Bazett QTc calculator
Result
432ms
Normal
How to use it
- 1
Measure QT interval on ECG. Lead II or V5. Start of QRS to end of T-wave. Average 3 consecutive beats.
- 2
Measure RR interval. In ms: 60,000 ÷ HR(bpm), or measure directly between two R-peaks.
- 3
Interpret QTc. Men: normal <440 ms. Women: normal <460 ms. QTc >500 ms: high torsades risk.
When to use it
- Drug initiation
- Always check QTc before azithromycin, antipsychotics, methadone, hydroxychloroquine, class III antiarrhythmics.
- Electrolyte replacement
- QTc monitoring during hypokalaemia/hypomagnesaemia correction.
- Congenital long QT
- Genotyping + QTc. LQTS1: beta-blockers. LQTS2: avoid class 1C drugs. LQTS3: mexiletine may help.
A reference for clinicians and students, not medical advice. A score supports a decision; it does not make one. Check every result against the patient in front of you and your local protocol.
At a glance
- Specialty
- Cardiology
- Inputs
- 2
- Type
- Formula
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