Affiliations: Department of Mechanics, Faculty of Mechanical Engineering, Czech Technical University in Prague, Technicka 4, 166 07 Prague 6, Czech Republic | Institute of Anatomy, First Faculty of Medicine, Charles University, U nemocnice 3, 128 00 Prague 2, Czech Republic
Note: [] Corresponding author: Jaroslav Valenta, Department of Mechanics, Faculty of Mechanical Engineering, Czech Technical University in Prague, Technicka 4, 166 07 Prague 6, Czech Republic. Tel.: + 420 2 24352523; Fax: + 420 2 33322482.
Abstract: An analytical model has been used to simulate the effects of tissue aging on residual strain, constitutive relations and stiffness parameter in the main right and left (ramus circumflexus) human coronary arteries, based on experimental data. The experimental opening angle θ scatters considerably with age. The optimum angle θop≈70°, which makes the circumferential stress uniform in the arterial wall at a normal blood pressure, is approximately constant throughout aging. Above age of the 15 years the estimated and experimental values of θ are greater than θop and therefore the mechanical load of the inner layers of the media and the intima decreases and the adventitia is overloaded. On the basis of nonlinear regression analysis, age‐related constitutive laws of arterial wall circumferential stiffness have been determined. Above the age of 30, arterial wall hardening increases rapidly. The left coronary artery is stiffer than the right artery for groups from 35 to 45 years of age. Hyperelasticity theory has been used to identify age‐related multiaxial stress through wall thickness. A theoretical model based on the reduced Green strain provides a very good representation of the coronary artery circumferential mechanical response and predicts its nearly isotropic behavior. Bio‐composite material forms non‐homogeneous stresses and, in the course of aging, it increases the adventitia loading. In groups aged from 10 to 15 years, whose coronary artery residual strains are low, the circumferential stress distribution has a classic form. Stiffness parameter β gradually increases with age and this increase is significant above the age of 60. Parameter β tends to decrease when the opening angle θ increases.
