Abstract: An implant for improving coaptation of an atrioventricular valve in a heart, the atrioventricular valve having a native first leaflet, a native second leaflet and optionally an annulus adjacent a wall of an atrium of the heart, the implant comprising an artificial leaflet to replace or support the first and/or second native leaflets, fixing means for fixing the implant to the annulus or to the first and/or second native leaflets and retention means for preventing prolapse of the artificial leaflet. The retention means comprise or consist of a backbone element extending along the artificial leaflet and towards a distal end of the artificial leaflet and being connected to the artificial leaflet at at least two attachment points, wherein the backbone element is configured to be bendable between first and second states of bending and wherein limiting means are provided for limiting the degree of bending.