A valve prosthesis device and methods for deployment is disclose. The device comprises an expandable support stent and a valve assembly comprising a flexible conduit having an inlet end and an outlet, made of pliant material attached to the support beams providing collapsible slack portions of the conduit at the outlet. Flow is allowed to pass through the valve prosthesis device from the inlet to the outlet, but reverse flow is prevented as the collapsible slack portions of the valve assembly collapse inwardly. The device is configured so that retrograde flow will be altered from laminar flow and directed towards the leaflets to effect closing. The device can be deployed in a native heart valve position using a deployment catheter advanced through a body lumen such as a blood vessel, including an aorta.