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Corrected QT (QTc)

Corrects QT for heart rate using the four most-used formulas and compares it with normal limits.

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Check the population, units and version. The result shows the formula or classification; it does not make an automatic treatment decision.

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Method · Limits of application

QTc/Bazett 1920, Fridericia 1920, Framingham 1992, Hodges 1983; QT ms/RR seconds; AHA 2009 and Vandenberk 2016 references

The Vandenberk 2016 study compared QT corrections in adults with sinus rhythm, narrow QRS and heart rate below 90 bpm, in a retrospective single-center analysis. These results do not establish equivalent performance in atrial fibrillation, conduction disorders or all heart rates accepted by the form. Bazett can overestimate QTc at high heart rates and underestimate it at low heart rates. Selection of the correction and interpretation require electrocardiographic context; a value alone does not determine treatment.

Conditions of use

Check the population, units, inclusion and exclusion criteria, and version in the original source. A result alone does not establish a diagnosis, discharge decision or prescription.

Documented parameters

Measured QT interval · ms
Heart rate · bpm
Sex

3/3 reference cases checked. Numerical tests are not clinical validation.

Sources and documentation

Documented formula

Transcribed from the source or a recorded revision; this is not a clinical recommendation.

RR (s) = 60 ÷ HR.

Bazett: QTc = QT ÷ √RR
Fridericia: QTc = QT ÷ ∛RR
Framingham: QTc = QT + 154 × (1 − RR)
Hodges: QTc = QT + 1.75 × (HR − 60)

References

Identifier: qtc

Original clinical content: Brazilian Portuguese.

Method version

QTc/Bazett 1920, Fridericia 1920, Framingham 1992, Hodges 1983; QT ms/RR seconds; AHA 2009 and Vandenberk 2016 references

qtc@native-2026-10-03+1bb40904dc12

Source for the active edition

The bibliographic edition identifies the source. By itself, it proves neither full conformity of the formula nor clinical approval.

Synthetic cases checked (3)

Synthetic cases for checking the implementation, with no patient data.

Case 1

reference-001

Inputs

Measured QT interval: 400 ms
Heart rate: 60 bpm
Sex: Male

{
  "qt": 400,
  "fc": 60,
  "sexo": "M"
}

Expected result

{
  "bazett": 400,
  "fridericia": 400,
  "framingham": 400,
  "hodges": 400
}

Actual result

{
  "bazett": 400,
  "fridericia": 400,
  "framingham": 400,
  "hodges": 400
}

Case 2

reference-002

Inputs

Measured QT interval: 360 ms
Heart rate: 100 bpm
Sex: Female

{
  "qt": 360,
  "fc": 100,
  "sexo": "F"
}

Expected result

{
  "bazett": 464.8,
  "fridericia": 426.9,
  "framingham": 421.6,
  "hodges": 430
}

Actual result

{
  "bazett": 464.75800154489,
  "fridericia": 426.8271965388075,
  "framingham": 421.6,
  "hodges": 430
}

Case 3

reference-003

Inputs

Measured QT interval: 520 ms
Heart rate: 60 bpm
Sex: Male

{
  "qt": 520,
  "fc": 60,
  "sexo": "M"
}

Expected result

{
  "level": "high"
}

Actual result

{
  "bazett": 520,
  "fridericia": 520,
  "framingham": 520,
  "hodges": 520
}

Code and reproducibility

This tool’s code on GitHub

Download code and tests

Sources, version and reproduction instructions

The code tests are technical checks. Clinical approval and professional translation review are recorded separately.

Relationship with cancer research

Support for research — context required

QT interval correction. It may support medication safety protocols when the method, heart rate and monitoring rules are defined in advance.

Applications: Pharmacology · Adverse effects and safety