stiehler.dev Marian Stiehler
QTc-Calculator.com
This is a translation of a German web site. Don’t be confused if you encounter poor wording. The presented data and the calculations are correct.
Please visit my new project about Short QT Syndrome!
Please note that the ESC has published new guidelines in 2022. Long QT guidelines are virtually unchanged. Short QT guidelines did change. The new guidelines are not yet included in this calculator, but you can find them on short-qt-syndrome.info.
Please enter values for heart rate or RR interval and QT interval.
QTc values are rounded to milliseconds.
Transgression of QTc limits is indicated by colors yellow and red, according to the ESC guidelines of 2015 – see below.
For formulae, see below.
Graphical representation of QT = 414 ms
At a measured QT of 408 ms, QTc is the following depending on heart rate:
Measuring the QT interval
Limits for Long/Short QT Syndrome
Unfortunately, the limits for Long and Short QT Syndrome are disputed. According to one of the most recent publications (ESC Guidelines, 2015):
- Long QT Syndrome: ≥480 ms even if asymptomatic; ≥460 ms, if symptomatic
- Short-QT-Syndrom: ≤340 ms even if asymptomatic; ≤360 ms if symptomatic or other factors (genetic mutation, relatives etc.)
Further information:
-
QT-Interval (Wikipedia)
-
Long QT Syndrome (Wikipedia)
-
Short QT Syndrome (Wikipedia)
Sources
ESC 2015, Mazzanti 2014, Gollob 2011, AHA 2009, FDA 2005, Schwartz 1993, Schwartz 1985
Distribution of QTc in the normal population
Please be advised that this section presents data from a single study which has some limitations. Be careful.
The exact distribution of QTc values in the normal population is unknown; there are, however, large scale studies.
The following is based on a study by Vandenberk et al., 2016 on 6,609 Europeans, aged 59.8±16.2 years. The recorded ECGs had heart rates of 68.8±10.6 beats per minute.
Fridericia
The distribution of Bazett values is shown in gray.
For women Vandenberk et. al. recorded a QTcFri interval of 417±25 ms.
For men they recorded a QTcFriinterval of 412±24 ms.
Assuming a normal Distribution, 20,000 measurements can be simulated. You can see clearly how rare long and short QT values are in the normal population:
QTc Calculator as an app for iPhone
There is a version of this QTc calculator for iPhone and iPad: nine correction formulas, graphical representation of results and a small knowledge base. more
Correction Formulae
QTc Bazett
correction formula: \(\text{QTc}_{\text{Bzt}} =\frac{\text{QT}}{\sqrt{\text{RR}}}\)
published in 1920; 39 subjects
original publication: https://onlinelibrary.wiley.com/resolve/doi?DOI=10.1111/j.1542-474X.1997.tb00325.x
QTc Fridericia
Sometimes spelled »Fredericia«.
correction formula: \(\text{QTc}_{\text{Fri}} = \frac{\text{QT}}{\sqrt[3]{\text{RR}}}\)
published in 1920; 50 subjects
original publication: https://onlinelibrary.wiley.com/doi/abs/10.1111/j.0954-6820.1920.tb18266.x
QTlc Sagie (Framingham Heart Study)
correction formula (for msec): \(\text{QTlc} = 1000 (\text{QT} + 0,154 (1 – \text{RR}))\)
published in 1992; 5.018 subjects
original publication: https://www.ajconline.org/article/0002-9149(92)90562-D/pdf
QTc Hodges
correction formula: \(\text{QTc}_\text{H} = \text{QT} + 1,75 (\text{HR} -60)\)
published in 1983; 607 subjects
original publication (page 694, bottom): http://www.onlinejacc.org/content/1/2_Part_2/577
QTc Rautaharju a
correction formula: \(\text{QTc}_\text{Mod} = \text{QT}(120 + \text{HR})/180\)
published 2014; 57,595 subjects
original publication: https://www.sciencedirect.com/science/article/pii/S0167527314008134
QTc Rautaharju b
correction formula men: \(\text{QTc}_\text{LogLin} = \text{QT} + 387 (1 - \text{RR}^{0,37})\)
correction formula women: \(\text{QTc}_\text{LogLin} = \text{QT} + 409 (1 - \text{RR}^{0,39})\)
published 2014; 57,595 subjects
original publication: https://www.sciencedirect.com/science/article/pii/S0167527314008134
Conversion heart rate ↔ RR interval
\(\text{RR} = \frac{60}{\text{HR}}\)
Copyright
You can use the images and information on this web site for free, for example in talks, at the university or even in publications. Please be fair and don’t offer your own QT calculator.
A short note or a link to this web site would be great–and you can always send me an email: [email protected].
Privacy / Liability
The calculations are performed locally in your browser. No data is being transmitted to the internet / a server. Your visit on this web site is not being tracked or analyzed. The connection to this web site is encrypted. This service is free of charge. Calculations and all information come without any liability.