QT Interval Correction Formulae
Why do we correct the QT interval for heart rate?
  Since heart rate is the major modifier of ventricular action potential, the QT interval changes with heart rate. This is the basis for QT interval correction. Before comparing QT intervals between individuals, they must be corrected according to the heart rate.
  Heart rate is INVERSELY related to the QT interval: As heart rate increases, QT interval decreases. As heart rate decreases, QT interval increases.
Proposed formulae for QT interval correction
Linearity of the QT interval correction formulae
  Nonlinear formuale
- Bazett
- Fridericia
  Linear formuale
- Framingham
- Hodges
Which QT interval correction formula is the best?
  The most frequently used one is the Bazett's formula (1920). However it is also the most criticized formula. Bazett's formula overcorrects the QT interval at fast heart rates, undercorrects the QT interval at slow heart rates.
  Hodges formula is suggested to be the best one.
References
  Journal of Electrocardiology 2004, Vol 37, Suppl:81-90.
  J Cardiovasc Electrophysiol 2010;21:905-913.
  J Am Coll Cardiol 1983;12:694.Am J Cardiol 79:797,1992
  Am J Cardiol 1992;79:797
  Acta Med Scan 1920;53:469.
  Heart 1920;7:353.J Cardiovasc Electrophysiol 2010;21:905-913.
  Clinical Arrhythmology and Electrophysiology: A Companion to Braunwald's Heart Disease. 2nd edition. 2012.