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Cardiology

Corrected QT interval (Bazett, Fridericia, Framingham, Hodges)

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Formula

RR = 60/HR (s). Bazett QT/sqrt(RR); Fridericia QT/RR^(1/3); Framingham QT + 154(1-RR); Hodges QT + 1.75(HR-60).

Limitations

  • Bazett over-corrects at high heart rates and under-corrects at low heart rates.
  • Not valid in atrial fibrillation without beat averaging, or with a wide QRS or bundle-branch block unless adjusted.
  • Thresholds (450/460/500 ms) are conventional and context-dependent; drug-safety thresholds differ.
  • The original Hodges publication is a conference abstract (J Am Coll Cardiol 1983;1:694).

References

  1. An analysis of the time-relations of electrocardiograms. Bazett HC. Heart. 1920;7:353-370.
  2. Fridericia: Die Systolendauer im Elektrokardiogramm bei normalen Menschen und bei Herzkranken. Fridericia LS. Acta Med Scand. 1920;53:469-486.
  3. An improved method for adjusting the QT interval for heart rate (the Framingham Heart Study). Sagie A, Larson MG, Goldberg RJ, Bengtson JR, Levy D. Am J Cardiol. 1992;70(7):797-801. PMID 1519533
  4. Bazett's QT correction reviewed. Evidence that a linear QT correction for heart rate is better. Hodges M, Salerno D, Erlien D. J Am Coll Cardiol. 1983;1:694.