Session SA4.1

Analyzing Heart Rate Variability in Infants Using Non-Linear Poincaré Techniques

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

University of Iowa
Iowa City, IA, USA

Congenital heart defects are the most prevalent type of birth defect. Infants born with Hypoplastic Left Heart Syndrome (HLHS) typically undergo a 3-stage reconstructive procedure to treat the underdeveloped left ventricle, aorta and aortic valve that characterize this disease. Other infants require a Blalock-Taussig (BT) shunt or aortic arch reconstruction (AA). Surgical processes may interrupt autonomic cardiac function. To assess cardiac autonomic tone, heart rate variability (HRV) is often characterized with classical linear, Fourier-based techniques. In order to more completely characterize HRV, we used a non-linear Poincaré technique and quantified the short-term (SD1) and long-term (SD2) variability of heart rate. SD1 is correlated with high frequency power while SD2 is correlated with low and high frequency powers. The ratio SD1/SD2 is associated with the randomness of the HRV signal. 28 infants were enrolled at the University of Iowa and 15 at the University of Michigan. Group I included 19 normal infants and Group II included 13 HLHS infants, 5 AA infants and 6 BT infants. 24-hour ECG data were collected and analyzed in 5-minute segments to study the infants’ HRV at birth and after a procedure, or at an age-matched time. At birth, SD1 and SD2 were lower in Group II infants than Group I infants (p<0.001). SD1/SD2 was greater in Group II than Group I (p<0.001). Between the pre-procedure and post-procedure time points, Group I infants showed a reduced SD1 (p<0.05), reduced SD2 (p<0.05) and no change in SD1/SD2 (p>0.05). SD1/SD2 decreased in HLHS infants and increased in BT infants after the procedure. Following the procedure, Group II infants showed greater SD1 (p<0.001) and greater SD2 (p<0.001) than Group I infants. No significant difference was seen between the SD1/SD2 of Group I and Group II infants post-procedure. No significant difference was seen between Group I and Group II infants for SD1, SD2 or SD1/SD2 at the follow-up time. Group I infants show change in cardiac innervations with normal growth and development. Congenital differences in autonomic cardiac function are seen between Group I and Group II infants pre-procedure. Group II infants show improved autonomic control and heart rate organization at the follow-up time.

(Abstract Control Number: 150)