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Figure 6 Distribution of Results (in Patients and Controls) and PPV for Different Cutoff Values of QT Interval, QTc Interval, and Tpeak–Tend
(Top panels) QT interval, QTc interval, and Tpeak–Tend values for patients with torsade de pointes (TdP) (red) and patients with uncomplicated bradyarrhythmias (blue). The horizontal black line represents the median value, the colored squares represent the interquartile range (IQR). The IQR includes 50% of all values: from the 25th to the 75th percentile. The bars represent the range, not including outliers. Outliers, which appear as dots, are defined as values above or below 1.5 times the IQR. (Lower panels) Positive predictive value (PPV) for different cutoff values of each 1 of the 3 tests above. Note that the risk for torsade increases gradually as the QT interval or the QTc interval increase. In contrast, Tpeak–Tend has an S-shape curve with a sudden increment in risk as Tpeak–Tend becomes longer than 60 ms.
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