heart rate variability; LF/HF index; blood pressure variability; development

We have shown previously how the dependency of the baroreflex sensitivity on the inter-beat intervals (IBI) can cover up the developmental changes. Therefore we decided to analyse LF/HF ratio. We have calculated mean IBI and heart rate (HR) and their power spectra in 424 subjects (11 - 20 years) from the 5-min continuous blood pressure monitoring at rest. LF/HF ratios of IBI and HR spectra were determined The statistic was done for a whole group (WG), and for subgroups of older children (C: 11-15 years), adolescents (A: 16-20 years), and for 10 particular age-subgroups. In the WG and the A, we shown significant relationship between age and mean IBI or HR, but LF/HFIBI or LF/HFHR were age-independent. LF/HFIBI or LF/HFHR was also significantly age-dependent. Negative correlation of IBI vs. LF/HFIBI and a positive correlation of HR vs. LF/HFHR in the WG and in C or A was found Relationship IBI vs. LF/HFIBI and HR vs. LF/HFHR were in particular age-subgroups from 11 to 14 years, but it was insignificant in subgroups from 15 to 20 years. Our analysis showed the increase of LF/HF ratio up to the age of 15 years when the development of sympathovagal balance seems to be finished Strong relationship between IBI or HR and LF/HF ratios could cover the development changes.