The QT interval varies with the heart rate: the faster the heart rate, the shorter the QT interval. To adjust for the heart rate a corrected QT interval must be calculated. Often Bazett’s formula is used:
- QTc = measured QT/√RR
where QTc is the QT interval corrected for heart rate, measured QT is the measured QT interval in seconds and the RR is the interval between two R waves measured in seconds.
The corrected QT interval (QTc) should be less than 0.44 seconds. If the QTc is prolonged there is a risk of ventricular arrhythmia, in particular torsades de pointes.
– Mathias
{ 1 trackback }