How to Read a Pediatric Electrocardiogram

In children, the electrocardiogram is not used as frequently as in adults, but it has a fundamental importance in the study of congenital heart disease and arrhythmias during childhood.

When interpreting a pediatric EKG, we must follow a sequence similar when we interpret an electrocardiogram of an adult, but taking into account the differences related to the child's age (see pediatric EKG).

How to Read the Electrocardiogram of a Child

Unlike the adult, the first thing that we must know in an electrocardiogram of a child is his age, because the normal EKG of a newborn has characteristics that can be considered pathological changes in a child of 10 years.

Then we must be sure that the EKG is well done, ensuring that speed and amplitude of the EKG are appropriate, all leads must be legible, and the electrocardiogram does not have too many artifacts.

In cases of doubt, the EKG should be done again, if possible.

As in an adult we recommend to always follow the same sequence, not having nothing is overlooked.

1. Heart Rate (HR)

It is the first thing to determine in any electrocardiogram. The simplest way to calculate it is to measure the amount of large squares between two QRS complexes, and divide 300 by the number of large squares; for example, 150 bpm if there are two squares, 100 bpm if there are three squares, 75 bpm if there are four squares.

This method is only valid if the heart rhythm is regular.

Check in our article how to determine heart rate the other methods for HR calculation.

Remember that the normal values of heart rate in a child are different with each age. Making a brief summary:

We also provide you with a heart rate calculator to make it simpler.

2. Heart Rhythm

Determining the heart rhythm is one of the most beautiful steps in the analysis of the pediatric electrocardiogram.

The algorithms to analyze the heart rhythm are different for an EKG with tachycardia, with normal HR or bradycardia.

Tachycardia

Important: wide or narrow QRS complex?

A wide QRS complex tachycardia, until proven otherwise, it is a ventricular tachycardia and a medical emergency.

In this article you can find the criteria of ventricular tachycardia.

If it is a narrow QRS complex tachycardia (or wide QRS tachycardia and has ruled out the VT), there are several mechanisms to determine the type of tachycardia present on the EKG; almost all are based on the presence or absence of P wave, its morphology and location with respect to the QRS, and whether the tachyarrhythmia is regular or irregular.

Here we named the most frequent types of tachycardias with a short description.

• Sinus tachycardia: the most frequent tachycardia, sinus P waves are always follow by a QRS complex.
• Atrial tachycardia: similar to sinus tachycardia but with ectopic P waves.
• Supraventricular tachycardia: the most frequent in children is the orthodromic tachycardia by accessory pathway, although, atrioventricular nodal reentrant tachycardia may also be seen.
• Atrial flutter: regular tachycardia where "saw-tooth waves" may be observed. Atrial flutter is a rare arrhythmia in children with healthy hearts, but may be seen in patients with congenital heart disease or post-heart surgery (see atrial flutter).
• Atrial fibrillation: irregular tachycardia, with no visible P waves, is not often seen in children with healthy hearts (see atrial fibrillation).

Normal Heart Rate

The method for determining the heart rhythm on a pediatric EKG with normal heart rate is different than when there is a tachycardia.

In general, we rely on the presence or absence of P wave, and whether or not the P waves are always conducted into the ventricles.

The characteristics of each rhythm with normal heart rate is described below.

• Sinus rhythm: it is the normal heart rhythm. Sinus P waves wich are always followed by a QRS complex (see sinus rhythm).
• Sinus arrhythmia: it is common in children. It is similar to sinus rhythm but with variations in heart rate with breathing (irregular rhythm). It is a normal rhythm (see sinus arrhythmia)
• Ectopic atrial rhythm: P waves are ectopic wich may always be followed by a QRS complex.
• Wandering atrial pacemaker: sinus P waves alternating with ectopic P waves. It is usually caused by increased vagal tone, rarely causes symptoms or requires treatment.
• First degree AV block: prolongation of the PR interval. It may be normal in children caused by increased vagal tone (see first degree AV block).
• Type I second degree AV block: there is a progressive PR interval lengthening until a P wave is not conducted. It may be normal in children caused by increased vagal tone.
• Type II second degree AV block: constant PR intervals before and after the blocked P wave (see second degree AV block).
• Complete AV block (third grade): AV dissociation. The P waves and the QRS complexes, bear no relation between them (see complete AV block).
• Atrial flutter: regular rhythm with "saw-tooth waves". It is a rare arrhythmia in children (see atrial flutter).
• Atrial fibrillation: it is also a rare arrhythmia in children. It is observed as an irregular rhythm without P waves (see atrial fibrillation).
• Junctional rhythm: regular rhythm originated in the AV node without P waves. It may be presence of retrograde P waves (negative in inferior leads, registered in the QRS complex or in the ST-segment). It may be caused by increased vagal tone.

Bradycardia

Determine the rhythm of bradycardias is similar to when HR is normal with the exception of bradycardias with absence of P wave.

Bradycardia with P waves:

• Sinus bradycardia and slow sinus arrhythmia: similar to sinus rhythm and sinus arrhythmia but with low hear rate. if the HR is very low or P-P intervals are very long, a sick sinus syndrome must be suspected.
• AV blocks: similar to what has been described for normal HR.

Bradycardia without P waves:

• Slow atrial fibrillation: irregular rhythm with minimal atrial activity.
• Slow atrial flutter or associated with complete AV block: the F waves or "saw tooth waves" are observed quite clearly by the distance between the QRS complexes (see atrial flutter with AV complet block).
• Sick sinus syndrome with junctional escape rhythm: regular rhythm, there may be retrograde P waves, negative in the inferior leads, which may be inscribed in the QRS complexes or in the ST segment.
• Junctional rhythm: similar to the previous, except that in this case the rhythm starts spontaneously in the AV node or secondary to very low HR.
• Atrial fibrillation with complete AV block: atrial fibrillation with regular rhythm, it differs from the previous by the f waves (variable atrial activity), and for not existing P retrograde, although sometimes it is impossible to distinguish both rhythm.

3. PR interval:

Related article: PR interval.

Once the heart rhythm has been determined, the PR interval must be assessed.

Alterations on the PR interval allow us to diagnose first-degree AV block (can be seen in children without clinical significance) if it is long, or the presence of accessory pathway if it is short and is accompanied by a delta wave (see Wolf-Parkinson-White syndrome).

More information: PR interval.

4. QT Interval (corrected):

Related article: QT interval.

After assessing the PR interval is important to estimate the QT interval.

A QT interval prolongation in the pediatric age may help us to diagnose congenital long QT syndrome, or a QT prolongation due to the use of some drugs.

We remind you that the QT interval varies depending on heart rate, so it must be adjusted with a formula (use our corrected QT calculator). In children the corrected QT interval or QTc is normal between 350 ms and 450 ms (see QT interval).

More information: QT interval.

5. Heart axis:

It is one of the most difficult steps on the electrocardiogram analysis. There are several methods to determine the axis that we summarized in this article.

In addition, on the pediatric EKG you must remember that normal values of heart axis are completely different in each age range.

6. ST-Segment Changes

ST-segment changes in a healthy child are rare. The most common finding is early repolarization, considered a normal pattern within normal ranges (see early repolarization).

Some diseases, such as pericarditis or myocarditis may cause ST segment elevation in childhood. Ischemic heart disease is very rare in children, but to be submitted would have electrical disturbances similar to those of the adult (see ST-segment analysis).

7. Assess the Rest of Waves and Intervals

The final step in the analysis of the pediatric electrocardiogram is to assess each of the waves and intervals that has not been previously measured.

We remind you that in the child, QRS complex morphology varies with age; there is also variations in the T wave, and the intervals are increasing in duration as the years pass.

We hope this article has helped you to interpret the pediatric electrocardiogram.

Normal Values of the Pediatric Electrocardiogram