1. A method for displaying an invasive instrument during an invasive examination of a heart of a patient, comprising: providing an X-ray system; arranging an orientation system for the invasive instrument in a fixed location relative to the X-ray system, the orientation system: transmitting a radio wave from a transmitter affixed to the X-ray system, receiving the radio wave from a receiver affixed to the invasive instrument, calibrating a relationship between the X-ray system and the orientation system, based on determining a distance between the X-ray system and the fixed location within the orientation system, determining a position of the receiver of the invasive instrument relative to the transmitter of the X-ray system, based on the transmitting, receiving and calibrating steps, without a registration relative to the X-ray system; generating a three-dimensional X-ray image data set of the heart with the X-ray image; determining a coordinate of the invasive instrument relative to a coordinate of the X-ray system via the orientation system; displaying the three-dimensional X-ray image data set with the invasive instrument being visible in the X-ray image data set on a screen; wherein a three-dimensional pre-operative image data set is acquired prior to the examination by an image system that is different from the X-ray system; and wherein the pre-operative image data set is aligned with the X-ray image data set in a correct position and dimension based on a position of the invasive instrument in a coordinate of the pre-operative image data set.