Artificial valve

An implantable valve cusp (30) to form a valve within a body lumen (44), comprising: a triangular leaflet (42) formed by a thin flexible material and having an inner face and an outer face; invertiblemente lamella being deformable between a first position, in which the inner face is concave lamella and a second position in which the inner face is convex lamella; and an anchoring element (38); and characterized in that the anchoring element (38) is located in an apex of the triangular leaflet and operable to attach the leaflet to the wall of the body lumen (44) only at the apex.