Early neonatal heart rate variability patterns in different subtypes of perinatal hypoxic-ischemic brain injury

Background This study aims to compare the longitudinal changes in heart rate variability (HRV) during therapeutic hypothermia in neonates with different subtypes of hypoxic-ischemic brain injury. Methods HRV was computed from 1 hour time-epochs q6 hours for the first 48 hours. Primary outcome was brain-injury pattern on MRI at 4(3–5) days. We fitted linear mixed-effect regression models with HRV metric, brain injury subtype and postnatal age. Results Among 89 term neonates, 40 neonates had abnormal brain MRI (focal infarct 15 (38%), basal-ganglia predominant 8 (20%), watershed-predominant 5 (13%), and mixed pattern 12 (30%)). There was no significant difference in the HRV metrics between neonates with normal MRI, focal infarcts and basal ganglia pattern. At any given postnatal age, the degree of HRV suppression (HRV measure in the brain-injury subtype group/HRV measure in Normal MRI group) was significant in neonates with watershed pattern (SDNN(0.63, p = 0.08), RMSSD(0.74, p = 0.04)) and mixed pattern injury (SDNN (0.64, p