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C. Michael White, Edward M. Grant, Richard Quintiliani, Moxifloxacin Does Increase the Corrected QT Interval, Clinical Infectious Diseases, Volume 33, Issue 8, 15 October 2001, Pages 1441–1442, https://doi.org/10.1086/323015
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Extract
SIR—We wish to respond to the letter of Iannini et al. [1], which contains several inaccuracies. These authors contend that the corrected QT (QTc) interval in an individual normally fluctuates by up to 70 ms over 24 h, but we believe they are, erroneously, quoting the value for QT interval variability rather than the value for QTc interval variability. To update the reader, we have provided data from 3 of 6 trials that show that there is no substantial circadian variability in the QTc interval.
In an evaluation of 6048 electrocardiograph (ECG) segments, Molnar et al. [2] found that the QTc interval varied only by 6 ms. This was the difference between the QTc interval in the period from 10 AM to 4 PM and that in the period from 12 AM to 6 AM As in the report of Iannini et al. [1], Molnar et al. observed major variation in the QT interval over the course of 24 h but not in the QTc interval. In a similar study of healthy subjects, the QTc interval only varied by 3.5 ms between the period from 1 PM to 5 PM and the period from 1 AM to 5 AM [3].
