Higher levels of baseline parasympathetic activity were noted in a group of premature infants suffering from bradycardic episodes during feeding. The heart rates of 12 infants (BW 1539 +/- 279; GA 31.0 +/- 169 wks) with feeding bradycardia and 10 controls (BW1710 +/- 304g; GA 32.0 +/- 1.4 wks) were recorded one hour before and after feeding by a Log-a-Rhythm Acquisition Unit(Nian-Crae, Inc). EKG data was digitized, and 3.2 minutes of data were analyzed to determine the power spectra at very low (VLF)=0.0-0.03 Hz, low(LF)=0.03-0.39 Hz, and high (HF)=0.40-1.00 Hz frequencies. The results are shown in the table below.

Table 1 No caption available.
Full size table

Infants with feeding bradycardia exhibited significantly higher HF power and higher LF/HF ratio prior to feeding compared to control infants(*p<0.05). Of note, HF was similar pre and post feeding in this group, but control infants showed higher levels of HF power post feeding compared to baseline (#p<0.05). In these symptomatic preterm infants, the higher parasympathetic tone prior to feeding may be responsible for the observed bradycardia.