Device defibrillation of a heart

The device (1) has a defibrillation electrode (4) connected to a stimulation electrode (5) in a use position such that a pole (6) of the defibrillation electrode is arranged on an outside of the stimulation electrode. The defibrillation electrode is moveable relative to the stimulation electrode, is retractable from the use position and is exchangeable relative to the stimulation electrode that remains implanted in the use position. The stimulation electrode is detached or separated from a cardiac pacemaker (3) or a plug provided on the pacemaker.