Baseline short-term variability of QT intervals was significantly higher in patients with drug-induced long-QT syndrome compared to controls (8.1 vs 3.6 ms, P=0.001).
Case-Control (n=40)
Single-blind
Does short-term variability of QT intervals (STV(QT)) identify patients at risk for drug-induced Torsades de pointes better than QTc prolongation?
Short-term variability of QT intervals (STV(QT)) is a superior non-invasive parameter compared to QTc for identifying patients at risk of drug-induced Torsades de pointes.
Absolute Event Rate: 8.1% vs 3.6%
p-value: p=0.001
AIMS: Torsades de pointes arrhythmias (TdP) occur by definition in the setting of prolonged QT intervals. Animal models of drug induced Long-QT syndrome (dLQTS) have shown higher predictive value for proarrhythmia with beat-to-beat variability of repolarization duration (BVR) when compared with QT intervals. Here, we evaluate variability of QT intervals in patients with a history of drug-induced long QT syndrome (dLQTS) and TdP in absence of a mutation in any of the major LQTS genes. METHODS AND RESULTS: Twenty patients with documented TdP under drugs with QT-prolonging potential were compared with 20 matched control individuals. An observer blinded to diagnosis manually measured lead-II, RR, and QT intervals from 30 consecutive beats. BVR was determined from Poincaré plots of QT intervals as short-term variability (STV(QT) = Sigma|QT(n)(+1) - QT(n)|/30 x radical2). QRS interval and cycle length was comparable between study groups and controls. No difference was found in QTc between dLQTS and controls (428 +/- 25 vs. 421 +/- 34 ms, P = 0.26), whereas STV(QT) was significantly higher in dLQTS when compared with controls (8.1 +/- 3.7 vs. 3.6 +/- 1.3 ms, P = 0.001). Proarrhythmic predictive power of STV(QT) was superior to that of the QTc interval (AUC: 0.89 vs. 0.57, 95% CI: 0.79-0.99 vs. 0.39-0.75). CONCLUSION: In the absence of QTc prolongation, baseline STV(QT) characterized patients with documented drug-induced proarrhythmia. STV(QT) could prove to be a useful non-invasive, easily obtainable parameter aiding the identification of the patient at risk for potentially life threatening arrhythmia in the context of drugs with QT prolonging potential.
Hinterseer et al. (Wed,) conducted a case-control in Drug-induced long-QT syndrome (dLQTS) and Torsades de pointes (TdP) (n=40). Short-term variability of QT intervals (STV(QT)) vs. Matched control individuals was evaluated on Short-term variability of QT intervals (STV(QT)) (p=0.001). Baseline short-term variability of QT intervals was significantly higher in patients with drug-induced long-QT syndrome compared to controls (8.1 vs 3.6 ms, P=0.001).