Developmental aspects of long QT syndrome type 3 and Brugada syndrome on the basis of a single SCN5A mutation in childhood.

Objectives: The aim was to investigate at what age electrocardiographic characteristics of long QT syndrome type 3 (LQT3) and Brugada syndrome (BS), based on a single SNC5A mutation, appear.

Background: The QT interval (QT) in LQT3 is prolonged during bradycardia. It is not clear yet if this is obvious in young children with a relative fast heart rate (HR).