1. A method for visualizing at least two different types of cardiac tissue by way of an imaging tomographic recording technique with the aid of x-ray radiation, the method comprising: scanning at least one cardiac region of a patient by x-ray radiation which passes through a first grating for the passing-through x-ray radiation, designed as an absorption grating, prior to reaching the patient; detecting at least locally caused phase-shifts of the x-ray radiation in the cardiac region by using a second grating for the passing-through x-ray radiation, designed as a phase grating, downstream of the patient in the emission direction; measuring and reconstructing a spatial distribution of detected at least locally caused phase-shifts, wherein an average specific phase-shift value is assigned to each spatial unit; assigning each of the at least two different tissue types to a region of a typical specific phase-shift value; and optically highlighting at least one region assigned to a tissue type in a view of the cardiac region.