Guest Blog Post By Dr Swati Gupta ACCS trainee

Introduction

As in most other aspects of paediatrics, it is important to remember that the child is not a small adult. Interpreting paediatric ECGs involves an appreciation that there are;

1.  Features that are considered abnormal in an adult ECG but may be normal in children
2. Specific paediatric diagnoses which are aided by ECG interpretation

Why do we do ECGs in the emergency department?

In a 2005 study of ECGs from 1500 paediatric ED patients in Denver, it was found that the indications for ECG were;

• chest pain (21%),
• seizure or syncope (18%),
• arrhythmias (17%),
• respiratory symptoms (16%),
• ingestion (10%),
• ca­­rdiac abnormality (10%)
• miscellaneous (8%)

Features considered abnormal in an adult ECG which can be normal in children

Key concepts

• In simplest terms, physiologically in utero the pulmonary circulation is very high resistance compared to the systemic circulation which incorporates the placenta. In order to push blood through this, the right ventricle (RV) is thicker and larger than the left ventricle (LV). This is demonstrable on an ECG as a pattern of RV dominance at birth similar to RV hypertrophy:
  • Right axis deviation
  • Tall R waves in right precordial leads (V1-V3)
  • Upright T waves in right precordial leads (V1-V3)

• With the first few breaths, there is a fall in intrathoracic pressure in the neonate and a subsequent decrease in pulmonary vascular resistance and increase in systemic vascular resistance that within the first month of life results in a larger and thicker LV compared to RV. Normally sometime during the first week of life the upright T waves in V1-V3 on a neonatal ECG will become inverted, resulting in the typical “Juvenile T wave inversion pattern” that may persist variably into adolescence. As a child ages the T waves will become upright first in V3 and then V2. Many adults will demonstrate ongoing T wave inversion in V1.

• Resting heart rates and conduction intervals differ in children and vary with age. Those such as PR and QTc tend to be shorter compared with adults. Population studies to create a normal range of values include a study of 1912 Dutch children by Rijnbeek et al. These studies comprise tables presenting age-specific limits of various ECG parameters.

Rijnbeek PR et al. New normal limits for the paediatric electrocardiogram. European heart journal. 2001; 22: 702-711

• Adolescents in particular may have elevated J points demonstrating early repolarisation and it may be challenging to differentiate this from ST segment elevation.

A normal paediatric ECG can therefore look pretty abnormal if you use adult criteria

Image from http://lifeinthefastlane.com/ecg-library/paediatric-ecg-interpretation/

Specific paediatric diagnoses which are aided by ECG interpretation

When evaluating the paediatric ECG, it is important to follow the same systematic approach taken when evaluating adult ECGs so as to not miss any abnormality. However, set out below are examples of diagnosis patterns to consider when evaluating paediatric ECGs.

Example 1 – Atrial chamber enlargement

This ECG is of a 15 year old boy from http://www.paedcard.com/interpretation.html

• It shows P waves that are taller than 2.5mm in lead II.
• This may suggest right atrial enlargement.
• Right atrial enlargement in isolation is non specific but may raise suspicion of congenital heart disease, particularly atrial septal defect, but also including tricuspid atresia, pulmonary stenosis and Ebstein’s anomaly.
• However anxious children may breath-hold, causing pooling of blood in the right atrium. Getting the child to relax and then repeating the ECG may get rid of the abnormality .

Example 2 Right ventricular hypertrophy

This ECG is of an 8 year old boy with breathlessnes. Image from http://www.resus.com.au/blog/how-to-read-the-paediatric-ecg/

• ECG shows RV hypertrophy
• Right axis deviation and dominant R waves particularly in right precordial leads
• RV hypertrophy is an important diagnosis in children, but difficult to establish in the infant ECG as some degree of RV dominance is expected and normal at this age. In young children that should display a juvenile T wave pattern (approximately age 7 days to 7 years), upright T waves in V1 are very specific for significant RV hypertrophy
  

  Differential diagnosis of RVH:

  • Congenital heart disease (CHD) usually evident at a younger age such as pulmonary stenosis, tetralogy of fallot, pulmonary valve atresia or hypoplastic left heart syndrome
  • CHD picked up at a later age may be ventricular or atrial septal defect
  • Primary pulmonary hypertension

Example 3 Left ventricular hypertrophy

This is an ECG of a 15 year old child with poor exercise tolerance and an episode of syncope. Image from http://emedicine.medscape.com/article/890068-workup#aw2aab6b5b3

• ECG shows LV hypertrophy and this child has hypertrophic cardiomyopathy.
• QRS complexes are dominant particularly in the lateral leads I, V5, V6, aVL.
• ECGs in children are poorly sensitive for LV hypertrophy.

Differential diagnosis of LVH:

• CHD, in particular ventricular septal defect
• CHD including those such as aortic stenosis and coarctation of the aorta causing LV outflow tract obstruction
• CHD resulting in a small RV including tricuspid atresia

Example 4 Rhythm abnormalities

Rhythm strip from a 2 year old girl with general lethergy and refusal to walk more than a few meters. Image from http://emedicine.medscape.com/article/894596-overview

• This shows complete heart block
• This may present early in the neonatal period with fetal hydrops and other signs of heart failure, but it may go undetected as some infants may have near normal resting heart rates from escape rhythms
• In later childhood it may present with poor lethargy, dizziness, blackouts and poor exercise tolerance
• It may be secondary to maternal autoimmune disease, and maternal referral to rheumatology is important for testing of anti-Ro and anti-La antibodies
• It may also be due to congenital structural disease
• Rhythm changes such as profound sinus arrhythmia, runs of 1^st degree heart block or Mobitz I 2^nd degree heart blocks may be entirely normal in the paediatric population

Example 5 Kawasaki’s disease

What abnormality would you expect to see on the ECG of the following patient?

A three year old irritable boy with a week history of high fever is brought to the Emergency department by his mother. Mum is concerned about his red eyes and lips and she has noticed his fingers and feet appear swollen. There is no history of foreign travel.

• This child has some features of Kawasaki’s disease
• This is a systemic vasculitis
• Sequelae include the formation of coronary artery aneurysms in about a quarter of untreated children within four weeks of fever onset
• These aneurysms may undergo thrombotic events
• ECGfeaturesmay be as follows:
  • Tachycardia out of proportion to fever
  • Prolonged PR or QTc interval
  • Abnormal Q waves
  • Arrhythmias
  • ST and T wave changes suggestive of cardiac ischaemia

Summary

Paediatric ECG’s interpretation requires a different approach to adult ECG interpretation. The normal ECG changes as the child grows and the heart develops. The ECG is an important clue to underlying disease and it is important to get an ECG in children presenting with syncope, seizures, palpitations, chest pain, overdose and specific circumstances such as suspected Kawasaki’s disease. If viewing paediatric ECGs is not routine then always use additional resources to guide your interpretation.

• Life In The Fast Lane Life in the Fast Lane has a section on paediatric ECGs with useful examples and description of a step-by-step interpretation process.
• Normal Paediatric ECG’s For a series of examples of normal ECGs ranging from 1 day to 15 years old follow this link to Tipple M. Interpretation of electrocardiograms in infants and children. Images paediatric cardiology. 1999; 1(1): 3-13.