Temporal Variability of the Electromechanical Window in Long-QT Syndrome and Drug-Induced QT Prolongation: Value for Enhanced Arrhythmia-Risk Assessment.

Background Arrhythmia-risk assessment in congenital long-QT syndrome (LQTS) and drug-induced QT prolongation (diQTP) is primarily based on clinical, genetic, and electrical parameters. Electromechanical-window (EMW; aortic-valve closure time minus QT interval) assessment outperformed QTc as a predictor of symptomatic status in LQTS.Objective Investigating the relationship between temporal QTc and EMW dynamics, and ventricular tachyarrhythmia (VT) timing in LQTS and diQTP.Methods 47 LQTS/-VT, 18 LQTS/+VT, nine diQTP/+VT and 26 controls were included. QTc and EMW were obtained from standard 12-lead ECGs and ECG-echocardiograms at two or three time points. +VT patients were included if EMW/QTc assessments were performed within two weeks before or after VT.Results In control subjects, EMW remained stably positive over time. In LQTS/-VT patients, EMW was negative without significant variation. In LQTS/+VT and diQTP/+VT patients, transient accentuations of EMW negativity were observed at the time point closest to VT (2 (1 to 7) days to arrhythmia), regardless of whether measured before or after VT. Temporary EMW negativity accentuation was driven by foreshortening of the mechanical systole despite concurrent QT prolongation. EMW recovery after VT was similar for patients with or without beta-blocker therapy. Multiple logistic regression analysis identified EMW negativity and EMW dynamics (ΔEMW) as independent predictors of imminent VT in LQTS. An EMW of -75 ms and ΔEMW of -39 ms were optimal cut-offs to predict emergent arrhythmic deterioration in the LQTS cohort.Conclusion Temporary accentuation of EMW negativity is a marker of impending VT in LQTS and diQTP patients.