Effects of electrode area on electrocardiographic voltages

Effects of two different sizes of chest electrodes--100 and 750 mm2 area--on x and z Frank leads were determined using electrocardiographic data from 25 subjects. In most cases, differences in Rx and Rz were below 50 uV, but in nine cases (36%) differences exceeded this value for either Rx or Rz or both. In six cases, differences exceeded 100 uV. For an additional 20 subjects, standard precordial leads were recorded using the same two electrode sizes. QRS amplitudes were significantly affected for V4 but not for V1 or V6. Variability caused by electrode size is greater than that caused by beat-to-beat variation and is comparable to that found in day-to-day variation. Interchangeability of data among ECG recording laboratories can be significantly improved by standardizing electrode size for precordial electrodes.