Errors and misconceptions in ECG measurement used for the detection of drug induced QT interval prolongation

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Malik M(2004) Errors and misconceptions in ecg measurement used for the detection of drug induced QT interval prolongation. J Electrocardiol 37 Suppl: 25–33.

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Abstract: Drug-induced changes in cardiac repolarisation receive substantial attention by regulatory agencies. Since there are presently no established accurate possibilities of testing the propensity to torsade induction during clinical drug development, the regulators require drug-related QT interval changes to be thoroughly investigated with almost all new pharmacological agents. Small QT interval changes are easy to miss and the regulators therefore expect the relevant studies to be very precise. Such a precision is not easy to achieve and different strategies have been proposed. The purpose of this article is to review the most frequent misconceptions and errors in the electrocardiogram handling and measurements related to the detection to drug-induced QT interval changes. Specifically, the article discusses (a) the possibilities of automatic measurement by standard electrocardiographic equipment, (b) the danger of casual measurement by central laboratories handling the electrocardiograms, (c) the selection of recording leads for QT interval measurement, and (d) the problem of the so-called heart rate hysteresis of the QT interval adaptation. Suggestions are made for drug developers of what study design and quality control aspects are needed to avoid the most frequent imprecisions.

Keywords: Thorough QT/QTc studies, proarrhythmia, drug approval


  • Review of QT measurement providing data on differences between manual and automated values, demonstration of errors made by automated detection methods, and comparison of QT across leads. Lag time of change in QT following change in heart rate (‘QT hysteresis’) is also discussed.


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