Isointegral analysis of body surface maps: Surface distribution and temporal variability in normal subjects

Isointegral analysis of body surface potential maps had been proposed as a useful approach to data reduction. To determine the normal magnitude and surface distribution of a series of time-integral measurements, we acquired body surface potential maps from 40 men and 15 women, ages 20-46 years, who were clinically normal. In a subset of 16 subjects, variability in serial maps was assessed as the root-mean-square difference in time-integral values between maps using the same electrode application (recordings separated by 15 minutes) as well as when different electrode applications were required (recordings separated by 1-7 days). Isointegral maps of the QRS, ST-T, QRST, ST-segment and Q-zone time integrals all demonstrated predominantly bipolar body surface distributions, with positive values located over the precordium and negative values over the right chest and back. Men had significantly (p <0.05) greater maximum and minimum values than women for all time integrals except Q zone. Variability in serial maps was small and was significantly greater (p <0.001) between maps acquired with different, compared to the same, electrode application. Moreover, variability tended to be greatest for time integrals that reflected repolarization events. We conclude that time-integral analysis of body surface potential mapping is a practical method for data reduction that holds considerable promise as a technique to rapidly assess the ECG effects of many drugs and interventions. Variability in sequential maps is small but must be considered before serial alterations in time integrals are accepted as meaningful.