ECG: Indications and Interpretation


These guidelines have been produced to guide clinical decision making for the medical, nursing and allied health staff of Perth Children’s Hospital. They are not strict protocols, and they do not replace the judgement of a senior clinician. Clinical common-sense should be applied at all times. These clinical guidelines should never be relied on as a substitute for proper assessment with respect to the particular circumstances of each case and the needs of each patient. Clinicians should also consider the local skill level available and their local area policies before following any guideline. 

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To guide Emergency Department (ED) staff to interpret 12 lead electrocardiograms (ECG) in children. 


Common indications for paediatric electrocardiography:

  • Syncope, seizures and “funny turns”
  • Cyanotic episodes
  • Chest pain or other symptoms related to exertion
  • Neonates that present with the combination of respiratory symptoms and mottled skin to exclude an underlying cardiac condition
  • Drug ingestion
  • Diagnosis and management of rheumatic fever, Kawasaki’s disease, pericarditis, myocarditis
  • Diagnosis and management of arrhythmia
  • Diagnosis and management of congenital heart disease
  • Family history of sudden death or life-threatening event
  • Electrolyte abnormalities


Failure to follow this guideline may lead to misinterpretation of paediatric ECGs


Age Variants

Normal heart rates (Beats per minute)
2 years
4 years
6+ years 

Full term newborn infant

  • Right axis deviation (up to +180 degrees)
  • Right ventricle (RV) dominance in praecordial (chest) leads:
    • Tall R waves in lead V1 (>10mm suggests right ventricular hypertrophy (RVH))
    • Deep S waves in lead V6
    • R/S ratio >1 in right chest leads, relatively small in left
  • QRS voltages in limb leads relatively small
  • T waves - low voltage in lead V1 may be upright for <72 hours (>72 hours suggests RVH).

1 week – 1 month

  • Right axis retained
  • R waves remain dominant across to lead V6, although dominant S waves may be normal
  • T wave negative in lead V1
  • T wave voltage higher in limb leads

1 – 6 months

  • QRS axis rotates to leftward (less than +120 degrees)
  • R wave remains dormant in lead V1
  • R/S ratio in lead V2 close to 1 but may be >1 in lead V1
  • T waves negative across right chest leads.

ECG, 2 month old

ECG – 2 month old

6 months – 3 years

  • QRS axis usually > +90 degrees
  • R wave dominant in lead V6
  • R/S ratio in lead V1 close to or less than 1
  • Large voltages in praecordial leads persist

ECG, 2 year old

ECG – 2 year old


3 – 8 years

  • Adult QRS progression in praecordial leads: dominant S waves in lead V1, dominant R waves in lead V6
  • Large praecordial voltages persist
  • Q waves in left chest leads may be large (<5mm)
  • T waves remain negative in right praecordial leads

8 – 16 years

  • QRS axis mean +60 degrees, range 0 to +90 degrees
  • Adult QRS progression
  • Large praecordial lead voltages, R waves in left leads larger than adult
  • T waves variable. Maybe upright in lead V1 but negative in lead V1-V4 (not abnormal)

ECG, 8 year old

ECG – 8 year old

ECG, 15 year old

ECG – 15 year old


  • QRS axis mean +50 degrees, range 0 to +100 degrees
  • Dominant left ventricle (LV)
  • T waves upright across praecordial leads


P Wave

  • P wave amplitude does not change significantly during childhood
  • P waves are normally upright in leads I and aVF
  • Amplitude < 3mm, if taller consider right atrial hypertrophy (RAH)
  • Duration < 0.09 seconds, if wider consider left atrial hypertrophy (LAH)

Q Wave

  • In most leads where a significant Q waves appears (I, III, aVF, V5, V6), there is a trend for amplitude to double over the first few months of life, reaching a maximum at about 3-5 years of age and declining thereafter back towards the newborn period
  • Abnormal if present in lead V1 or absent in leads V5 or V6
  • Normal duration 0.02-0.03 seconds
  • Normal amplitude < 5mm
  • Amplitude > 5mm consider:
    • Hypertrophy
    • Volume overload

QRS Axis

  • The relative right ventricular hypertrophy (RVH) of the neonate regresses over the first few months of life
Age  Mean  Range 
1 week - 1 month  +100 degrees +30 - +180 degrees
1 month - 3 months  +70 degrees +10 - +125 degrees
3 months - 3 years  +60 degrees +10 - +110 degrees
3 years +  +60 degrees +20 - +120 degrees
Adult  +50 degrees -30 - +105 degrees
  • The amplitude of R waves in the right pericardial leads of normal children decreases with age while the amplitude increases in the left praecordial leads.
  • Similar but inverse changes occur in respect of the S wave amplitude

T Wave

  • In the first 2-3 days of life upright T waves in the right praecordial leads (V1 and V3R) are normal
  • It is usual for the T waves in these leads to invert in the majority of infants during the first week of life
  • Persistence of a positive T wave in lead V1 or V3R beyond the first week of life should therefore raise the suspicion of abnormality, usually RVH
  • In the intermediate leads, V2 and V3, the T wave is often inverted in early childhood and there is progression to the T wave becoming upright in sequence lead V3, lead V2, lead V1
  • The T wave in lead V5 and V6 should be upright at all ages, but in a very small number of newborn babies the T wave in these leads may be flat or inverted for 1-3 days. Inversion after this suggests left ventricular hypertrophy (LVH).
  • Tall T waves
    • Hyperkalaemia
    • LVH
  • Flat T waves
    • Hypokalaemia
    • Pericarditis
    • Myocarditis
    • Newborns
    • Hypothyroidism

Variation in P-P interval

  • The diagnosis of sinus arrhythmia is easily confirmed in most cases by observing the relation of the change to respiration (slowing in expiration, accelerating in inspiration).

Common variations in rhythm which may be normal

  • Pronounced sinus arrhythmia
  • Short sinus pauses <1.8 seconds
  • First degree atrioventricular block (Prolonged PR interval)
  • Mobitz type 1 second degree atrioventricular block
  • Junctional rhythm

PR Interval

  • In infants PR interval would be in the range 80-110 milliseconds
  • In children up to 150 milliseconds
  • In teenagers with slower heart rates the upper limit of normal is 180 milliseconds
  • Prolonged PR interval
    • Congenital Heart Disease (CHD)
    • Myocarditis
    • Hyperkalaemia
  • Shortened PR interval
    • Wolff-Parkinson-White (WPW)
    • Glycogen Storage Disease (GSD)

ECG, Wolff Parkinson White

ECG – Wolff-Parkinson-White


  • Isolated ventricular premature beats may be identified on a routine resting ECG in 0.2-2.2% of normal children
  • Extrasystoles which conform to this pattern and suppress on exercise are almost certainly benign

QRS Duration

There is a progressive increase in QRS duration with age, with a normal range from about: 

  • 50-70 milliseconds in neonates
  • 60-90 milliseconds in children 
  • 90-100 milliseconds in adolescents
  • Prolonged QRS duration
    • Bundle branch blocks (BBB)
    • Wolff-Parkinson-White (WPW)
    • Ventricular arrhythmia
  • Decreased amplitude
    • Myocarditis
    • Pericarditis

QT interval

  • Detecting prolongation of the QT interval is important in the identification of individuals at risk of life-threatening arrhythmia associated with syncope and sudden death
  • Under 6 months: corrected QT interval (QTc) < 0.49 seconds
  • Over 6 months: QTc < 0.44 seconds
  • For practical purposes Bazett’s formula (QTc = QT  ⁄  √R-R interval) remains the most commonly used method for determining the rate corrected.
  • Prolonged QTc is seen in:
    • Hypokalaemia
    • Hypomagnesaemia
    • Hypocalcaemia
    • Hypothermia
    • Head injury
    • Myocarditis
  • Commonly used drugs such as azithromycin, erythromycin, clarithromycin, fluconazole and domperidone
  • Various online calculators can be used to help calculate QTc

Differential diagnoses

ECG signs of Pericarditis  ECG signs of Myocarditis   ECG abnormalities in patients with Syncope 
↑ST in left ventricular leads returns to normal within 2-3 days
Flat T waves initially then inverts after 2-4 weeks
↓QRS amplitude
↑PR interval
↓T wave amplitude
↑QT interval
↓QRS amplitude
Long QT interval
Wide complex tachycardia
Hypertrophic Obstructive Cardiomyopathy (LVH)



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  2. Myung K, Park MK, Guntheroth WG. St Louis: Elselvier, 2006. How To Read Pediatric ECGs 4th Edition
  3. P.R Rijnbeek, M Witsenburg, E Schrama, J Hess, J.A Kors, New normal limits for the paediatric electrocardiogram, European Heart Journal, Volume 22, Issue 8, 1 April 2001, Pages 702–711
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  6. Wernovsky G, Anderson RH et al. Anderson’s Pediatric Cardiology: Expert Consult - Online and Print 4th Edition. Elselvier 2019
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Endorsed by: Nurse, Co-director Surgical Services  Date: Nov 2022

 Review date:  Nov 2025

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