Dispersion of QT interval in premature ventricular beats as a marker of susceptibility to arrhythmic events.

BACKGROUND: Clinical observations indicate that increased QT interval dispersion in sinus beats may portend malignant ventricular arrhythmias and sudden cardiac death. The purpose of this study was to test the hypothesis that measures of QT dispersion in ventricular premature beats (QTd-V) may be also useful in identifying patients at high risk of arrhythmic events.

METHODS: In the group of 303 patients with ventricular premature beats on standard 12-lead ECG, the QTd-V was calculated as a difference between maximum and minimum QT interval in premature ventricular beats. During follow-up for 26 +/- 19 months the arrhythmic events (sustained ventricular tachycardia, ventricular fibrillation or sudden cardiac death) were noted in 42 patients.

RESULTS: Patients with arrhythmic events had significantly (P < 0.005) greater values of QTd-V than those without arrhythmic events. Univariate predictors of arrhythmic events included QTd-V > or = 100 ms, left ventricular ejection fraction < 40%, QRS complex duration of ventricular premature beats > 150 ms, underlying heart disease and complete bundle branch block. Multivariate analysis using the Cox proportional hazard model showed that only QTd-V > or = 100 ms and ejection fraction < 40% were independent predictors of arrhythmic events.

CONCLUSIONS: The results of this study indicate a significant relationship between QTd-V and the risk of arrhythmic events. The assessment of QTd-V may be useful for identifying patients with ventricular premature beats at high and low risk of subsequent arrhythmic events.