JT dispersion in Wolff-Parkinson-White syndrome: effect of eccentric ventricular depolarization on the dispersion of repolarization.

There is much interest in QT dispersion for noninvasive risk stratification of patients at risk of arrhythmias. However, little is known about the genesis of abnormal QT dispersion. In particular, whether eccentric ventricular depolarization, as seen in preexcitation, can lead to abnormal dispersion of repolarization is unknown. We studied 24 children aged 1-19 years (mean +/- SD, 11 +/- 5 years) with manifest preexcitation due to Wolff-Parkinson-White syndrome who had successful catheter ablation. Standard ECGs done preablation, early postablation (< 1 week), mid postablation (> 1 week, < 2 months), and late postablation (> 2 months) were reviewed. The QRS duration prior to ablation ranged from 90-160 ms (mean +/- SD, 123 +/- 21 ms). On the preablation ECG, the JT and JTc dispersions showed no relationship to the QRS duration (r = 0.04 and 0.07, respectively). There was no change in JT dispersion when the preablation (42 +/- 15 ms) ECG was compared to early (43 +/- 15 ms), mid (44 +/- 13 ms), and late postablation (48 +/- 19 ms) ECGs. There was no significant change in JTc dispersion as well. Thus, JT dispersion is unrelated to QRS duration and unaffected by catheter ablation in patients with Wolff-Parkinson-White syndrome. Eccentric ventricular depolarization does not lead to abnormal dispersion of repolarization.