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In medicine, specifically cardiology, the QT interval is a measure of the time between the start of the Q wave and the end of the T wave in the heart's electrical cycle. The QT interval is dependent on the heart rate in an obvious way (the faster the heart rate, the shorter the QT interval) and has to be adjusted to aid interpretation.
The standard clinical correction is to use Bazett's formula, named after physiologist Henry Cuthbert Bazett, calculating the heartrate-corrected QT interval QTc.
In the same year, Fridericia  published an alternative adjustment:
There are several other methods, but a regression based approach is the most accurate according to the current knowledge. An example of the regression-based approach is that developed by Sagie et al., as follows:
Normal values for the QT interval are between 0.30 and 0.44 (0.45 for women) seconds. QT interval can be measured by different methods such as the threshold method in which the end of the T wave is determined by the point at which the component of the T wave merges with the isoelectric baseline or the tangent method in which the end of the T wave is determined by the intersection of a line extrapolated from the isoelectric baseline and the tangent line which touches the terminal part of the T wave at the point of maximium downslope.
Additional recommended knowledge
If abnormally prolonged or shortened, there is a risk of developing ventricular arrhythmias.
Due to adverse drug reactions
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "QT_interval". A list of authors is available in Wikipedia.|