Dispersion of ventricular repolarization in dilated cardiomyopathy

Increased dispersion of ventricular repolarization has been shown to be a marker for increased risk of ventricular tachyarrhythmias in various cardiac disorders. The present study is aimed at comparing the values of four dispersion indices in four clinical groups: normal subjects (n = 23), patients with intraventricular conduction defects (QRS > 0.12 s) without underlying cardiac disease (n = 30), patients with dilated cardiomyopathy (n = 36), and patients with both dilated cardiomyopathy and ventricular conduction defects (n = 18).

On an averaged cycle from a 10 s record of 15 simultaneous leads (12-lead ECG and XYZ leads), and after interactive editing, four intervals were computed: JTapex, JTend, QTapex and QTend. For each interval, the dispersion is defined as the difference between the maximal and minimal values across the 15 leads.

The mean values of all four dispersion indices were significantly smaller in the normal group than in the three other groups (P < 0.001). Among patients with dilated cardiomyopathy, those with intraventricular conduction defects had significantly higher dispersion values than those without, even disregarding the QRS duration (P < 0.01). Thus, patients with both dilated cardiomyopathy and ventricular conduction defects have larger dispersion values than patients with ventricular conduction defects alone (P < 0.01) and than those with dilated cardiomyopathy without intraventricular conduction defects.

Dispersion of ventricular repolarization is increased in patients with dilated cardiomyopathy, especially in those with ventricular conduction defects, suggesting that they are at higher risk of arrhythmic events.