Clinical determinants of electrocardiographic and spatial vectorcardiographic descriptors of ventricular repolarization in healthy children.

Abstract

Although the association of repolarization alterations to the development of life-threatening ventricular arrhythmias has received considerable research attention, there is paucity of data regarding what may be considered as normal, especially in children. To define electrocardiographic (ECG) and vectorcardiographic (VCG) descriptors of ventricular repolarization in healthy school-age children, 12-lead digital ECGs were obtained from 646 children (348 males/298 females, mean age 8.54 ± 1.86 years). All QT intervals were measured manually using the digitally stored ECGs. Orthogonal X, Y, and Z leads were reconstructed from the standard 12-lead ECGs and the maximal amplitudes of the spatial QRS and T vectors were calculated, as well as the spatial QRS-T angle. The mean heart rate was 95.3 ± 15.8 bpm and the QRS duration was 83.4 ± 9.3 ms. Mean QT interval was 334.1 ± 24.2 ms and the corrected QT interval was 436.5 ± 23.8 ms (Bazzet) and 404.3 ± 19.4 ms (Fridericia). Although the uncorrected maximum and mean QT intervals were significantly higher in boys (P values 0.011 and 0.009, respectively), there was no difference in the rate-corrected QT interval. The spatial QRS and T-vector amplitudes were 1512.0 ± 365.7 μV and 478.8 ± 149.3 μV, respectively. The spatial QRS-T angle was 14.1 ± 8.0 degrees. Although the mean QT interval showed significant increase with age (P = 0.014), all VCG parameters did not show significant variance with age. A range of ECG and VCG descriptors of ventricular repolarization was determined in a large sample of healthy school-age children to provide a data basis of normal values for future reference.