Evaluation of the QT Interval in Patients with Drug-induced QT Prolongation and Torsades de Pointes.

Krisai, Philipp; Vlachos, Konstantinos; Daniel Ramirez, F; Nakatani, Yosuke; Nakashima, Takashi; Takagi, Takamitsu; Kamakura, Tsukasa; Surget, Elodie; André, Clémentine; Cheniti, Ghassen; Welte, Nicolas; Chauvel, Rémi; Tixier, Romain; Duchateau, Josselin; Pambrun, Thomas; Derval, Nicolas; Hocini, Mélèze; Pierre, Jaïs; Michel, Haïssaguerre; Sacher, Frédéric

BACKGROUND Data on the optimal location of the ECG leads for the diagnosis of drug-induced long QT syndrome (diLQTS) with Torsades de Pointes (TdP) are lacking. METHODS We systematically reviewed the literature for ECGs of patients with diLQTS and subsequent TdP. We assessed T-wave morphology in each lead and measured the longest QT interval in the limb and chest leads in a standardized fashion. RESULTS Of 84 patients, 61.9% were female and mean age was 58.8 years. QTc was significantly longer in chest versus limb leads (mean (standard deviation) 671 (102) vs 655 (97) ms, p=0.02). Using only limb leads for QT interpretation, 18 (21.4%) ECGs were non-interpretable: 10 (11.9%) due to too flat T-waves, 7 (8.3%) due to frequent, early PVCs and 1 (1.2%) due to too low ECG recording quality. In the chest leads, ECGs were non-interpretable in 9 (10.7%) patients: 6 (7.1%) due to frequent, early PVCs, 1 (1.2%) due to insufficient ECG quality, 2 (2.4%) due to missing chest leads but none due to too flat T-waves. The most common T-wave morphologies in the limb leads were flat (51.0%), broad (14.3%) and late peaking (12.6%) T-waves. Corresponding chest lead morphologies were inverted (35.5%), flat (19.6%) and biphasic (15.2%) T-waves. CONCLUSIONS Our results indicate that QT evaluation by limb leads only underestimates the incidence of diLQTS experiencing TdP and favors the screening using both limb and chest lead ECG. This article is protected by copyright. All rights reserved.