Computational hemodynamic models of the cardiovascular system are often limited to finite segments of the system and therefore need well-controlled inlet and outlet boundary conditions. Classical boundary conditions are measured total pressure or flow rate imposed at inlet and impedances of RLR, RLC or LR filters at outlet. We present a new approach based on a unidirectional propagative hypothesis (UPH) to model the inlet/outlet boundary conditions on the axisymmetric Navier-Stokes equations. This condition is equivalent to a non-reflecting boundary condition in a fluid-structure interaction model of an axisymmetric artery. First we compare the UPH to the best impedance filter (RLC). Second, we apply this approach to a physiological situation i.e. the presence of a stented segment into a coronary artery. In that case a reflection index is defined which quantifies the amount of pressure waves reflected upon the singularity.