[Clinical conditions associated with abnormal QT interval: clinical implications].

Impressive progress has been made in the last 40 years in the understanding of the role of QT interval and its genetic basis in sudden cardiac death risk. The present review will provide a first practical part on QT measurement and its correction for heart rate. Subsequently, the long QT syndrome and short QT syndrome will be described, as the two main arrhythmogenic congenital heart diseases characterized by abnormal QT length. Furthermore, we will discuss about prolonged QT in the pathogenesis of sudden infant death syndrome and the preventive role of neonatal ECG screening. The prognostic role of QT interval will be presented also in the context of myocardial infarction and hypertrophic cardiomyopathy. The last part of the review is devoted to future perspectives and latest results on modifier genes.