Analysis of heart rate variability in paediatric patients with vasovagal syncope

Introduction: The aim of the study was to detect any abnormalities of the autonomic nervous system in children and adolescents with vasovagal syncope. Material and methods: We studied 56 children, ages eight to 17 years, with a history of vasovagal syncope and 41 healthy volunteers. Heart rate variability was calculated over a 24-hour period for heart rate, standard deviations of the averages of the R-R intervals in all 5-min segments of R-R intervals (SDANN), the root of the 24-hour square (RMSSD), the proportion of adjacent normal R-R intervals < 50 ms (pNN50), the total power (TP), the low frequency index (LF), the high frequency index (HF), and the LF/HF ratio. Results: Patients with vasovagal syncope had significantly reduced values of 24-hour (256.21 ±190.97 ms, 366.51 ±264.7 ms, p = 0.048) and night-time SDANN (168.56 ±140.59 ms, 251.54 ±189.92 ms, p = 0.034); 24-hour (292.96 ±226.25 ms, 390.49 ±254.06 ms, p = 0.046), daytime (349.52 ±298.32 ms, 479.23 ±350.39 ms, p = 0.040), and night-time RMSSD (188.47 ±161.07 ms, 271.05 ±200.70 ms, p = 0.029); daytime pNN50 (25.10 ±13.10%, 32.10 ±14.19%, p = 0.037); and increased value of night-time LF/HF ratio (1.43 ±1.50, 0.86 ±1.00, p = 0.015), in comparison to healthy subjects. In adolescents with vasovagal syncope we found significantly lower values of 24-hour (7578.29 ±5409.74 ms2, 12236.00 ±5651.45 ms2, p = 0.025) and daytime TP (4776.19 ±4146.56 ms2, 10488.70 ±8326.43 ms2, p = 0.039), 24-hour (2120.90 ±2057.00 ms2, 3634.22 ±3026.90 ms2, p = 0.015) and daytime HF (930.10 ±1101.66 ms2, 7832.90 ±18825.10 ms2, p = 0.015), in comparison with children. Males presented lower values of 24-hour (207.4 ±134.63 ms, 324.00 ±236.95 ms, p = 0.042) and daytime SDANN (264.56 ±208.16 ms, 432.65 ±320.52 ms, p = 0.044), and daytime RMSSD (282.54 ±248.94 ms, 446.28 ±342.35 ms, p = 0.041) compared with females. Conclusions: Paediatric patients with vasovagal syncope had alterations in basal autonomic balance, which indicated an increased sympathetic modulation. More severe autonomic imbalance occurs in adolescent males.