Comparison of three measures of QT dispersion

QT dispersion quantifies the variability of QT intervals observed in the 12-lead ECG. The standard measure is the range of the QT intervals from the collection of the 12 ECG leads. The authors investigated the relationship between the standard measure, Range, and two alternative measures, standard deviation (SD) and interquartile range (IQR). The measures were assessed for their ability to differentiate between normal and two pathological groups. SD was highly correlated to Range in all subject groups. Weaker correlations were found between IQR and Range in the pathological groups and a very small correlation for the normal group. Of the measures considered, the current standard measure of QT dispersion was found to be the least effective in differentiating between normal and pathological subject groups. IQR appears to be a more discriminant measure of QT dispersion.