Heart rate variability in infants with apparent life-threatening events

Heart rate variability (HRV) is often used as an index of sympatho-vagal ba lance. A decreased HRV has been observed in patients with central hypoventi lation and in infants who have later succumbed to sudden infant death syndr ome (SIDS). The aim of the present study was to investigate whether HRV is altered in infants with apparent life-threatening events (ALTE), a group wi th an increased risk of SIDS. Fifty infants with ALTE were compared with 50 age- and sex-matched controls. ECG was recorded overnight in all infants. Two sequences of RR intervals free of artefacts were selected from each sle ep state and spectral analysis of RR variability was performed. The mean an d SD of RR and the low (LFPow) and high (HFPow) frequency power were analys ed. In active sleep (AS) the LF/HF ratio was lower in ALTE infants, but no differences were seen in either the LFPow or the HFPow. In quiet sleep (QS) , however, ALTE infants had higher SD-RR (p = 0.006), greater HFPow (p = 0. 02) and VLFPow (very low frequency power, p = 0.02) than the control infant s. The same results were seen when the two sleep states were combined for a nalysis, ALTE infants had higher SD-RR (p = 0.004), HFPow (p = 0.006) and V LFPow (p = 0.04). Conclusions: The different HRV pattern in ALTE infants compared to healthy controls suggests an altered autonomic control.