The present invention relates to an apparatus and a corresponding method for non-invasive intracardiac electrocardiography (ECG) by use of a magnetic and electrically conducting interference device (210). An MPI-based ECG mapping technique is proposed, wherein an interference device (210), e.g. an electrically conducting rod containing soft magnetic material, is steered through the vessel system and the heart using magnetic fields generated by a magnetic particle imaging (MPI) system so that the ECG signals measured in parallel are influenced. Using appropriately adapted evaluation means (153) this influence of the interference device (210) on the ECG signals can be evaluated to gain spatially resolved information about the electrical heart activity.