Fluid flow prosthetic device

A prosthetic device, comprising:

• a valve-orifice attachment member at an upstream end of said prosthetic device, said valve-orifice attachment member configured for attachment to a native valve site of a patient;
• a diverging blood flow pathway, comprising a pathway fluid inlet coupled to said valve-orifice attachment member,
• said pathway configured to flex between an open position thereof and a closed position thereof in response to a cardiac cycle of said patient,
• said diverging blood flow pathway defining a single blood flow field that extends downstream from said pathway fluid inlet,
• said pathway fluid inlet having at its narrowest cross-section a first cross-sectional area for blood flow therethrough,
• said pathway comprising an outlet having a second cross-sectional area at a downstream end of said prosthetic device;
• and
• a pathway support configured for attachment to said pathway, and that is operative, when attached to said pathway, generally to maintain a diverging configuration of said diverging blood flow pathway,
• wherein, regardless of whether said pathway support is attached to said pathway, said second cross-sectional area is greater than said first cross-sectional area when said pathway is in said open position thereof.