The aim of the study was to demonstrate a biomathematical model for the topographic presentation of orthogonal electrocardiogram DECARTO, to present the possibilities for visualisation and processing of ECG in relation to others cardiological imaging methods. In DECARTO (Dipolar ElectroCARdioTOpography), the orthogonal ECG is used as an input signal, the signal is processed by the means of a biomathematical model and presented as areas of activated points on a spherical surface closely surrounding the heart, so-called decartograms. Decartograms can be visualised using the projection of the spherical image surface onto geometrically defined planar or 3D surfaces. The selection of the surface depends on the purpose of ECG imaging, on the evaluation of advantages and limitation of the particular possibilities, such as the degree of deformation, and their comparability with other imaging methods. Another possibility of 3D visualisation of decartograms is the utilisation of time as a 3rd dimension of the space. Additionally to analytically defined geometrical surfaces, it is possible to project decartograms onto a real surface of the heart, constructed from data of other image techniques. In this paper we present a superposition of decartogram and SPECT imaging, which combines graphic presentation of two diagnostic methods providing different but complementary information on the heart. The combination of comparable information allows to study the relationship between electrogenesis and perfusion of myocardium and its metabolism, to study diagnostic and prognostic importance of both agreements and disagreements of used methods. The fusion of information on the structure and function of the heart could potentially increase the diagnostic power of both methods.