What is the normal range for QT interval?

As a medical professional with expertise in cardiology, I can provide you with information on the normal range for the QT interval. The QT interval is a measure of the time between the start of the Q wave and the end of the T wave in the heart's electrical cycle, as measured on an electrocardiogram (ECG). It represents the duration of both the depolarization and repolarization phases of the ventricles. The normal QT interval can vary based on several factors, including sex, age, and heart rate. To account for the effect of heart rate, the QT interval is often corrected using a formula such as the Bazett's formula, which results in the QTc (corrected QT) interval. The QTc is considered prolonged if it is greater than 440 milliseconds in men or greater than 460 milliseconds in women. A QTc value greater than 500 milliseconds is associated with an increased risk of a potentially life-threatening heart rhythm disturbance known as torsades de pointes. On the other hand, a QTc that is abnormally short, less than 350 milliseconds, can also be of concern. A simple rule of thumb for the normal QT interval is that it should be less than half the duration of the preceding RR interval, which is the time between two successive QRS complexes on an ECG.

Normal QTc values. QTc is prolonged if > 440ms in men or > 460ms in women. QTc > 500 is associated with increased risk of torsades de pointes. QTc is abnormally short if < 350ms. A useful rule of thumb is that a normal QT is less than half the preceding RR interval.