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Heart rate variability by triangular index in infants exposed prenatally to cocaine
Sudhir Ken Mehta1, Dennis M Super, Ann Salvator
1Department of Pediatrics, MetroHealth Campus, Case Western Reserve University, Fairview Hospital, 18101 Lorain Avenue, Cleveland, Ohio 44111-5656, USA. ken.mehta@fairviewhospital.org
Insights
Heart rate variability triangular index (HRVi) is a reliable measure for newborns. Infants exposed to cocaine in utero show significantly lower HRVi, indicating potential clinical use for abnormal values.
Area of Science:
- Neonatal cardiology
- Pediatric autonomic nervous system function
- Prenatal substance exposure effects
Background:
- Heart rate variability triangular index (HRVi) is a reproducible measure of heart rate variability (HRV) in adults, suitable for longitudinal studies.
- Normative HRVi data exist for newborns, but studies on infants with pathological conditions are limited.
- This study addresses the lack of data on HRVi in newborns with prenatal substance exposure.
Purpose of the Study:
- To evaluate the reliability of HRVi in newborns.
- To compare HRVi in cocaine-exposed newborns with control groups.
- To establish a threshold for abnormal HRVi in neonates.
Main Methods:
- Prospective evaluation of HRVi using Holter monitoring in 97 asymptomatic, cocaine-exposed newborns within 4 days of life (1997-2000).
- Comparison of HRVi data with two control groups: 102 infants with no in utero drug exposure and 111 infants exposed to alcohol, nicotine, or marijuana but not cocaine.
- Assessment of inter- and intra-operator concordance for HRVi measurements.
Main Results:
- High inter- and intra-operator concordance for HRVi (intraclass correlations 0.983 and 0.997, respectively), confirming reliability.
- Significantly lower HRVi in infants with in utero cocaine exposure compared to controls (P < 0.0001).
- Abnormal HRVi (< fifth percentile of controls, i.e., < 8) was found in 10% of cocaine-exposed newborns versus 2% in control groups (P = 0.003).
Conclusions:
- HRVi is a reliable measure for assessing heart rate variability in newborns.
- Asymptomatic infants exposed to cocaine in utero exhibit reduced HRVi.
- An abnormal HRVi value below 8 is supported for clinical use in newborn infants.
Background:
In adults, heart rate variability triangular index (HRVi) is a highly reproducible measure of heart rate variability (HRV), which makes it more suitable for use in longitudinal studies. Although normative data have been published for newborns, studies in infants with pathological conditions are lacking.
Methods:
From 1997 to 2000, within the first 4 days of life, we prospectively evaluated HRVi in cocaine-exposed asymptomatic newborns (N = 97) by Holter monitoring. Their data were compared with infants from two control groups (one with no in utero drug exposure, N = 102; the other with exposure to alcohol, nicotine, or marijuana but no cocaine, N = 111).
Results:
In assessing concordance between and within operators for HRVi, the intraclass correlations were 0.983 (95% CI: 0.958, 0.994) and 0.997 (95% CI: 0.984, 0.999), respectively. Infants with in utero cocaine exposure had significantly (P < 0.0001) lower HRVi than those exposed to other drugs and to no drugs in utero. If abnormal HRVi is defined as < fifth percentile for the no drug exposed group (HRVi < 8), 10% of the cocaine-exposed newborns, in contrast to 2% in each of the control groups (P = 0.003) had abnormal values.
Conclusion:
HRVi is a reliable measure to study heart rate variability in newborns. Asymptomatic infants with in utero cocaine exposure have lower HRVi. Our study supports the clinical use of an abnormal HRVi as a value < 8 for newborn infants.