What is the Q-T interval in an ECG?

What is the Q-T interval in an ECG?

• A. The time from ventricular depolarization (QRS complex) to ventricular repolarization (T wave).
• B. The time from atrial depolarization to ventricular depolarization.
• C. The duration of the P wave.
• D. The interval from Q wave to the end of the T wave.

Answer: (A)

The QT interval represents the total time of ventricular electrical activity in one beat, from the start of ventricular depolarization to the end of ventricular repolarization. The onset of ventricular depolarization is seen as the beginning of the QRS complex, and ventricular repolarization completes with the end of the T wave. So the interval spans the entire ventricular action potential duration. This is why the best description is the time from the start of ventricular depolarization (the QRS onset) to the end of ventricular repolarization (the T wave). Clinically, QT length can change with heart rate and certain drugs or electrolyte issues, and a prolonged QT can raise the risk of arrhythmias.

The QT interval represents the total time of ventricular electrical activity in one beat, from the start of ventricular depolarization to the end of ventricular repolarization. The onset of ventricular depolarization is seen as the beginning of the QRS complex, and ventricular repolarization completes with the end of the T wave. So the interval spans the entire ventricular action potential duration. This is why the best description is the time from the start of ventricular depolarization (the QRS onset) to the end of ventricular repolarization (the T wave). Clinically, QT length can change with heart rate and certain drugs or electrolyte issues, and a prolonged QT can raise the risk of arrhythmias.