The development of autonomic cardiovascular control is altered by preterm birth.
OBJECTIVE
Autonomic dysfunction, either sympathetic or parasympathetic, may explain the increased incidence of Sudden Infant Death Syndrome (SIDS) among preterm infants, as well as their subsequent heightened risk of hypertension in adulthood. As little is known about the development of autonomic function in preterm infants, we contrasted autonomic cardiovascular control across the first 6months after term-corrected age (CA) in preterm and term infants.


METHODS
Preterm (n=25) and age matched term infants (n=31) were studied at 2-4weeks, 2-3months and 5-6months CA using daytime polysomnography. Blood pressure and heart rate were measured during quiet (QS) and active (AS) sleep. Autonomic control was assessed using spectral indices of blood pressure and heart rate variability (BPV and HRV) in ranges of low frequency (LF, reflecting sympathetic+parasympathetic activity), high frequency (HF, respiratory-mediated changes+parasympathetic activity), and LF/HF ratio (sympatho-vagal balance).


RESULTS
In preterm infants, HF HRV increased, LF/HF HRV decreased and LF BPV decreased with age (p<0.05); these changes were most evident in AS. Compared to term infants, preterm infants in QS exhibited lower LF, HF and total HRV at 5-6months; higher HF BPV at all ages; and lower LF BPV at 2-4weeks (p<0.05).


CONCLUSIONS
With maturation, in preterm infants, parasympathetic modulation of the heart increases while sympathetic modulation of blood pressure decreases. Compared to term infants, preterm infants exhibit lesser parasympathetic modulation of the heart along with greater respiratory-mediated changes and lower sympathetic modulation of blood pressure. Impaired autonomic control in preterm infants may increase their risk of cardiovascular dysfunction later in life.
The Ritchie Centre, Monash Institute of Medical Research, Monash University, Melbourne, Victoria, Australia. stephanie.yiallourou@monash.edu
Stephanie R
SR
Yiallourou
Nicole B
NB
Witcombe
Scott A
SA
Sands
Adrian M
AM
Walker
Rosemary S C
RS
Horne
D000367:Age Factors; D000704:Analysis of Variance; D001341:Autonomic Nervous System / Q000502:physiology*; D001794:Blood Pressure; D002320:Cardiovascular Physiological Phenomena; D006339:Heart Rate; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature; D017286:Polysomnography; D047928:Premature Birth / Q000503:physiopathology*; D012307:Risk Factors; D014739:Victoria