An articulated prosthesis for a tricuspid or a mitral valve, comprising: a distal annular portion, a central annular portion and a proximal annular portion; a first plurality of arms hinged to an outer side surface of said distal annular portion; a second plurality of arms hinged to an outer side surface of said proximal annular portion; a third plurality of arms each of which is hinged to an outer side surface of said central annular portion, from one end, and to a corresponding end of a arm of said first plurality, from an opposite end; a fourth plurality of arms each of which is hinged to an outer side surface of said central annular portion, from one end, and to a corresponding end of a arm of said second plurality, from an opposite end; said distal annular portion having an internal screw thread, said proximal annular portion having: - a cylindrical collar on a side surface of which said second plurality of arms is hinged, and - a screw engaged into said collar and supported thereby so as to be free to rotate along a longitudinal axis of the screw, the screw being configured to engage with said internal screw thread, said central annular portion defining a through hole for letting said proximal annular portion pass through; the articulated prosthesis being movable from a distended configuration, in which all said arms hinged in correspondence of their ends are distended, to an expanded configuration, in which said proximal annular portion is threaded throughout said central annular portion and is engaged with said distal annular portion, the arms of said third plurality and fourth plurality being configured to hold therebetween leaflets of a tricuspid or mitral valve, characterized in that said arms of said third plurality and/or of said fourth plurality are equipped with sliders, each slider of said sliders being configured to be suspended between a respective pair of said arms of said third plurality and/or of said fourth plurality and to slide back and forth along said respective pair of arms in a radial direction of said articulated prosthesis when the prosthesis is in said expanded configuration; each slider of said sliders has a catching surface configured to grasp by friction leaflets of a tricuspid or mitral valve, and has at least one respective wire fixed thereto and configured to pull said slider radially outwards, when the wire is pulled in a first direction, and to pull said slider radially inwards, when the wire is pulled in a second direction opposite to said first direction; said proximal annular portion being equipped with a holding mechanism configured to hold pulled said at least one wire. a distal annular portion, a central annular portion and a proximal annular portion; a first plurality of arms hinged to an outer side surface of said distal annular portion; a second plurality of arms hinged to an outer side surface of said proximal annular portion; a third plurality of arms each of which is hinged to an outer side surface of said central annular portion, from one end, and to a corresponding end of a arm of said first plurality, from an opposite end; a fourth plurality of arms each of which is hinged to an outer side surface of said central annular portion, from one end, and to a corresponding end of a arm of said second plurality, from an opposite end; said distal annular portion having an internal screw thread, said proximal annular portion having: - a cylindrical collar on a side surface of which said second plurality of arms is hinged, and - a screw engaged into said collar and supported thereby so as to be free to rotate along a longitudinal axis of the screw, the screw being configured to engage with said internal screw thread, - a cylindrical collar on a side surface of which said second plurality of arms is hinged, and - a screw engaged into said collar and supported thereby so as to be free to rotate along a longitudinal axis of the screw, the screw being configured to engage with said internal screw thread, said central annular portion defining a through hole for letting said proximal annular portion pass through; the articulated prosthesis being movable from a distended configuration, in which all said arms hinged in correspondence of their ends are distended, to an expanded configuration, in which said proximal annular portion is threaded throughout said central annular portion and is engaged with said distal annular portion, the arms of said third plurality and fourth plurality being configured to hold therebetween leaflets of a tricuspid or mitral valve, characterized in that said arms of said third plurality and/or of said fourth plurality are equipped with sliders, each slider of said sliders being configured to be suspended between a respective pair of said arms of said third plurality and/or of said fourth plurality and to slide back and forth along said respective pair of arms in a radial direction of said articulated prosthesis when the prosthesis is in said expanded configuration; each slider of said sliders has a catching surface configured to grasp by friction leaflets of a tricuspid or mitral valve, and has at least one respective wire fixed thereto and configured to pull said slider radially outwards, when the wire is pulled in a first direction, and to pull said slider radially inwards, when the wire is pulled in a second direction opposite to said first direction; said proximal annular portion being equipped with a holding mechanism configured to hold pulled said at least one wire.