The invention relates to an implantable device for use in the human and/or animal body to replace an organ valve, comprising a main body having a first end and a second end, wherein the first end and the second each have an opening to provide a fluid connection through the main body between the first end and the second end a first membrane element arranged inside or at one end of the main body, wherein the membrane element is formed in such a manner that it allows the fluid connection through the main body in a first flow direction and blocks the same in a second flow direction opposite the first flow direction wherein the main body has a large ratio of length to transverse expansion along the longitudinal axis of the main body in a first operating state (primary form) and a smaller ratio of length to transverse expansion along the longitudinal axis of the main body in a second operating state (secondary form) and wherein the main body can be reversibly transferred from the secondary form to the primary form counter to elastic material forces by the application of a force and wherein the main body is formed from a single wire-like element or from a plurality of wire-like elements connected to each other by means interlocking winding and/or twisting and/or weaving in the manner of a woven and/or layered fabric and/or net.
