The invention relates to medicine, namely to cardiology, cardiovascular surgery, functional diagnosis and clinical electrophysiology of the heart. The invention consists in reconstructing electrograms, whose experimental registration requires an invasive access, by computational way on unipolar ECGs recorded at 80 and more points of the chest surface. An application of the method allows one to improve the accuracy of non-invasive diagnosis of cardiac rhythm disturbances and other cardio-vascular diseases.