ECG Topic - Pediatric ECGs - What is Normal?

Learning Objectives:

1. Utilize understanding of anatomical changes of the heart from birth to adulthood and apply it to ECG interpretation
2. Recognize common patterns of normal pediatric ECGs, and differentiate those that fall out of this pattern

Why do I, an Emergency Physician, need to interpret a pediatric ECG? Can’t I just call Pediatric Cardiology?

Do you have one on speed dial? If not, it can be helpful to know how to interpret normal from abnormal.

I’ve never received any training on this, how would I be expected to interpret these?

That’s what we are here for. Thankfully, pediatric ECGs tend to follow particular rules. Those that don’t usually have some underlying abnormality that you can pick out. Let’s dive in. We’ll use a Rate, Rhythm, Axis, Interval approach with associated rules that ECGs should follow, then discuss more specialized topics

Rate

As we know, pediatric patients have a baseline higher heart rate from an increased metabolic rate and decreased influence of vagal tone; don’t need to belabor this point much

Rhythm

These are general tips for all ECG interpretation

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P waves should be small and one wave

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Upright P waves in inferior leads with constant PR interval

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V1 should be biphasic, then upright by V2

Axis

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Right axis deviation is ok until around 6 months of age

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There should be no extreme axis deviation after 1st week of life

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Left axis deviation is associated with heart disease, but can be found in a normal heart

Intervals

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All intervals are generally shorter the younger the patient

PR Interval

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1st degree heart block and Mobitz I can be normal

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Symptomatic or higher grade blocks warrant investigation

QRS Interval

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Bundle Branch Blocks (BBB) are common post Congenital Heart Disease (CHD) surgeries

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If no history of CHD surgery and new BBB, assume pathology

QT Interval

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Measure your own QT interval when relevant

Q Waves

A pediatric specific rule

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Q waves should only be in inferior and lateral leads (V5-V6), not deeper than 10 mV

R Wave Progression

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Neonatal (0-1 month) → V1 R wave dominant, V6 S wave dominant

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Infant (Birth - 3 years) → V1 R wave dominant, V6 R wave dominant

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Adult (2-3 years and later) → V1 S wave dominant, V6 R wave dominant

T Waves

• Think of abnormal T waves as representing some form of increased pressure (strain). To make things easier for precordials, only focus on V1-V3 and V6 separately

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Less than 7 days old → V1-V6 expect T waves to be up, but can be anything

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7 days old - 8-10 years → V1-V3 inverted, V6 upright

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8-10 years or older → V1-V3 inverted or upright, V6 upright

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T Wave Inversions are not normal in the limb leads (exception: isolated T Wave Inversion in III and aVR)

Extras - RVH and LVH

• Remember that ECG is rarely specific or diagnostic for RVH or LVH, but they can increase you suspicion for these pathologies.
• There are voltage criteria that can be memorized, but it isn’t worth the brain space. You will pick up most of these with the rules above, but we will introduce two new rules to consider looking for

Rules that point toward LVH

• 7 days old - 8-10 years? → V1-V3 inverted, V6 upright
• Left axis deviation is associated with heart disease, but can be found in a normal heart
• Q waves should only be in inferior and lateral leads (V5-V6), not deeper than 10 mV
• T wave inversions are not normal in the limb leads (exception: isolated T wave inversion in III and aVR

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Evans Rule: if the R wave in V6 intersects the baseline of V5 → strongly consider LVH

Rules that point toward RVH

• 7 days old - 8-10 years? → V1-V3 inverted, V6 upright
• If no history of CHD and new BBB (especially RBBB) → assume pathology

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R wave only in V1 after 6 months is abnormal

Resources

• Free:
• Pediatric Cardiology Part 2
• Ed Burns Normal paediatric ECG
• PubMed Central (PMC) How to interpret an electrocardiogram in children
• Good book
• Maria Albina Galli, Gian Battista Danzi A Guide to Neonatal and Pediatric ECGs