🫀 Corrected QT (Multi-Formula Comparison)

When to use

Enter the measured QT and heart rate (or RR); the tool returns QTc by several methods. At extreme heart rates, prefer Fridericia/Framingham over Bazett, which over-corrects at high rates and under-corrects at low rates.

How it works

RR(s) = 60/HR. Bazett QTc = QT/√RR; Fridericia QTc = QT/RR^(1/3); Framingham QTc = QT + 154×(1−RR); Hodges QTc = QT + 1.75×(HR−60). Prolonged: > 450 ms (male) / > 470 ms (female); > 500 ms markedly raises torsades risk.

Key points

• Bazett systematically over-corrects at tachycardia and under-corrects at bradycardia; Fridericia and Framingham are more rate-stable and preferred outside HR 60–100. (original synthesis · not guideline verbatim)
• QTc > 500 ms, or a drug-induced increase ≥ 60 ms from baseline, substantially raises the risk of torsades de pointes.
• Correct hypokalemia/hypomagnesemia and review QT-prolonging drugs; in wide QRS or bundle branch block, raw QT measurement and correction both become unreliable.

References

• Vandenberk B, et al. Which QT Correction Formulae to Use for QT Monitoring? J Am Heart Assoc. 2016;5(6):e003264.
• Postema PG, Wilde AAM. The measurement of the QT interval. Curr Cardiol Rev. 2014;10(3):287-294.

Other tools