The ABC of paediatric ECG interpretation In paediatric patients, ECG is used as a tool for investigation of arrhythmias, chest pain, syncope, intoxications and congenital heart abnormalities. Paediatric ECGs differ significantly from adult ECGs, and change gradually during childhood, largely because of the changes that start with the transition of foetal circulation at birth. This evolution is most prominent during the first year of life, but it is not until the late adolescent years that the ECG corresponds to that of adults. This article focuses on practical paediatric ECG interpretation. The first section presents normal age-related values for different ECG parameters. For example, in small children heart rate is higher, QRS-complexes narrower, T-waves in right precordial leads are negative, and the electrical axis rightward. Then, pathological changes in ECG are presented, e.g. tachy- and bradyarrhythmias, ST changes and long QT. Finally, we suggest which patients to refer to a specialist in paediatric cardiology.