Frequently Asked Questions
Which formula should I use, Bazett or Fridericia?
Bazett is the most widely reported formula and the default in most clinical guidelines. Fridericia is more accurate when heart rate is outside the 60-100 bpm range. When in doubt, report both and let the clinician decide which is most relevant.
What is a dangerous QTc level?
A QTc of 500 ms or greater is generally considered high risk for torsades de pointes, a potentially life-threatening ventricular arrhythmia. Immediate clinical evaluation is warranted. Values between 480 and 500 ms require careful clinical judgment, particularly in the context of medications and electrolytes.
Can normal people have a borderline QTc?
Yes. A borderline QTc (450-479 ms) without symptoms, a normal family history, and no QT-prolonging medications often requires only monitoring. Genetic testing for congenital long QT syndrome may be considered in some cases.
Does QTc differ by sex?
Yes. Women naturally have slightly longer QTc values, and some guidelines use sex-specific upper normal limits (450 ms for men, 460 ms for women). This calculator uses the simpler combined threshold of 450 ms as the normal-borderline boundary.
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General information only. Not medical advice.
Health & Medical Disclaimer: General information only. Not medical advice.
This calculator provides general health information only and is not medical advice. Results do not replace professional medical evaluation or diagnosis. Consult a licensed healthcare provider before making health decisions. Always seek immediate medical attention for emergencies.