Spectral Analysis of Heart Rate Variability in Premature Infants with Feeding Bradycardia

An elevated level of baseline parasympathetic activity was noted in a group of premature infants suffering from bradycardia during feeding. At approximately 34 wk post-conceptional age, the heart rates of 12 infants with feeding bradycardia (birth weight = 1539 ± 279 g; gestational age = 31.0 ± 1.6 wk) and 10 controls (birth weight = 1710 ± 304 g; gestational age = 32.0 ± 1.4 wk) were recorded 1 h before and 1 h after feeding. EKG data were digitized and 3.2-min segments of data were analyzed to determine the spectral power at very low (VLF = 0.003–0.03 Hz), low (LF = 0.03–0.39 Hz), and high (HF = 0.40–1.00 Hz) frequencies. In preterm infants with feeding bradycardia, an elevation in baseline parasympathetic activity was evident before feeding, as indicated by significantly higher HF power and a lower LF/HF ratio. This elevation in baseline parasympathetic activity may contribute to the observed bradycardia during feeding.