Corrected QT interval from QT and heart rate
Calculates the corrected QT interval from the measured QT and the heart rate using Bazett's formula. Correction is necessary because the QT interval shortens as heart rate rises, so an uncorrected QT cannot be compared against a reference range.
Thresholds differ by age and sex and by the reference used, so the measured value should be interpreted against an appropriate paediatric reference rather than an adult cut-off.
The square-root relationship does not hold well at rate extremes. In a markedly tachycardic infant it can produce a falsely high QTc, so the ECG should be repeated when the rate settles.
Conventionally the lead with the clearest T wave offset, commonly lead II or V5. The calculator uses whatever QT you measure.
Fridericia, Framingham and Hodges are alternatives that behave better at rate extremes. This tool implements Bazett, which remains the most widely reported.