[Theory of methods to compare lead fields in electrocardiography (author's transl)].

A method is theoretically described to test the accuracy of various lead system of the ecg. The priniciple of this method consists in the following procedure. The heart position is changed maximally in a proband by varying the position of the body and by deep inspiration and exspiration. If the lead field is parallel, the recorded vector loops should by conventible into each other by merely rotating them electronically, because the cardiac determinants of the veg will scarcely be changed by a change in heart position. The deformations of the veg in the edgeside and broadside view are an appropriate measure of the inhomogenities (the "accuracy") of the lead field, mostly caused by the configuration of the chest and the inhomogeneous conductivity of the tissues and the resulting lack of parallelity in the lead lines of the field. Criteria to test the form of the vector loop are developed, measuring quantitatively the similarly of the loops recorded in different heart positions. The "best" lead is regarded to be that with greatest similarity of the loops in extreme dislocations of the heart.