RESUMEN
The ECG in children has a number of characteristic differences compared to the ECG of the adult. The transition of the ECG in neonates after birth represents dynamic changes of the circulatory system due to the postnatal adaptation, different physiologic properties of the fetal and neonatal myocardium, the location and orientation of the heart in the chest and influence of body mass during that period and later on in childhood. The complexity of the changes implies a broad variation of ECG changes during the first days and weeks of life, whose interpretation requires expert knowledge. The ECG is an obligatory diagnostic tool in childhood arrhythmias. The long QT syndrome is an inherited rhythm disorder with risk of sudden cardiac death in early childhood. Electrocardiographic screening in neonates for the early detection of LQTS might identify individuals with an abnormal repolarization and prevent sudden death. The potential benefits of a universal screening program, even if achievable logistically and in a cost-effective manner, are however highly debatable.