Corrected QT Interval (Bazett)
Corrects QT interval for heart rate using Bazett's formula. Identifies prolonged QTc risk.
Score interpretation
QTc < 450 ms: normal in men and women.
→ No action required for QTc alone.
QTc ≥ 450 ms is prolonged in men; below 460 ms is still normal in women (Khatib 2021). Review QT-prolonging medicines.
→ Review drug list for QT-prolonging agents. Monitor electrolytes (K⁺, Mg²⁺).
QTc ≥ 460 ms: prolonged in women and men. Increased risk of torsades de pointes.
→ Correct electrolytes. Review and stop QT-prolonging drugs. Cardiology review.
QTc > 500 ms: high risk of torsades de pointes and sudden cardiac death.
→ Urgent cardiology review. Stop all QT-prolonging drugs. Continuous cardiac monitoring. Consider IV magnesium.
Interpretation bands for the QTc (Bazett). Apply clinical judgement and local guidance.
References
- Bazett HC. An analysis of the time-relations of electrocardiograms. Heart. 1920.
- Al-Khatib SM et al. 2017 AHA/ACC/HRS Guideline on the Evaluation and Management of Patients with Ventricular Arrhythmias.
- Khatib R et al. Managing drug-induced QT prolongation in clinical practice. Postgrad Med J. 2021;97(1149):452–458.
Related
Curated clinical cross-links plus same-class fallbacks.
- Pancuronium · Non-Depolarising Neuromuscular Blocking Agent (Long-Acting)
- Pancuronium bromide · Long-acting non-depolarising neuromuscular blocker
- Ropivacaine hydrochloride · Long-acting amide local anaesthetic
- Bupivacaine hydrochloride · Long-acting amide local anaesthetic
- Bupivacaine with adrenaline · Long-acting amide LA + vasoconstrictor
- Lidocaine IV (Cardiac Arrhythmia) · Antiarrhythmic
- Acute Heart Failure · ESC 2021 Heart Failure Guidelines; NICE NG106
- NSTEMI / Unstable Angina · ESC 2020 NSTEMI Guidelines; NICE NG185
- New-Onset Atrial Fibrillation · ESC 2020 AF Guidelines; NICE NG196
- Hypertensive Emergency · ESC/ESH 2018 Hypertension Guidelines; NICE NG136
- Bradycardia Management · Resuscitation Council UK ABCDE; ESC 2021 Pacing Guidelines
- Ventricular Tachycardia / Fibrillation · Resuscitation Council UK ACLS; ESC 2022 Ventricular Arrhythmia Guidelines
Featured in these MRCEM clinical pathways
The QTc (Bazett) is covered in detail — with RCEM/NICE evidence base, indications and pitfalls — in the following exam-focused pathways on our sister siteReviseMRCEM.
MRCEM Primary / Intermediate / OSCE candidates: each pathway includes exam-style questions, RCEM/NICE citations, and FAQ summaries.
Decision support only — verify against a current formulary, NICE, or your local guideline before clinical use.