Age and sex variability of initial parts of the QRS complex displayed in isointegral maps of young people.

Although body surface electrocardiographic mapping is used also in clinical practice, there are only a few papers concerning the isointegral maps (IIMs) in children. We constructed IIMs of 169 healthy young people during the initial parts of the QRS complex: the first 20 ms (QRS20), 30 ms (QRS30), 40 ms (QRS40), and from 20 ms to 40 ms (QRS(20-40)). Subjects were divided into 6 groups: 9-10 y (F1, M1), 13-14 y (F2, M2), 18-19 y (F3; M3). We analysed the extreme values of each time integral. We found maxima and peak-to-peak values decreasing with age, while minima tended to increase (became less negative). Most age differences were found in IIM QRS(20-40) and between peak-to-peak values. Least differences were between minima. Maxima and peak-to-peak values were higher in males than in females. No significant differences were found in any extreme value between groups F1 and M1 except for IIM QRS20 maxima. Significant sex differences increased with age. The only significant difference found in minima was between F2 and M2. Most sex differences were found in IIM QRS20. We assume that our findings can be explained (at least in part) by the influence of heart-chest geometry.