What does a prolonged QT interval signify on an electrocardiogram?

A prolonged QT interval on an electrocardiogram (ECG) is a significant finding that indicates an increased risk of life-threatening arrhythmias, particularly Torsades de Pointes, which is a type of polymorphic ventricular tachycardia. The QT interval represents the time it takes for the heart's ventricles to depolarize and repolarize during the cardiac cycle. When this interval is prolonged, it suggests an abnormality in the heart's electrical recovery phase, which can predispose individuals to dangerous rhythms.

In the case of Torsades de Pointes, the prolonged QT can lead to a situation where the ventricular depolarization and repolarization are not synchronized properly, increasing the risk of sudden cardiac events. This can be particularly dangerous as it can lead to syncope or even sudden cardiac death.

A normal heart rhythm is characterized by a normal QT interval, indicating that the ventricular depolarization and repolarization are occurring in a healthy timeframe. Increased risk of heart block relates more to delays in the conduction system of the heart, rather than the electrical recovery indicated by the QT interval. Heart valve dysfunction typically does not directly affect the QT interval on an ECG and is assessed through different means. Thus, the primary clinical