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Study of cardiac rhythm in healthy newborn infants
Insights
This study reveals that common heart rate variations and rhythm disturbances in newborns, such as sinus bradycardia and pauses, are normal findings in healthy infants. These electrocardiogram (ECG) patterns are not indicative of underlying cardiac issues in early life.
Area of Science:
- Neonatal Cardiology
- Pediatric Electrophysiology
- Infant Health
Background:
- Standard electrocardiogram (ECG) interpretation in neonates often flags certain heart rate variations and rhythm disturbances as abnormal.
- Previous studies have not comprehensively characterized the prevalence of these findings in healthy newborns.
Purpose of the Study:
- To establish normative data for heart rate and rhythm in healthy, full-term infants during the first 10 days of life.
- To determine the incidence of specific electrocardiographic findings previously considered abnormal in this population.
Main Methods:
- Long-term (24-hour) electrocardiograms were performed on 134 healthy, full-term infants (birthweight > 2.5 kg) within the first 10 days of life.
- Analysis included heart rate variability, presence of bradycardia, escape rhythms, P wave changes, premature atrial beats, and various sinoatrial (SA) conduction disturbances.
Main Results:
- The highest mean heart rate was 175 bpm. Lowest rates averaged 82 bpm (sinus bradycardia) and 93 bpm (junctional escape rhythms).
- Sinus pauses were observed in 72% of infants. Sinoatrial conduction abnormalities, including SA exit block, SA block, and SA Wenckebach, were present in 7-32% of infants.
- P wave configuration changes and premature atrial beats were also noted in a significant proportion of healthy infants.
Conclusions:
- This study demonstrates that many electrocardiographic findings, including sinus bradycardia, pauses, and SA conduction disturbances, are common and normal variations in healthy newborns.
- These findings challenge previous interpretations and suggest a need to revise diagnostic criteria for neonatal cardiac rhythm abnormalities.
Abstract:
Twenty-four-hour electrocardiograms were recorded in the first 10 days of life on 134 healthy full-term infants with birthweights greater than 2.5 kg. The highest heart rate a minute, measured over nine beats, was 175 +/- 19 (SD). The lowest rates, measured over three, five, and nine beats were 82 +/- 12, 87 +/- 12, and 93 +/- 12, respectively. At their lowest rates 109 infants had sinus bradycardia and 25 had junctional escape rhythms. Thirty-three infants showed changes in P wave configuration with or without pronounced variation in PR interval. Atrial premature beats were present in 19 infants but only one had more than 12 per hour. In a randomly selected subgroup of 71 infants sinus pauses were found in 51 (72%). Five (7%) had electrocardiographic patterns and rhythm disturbances that could not be differentiated from those previously described as complete sinuatrial exit block or sinus arrest, eight (11%) had patterns indistinguishable from 2:1 sinuatrial block, and 23 (32%) had pattern indistinguishable from sinuatrial Wenckebach block. This study shows that normal infants have variations in heart rate and rhythm hitherto considered to be abnormal.