Pedemy All toolsEnter the heart rate (or RR) and QT; the corrected QT and what to do next are shown, with normal ECG values by age.
This calculator works out the corrected QT interval (QTc) from the heart rate or RR interval and the measured QT, and compares it with pediatric limits by age and sex. It is meant for clinicians reading children’s ECGs, and it also shows normal heart rate, PR and QRS values by age.
The tool gives the QTc by four formulas: Bazett (the standard for children), Fridericia, Hodges and Framingham. Grading uses Bazett with borderline and prolonged limits of 450 and 470 ms under 6 months, 440 and 460 ms from 6 months to puberty, 430 and 450 ms in post-pubertal males, and 450 and 460 ms in post-pubertal females. A QTc of 500 ms or more is markedly prolonged and under 340 ms is flagged as short. Bazett overcorrects at heart rates over about 120, so Fridericia is shown for comparison. Machine QTc readings are often wrong in children, so the QT should be measured by hand.
For a prolonged QTc, next steps include repeating the ECG, stopping QT-prolonging drugs, checking potassium, magnesium and calcium, asking about syncope and family history, and referral to cardiology. Normal values come from Davignon 1979, with QT guidance from the AHA/ACCF/HRS 2009 recommendations and the HRS/EHRA/APHRS 2013 consensus.
Using Bazett, the tool flags borderline and prolonged at 450/470 ms under 6 months, 440/460 ms from 6 months to puberty, 430/450 ms in post-pubertal males and 450/460 ms in post-pubertal females. A QTc of 500 ms or more is markedly prolonged.
Bazett is the standard for children. It overcorrects at heart rates over about 120 bpm, so the tool suggests repeating the ECG at a slower rate or comparing with Fridericia, which works better at fast or slow rates.
Repeat the ECG and measure by hand in lead II or V5, averaging 3–5 beats. Stop QT-prolonging drugs, correct potassium, magnesium and calcium, ask about syncope and family sudden death, and refer to cardiology. At 500 ms or more, use continuous monitoring and get same-day cardiology.
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