A prosthetic mitral valve assembly (260) is disclosed, which comprises a radially-compressible and self-expandable stent (10) having a non-uniform cross-sectional shape, the stent (10) including an upper portion (12) having an enlarged or flared end (14) that tapers to a lower portion (16) having a reduced diameter to generally conform the contours of the native leaflets within the native valve, the flared end (14) of the upper portion (12) being positioned above or just below an annulus (30) of the native mitral valve (24). It is further characterized by having a substantially D-shape cross-section configured to conform to the natural opening of the native mitral valve, the D-shape cross-section including a substantially straight portion (262) configured to extend along an anterior side of the native mitral valve and a substantially curved portion (264) configured to extend along a posterior side of the native mitral valve. The prosthetic mitral valve assembly (260) furhter comprises a valve (18) mounted within said stent, the valve having leaflets (62) replacing the function of the native mitral valve； wherein said mitral valve assembly (260) is mountable in a compressed state on the distal end of a delivery catheter (124) for insertion through the apex and into the heart.
