QTc Bazett calculator online: heart-rate corrected QT interval
Heart-rate corrected QT interval by Bazett formula: QTc = QT/√RR. Used to assess risk of life-threatening arrhythmias (torsade de pointes), when prescribing QT-prolonging drugs, and in long QT syndromes.
About this calculator
Corrected QT interval (QTc) is an ECG parameter that removes the heart-rate dependence of the QT interval. Bazett formula (1920): QTc = QT/√RR, where RR is the interval between adjacent R waves in seconds. Used in cardiology, psychiatry, addiction medicine, oncology, and infectious diseases – any setting prescribing QT-prolonging drugs. Upper normal limit: 450 ms in men, 460 ms in women, 440 ms in adolescents. QTc 450–500 ms is borderline and requires monitoring with dose escalation; >500 ms carries high torsade de pointes risk and warrants drug discontinuation or correction of electrolytes (potassium, magnesium, calcium). QT-prolonging drugs: class IA and III antiarrhythmics (quinidine, amiodarone, sotalol), macrolides (azithromycin, clarithromycin), fluoroquinolones, azole antifungals, antipsychotics (haloperidol, thioridazine), antidepressants (citalopram, escitalopram), methadone, ondansetron. The complete current list is on CredibleMeds.org. Bazett overcorrects at tachycardia >100 bpm and undercorrects at bradycardia <60 – Fridericia (QT/RR^1/3) or Framingham formulas are more accurate in these settings. In atrial fibrillation QTc is averaged over 10 RR cycles.
Source
Bazett HC. An analysis of the time-relations of electrocardiograms. Heart. 1920;7:353-370.
Formula version: bazett-1920-v1
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