It has been demonstrated on an model of the cardiac electrical activity that, during the course of proportional homothetic transformations of the heart and His-Purkinje system, the values of the spatial heart vector change, as a first approximation under comparable conditions, in proportion to the extension of the heart ventricle surface rather than the myocardium mass, since the magnitude of the electrocardiosignal is determined at every instant by the area of depolarized regions on the epicardium and endocardium, which corresponds to the model of a double electrical layer on the surface of the electrically active myocardium.