A comparison of the standard 12-lead electrocardiogram to exercise electrode placements.

In order to determine the effect of electrode placement and standing on the 12-lead electrocardiogram required prior to exercise testing, 104 male patients with stable coronary heart disease were studied. Electrocardiograms were recorded with two different placements of the arm electrodes commonly used for exercise testing with the patient supine and standing. These were compared to a standard ECG with the electrodes placed at the wrists and ankles with the patient supine. The four ECGs gathered on each patient were analyzed using standard visual techniques for diagnostic changes and using a computer for analysis of axis, amplitudes, and durations. There were important differences between the standard 12-lead ECG and the ECGs gathered with the pre-exercise test modifications. These differences were minimized by placing the arm electrodes as close to the shoulders as possible and by recording the ECG with the patient supine.