Postextrasystolic U Wave Augmentation, New Marker of Increased Arrhythmic Risk in Patients Without the Long QT Syndrome

Objectives. We attempted to determine the correlation between the presence of postextrasystolic changes in the STU segment and history of sustained ventricular arrhythmias. Background. Postextrasystolic U wave augmentation ( marked increment in U wave amplitude after premature ventricular complexes [PVCs]) is an adverse prognostic sign in the “pause-dependent long QT syndrome.” However, the prevalence of postextrasystolic changes in patients without the long QT syndrome is unknown. Methods. We compared the configuration of the STU segment of the postextrasystolic beat (the sinus beat after PVC) with the STU configuration during sinus rhythm in three patient groups: 1) 41 patients with spontaneous ventricular tachycardia/fibrillation (VT/VF) (VT/VF group), 2) 63 patients with heart disease and high grade ventricular arrhythmias (control group), and 3) 29 patients with high grade ventricular arrhythmias but no heart disease (reference group). Results. Postextrasystolic T wave changes did not correlate with history of ventricular tachyarrhythmias. However, postextrasystolic U wave changes were more common among the patients with VT/VF than among control subjects (39% vs. 8.7%, p < 0.001). By logistic multiple regression analysis, low left ventricular ejection fraction (p < 0.001) and postextrasystolic U wave changes (p < 0.005) were independent predictors of ventricular tachyarrhythmias. Conclusions. Postextrasystolic T wave changes are common and lack predictive value. Postextrasystolic U wave changes may be specific marker of tendency to the development of spontaneous ventricular arrhythmias. Prospective studies should be performed to confirm this association.