Antenatal steroid exposure and heart rate variability in adolescents born with very low birth weight.

BACKGROUND: Reduced heart rate variability (HRV) suggests autonomic imbalance in the control of heart rate and is associated with unfavorable cardiometabolic outcomes. We examined whether antenatal corticosteroid (ANCS) exposure had long-term programming effects on HRV in adolescents born with very low birth weight (VLBW). METHODS: Follow-up study of a cohort of VLBW 14-y olds born between 1992 and 1996 with 50% exposed to ANCS. HRV in both the time and frequency domains using Nevrokard Software was determined from a 5-min electrocardiogram tracing. RESULTS: HRV data from 89 (35 male, 53 non-black) exposed (ANCS+) and 77 (28 male, 29 non-black) unexposed (ANCS-) adolescents were analyzed. HRV did not differ between ANCS+ and ANCS- black participants. However, in non-black participants, a significant interaction between ANCS and sex was observed, with ANCS- females having significantly greater HRV than ANCS+ females and males, and ANCS- males for both time and frequency domain variables. CONCLUSION: Among non-black adolescents born with VLBW, ANCS exposure is associated with reduced HRV with apparent sex-specificity. Reduced HRV has been associated with development of adverse cardiometabolic outcomes, thus supporting the need to monitor these outcomes in VLBW adolescents as they mature.

Mortality reduction by heart rate characteristic monitoring in very low birth weight neonates: a randomized trial.

OBJECTIVE: To test the hypothesis that heart rate characteristics (HRC) monitoring improves neonatal outcomes. STUDY DESIGN: We conducted a two-group, parallel, individually randomized controlled clinical trial of 3003 very low birth weight infants in 9 neonatal intensive care units. In one group, HRC monitoring was displayed; in the other, it was masked. The primary outcome was number of days alive and ventilator-free in the 120 days after randomization. Secondary outcomes were mortality, number of ventilator days, neonatal intensive care unit stay, and antibiotic use. RESULTS: The mortality rate was reduced in infants whose HRC monitoring was displayed, from 10.2% to 8.1% (hazard ratio, 0.78; 95% CI, 0.61-0.99; P = .04; number needed to monitor = 48), and there was a trend toward increased days alive and ventilator-free (95.9 of 120 days compared with 93.6 in control subjects, P = .08). The mortality benefit was concentrated in infants with a birth weight <1000 g (hazard ratio, 0.74; 95% CI, 0.57-0.95; P = .02; number needed to monitor = 23). There were no significant differences in the other outcomes. CONCLUSION: HRC monitoring can reduce the mortality rate in very low birth weight infants.