The development of LF/HF ratio and its dependence on the mean heart rate in children and adolescents

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 -1 5 years), adolescents (A:16-20 years), andfor 10 particular age-subgroups. In the WG and the A, we shown significant relationship between age and mean IBI or HR, but LF/HF_IBI or LF/HF_HR were age-independent. LF/HF_IBI or LF/HF_HR was also significantly age-dependent. Negative correlation of IBI vs. LF/HF_IBIand a positive correlation of HR vs. LF/HF_HR in the WG and in C or A was found. Relationship IBI vs. LF/HF_IBI and HR vs. LF/HF_HR 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.