Signal-averaged electrocardiographic late potentials in children with complete heart block

The purpose of this study was to examine signal-averaged electrocardiographic (SA-ECG) late potentials to predict ventricular arrhythmias during intrinsic cardiac rhythm and during ventricular pacing in children with complete heart block (CHB). Recordings of SA-ECG were obtained from eight patients (aged 3-18 years) with documented CHB. The etiology of CHB was congenital in four cases and acquired in four cases. Six of these patients underwent permanent pacemaker implantation. Comparisons of the SA-ECG were made before and during ventricular pacing. Abnormalities of SA-ECG during intrinsic cardiac rhythm were noted in four patients, all of whom were older than 14 years. Although there was no significant difference in SA-ECG parameters between patients with congenital CHB and acquired CHB, abnormal SA-ECG was noted in one of four patients with congenital CHB and in three of four patients with acquired CHB. Two patients without permanent pacemaker implantation had normal SA-ECG, but four of six patients with permanent pacemaker implantation had abnormal SA-ECG. Three of the four patients had abnormal SA-ECG during ventricular pacing, but the abnormal SA-ECG in one patient had normalized during ventricular pacing. It is important to record SA-ECG before and during ventricular pacing to detect late potentials in patients with CHB. It may be useful to record SA-ECG while changing the pacing site to find ideal sites for electrode implantation for the potential prevention of ventricular arrhythmias.