The QT interval reflects which sequence of ventricular activity?

• A. Atrial Activation
• B. Ventricular Depolarization And Repolarization
• C. AV Nodal Conduction Delay
• D. Ventricular Systole Duration

Answer: (B)

The QT interval measures the duration of the ventricles’ electrical activity. It starts with the beginning of ventricular depolarization (the start of the QRS complex) and ends with the completion of ventricular repolarization (the end of the T wave). In other words, it covers the whole time the ventricles are activated and then recover electrically.

Atrial activation is represented by the P wave, not the QT interval. The AV nodal conduction delay is reflected in the PR interval, not the QT. While the QT interval relates to the electrical cycle that underlies ventricular contraction, it is not a direct measure of mechanical systole; it specifically spans electrical activation and recovery. Prolongation of the QT can indicate risk for certain arrhythmias, and QT duration is often corrected for heart rate (QTc) in practice.