Normal variability of the peak-to-trough amplitude of isointegral QRST body surface maps.

The peak-to-trough amplitude (sum of absolute values of maximum and minimum) of an isointegral QRST body surface map was shown, according to literary data, to be sensitive to changes in ventricular sympathetic tone. Statistics of this parameter were obtained, with an 80 electrodes array, in 135 healthy subjects of both sexes, aged from 10 to 67 years (37 +/- 16). The QRST amplitudes were smaller in females than in males in average by 28% (P < .0001). They decreased with increasing age (r = -0.237, P < .01). Larger QRST amplitudes went with longer RR intervals (r = .449, P < .0001). In held deep inspiration, the amplitude decreased in 79% and increased in 21% of subjects. The change of the amplitude was related to the inspiratory change of the RR interval (r = .343, P < .0001), but not to the RR interval preceding the deep inspiration. Body mass index and somatometric characteristics of chest configuration did not significantly affect the QRST amplitude. The results may serve as a basis for further studies on the usefulness of the QRST amplitude as another variable reflecting changes of ventricular recovery properties.