- The QT Interval
- The QT interval begins at the onset of the QRS complex and to the end of the T wave. It represents the time between the start of ventricular depolarization and the end of ventricular repolarization. It is useful as a measure of the duration of repolarization. The QT interval will vary depending on the heart rate, age and gender. It increases with bradycardia and decreases with tachycardia. Men have shorter QT intervals (0.39 sec) than women (0.41 sec). The QT interval is influenced by electrolyte balance, drugs, and ischemia.
The animation below shows conduction during the QT segment. Note the QRS complex followed by the isoelectric ST segment. Also note that the animation had been slowed about 10 times the normal heart rate to show the details.