An implantable electrode catheter device comprising an inner electrode catheter and an outer electrode catheter. The outer electrode catheter including a catheter shaft having at least one electrode at a distal end and a lumen to receive the inner electrode catheter therein. The outer electrode is adjustable or movable relative to the inner electrode catheter in an axial direction. The inner electrode catheter has a fixation element disposed at a distal end. The inner electrode catheter together with the fixation element forms an indifferent electrode whereby radio frequency catheter ablation occurs between the electrode and the indifferent electrode.
