Relation between QT dispersion and slow intraventricular conduction in patients with acute anterior wall myocardial infarction

Background QT dispersion has been proposed as a simple, noninvasive measure for identifying patients at risk of postinfarction arrhythmia. It is assum ed to reflect nonuniform ventricular repolarization, which, in turn, may re sult from regional differences in repolarization time as well as from local ized activation delay. The aim of this study was to examine the relation be tween QT dispersion and intraventricular conduction abnormalities in patien ts with acute anterior wall myocardial infarction. Methods and Results standard 12-lead electrocardiographic and 12-lead signa l-averaged electrocardiographic recordings were performed in 25 patients wi th a first Q-wave anterior wall myocardial infarction. Measures calculated by using the 6 precordial (V-1 through V-6) leads for QT dispersion were (1 ) difference between maximum and minimum QT and QTc intervals and (2) stand ard deviation of QT and QTc intervals. Measures calculated from the signal- averaged electrocardiogram were (1) maximum filtered QRS duration; (2) mean ; and (3) standard deviation of filtered QRS duration. No relation was foun d between any measure of filtered QRS duration and that of QT dispersion by using linear correlation analysis. Similarly, no significant association w as demonstrated between the filtered QRS duration and corresponding QT inte rval measurements (total 131 leads). Conclusions The lack of correlation between signal-averaged electrocardiogr am indexes of slow intraventricular conduction and electrocardiogram variab les of QT dispersion suggests an independent predictive value for the 2 met hods in identifying patients at risk of postinfarction arrhythmia. This sug gestion is further supported by the finding that altered activation sequenc e is an unlikely mechanism of QT dispersion in patients with acute myocardi al infarction, as indicated by the lock of association between the Filtered QRS duration and corresponding QT interval measurements.