The QT interval, its origin and importance of the knowledge of formulas for its measurement in different clinical circumstances

Abstract

The long QT syndrome is an arrhythmogenic channelopathy characterized by severe alterations in ventricular repolarization, electrocardiographically translated as a QT interval prolongation. The involvement of various ion channels in the genesis of cardiac action potential causes that alterations in their structure and function lead to the so-called syndrome and to the presence of malignant ventricular arrhythmias. In 1920, Bazett adapted the formula of the cardiac electrical systole duration to the QT interval of the electrocardiogram, and proposed normal values of QT for a given heart rate. After Bazett’s description, several formulas were described in different clinical situations to calculate the corrected QT interval. The knowledge about how to measure the QT interval and about its correction as a tool for the diagnosis of arrhythmogenic conditions and prevention of primary or secondary malignant ventricular arrhythmias is of vital importance for its clinical use.