Steep repolarization time gradients in pig hearts cause distinct changes in composite electrocardiographic T-wave parameters

Background: The T wave of the electrocardiogram (ECG) reflects ventricular repolarization. Repolarization heterogeneity is associated with reentrant arrhythmias. Several T-wave markers (including QT interval) have been associated with ventricular arrhythmias, but studies linking such markers to underlying local repolarization time (RT) inhomogeneities are lacking. We aimed to investigate the relation of several T-wave markers to controlled drug-induced regional RT gradients in intact pig hearts. Methods: Repolarization time gradients were created by regional infusion of dofetilide and pinacidil in four atrially paced porcine Langendorff-perfused hearts placed inside a torso tank. From the 12-lead ECG on the torso tank, the mean, maximum, and dispersion (max–min) of QT_time, JT_time, T_peak–end, T_width, TQ_ratio, dV/dt_max, T_area, T_amp, and T-upslope duration were determined, as well as upslope end difference between leads V₁ and V₆. Results: Temporal T-wave parameters T_peak–end, T_width, and TQ_ratio show a significant and high correlation with RT gradient, best reflected by mean value. T_area (mean, max and dispersion) and dV/dt_max dispersion show only a moderate significant correlation. T-upslope duration shows a significant correlation in particular for mean values. Mean, maximum, or dispersion of QT_time and V₁–V₆ upslope end difference were not significantly correlated with RT gradient. Conclusion: Composite 12-lead ECG T-wave parameters T_peak–end, T_width, TQ_ratio, upslope duration, and T_area show a good correlation with underlying RT heterogeneity, whereas standard clinical metrics such as QT_time do not reflect local RT heterogeneity. The composite T-wave metrics may thus provide better insights in arrhythmia susceptibility than traditional QT_time metrics.