QT and TdP. QT: an unreliable predictor of proarrhythmia

When triangulation, reverse use dependence, instability and dispersion (TRIaD) of the action potential are associated with drug-induced prolongation of the QT interval, then proarrhythmia in the form of torsade de pointes is most likely. However, as the QT interval is shortened, TRIaD increasingly leads to ventricular fibrillation (VF). Thus, use of QT prolongation by itself may not recognize drug-induced VF (false negatives) and in the absence of TRIaD may erroneously incriminate valuable and safe agents (false positives). In patients,TRIaD equivalents in the ECG may likewise be more important than QT interval.