The main objective of this thesis is to study and investigate the mechanical behavior of the aortic valve with an emphasis on aortic stenosis. Moreover, this thesis aims to characterize the severity of AS in terms of material properties. The development of percutaneous heart valves allows valve replacement without open chest surgery. This is the most desirable option for patients with elevated surgical risks. To avoid the risk of failure in percutaneous valve implantation, determination of material properties of diseased leaflets before surgery is necessary. Therefore in this study, a series of numerical simulations, including both structural and fluid-structure interaction approach, and experimental studies were performed to achieve the objectives of this research. The results of the numerical simulations of the aortic stenosis are compared with in vitro results before testing the method using in vivo data. There is good agreement between the results of the numerical simulation and the in vitro experiments and the literature. An algorithm is suggested to estimate the material properties of the stenotic valve, considering the realistic material of the aortic valve with hyperelastic, nonlinear and anisotropic properties. The simulations using the structural modeling allow determination of the patient’s specific material property of a calcified aortic valve, knowing invasively measured aortic and ventricular pressure waveforms and the geometrical orifice area prior to percutaneous valve replacement. Also, fluidstructure interaction modeling helps to estimate a more realistic dynamic behavior of the aortic valve and also obtains the hemodynamic performance
