Mapping of blood pressure and heart rate variability: A model for pediatricians

In order to assess the development of several chronome components of the electrocardiogram, around-the-clock ambulatory ECG records were obtained from 19 infants (25 days to 3 months of age), 22 children (3-9 years of age), 18 boys and girls (10-14 years of age), 14 pubertal boys (15-20 years of age), and 19 young men (21-29 years of age). Time- and frequency-domain measures of heart rate variability (HRV) were obtained by spectral analysis, using the maximal entropy method (MEM). The frequency of detection of the circadian, circasemidian and circaoctohoran components, with periods of about 24, 12 and 8 hours, respectively, was compared among the five groups for several HRV endpoints, notably the 1/f fractal scaling, total spectral power within a 180-min span, and its distribution in several frequency regions. A circadian component is already detectable in a sizeable proportion of infants and children for most of the HRV indices considered. The incidence of detection of the circadian component increases with age for the spectral power in different frequency regions, notably around 10.5 seconds ('LF') and around 3.6 seconds ('HF'); it peaks around puberty for 1/f; and it does not change with age for the total spectral power. Similar changes with age are not observed for the circasemidian or circaoctohoran components. The latter characterizes primarily 1/f and less so 'HF'. Several aspects of the HRV chronome may thus develop differently as a function of age, in keeping with the time-macroscopic findings of Theodor Hellbrügge nearly half a century ago. The results are interpreted in the light of gender differences found for several time-domain measures of HRV and of trends as a function of age, which are not necessarily linear. Effects of geomagnetic disturbance on HRV, the 1/f fractal scaling in particular, are assessed in adults living at a high latitude where magnetic storms are felt more strongly, that may constitute a signal and possibly a mechanism underlying both undesirable and desirable effects, depending upon circumstances yet to be elucidated. The possibly circadecadal stage-dependence of morbidity and/or mortality from certain conditions, such as myocardial infarctions, remains to be studied in pediatric populations. Further work could thus examine whether any effects of geomagnetic disturbances may account, at least in part, through effects upon the circulation, for long-term infraannual changes, possibly anchored in the population's gene pool, observed in a number of anthropologic measurements at birth as well as in other population statistics.