How to Read The Paediatric ECG

Below is an ECG taken of a 0ne week old infant, who has some shortness of breath whilst feeding according to the parents. What does it show? Is it normal?

ECG’s can already present a significant challenge, however there is a fear associated with the paeds ECG. There should not be, as the same principles that apply to the adult ECG and the use of the ‘ECG in 20 Seconds Approach’, also apply to children.

There are only 3 things to remember, in fact there is only one new thing to remember in a paediatric ECG i.e.., In young children, the right ventricle is dominant. As they grow, the left ventricle becomes dominant. That’s it. Everything else follows.

Here is the approach as per the ‘ECG in 20 Seconds’

Rate: just count the number of complexes and multiply by 6 ( an ECG takes 10 seconds to print).

What is an appropriate rate for children? I use this very rough rule of thumb and usually also look it up:

• < 2yo max HR is 160
• 2-7yo max 140
• 7-15 yo max 130

Rhythm: make sure that it is sinus. For sinus rhythm, there must be a P wave before each QRS and the P wave must be upright in II and inverted in aVR. If not, then it is not sinus rhythm and the pacemaker is in the low right/left atrium

QRS: is it too tall or too small, ie is there hypertrophy? Remember that in the child the right ventricle is bigger than the left. To judge hypertrophy look at V6. If the R wave intersects the baseline of the V5 tracing above, then there is LVH

In terms of Right ventricular hypertrophy, in adults it is usually hidden by the left ventricle, however in children the clues are in V1. There is RVH if there is an rsR pattern in V1, or a pure R wave in V1 after 6 months.

It is also helpful to look at the R wave to S wave ratio. Remember that the young heart is right heart dominant, so you would expect that the R wave is more predominant than the S wave in the right leads, however if the opposite is true, then there is left ventricular hypertrophy.

The QRS is normally < 1 small box i.e.., 0.04sec. If longer than 2-3 small squares it is a bundle branch block.

The QRS is normally +ve in aVF

• If it is negative in aVF, there may be cardiac malformations, such as AV septal defect.
• If it is biphasic in aVF, it may be normal, but needs cardiology discussion.

Look for the abnormal QRS morphology i.e.., the delta wave of WPW
ST-T: The T wave is upright for the first week of life, then is inverted until adolescence. This is normal.

Intervals:

PR- In anyone, an interval > 0.2 sec is abnormal

• In infants and young children an interval of > 0.16 (4 small squares) is abnormal.

QT- >0.45sec is abnormal in anyone

• In < 6 months <0.49sec
• In > 6 months <0.44

Lets go back to the ECG above:

Rate: 23 complexes x 6 = 138
Rhythm: There are P waves before each QRS and they are upright in II and inverted in aVR. This normal sinus rhythm.
QRS: Not too narrow or too wide i.e. about 1 small square. No abnormal morphology. No LVH.
ST-T: the one obvious characteristic is inverted T waves in the anterior leads. This is normal in children between about 1 week and adolescence.
Intervals: PR is normal, QT is normal.

This is normal sinus rhythm.

Lets look at some differences:

Rate and rhythm you know; how about:

QRS

This ECG is of an infant with Downs Syndrome

Look at the QRS in V1- there is an rsR pattern indicating right ventricular hypertrophy. This patient had primary pulmonary hypertension.
How about this one of a 10 year old ( Am J Emerg Med (2008) 26, 221-228):
Note that the QRS are the right width, however there is a pure R wave in V1 indicating RVH. If we look at aVF the QRS is biphasic. This may be abnormal, certainly abnormal if the QRS is -ve in this lead. The T waves are inverted as we would expect in a 10 yo. This is right ventricular hypertrophy secondary to primary pulmonary hypertension.

I hope that helps.

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