What does the ECG QTc interval mean?

The electrocardiographic QTc interval refers to the corrected QT interval and is an important indicator in electrocardiography or cardiac electrophysiology. The QT interval represents the time required for the entire electrical activity process of the ventricles from depolarization to repolarization, specifically the duration from the onset of the QRS complex to the end of the T wave. However, because the QT interval is significantly affected by heart rate—potentially shortening with tachycardia and prolonging with bradycardia—it must be converted into a heart rate-independent QTc interval using correction formulas (such as Bazett's formula) to more accurately reflect the stability of ventricular electrical activity. The normal range of the QTc interval varies by gender, generally less than 430 milliseconds in males and less than 450 milliseconds in females. Prolongation of the QTc interval indicates delayed cardiac repolarization and may reflect abnormal electrical activity in the heart. It is typically closely associated with increased susceptibility to arrhythmias. QTc prolongation can be caused by multiple factors, including heart failure, coronary artery insufficiency, electrolyte disturbances, and the use of certain medications. If concerned, please consult a relevant physician.