elastin content of the arterial wall which is responsible for the elastic behavior of the arterial wall and helps tissue to reserve its initial shape after contracting or stretching. It is believed that the arterial walls are almost incompressible with nonlinear anisotropic mechanical response under axial or circumferential loading. Although the elastic modulus and Poisson's ratios were both originally stemmed from the linear solid mechanics, they can be employed to address the linear elastic mechanical properties of the arterial wall under small deformation/strain. To date, many studies assumed the arterial wall as an incompressible material whether via a direct mechanical measurement or a fluid simulation study in the arterial wall, despite there is no enough supporting evidence. The present study was planned to discover this issue in detail using Digital Image Correlation (DIC) technique to lively measure the induced strains of 9 healthy and 8 atherosclerotic human coronary arteries at two different longitudinal strain rates, i.e., 5 and 20 mm/min. The Poisson's ratio of the arterial walls, thereafter, were measured as a value of transverse strain with respect to the longitudinal strain. The results revealed the mean Poisson's ratio of 0.49098 and 0.49330 for the healthy and atherosclerotic arterial walls, respectively, under the strain rate of 5 mm/min. Furthermore, the Poisson's ratio of 0.49156 and 0.49702 were seen in the healthy and atherosclerotic arterial walls, respectively, under the strain rate of 20 mm/min. The results well verified the incompressibility of the coronary arterial walls regardless of being healthy or atherosclerotic under the both strain rates.
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