A tension adapter for a catheter is disclosed, in which a wire is arranged for electrical stimulation. The tension adapter tensions the catheter by means of a hollow cylindrical elastic tensioning piece (26) which is axially flattened. A contact lug (24) is proximally connected to the tensioning piece (26), into which the proximal end of the catheter extends, whereby the outwardly-bent wire on the catheter comes into contact with the contact lug (24). The contact lug (24) comprises an electrical lead running to the exterior.