Altered heart rhythm dynamics in very low birth weight infants with impending intraventricular hemorrhage.

Despite advances in obstetrics and neonatal intensive care, the prevalence of severe intraventricular hemorrhage (IVH) among very low birth weight (VLBW; birth weight ≤1500 g) infants has not improved over the last 15 years.1–6 Long-term neurodevelopmental abnormalities such as behavioral and learning disabilities, mental retardation, seizures, and cerebral palsy can be seen as a result of IVH.7 A conservative cost estimate of the lifetime care expenses for a yearly cohort of surviving VLBW infants with severe IVH affected with adverse neurodevelopmental sequelae is $3 billion.8,9 Given this important public health problem, it would be quite valuable to identify VLBW infants who are at highest risk for developing IVH, before they actually develop it, so that they may benefit from prevention and intervention strategies. Unfortunately, accurate prediction methodologies of impending IVH have not been developed. Altered autonomic function has been observed by heart rate variability (HRV) analysis in premature infants after IVH.10–12 HRV refers to the beat-to-beat (R-R interval from the electrocardiogram) fluctuation of heart rate and reflects the balance between parasympathetic and sympathetic impulses to the heart that is under central nervous system control. Researchers have used HRV analysis as a tool to estimate autonomic neural control of the heart and for predicting impending arrhythmia13 and long-term outcome of VLBW infants.11,14 The objective of this study was to determine if impending IVH in VLBW infants may be predicted by altered autonomic function. We hypothesized that autonomic dysfunction precedes the development of IVH in VLBW infants. We used a nonlinear method, called detrended fluctuation analysis (DFA),11,15 to examine the HRV characteristics of VLBW infants at risk for IVH. Identification of noninvasive predictors of IVH and potential preventive measures may help in reducing the burden of IVH in VLBW survivors of neonatal intensive care.