Correlations between indices of heart rate variability in healthy childrenand children with congenital heart disease

Heart rate variability, as determined from 24-hour Holter recordings, repre sents a noninvasive parameter for studying the autonomic control of the hea rt. It decreases with certain disease states characterized by autonomic dys function such as congestive heart failure. No study in healthy or cardiac c hildren has been performed to determine the correlations between and within time and frequency domain indices of heart rate variability. We examined f ive time domain (SDNN, SDNNi, SDANNi, rMSSD and pNN50) and five frequency d omain measures (ULF, VLF, LF, HF and balance LF/HF) in 200 healthy children and 200 children with congenital heart disease, aged 3 days to 14 years. A ll measures were significantly correlated with each other. However, the str ength of correlation varied greatly. Our data show that variables strongly dependent on vagal tone (rMSSD, pNN50 and HF) were highly correlated (r val ue > 0.90), as well as SDNN and SDANNi. We conclude that certain time and f requency domain indices correlate so strongly with each other that they can act as surrogates for each other.