A heart therapy device having a right-ventricular electrode and a left-ventricular electrode connected to a tachycardia identification unit. The tachycardia identification unit identifies ventricular tachycardia and simultaneously evaluates the heart rate at the right-ventricular and left-ventricular electrodes. The ventricular electrodes each include an electrode line having a corresponding sensing electrode pole that senses electric potential courses in the myocardium of the respective ventricle. The heart therapy device includes a dislocation identification unit that detects a possible dislocation of one of the ventricular electrodes, simultaneously evaluates the heart rate at both ventricular electrodes, and signals a right-ventricular or left-ventricular dislocation when a sudden rise in heart rate is sensed at the right-ventricular or left-ventricular electrode, without detecting a considerable change in rhythm at the respective electrode. In the event of the dislocation of one of the ventricular electrodes, the rhythm information of the electrode in question is ignored for tachycardia detection.
