You have now completed the discussion of the normal ECG in the adult. Interpretation of the pediatric ECG differs from that of the adult.
Infant and child
Interpretation of electrocardiograms in the infant and child differs from the adult in several important ways.
In normal newborns these differences reflect fetal and neonatal physiology and, with increasing age, changes in the physiology. Understanding the corresponding findings on the electrocardiogram is key to its interpretation in this age group.
Special techniques in the infant
Special techniques are required to record a suitable electrocardiogram from an infant. In addition to quieting the infant, a small electrode ½ inch in diameter should be used for precordial leads. Either lead V3R or V4R should be taken routinely in infants to obtain more information about the right ventricle. These leads are placed on the right chest in a position analogous to V3 and V4 respectively. Precordial lead V3 or V4 may then be omitted. Similarly, lead V7 may be obtained instead of V5 in order to gain more information about the left ventricle. Lead V7 is placed in the left posterior axillary line at the same level as V4.
Infant ECG
Infants at birth demonstrate equal right and left ventricular pressures, and therefore, relative right ventricular dominance on the electrocardiogram. The mean QRS axis is rightward with dominant R waves and positive T waves in leads V3R and V1.
Increased precordial lead QRS voltage is common in children and younger adults due to a variety of factors including a thin chest wall producing closer proximity of the heart to the chest wall.
Older children ECG
In children, the T waves in the limb leads are similar to those of the adult, but, depending on age, the precordial T waves differ.
T waves in the right precordial leads are positive at birth. After a week, as the right ventricular systolic pressure decreases, these T waves become negative and this negativity may extend as far as V4. In fact, an upright T wave in precordial lead V1 in a child less than six years old indicates right ventricular hypertrophy. As the child grows older, T wave positivity shifts progressively towards the right. In an older child, as in the normal adult, an inverted T wave is common in lead V1, frequent in V2 and rare in V3. Inverted T waves in the anterior leads may persist into the third decade of life. This is called persistent juvenile T wave pattern and is more common in women. This is normal as long as the depth of the T wave decreases as the leads progress across the chest.