Corrected QT Interval (QTc)
Corrects the QT interval for heart rate extremes (includes Bazett, Fridericia, Framingham, Hodges & Rautaharju formulas.
Formula Options
Min 0 – Max 500
Reference
Summary
Usage
Summary
Corrected QT interval (QTc)
- 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
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 / √ 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).
Prolonged QT (≥440 msec):
- QTc is prolonged if ≥ 440ms in men or ≥ 460ms in women
- QTc > 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
Literature
- QT Interval — Burns & Buttner (2022)
- Lightning Learning: Long QT Syndrome — Spilman-Henham, Pandora
- The ECG leads: Electrodes, limb leads, chest (precordial) leads and the 12-lead ECG — ECG & ECHO Learning
- The QT interval: too long, too short or just right. — Viskin, Sami
- Drug-induced QT prolongation and torsades de pointes: evaluation of a QT nomogram. QJM. 2007 Oct;100(10):609-15. — Chan A, Isbister GK, Kirkpatrick CM, Dufful SB.
- An Analysis of the time-relations of Electrocardiograms. Annals of Noninvasive Electrocardiology. (1997) 2: 177-194. — BAZETT, H.C.
- The duration of systole in an electrocardiogram in normal humans and in patients with heart disease. 1920. Ann Noninvasive Electrocardiol. 2003 Oct;8(4):343-51. — Fridericia LS.
- Bazett's QT correction reviewed : Evidence that a linear QT correction for heart rate is better. Journal of the American College of Cardiology. (1983) 1, 694. — Hodges, M.
- An improved method for adjusting the QT interval for heart rate (the Framingham Heart Study). Am J Cardiol. 1992 Sep 15;70(7):797-801. — Sagie A, Larson MG, Goldberg RJ, Bengtson JR, Levy D.
- New age- and sex-specific criteria for QT prolongation based on rate correction formulas that minimize bias at the upper normal limits. Int J Cardiol. 2014 Jul 1;174(3):535-40. — Rautaharju PM, Mason JW, Akiyama T.
- Jennifer Glen , DNP, FNP-BC — EVAL Health, Chief Medical Officer