Predictive power of increased QT dispersion in ventricular extrasystoles and in sinus beats for risk stratification after myocardial infarction.

Abstract

QT dispersion, commonly measured in sinus beats (QTd-S), can also be calculated in premature ventricular beats (QTd-V). To date, no studies have addressed the relation between these 2 variables. In 148 patients with remote myocardial infarction and premature ventricular beats on a routine ECG, QT dispersion, defined as the difference between the maximum and the minimum QT interval across the 12-lead ECG, was calculated separately for the ventricular extrasystole and the preceding sinus beat. In the total group of patients, QTd-V was greater than QTd-S (83+/-33 versus 74+/-34 ms, respectively; P=0.001). During a follow-up period of 35+/-17 months, arrhythmic events (sustained ventricular tachycardia, ventricular fibrillation, or sudden death) were noted in 30 patients. A QTd-V of >/=100 ms was a stronger univariate marker of arrhythmic events than was a QTd-S of >/=100 ms, and multivariate analysis selected only prolonged QTd-V (hazard ratio 3.81, 95% CI 2.2 to 11.2) and low ejection fraction (hazard ratio 3.05, 95% CI 1.6 to 7.6) as independent predictors of arrhythmic events. The magnitude of QTd-V was greater than that of QTd-S in the total group of patients. Prolonged QTd-V is associated with a significantly increased risk for arrhythmic events in postinfarction patients, and the prognostic significance of QTd-V exceeds that of QTd-S.