A mitral valve prosthesis comprising: an at least partially self-expanding stent (2; 4; 21) having an expanded and an unexpanded state and that includes a long axis (Y); a middle region comprising a framework that defines inner and outer surfaces; a lower flange portion (8; 24) at a first longitudinal end of the middle region that comprises a plurality of protruding stent elements (7; 26); an upper flange portion (6; 22) at a second longitudinal end of the middle region that comprises a plurality of protruding stent elements (7; 26); and, a valve that is attached to the inner surface of the middle region of the stent (2; 4; 21), wherein, when said stent (2; 4; 21) is in the unexpanded state, the upper and lower flange portions are oriented substantially along the long axis (Y) of the stent (2; 4; 21); wherein the lower flange (8; 24) has at least one geometric dimension that is greater than the corresponding dimension of the upper flange (6; 22), wherein during transition of the stent (2; 4; 21) from the unexpanded state to the expanded state, the upper (6; 22) and lower (8; 24) flange portion both transition in space so that they are no longer oriented substantially along the long axis (Y) of the stent (2; 4; 21), and, characterized in that the lower flange portion (8; 24) is configured to grasp tissue at a ventricular side of a mitral annulus by trapping it between the lower flange portion (8; 24) and the outer surface of the middle region as the stent (2; 4; 21) transitions from the unexpanded state to the expanded state, wherein the lower flange portion (8; 24) is substantially bent back towards the middle region when the stent (2; 4; 21) is in the expanded state. a long axis (Y); a middle region comprising a framework that defines inner and outer surfaces; a lower flange portion (8; 24) at a first longitudinal end of the middle region that comprises a plurality of protruding stent elements (7; 26); an upper flange portion (6; 22) at a second longitudinal end of the middle region that comprises a plurality of protruding stent elements (7; 26); and, a valve that is attached to the inner surface of the middle region of the stent (2; 4; 21), wherein, when said stent (2; 4; 21) is in the unexpanded state, the upper and lower flange portions are oriented substantially along the long axis (Y) of the stent (2; 4; 21); wherein the lower flange (8; 24) has at least one geometric dimension that is greater than the corresponding dimension of the upper flange (6; 22), wherein during transition of the stent (2; 4; 21) from the unexpanded state to the expanded state, the upper (6; 22) and lower (8; 24) flange portion both transition in space so that they are no longer oriented substantially along the long axis (Y) of the stent (2; 4; 21), and, characterized in that the lower flange portion (8; 24) is configured to grasp tissue at a ventricular side of a mitral annulus by trapping it between the lower flange portion (8; 24) and the outer surface of the middle region as the stent (2; 4; 21) transitions from the unexpanded state to the expanded state, wherein the lower flange portion (8; 24) is substantially bent back towards the middle region when the stent (2; 4; 21) is in the expanded state. <EOS>