The corrected QT interval (QTc) estimates the QT interval at a standard heart rate of 60 bpm.

    This allows comparison of QT values over time at different heart rates and improves detection of patients at increased risk of arrhythmias.

    There are multiple formulas used to estimate QTc (see below). It is not clear which formula is the most useful.

Bazett formula: QTC = QT / √ RR

Fridericia formula: QTC = QT / RR 1/3

Framingham formula: QTC = QT + 0.154 (1 – RR)

Hodges formula: QTC = QT + 1.75 (heart rate – 60)

Note: The RR interval is given in seconds (RR interval = 60 / heart rate).