Go Back to tools
Sign Up Corrected QT Interval
The QT interval shortens with rapid heart rates and lengthens at slower heart rates, as a compensatory mechanism. In order to truly estimate risk of ventricular arrhythmia it is important to correct for the heart rate, i.e. estimating what the QT interval would be at 60 beats per minute.
Adjust the QT interval according the to heart rate using the Bazett, Fridericia or Framingham method. The Bazett formula is the most commonly used, and is validated for heart rates between 60-100bpm. In the presence of tachycardia or bradycardia, one of the other two formulae should be used.
Adjust the QT interval according the to heart rate using the Bazett, Fridericia or Framingham method. The Bazett formula is the most commonly used, and is validated for heart rates between 60-100bpm. In the presence of tachycardia or bradycardia, one of the other two formulae should be used.
RR Interval =
60 Heart Rate
Bazett
QTc =
QT √RR Interval
Fridericia
QTc =
QT RR 1/3
Framingham
QTc = QT + 0.154(1000 - RR Interval)
References
Bazett HC. An analysis of time relations of the electrocardiogram. Heart. 1920; 7: 353-70.
Fridericia LS. Die Systolendauer im Elektrokardiogramm bei normalen Menschen und bei Herzkranken. Acta Med Scand 1920, 53: 469.Luo S, Michler K, Johnstone P, Macfarlane PW. A comparison on commonly used QT correction formulae: the effect of heart rate on the QTc of normal ECGs.