Body Surface Distribution of Equipotential Lines during Atrial Depolarization and Ventricular Repolarization

In 15 normal male human subjects and 6 dogs, 200 chest electrocardiograms were sequentially recorded. The distribution of equipotential lines on the thoracic surface was determined at 20 to 30 instants of time during atrial activation and ventricular recovery. In humans, the potential pattern is constantly dipolar, with one maximum and one minimum, during the P wave. The motion of the potential maximum and minimum on the chest surface appears to be related to the progress of the excitation through the auricular walls. At the end of the QRS interval, the simultaneous presence of activation and recovery potentials is generally observed, giving rise to several simultaneous maxima and minima. During the ST and T interval, recovery potentials show a dipolar distribution in normal subjects, but tripolar patterns are observed when the recovery process is altered in a circumscribed myocardial region. In dogs, multipolar distributions are frequently observed during the P wave, the ST segment and the T wave. During atrial activation and ventricular recovery, chest maps yield more information on the electrical activity of the heart (both normal and abnormal) than is offered by ordinary limb and precordial leads.