Establishing normative values for short-term heart rate variability indices in healthy infants in the emergency department.

Background: Heart rate variability (HRV) has been used as a marker of cardiovascular health and a risk factor for mortality in the adult and paediatric populations, and as an indicator of neonatal sepsis. There has been an increasing interest in using short-term (5 minutes) HRV to identify infants ≤90 days of life with serious bacterial infections. However, there has not been any normative data range reported for short-term HRV indices in this infant population. The aim of this study was to evaluate short-term HRV indices in awake, healthy young infants >48 hours and ≤90 days of life and to establish a reference range. We also aimed to produce a clinical calculator that can be used in this population for evaluation of short-term HRV variables in young infants in the emergency department (ED) setting that can be potentially used in future clinical validation and research. Methods: We conducted a prospective observational study of short-term HRV analysis of awake, well infants ≤90 days of life in the ED setting. Results: One hundred and eight infants with complete data [51.9% male, median age 9 days (interquartile range, 4-35 days)] were included. We found that heart rate (HR) is correlated with HRV. Thus, normalisation of HRV parameters was done to remove their dependence on HR. We then provided normative reference range of widely used short-term HRV time-domain, frequency-domain, and non-linear HRV metrics in our cohort. Conclusions: We established normative values and HRV calculator for evaluation of these short-term HRV variables in young infants in ED settings that can be used for further clinical validation and clinical research.