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QTc Calculator
Input
ms
bpm
QTc (Bazett)
—
QTc (Fridericia)
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About
The corrected QT interval (QTc) adjusts the measured QT interval for heart rate, since the QT interval naturally shortens at faster heart rates. A prolonged QTc increases the risk of ventricular arrhythmias, including Torsades de Pointes. Bazett's formula is the most commonly used but tends to overcorrect at high heart rates; Fridericia's formula is more accurate at extreme heart rates.
Formula
Bazett: QTc = QT / √(RR interval in seconds)
Fridericia: QTc = QT / ∛(RR interval in seconds)
RR interval (sec) = 60 / Heart Rate (bpm)
Interpretation
| QTc (ms) | Interpretation |
|---|---|
| ≤ 440 (male) / ≤ 460 (female) | Normal |
| 441–499 (male) / 461–499 (female) | Borderline prolonged |
| ≥ 500 | Prolonged — high risk |
References
- Bazett HC. An analysis of the time-relations of electrocardiograms. Heart. 1920;7:353-370.
- Fridericia LS. Die Systolendauer im Elektrokardiogramm bei normalen Menschen und bei Herzkranken. Acta Med Scand. 1920;53:469-486.
- Goldenberg I, et al. QT interval: how to measure it and what is "normal". J Cardiovasc Electrophysiol. 2006;17(3):333-336.
FAQ
Disclaimer
For educational and informational purposes only. Not intended to replace professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional.