Corrected QT Interval (QTc)

Usage Corrected QT interval (QTc)The corrected QT interval (QTc) estimates the QT interval at a standard heart rate of 60 bpmThis allows comparison of QT values over time at different heart rates and improves detection of patients at increased risk of arrhythmias. Summary The Life in the Fastlane website provides a concise overview with examples in an article called QT Interval (Burns & Buttner, 2022). Here are a few key points. There are multiple formulas used to estimate QTc. It is not clear which formula is the most useful:Bazett formula: QTC = QT / √ RRFridericia formula: QTC = QT / RR 1/3Framingham 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). Prolonged QT (≥440 msec): QTc is prolonged if ≥ 440ms in men or ≥ 460ms in womenQTc > 500 is associated with an increased risk of torsade de pointes Short QT (<350ms)Congenital short QT syndrome has been found to be associated with an increased risk of paroxysmal atrial and ventricular fibrillation and sudden cardiac death.