🫀 Corrected QT (Multi-Formula Comparison)
Computes the corrected QT interval (QTc) using multiple formulas (Bazett, Fridericia, Framingham, Hodges), reducing the heart-rate dependence of QTc estimation.
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)
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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.
Worked calculation
The values below come from this tool's own example placeholders and are computed server-side with the formula shown on this page, so the arithmetic can be checked quickly. It demonstrates how to substitute values only — it is not clinical advice and not a real case.
| QT interval | 400 ms |
|---|---|
| Heart rate | 75 bpm |
| Sex | Male |
→QTc (Fridericia)431ms
- Bazett：447 ms
- Fridericia：431 ms
- Framingham：431 ms
Frequently asked questions
- What is Corrected QT (Multi-Formula Comparison)?
- Computes the corrected QT interval (QTc) using multiple formulas (Bazett, Fridericia, Framingham, Hodges), reducing the heart-rate dependence of QTc estimation.
- How is Corrected QT (Multi-Formula Comparison) calculated? What is the core formula?
- 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.
- When is Corrected QT (Multi-Formula Comparison) used?
- 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.
- What are the key clinical points for Corrected QT (Multi-Formula Comparison)?
- 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.
- What are the limits and cautions when using Corrected QT (Multi-Formula Comparison)?
- For licensed clinicians and clinical researchers. Interpret results with history, investigations and local protocols; not a diagnosis or prescription, and not a substitute for multidisciplinary decision-making or local guidelines.
- How is Corrected QT (Multi-Formula Comparison) calculated in practice? Can you show a worked example?
- Inputs: QT interval 400 ms, Heart rate 75 bpm, Sex Male → Result: QTc (Fridericia) 431 ms（Bazett: 447 ms, Fridericia: 431 ms, Framingham: 431 ms）