Human body surface mapping during atrial depolarization in normal and diseased subjects

Body surface isopotential distributions during atrial excitation were examined in 21 normal subjects--12 cases with right atrial overload (RAO-group) and nine cases with left atrial overload (LAO-group). Each subject showed both a single maximum and a minimum during the atrial excitation. In normal subjects, a maximum initially appeared throughout the central region of the anterior chest. Later, it moved to the left and to the subjects' back. To analyze this movement we divided a maximum into two parts and named them the anterior maximum and the left maximum, respectively, dependent upon their location relative to the left midclavicular line. We measured durations of three parameters of the maxima movements, namely: (A) the duration of the anterior maximum, (B) the duration of the left maximum and (C) the shift time from the anterior maximum to the left maximum. In the normal group, (A) was 32 +/- 11 msec (mean +/- S.D.), (B) was 38 +/- 6 msec and (C) was 51 +/- 12 msec. In the RAO-group, (A) time period was prolonged, (B) time period was shortened, and (C) time period was delayed in comparison to the respective values in the normal group. In the LAO-group, the (B) time period was longer than in the normal group. These changes were statistically significant, so that these findings suggest that the anterior maximum reflects mainly right atrial activation, and the left maximum, left atrial activation.