A excellent description of the neonatal electrocardiogram has been made by Schwarz et al.[1][2]

Heart Axis

Normal heart axis values[3]
Age QRS Axis Normal Values Abnormal Values Description
Adult -30° to 90°
<-30°
-30° to -45°
-45° to -90°
90° to 120°
90° to 180°
Left-axis deviation
Moderate left-axis deviation
Marked left-axis deviation
Moderate right-axis deviation
Marked right-axis deviation
8 to 16 years 0° to 120° >120° Right-axis deviation
5 to 8 years 0° to 140° >140°

<0°

Right-axis deviation

Left-axis deviation

1 year to 5 years 5° to 100° >100° Right-axis deviation
1 mo to 1 y 10° to 120° >120°

<10° to -90°

Right-axis deviation

Left-axis deviation

Neonate 30° to 90° >190° to -90°

<30° to <-90°

Extreme right axis deviation

Left axis deviation

Conduction

RBBB: if consistent morphology and if QRS width >90ms in children < 4 years and >100ms in children 4-16 years[3] LBBB: if consistent morphology and QRS width >90ms in children < 4 years and >100ms in children 4-16 years[3]

Normal neonatal ECG standards

Normal neonatal ECG standards
Age group Heart rate
(beats . min-1)
Frontal plane
QRS axisa
(degrees)
P wave
amplitude
(mm)
P-R
intervala
(s)
QRS
durationa
V5
Q IIIc (mm) QV6c (mm) RV1b (mm) SV1b (mm) R/S V1c RV6b (mm) SV6b (mm) R/S V6c SV1 + RV6c (mm) R + SV4c (mm)
0–1 days 93–154 (123) +59 to +192 (135) 2·8 0·08–0·16 (0·11) 0·02–0·08 (0·05) 5·2 1·7 5–26 0–22·5 9·8 0–11 0–9·8 10 28 52
1-3 days
3-7 days
7-30 days
1-3 months

References

Error fetching PMID 19228822:
Error fetching PMID 12269267:
Error fetching PMID 12739597:
  1. Error fetching PMID 12269267: [schwarz1]
  2. Error fetching PMID 12739597: [schwarz2]
  3. Error fetching PMID 19228822: [aha]

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