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 approxi mately 34 wk post-conceptional age, the heart rates of 12 infants with feed ing bradycardia (birth weight = 1539 +/- 279 g; gestational age = 31.0 +/- 1.6 wk) and 10 controls (birth weight = 1710 +/- 304 g; gestational age = 3 2.0 +/- 1.4 wk) were recorded 1 h before and 1 h after feeding. EKG data we re digitized and 3.2-min segments of data were analyzed to determine the sp ectral power at very low (VLF = 0.003-0.03 Hz), low (LF = 0.03-0.39 fit), a nd high (HF = 0.40-1.00 Ut) frequencies. In preterm infants with feeding br adycardia, an elevation in baseline parasympathetic activity was evident be fore feeding, as indicated by significantly higher HF power and a lower LF/ HF ratio. This elevation in baseline parasympathetic activity map contribut e to the observed bradycardia during feeding.