A valve prosthesis for percutaneous placement within a vein is disclosed that includes a valve scaffold and a backflow barrier. The valve scaffold is of a shape memory or resilient material and the backflow barrier is a flap of flexible material attached to the valve scaffold. The valve prosthesis is operable to alternate between open and closed configurations in response to changes in retrograde blood flow pressure. In the open configuration, the valve scaffold has a frustoconical coil shape of consecutive windings with open spaces therebetween and the backflow barrier allows antegrade blood flow through the open spaces. In the closed configuration, the consecutive windings of the valve scaffold are collapsed such that the valve scaffold has a substantially flat profile and the backflow barrier covers the opens spaces of the flattened valve scaffold to prevent retrograde blood flow from leaking there through.
