An implantable stent (10) which is installed as a support sleeve in the region of an vasoconstriction expandable especially by means of a balloon catheter (2), is continuously broken along the one long side. On both sides of the break (4), recesses, eyelets or punchings (6) are provided on which at least one removable holding element engages in order to keep the break (4) closed at first. After removing the holding element by withdrawing or gradual dissolution of its material, the break (4) can be exposed so that the previously selected stent (1) can be subsequently expanded again while enlarging the break (4) in order, for example to take the growth of a patient into consideration.