The pediatric ECG is characterized by age-related variations
and, because of this, can be very difficult to interpret. The age-related
variations reflect the maturation of the pediatric myocardium and
vascular system from birth to adulthood. Developmental changes in
the pediatric ECG from birth to adolescence include a gradual shift
from right to left ventricular dominance, a decrease in the resting
heart rate, a lengthening of the PR and QRS intervals, and a change
from inverted to upright T waves in the precordial leads.1–3 Use
a systematic approach to ECG interpretation, checking rate, rhythm,
axis, hypertrophy of the atria and ventricles, and repolarization
changes. Reference tables with age-specific values are necessary
to deal with the progressive changes in heart rate, axis, interval duration,
and morphology. The most important changes are described in the
The normal heart rate is age dependent (Table 143D-1).4 The neonatal and infant heart has
a limited capacity to increase stroke volume, and cardiac output
depends largely on rate. Rate is relatively high in the young infant
to meet metabolic demands. Significant state-dependent and beat-to-beat
variability in resting heart rate is characteristic of the
normal neonatal and infant heart. Sinus tachycardia in the neonate
can often reach 200 to 220 beats/min, and rates this high
are common with fever or pain. In general, bradycardia with normal
perfusion and without evidence of heart block (discussed below in Atrioventricular
Block) rarely requires treatment or investigation.
143D-1 Normal Pediatric Heart Rates
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143D-1 Normal Pediatric Heart Rates
|Age||Heart Rate (beats/min)|
The right ventricle predominates in the neonate, because in utero
blood is shunted away from the fetal lungs and the right ventricle
provides the majority of systemic blood. So the ECG in the first
few months of life is characterized by right ventricular dominance
and right axis deviation. P waves are upright in leads I and aVF,
and the P axis ranges between 0 and +90 degrees. The R-wave
amplitude is increased in V1 and V2 and decreased
in V5 and V6. As the left ventricle increases
in size during infancy and early childhood, the QRS axis shifts
leftward, so that R-wave amplitude decreases in V1 and
V2 and increases in V5 and V6 (Table 143D-2).1–4
Table 143D-2 Age-Specific
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