Which ECG interval represents the total time for ventricular depolarization and repolarization?

Which ECG interval represents the total time for ventricular depolarization and repolarization?

• A. QT interval
• B. PR interval
• C. T wave duration
• D. QRS duration

Answer: (A)

The total time the ventricles are electrically active—from the start of their activation to the end of recovery—is shown by the QT interval. On the ECG, this interval runs from the start of the Q wave to the end of the T wave. The QRS complex represents ventricular depolarization, and the T wave represents ventricular repolarization, so the QT interval combines both processes into one measurement. The PR interval reflects atrial depolarization and AV conduction, not ventricular activity, and the duration of the T wave alone isn’t used as the standard measure of the whole ventricular cycle. Therefore, the QT interval best represents the combined time for ventricular depolarization and repolarization.

The total time the ventricles are electrically active—from the start of their activation to the end of recovery—is shown by the QT interval. On the ECG, this interval runs from the start of the Q wave to the end of the T wave. The QRS complex represents ventricular depolarization, and the T wave represents ventricular repolarization, so the QT interval combines both processes into one measurement. The PR interval reflects atrial depolarization and AV conduction, not ventricular activity, and the duration of the T wave alone isn’t used as the standard measure of the whole ventricular cycle. Therefore, the QT interval best represents the combined time for ventricular depolarization and repolarization.