Session S73.2

Heart Rate Variability Analysis in Normal Infants and Infants with Single Ventricle Anatomy Using Power Spectral Density

ER Wathen, RL Smith, P Cetin Abaci, NH Von Bergen, IH Law,
M Dick, CE Connor, EL Dove*

University of Iowa
Iowa City, IA, USA

Heart rate variability (HRV) is a measure of the magnitude of autonomic cardiac tone produced by sympathetic and parasympathetic innervation. Hypoplastic Left Heart Syndrome (HLHS) is characterized by the underdevelopment of the left ventricle, aorta, and aortic valve and is fatal if reconstructive surgery is not performed within the first week of life. Still, unexpected cardiac failure occurs in some infants after these procedures. Infants with similar congenital heart defects have an aortic arch reconstruction (AA) or Blalock-Taussig (BT) procedure only, both parts of the standard HLHS reconstructive procedure. This study analyzes HRV in the first few months of life in normal (NN) infants and infants with single ventricle congenital heart defects (AN). We analyzed data from 14 NN and 10 AN infants enrolled at the University of Iowa and the University of Michigan. 24-hour Holter monitors collected ECG data for each infant at three age-matched times: 1-10 days (pre-surgical reconstruction), 1-2 months (post-surgical reconstruction), and 4-6 months old (follow-up). Power spectral density was calculated with the Lomb periodogram that corrects for irregularly sampled time series data. Analyses were performed using traditional frequency bands (LF: 0.04-0.15 Hz, HF: 0.15-0.4 Hz) and frequency bands modified for infants (LF: 0.04-0.2 Hz, HF: 0.4-1.2). Changes in LF power (LFP) imply changes in sympathetic tone, and changes in HF power (HFP) imply primarily changes in parasympathetic tone. Traditional LFP changed from the pre-surgical to follow-up age for both the NN and AN groups (p<0.05). LFP/HFP ratio did not change (p>0.05) with age for the NN group but the ratio increased with age for the AN group (p<0.05). Modified HFP increased in all but one of the NN infants. HFP decreased in all infants with HLHS that survived surgery. In all AA and BT infants, modified HFP increased. The increase in HFP with age of the NN group implies that these infants developed parasympathetic cardiac tone over time. The AN group showed decreased sympathetic (LFP) and increased parasympathetic (HFP) tone directly after surgery, but cardiac tone did not develop further with age. Innervation may be missing or damaged due to surgery in AN infants.

(Abstract Control Number: 148)