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The incidence of sudden death in children with congenital aortic stenosis (CAS) varies between 4 and 20%. In several syndromes sudden death is associated with a long QT interval in the electrocardiogram (ECG). The aim of the study was to evaluate the cardiac repolarization in CAS during stress. We included 40 children and young persons, 20 with CAS and 20 healthy controls. All underwent echocardiographic study and treadmill stress test. The QT and relative RR intervals were measured in leads II and V6 at rest and during exercise at preselected heart rates. Mean values of QT were compared by analysis of variance, Student's t-test, and linear regression method. No statistically significant differences in the resting ECG were found between the two groups, whereas during exercise the mean QT of the CAS group was significantly longer than in the controls (p < 0.05), except at a heart rate of 140 +/- 5. Our study demonstrates that patients with CAS have transiently altered cardiac repolarization when there are sudden variations in heart rate. Such a defect could predispose patients with CAS to fatal arrhythmias and sudden death.

A newborn infant with familial Wolff-Parkinson-White (WPW) syndrome presented with a supraventricular tachycardia of 300 beats/min, refractory to digoxin and flecainide administration. Serial electropharmacologic tests were performed via the esophagus before and during oral therapy with verapamil at 40, 80, and 60 mg daily. Before treatment, tachycardia could be induced with programmed stimulation. A regimen of verapamil at 60 mg daily, which resulted in the initiation of nonsustained (less than 10 s) reciprocating tachycardia only, without clinical recurrences, was identified as suitable long-term oral therapy. The efficacy of this drug regimen in preventing episodes of tachycardia was confirmed during a 1-month follow-up period. It is concluded that transesophageal atrial pacing is a useful, noninvasive means of selecting treatment in neonates with supraventricular tachycardia, when nonconventional drugs are considered for prophylaxis.