What does the QT interval represent?

What does the QT interval represent?

• A. Summation of depolarization and repolarization of the ventricles
• B. Ventricular depolarization
• C. Atrial depolarization
• D. ST segment elevation

Answer: (A)

The QT interval reflects the total time for ventricular electrical activity—from the start of ventricular depolarization to the end of ventricular repolarization. On the ECG this is from the beginning of the Q wave (or R wave if no Q) through the end of the T wave. It includes the entire QRS complex (ventricular depolarization), the ST segment (the plateau of the ventricular action potential), and the T wave (ventricular repolarization). It does not represent atrial depolarization, which is the P wave. Clinically, a longer QT means a longer ventricular action potential duration and can predispose to certain dangerous arrhythmias, hence the use of QTc to correct for heart rate.

The QT interval reflects the total time for ventricular electrical activity—from the start of ventricular depolarization to the end of ventricular repolarization. On the ECG this is from the beginning of the Q wave (or R wave if no Q) through the end of the T wave. It includes the entire QRS complex (ventricular depolarization), the ST segment (the plateau of the ventricular action potential), and the T wave (ventricular repolarization). It does not represent atrial depolarization, which is the P wave. Clinically, a longer QT means a longer ventricular action potential duration and can predispose to certain dangerous arrhythmias, hence the use of QTc to correct for heart rate.