Geometric indexes of heart rate variability in obese and eutrophic children.

BACKGROUND Obesity causes changes in cardiac autonomic modulation. OBJECTIVE To investigate the autonomic modulation of eutrophic and obese children by means of indexes of heart rate variability (HRV) obtained through geometric methods. METHODS We analyzed data from 133 children aged 8 to 13, divided into two groups: obese (n = 61) and eutrophic (n = 72) according to body mass index for age and sex. For the analysis of HRV, heart rate was recorded beat-to-beat. The RR intervals were transformed into geometric figures, and from them, we calculated the triangular index (RRtri), triangular interpolation of RR intervals (TINN), the indexes SD1, SD2 and SD1/SD2 ratio, obtained from the Poincaré plot. Visual analysis of the plot was also performed. Student's t test was performed for unpaired data and Mann-Whitney's test, with significance level of 5.0%, for data analysis. RESULTS In obese children, RRtri indexes were proven to be reduced (0.0730 vs 0.1084 [median]), TINN (171.80 +/- 55.08 vs 218.26 +/- 51.12), SD1 (19.93 +/- 9.10 vs 24.10 +/- 8.03) and SD2 (51.63 +/- 16.53 vs 69.78 +/- 17.19). The SD1/SD2 ratio showed no significant differences (0.3781 +/- 0.12 vs 0.3467 +/- 0.08). Visual analysis of the plot, in obese children, revealed a smaller dispersion of RR intervals both beat-to-beat, and in the long term, indicating lower HRV. CONCLUSION Obese children presented changes in the autonomic nervous system characterized by decreases in parasympathetic activity and overall variability.