LATE POTENTIALS AND INDUCIBLE VENTRICULAR-TACHYCARDIA IN SURGICALLY REPAIRED CONGENITAL HEART-DISEASE

We compared signal-averaged electrocardiography with invasive electrophysiological study in patients after surgical repair of congenital heart disease to determine if potentially useful correlations exist between the two methods for assessment of risk for ventricular tachycardia. Thirty-one patients (age, 1-49 years; mean, 10.6 years) with congenital heart disease repaired with right ventriculotomy or postrepair right bundle branch block (77% postoperative tetralogy of Fallot) who had electrophysiological study were studied with signal-averaged electrocardiography. Patients were classified by electrophysiological study results as having no inducible ventricular tachycardia, nonsustained ventricular tachycardia, or sustained ventricular tachycardia. Signal-averaged electrocardiograms were examined for the duration of low-amplitude (≤40 μV) QRS signal, duration of total QRS, and root-mean-square voltage of the terminal 40 msec of the QRS. Low-amplitude terminal root-mean-square voltage of 100 μV or less had 91% sensitivity and 70% specificity for ventricular tachycardia inducible by electrophysiological study. Similar sensitivity but less specificity were seen using the criterion of 20 msec or more total low-amplitude QRS signal (initial plus terminal) or using total QRS duration of 128 msec or more. There was a weaker association between terminal low-amplitude QRS signal of 15 msec or more and inducible ventricular tachycardia. The signal-averaged electrocardiogram did not reliably distinguish sustained from nonsustained inducible ventricular tachycardia. Results of our study suggest that signal-averaged electrocardiography in patients with surgically repaired congenital heart disease correlate with presence or absence of either sustained or nonsustained ventricular tachycardia by electrophysiological study and that 100 μ or less terminal root-mean-square voltage is an appropriate cutoff for interpretation of signal-averaged electrocardiography in this patient group.