A tool to support the clinical decisions of doctors and health professionals, not for self-diagnosis or self-treatment.
This calculator is inside the patient's file in Clinicato: open it from "Medical tools" while you chart the visit, it fills in from the patient's details and vital signs where they are recorded, and adds its result to the visit's plan in one tap, with the "Medical tools" add-on. Try it in your clinic
Calculator
How it works and when to use it
The calculator corrects QT for heart rate: Bazett divides QT by the square root of the RR interval, Fridericia by the cube root, and Framingham adds a linear correction.
Bazett overcorrects at fast and undercorrects at slow heart rates, so the band uses Fridericia: prolonged from 450 ms in men and 460 ms in women by AHA/ACCF/HRS, and 500 ms or more is marked prolongation.
Reference: Bazett HC. Heart 1920;7:353-70; Fridericia LS. Acta Med Scand 1920;53:469-86; Sagie A et al. Am J Cardiol 1992;70:797-801 (Framingham); thresholds: Rautaharju PM et al. (AHA/ACCF/HRS) Circulation 2009;119:e241-50; 500 ms: Drew BJ et al. Circulation 2010;121:1047-60
Frequently asked questions
Why do the formulas give different results?
Each corrects for heart rate differently, and the gap grows the further the rate is from 60 a minute.
When does QTc matter?
Before and during drugs that prolong QT, such as some antibiotics and antipsychotics, and with electrolyte disorders or unexplained fainting.
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Clinic software for this specialty
Try Clinicato for your clinic
These calculators are free here for everyone, and in Clinicato 49 medical tools work inside the patient's file with the "Medical tools" add-on: filled from the visit and the vital signs, with the result added to the visit's plan, next to appointments, prescriptions and invoices.