Heart rate variability in hypoxic ischemic encephalopathy: correlation with EEG grade and 2-y neurodevelopmental outcome

BACKGROUND: The study aims to describe heart rate variability (HRV) in neonatal hypoxic ischemic encephalopathy (HIE) and correlate HRV with electroencephalographic (EEG) grade of HIE and neurodevelopmental outcome. METHODS: Multichannel EEG and electrocardiography (ECG) were assessed at 12-48h after birth in healthy and encephalopathic full-term neonates. EEGs were graded (normal, mild, moderate, and severe). Neurodevelopmental outcome was assessed at 2 y of age. Seven HRV features were calculated using normalized-RR (NN) interval. The correlation of these features with EEG grade and outcome were measured using Spearman's correlation coefficient. RESULTS: HRV was significantly associated with HIE severity (P < 0.05): standard deviation of NN interval (SDNN) (r = -0.62), triangular interpolation of NN interval histogram (TINN) (r = -0.65), mean NN interval (r = -0.48), and the very low frequency (VLF) (r = -0.60), low frequency (LF) (r = -0.67) and high frequency (HF) components of the NN interval (r = -0.60). SDNN at 24 and 48h were significantly associated (P < 0.05) with neurodevelopmental outcome (r = -0.41 and -0.54, respectively). CONCLUSION: HRV is associated with EEG grade of HIE and neurodevelopmental outcome. HRV has potential as a prognostic tool to complement EEG.