The invention relates to a method and to a device for visually assisting a catheter application on the heart (H) of a patient (P) using at least one image of the patient (P) obtained by means of a C-arm X-ray device (1) and using electroanatomic mapping-data of the patient (P) that is obtained by means of an electromagnetic position detection system and mapping system (2). The C-arm X-ray device (1) and the electromagnetic position detection system and mapping system (2) are calibrated in relation to each other, by means of the determination of a co-ordinate transformation between a co-ordinate system (CR) assigned to the C-arm x-ray device (1) and/or a co-ordinate system (CB) that is assigned to the at least one image generated by the C-arm X-ray device (1) and a co-ordinate system (CM) assigned to the electromagnetic position detection system and mapping system (2). The position of the patient (P) is determined during the detection of the image and/or during the detection of the electroanatomic mapping-data and is at least indirectly assigned to the image and/or the electroanatomic mapping-data.
