Repolarization terminal portion dispersion predicts ventricular arrhythmias in patients with structural heart disease and mildly reduced left ventricular ejection fraction

Introduction: Depressed left ventricular ejection fraction (LVEF) is the major indication for primary prevention implantable cardioverter-defibrillator (ICD) implantation. However, sudden cardiac death (SCD) also occurs without a reduced LVEF, and additional predictors are needed. Ventricular arrhythmias (VAs) are associated with increased cardiac repolarization variability. We assessed the intra-QT phase in patients with structural heart disease (with a relatively preserved LVEF and with a depressed LVEF) with and without sustained VAs. Methods: A total of 173 patients (96 with LVEF > 0.35: 21 with VAs vs. 75 free from VAs; 77 with LVEF ≤ 0.35: 15 with VAs vs. 62 without VAs) were enrolled in the study. Data were acquired from a 5 min-lasting ECG recording. The spectral coherence and the variability indexes (VI) of the intra-QT phase were calculated. Corrected QT (QTc) was calculated from a 12-lead ECG. Results: When LVEF was >0.35, the only statistically different variables were: a higher QTVI in VAs patients (0.14 ± 0.81 vs. -0.46 ± 0.76, p=.0019. ROC curve values AUC: 0.703, CI 95%: 0.580-0.827, p = 0.005, cut-off:-0, 04, Se: 0.62, Sp: 0.75); a greater Q-Tpeak VI in VAs patients (0.64 ± 1.07 vs. -0.24 ± 0.98, p=.0005 ROC curve values AUC: 0.769, CI 95%: 0.658-0.879, p < 0, 0001, cut.off: 0.064, Se: 0.71, Sp: 0.72); a lower QTpeak-Tend spectral coherence in VAs patients (0.496 ± 0.118 vs. 0.580 ± 0.174, p=.042 ROC curve values: AUc: 0.666, CI95%: 0.546-0.785, p = 0.021, cut-off: 0.567, Se: 0.71, Sp: 0.56). When LVEF was ≤0.35, the only statistically different variables were: a higher QTVI in VAs patients (0.57 ± 1.06 vs. -0.21 ± 0.68, p=.0006 ROC curve values AUC: 0.706, CI95%: 0.536-0.876, p = 0.014, cut-off:-0.19, Se: 0.73, Sp: 0.55); a greater TendVI in VAs patients (1.84 ± 0.83 vs. 1.34 ± 0.68, p=.018 ROC curve values AUC: 0.648, CI95%: 0.479-0.817, p = 0.076, cut-off: 1.62, Se: 0.60, Sp: 0.68). Conclusions: Analysis of repolarization variability could help assess the susceptibility for SCD, especially in LVEF > 0.35 patients with structural heart disease, belonging to an otherwise undertreated population.