Corrected QT (Fridericia)

The Fridericia correction adjusts the measured QT interval to account for heart rate, because the QT interval naturally shortens when the RR interval shortens and lengthens when the heart slows. Using the cube root of RR is an empirical way to remove much of this rate dependence, giving a QTc value that is easier to compare across different heart rates. It is commonly used as a more stable alternative to simpler corrections when heart rate is far from normal.

Use this when interpreting an ECG QT interval in a patient whose heart rate is not close to resting baseline, especially in drug safety, cardiology, or research settings. It is helpful when comparing repolarization duration across recordings taken at different heart rates.

• Using RR in milliseconds when QT is in seconds, which makes the result inconsistent
• Taking the square root instead of the cube root
• Confusing QTc with the uncorrected QT interval and interpreting it without accounting for heart rate