Corresponding address: Shakuntala Prabhu, Div. of Pediatric Cardiology, Dept. of Pediatrics, B.J.Wadia Hospital for Children, Mumbai.
Email : ssprabhu1@hotmail.com

Electrocardiography records the electrical activity of the heart and is a useful, though under-utilized investigation in pediatric practice. It supplements the information obtained by clinical examination and chest radiography. ECG helps mostly in the assessment of chamber size, arrhythmias and ischemia. There are many nuances to the pediatric ECG that relate to age-specific changes. These findings relate directly to changes in the myocardium and circulatory system as the individual matures from infancy to adulthood. A recent review of pediatric emergency department use reveals that the most common reasons for obtaining ECGs in children are chest pain, suspected dysrhythmias, seizure, syncope, drug exposure, electrical burns, electrolyte abnormalities, and abnormal physical examination findings. Although a complete review of ECG interpretation is beyond the scope of this article, the authors suggest the use of a systematic approach to ECG interpretation.

The limitations of pediatric ECG are as follows:

Basics of recording and interpretation :

What does each wave represent ?

P wave represents atrial depolarization. This is the time taken by an electrical impulse to spread from the sino-atrial node through the atrial musculature. This wave precedes the QRS complex and is best measured in lead II.
The PR interval represents the time taken by an impulse to travel from the atria to the Purkinje fibres through the AV-node, bundle of His and the bundle branches. This is measured from the beginning of the P wave to the beginning of the QRS complex.
Q wave - Septal depolarization
RS wave - Ventricular depolarization
The QRS complex follows the PR interval and consists of 3 waves- the Q wave, R wave and S wave. The Q wave is always at the beginning of the QRS complex and may or may not be present. The R wave is the first positive deflection and is followed by the S wave which is a negative deflection.
The QT interval extends from the beginning of the QRS complex to the end of T wave and represents the time necessary for ventricular depolarization and repolarization. This interval is best measured in leads II, V5 and V6 and the longest interval is used.
The corrected QT interval or QTc is calculated by using Bazett's formula:

QTc = QT interval / Ö RR

The T wave represents ventricular repolarization and follows the S wave and S-T segment. At times, a U-wave follows the T wave and represents the repolarization of His and Purkinje fibres.