Methods: Continuous 24-hour electrocardiographic (ECG) recordings from 55 newborn infants, hospitalized at birth for treatment of CCHD, will be used to calculate heart rate variability (HRV) as an index of ANS function.6 ECG waveforms before and after surgical intervention were obtained from Philips bedside monitors, equipped with the Excel Medical Electronics Bedmaster research export tool, stored in the hospital’s central server, and exported to an encrypted research server. Raw ECG waveform data were then imported into the GE Healthcare MARS ECG analysis and Editing System (General Electric, Inc.) for HRV analysis. Each ECG complex was identified and characterized as to morphology by the computer software. This preliminary analysis is currently being verified by the PI to assure proper labeling of heart beats and artifact. Interbeat intervals associated with ectopic beats, non-sinoatrial node-initiated complexes, and artifact will be excluded from analysis. Power in three frequency domains will then be calculated: very low frequency (reflecting effects of thermoregulation and neurohormones on heart rate), low frequency (reflecting the combined effect of sympathetic and parasympathetic influences on heart rate), and high-frequency (reflecting parasympathetic influences on heart rate). Data related to growth (weight-for-age Z-scores), development (Bayley Scales of Infant Development III; occupational, physical, or speech intervention), and survival over 12 months will be obtained from the electronic medical record. Relationships among neonatal HRV and growth and development over 12 months will be analyzed using latent growth models with adjusting covariates. Relationships between neonatal HRV and survival at 12 months will be analyzed using logistic regression.
Results: We expect infants with more regulated ANS function during the neonatal time period will demonstrate improved growth and development. In addition, we expect markedly impaired neonatal ANS function to be associated with mortality within the first 12 months.
Conclusion: Identification of a non-invasive marker for morbidity and mortality in infants with CCHD will stimulate feasibility testing and implementation of low-cost, low-risk nursing interventions known to enhance autonomic function, such as skin-to-skin contact, comforting touch, and breast-feeding. Although these interventions are considered to be standard of care in neonatal intensive care units, they are rarely used in pediatric cardiac intensive care units where the majority of infants with CCHD currently receive care. Increasing our knowledge of relationships between early patterns of development of the ANS and later outcomes has the potential to improve nursing care and, ultimately, improve the quality of these infants’ lives.