An apparatus for non-invasive intracardiac electrocardiography configured to be used with a magnetic and electrically conducting interference device, which apparatus comprises: - ECG means (151, 230) for recording ECG signals, - selection means comprising a selection field signal generator unit and selection field elements, comprising in particular selection field magnets or coils, for generating a magnetic selection field having a pattern in space of its magnetic field strength such that a first sub-zone having a low magnetic field strength and a second sub-zone having a higher magnetic field strength are formed in a field of view, - drive means comprising a drive field signal generator unit and drive field coils (136a, 136b, 136c) for changing the position in space of the two sub-zones (52, 54) in the field of view by means of a magnetic drive field so that the magnetization of the interference device in the field of view changes locally, - receiving means comprising at least one signal receiving unit and at least one receiving coil for acquiring detection signals, which detection signals depend on the magnetization of the interference device in the field of view, which magnetization is influenced by the change in the position in space of the first and second sub-zone (52, 54), - control means for controlling said signal generator units (110, 130) to generate and provide control currents to the respective field coils to generate magnetic fields suitable for moving the interference device through the vessel system and the heart in a direction instructed by movement commands and/or for holding the interference device at a constant position, - processing means for processing said detection signals acquired when the magnetic fields are applied for determining the position of the interference device within the vessel system and the heart from the processed detection signals, and - evaluation means for evaluating the influence of the interference device on the ECG signals recorded by the ECG means (151, 230). - ECG means (151, 230) for recording ECG signals, - selection means comprising a selection field signal generator unit and selection field elements, comprising in particular selection field magnets or coils, for generating a magnetic selection field having a pattern in space of its magnetic field strength such that a first sub-zone having a low magnetic field strength and a second sub-zone having a higher magnetic field strength are formed in a field of view, - drive means comprising a drive field signal generator unit and drive field coils (136a, 136b, 136c) for changing the position in space of the two sub-zones (52, 54) in the field of view by means of a magnetic drive field so that the magnetization of the interference device in the field of view changes locally, - receiving means comprising at least one signal receiving unit and at least one receiving coil for acquiring detection signals, which detection signals depend on the magnetization of the interference device in the field of view, which magnetization is influenced by the change in the position in space of the first and second sub-zone (52, 54), - control means for controlling said signal generator units (110, 130) to generate and provide control currents to the respective field coils to generate magnetic fields suitable for moving the interference device through the vessel system and the heart in a direction instructed by movement commands and/or for holding the interference device at a constant position, - processing means for processing said detection signals acquired when the magnetic fields are applied for determining the position of the interference device within the vessel system and the heart from the processed detection signals, and - evaluation means for evaluating the influence of the interference device on the ECG signals recorded by the ECG means (151, 230).