A prosthetic device for replacing a deficient native aortic valve is disclosed, comprising: - a collapsible and expandable support stent formed of a shape memory alloy, - the support stent comprising a proximal stent portion (310) configured to expand to a first diameter and - an distal stent portion (320) configured to expand to a second diameter, the first diameter being smaller than the second diameter for preventing deformation of the mitral valve by over expansion and for providing a difference between the support stent and the openings of the coronary arteries； and - a collapsible and expandable valve assembly formed of natural tissue, whereby the valve assembly is attached to the support stent circumferentially along an inlet and sutured to the support stent along commissures for supporting the valve leaflets； wherein the first diameter of the support stent is sized for engagement with leaflets of the native aortic valve and the second diameter of the support stent is sized for engagement with the inner wall of the ascending aorta and wherein the stent is sized to avoid a contact with the inner wall of a left ventricle when implanted.
