QT interval

In cardiology and the electrocardiogram, the QT interval is the time from the start of the Q wave and the end of the T wave.

To correct the QT interval for heart rate:

${\mbox{QTc}}={\frac {\mbox{measured QT interval}}{\sqrt {RR\ interval\ (in\ sec)}}}$

Normal values for the corrected QT interval are between 0.36 and 0.44 seconds.

A prolonged QT internal may lead to Torsades de Pointes. Drugs may prolong the QT interval. A list of these drugs is available at the Arizona Center for Education & Research on Therapeutics.