A Simple Geometric Analysis of Cardiac Potentials as Recorded at Points Close to the Heart

A simple geometric method is employed to investigate the theoretically expected potentials at an electrode close to the heart as a dipole moves about in an area in the chest occupied by the heart. The considerable error resulting from the assumption that the dipole remains at the center of a geometric frame of reference is thus disclosed. It is pointed out that errors in polarity which occur cannot be compensated for by alteration of the characteristics of the recording device. It is suggested that such errors account for the finding by spatial vectorcardiographers that many normal QRS loops point forward, a finding which does not correlate well with the Gardberg-Ashman hypothesis of ventricular accession. It is further suggested that the limb leads are not free of these effects and that exaggeration of the electrical rotation of the heart is thus accounted for. It is further pointed out that derivation of precordial potentials from vector loops or vice versa is not permissible.