Electrocardiographic Manifestations: Pediatric ECG

Theodore C. Chan, MD, FAAEM, FACEP; Ghazala Q. Sharieff, MD, FAAEM, FACEP, FAAPMD, FAAEM, FACEP; William J. Brady, MD, FAAEM, FACEP

Disclosures

J Emerg Med. 2008;35(4):421-430. 

In This Article

Age-Related Pediatric ECG Findings

Rapid changes occur over the first year of life as a result of the dramatic evolution in circulation and cardiac physiology. After infancy, subsequent changes are more gradual until late adolescence and adulthood. In the fetus, blood is shunted away from the lungs by the patent ductus arteriosus (PDA), and systemic circulation relies primarily on the right side of the heart. As a result, at birth the right ventricle is larger than the left ventricle. Subsequently, as the PDA closes during infancy, there is increased work of the left ventricle from the systemic circulation. The left ventricle enlarges and thickens such that by late infancy and early childhood it is more than twice as thick as the right ventricle.[2,3]

With these changes, there is a progression of alterations in the normal ECG findings, including rate, axis, interval duration, and complex morphologies in pediatric patients. Table 1 lists the normal pediatric ECG values seen in the newborn, infant, child, and adolescent, including ranges for heart rate, QRS complex axis, PR segment and QRS complex intervals, and R and S wave amplitudes, and their changes with age.[4,5,6,7,8]

Heart Rate

Normal heart rate varies with age and is generally higher in children than adults. Table 1 lists the normal ranges for heart rate, which tends to peak at 3-8 weeks and then decreases through adolescence. Due to the smaller stroke volume in neonates and young children, cardiac output is maintained by the higher heart rate. With age, stroke volume increases and contributes more significantly to overall cardiac output. When assessing heart rate, it is important to consider the patient's activity and stress levels, which can result in physiologic elevations of heart rate. Rates significantly outside the normal range for age, however, should be closely scrutinized for dysrhythmias.

Axis

As discussed above, the right ventricle is larger than the left ventricle in the newborn infant, and the ECG will show right ventricular dominance and right axis deviation. Across the precordium, the R wave amplitude will be increased in leads V1 and V2, and decreased in leads V5 and V6. With the cardiac changes described above occurring in the first 1-3 years of life, the left ventricle increases in size and the QRS axis will shift from rightward to a more leftward axis. Across the precordium, the R wave amplitude decreases in leads V1 and V2, and increases in leads V5 and V6.

Intervals

QRS Complex. The normal QRS complex duration is shorter in children than adults. This finding may be the result of the smaller cardiac muscle mass in children. For neonates, the normal QRS complex duration can be as short as 30 ms and increases progressively with age ( Table 1 ). Accordingly, conduction abnormalities may be present in what appears as a normal or nearly normal QRS complex duration in young children.

PR Interval. The normal PR interval duration is shorter in children and increases with age. Similar to the change in normal QRS complex duration, this finding may be the result of smaller cardiac muscle mass. In neonates, the normal PR interval duration can be as short as 80 ms ( Table 1 ). As a result, AV conduction delay may be present in young children with minimal prolongation or a "normal"-appearing PR interval.[4]

QT Interval. The QT interval duration varies with heart rate in both children and adults. Similar to adults, the QT interval must be corrected for heart rate (which is normally higher in children) to obtain the corrected QTc interval. In infants, the normal QTc is longer than in older children and, in fact, can be as long as 490 ms. This discrepancy in the evaluation of the QTc interval in infants and children should be noted, particularly when relying on computer analysis of ECG intervals.

T Waves. T wave morphology can be difficult to interpret in neonates and children. At birth, the T wave may be upright, flat, or inverted. Within a few days after birth, however, the T wave can become inverted normally. In fact, upright T waves at this age may indicate right ventricular hypertrophy (RVH). The "juvenile pattern" of T wave inversion usually seen in the anterior leads (leads V1-V3) typically lasts up until 8 years of age (Case 1, Figure 1), but can persist into early adolescence (Case 2, Figure 2).

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