A catheter for cardiovascular application includes an elongated catheter shank; a lumen inside the catheter shank; a mandrel sleeve that extends in the lumen; a guide wire which runs in the mandrel sleeve and is extendable through a sluice gate out of the catheter at a distal end thereof; and a sealing unit for sealing the lumen, the sealing unit being disposed proximally in front of the sluice gate and reversibly pierced by the replaceable mandrel sleeve.