An expandable stent for an endoprosthesis used in the treatment of a narrowing of a cardiac valve and/or a cardiac valve insufficiency for reducing longitudinal displacement of a valvular prosthesis relative a stent when implanted. In one embodiment, the stent may comprise at least one fastening portion by which the valvular prosthesis is connectable to the stent. In another embodiment, the stent further comprises positioning arches and retaining arches, whereby at least one positioning arch is connected to at least one retaining arch via a first connecting land. In another embodiment, the stent may comprise at least one auxiliary arch which connects the respective arms of the at least one retaining arch connected to the at least one positioning arch.