A system for treating a native mitral valve, comprising: a delivery catheter (124)； a prosthetic mitral valve assembly (260) comprising a self-expanding stent (10) and a valve (18) made of pericardial tissue, the valve being mounted inside the stent (10) and forming collapsible leaflets (62) to replace the function of the native mitral valve, the stent having a substantially D-shaped cross section configured to adapt to the natural opening of the native mitral valve, the stent including an upper part (12) having an enlarged or enlarged end (14) that it narrows to a lower part (16) having a reduced diameter, the enlarged or widened end (14) being sized to be placed above the ring (30) of the native mitral valve (24)； and a tie rod (80) connected between a lower part of the prosthetic mitral valve assembly and a heart wall to prevent upward movement of the prosthetic mitral valve assembly (260)； wherein the prosthetic mitral valve assembly (260) is adapted to be advanced in a radially compressed state along a distal end of the delivery catheter (124) for insertion through the heart wall.Un sistema para tratar una válvula mitral nativa, que comprende: un catéter de envío (124)； un conjunto de válvula mitral protésica (260) que comprende un stent autoexpansible (10) y una válvula (18) hecha de un tejido pericárdico, estando la válvula montada dentro del stent (10) y formando valvas colapsables (62) para sustituir la función de la válvula mitral nativa, teniendo el stent una sección transversal con forma sustancialmente de D configurada para adaptarse a la abertura natural de la válvula mitral nativa, incluyendo el stent una parte superior (12) que tiene un extremo aumentado o ensanchado (14) que se estrecha hasta una parte inferior (16) teniendo un diámetro reducido, estando el extremo aumentado o ensanchado (14) dimensionado para ser colocado por encima del anillo (30) de la válvula mitral nativa (24)； y un tirante (80) conectado entre una parte inferior del conjunto d
