Tachyarrhythmic syncopes in children with structurally normal hearts with and without QT-prolongation in the electrocardiogram.

Forty children with presumed ventricular tachyarrhythmic syncopes in the absence of structural heart disease were studied. Twenty-nine patients, one of whom was deaf, had a prolonged QT-interval in the resting electrocardiogram (Group 1); eleven patients had a normal QT-interval (Group 2). The median QTc-interval vas 0.51 s in Group 1 and 0.40 s in Group 2. Familial occurrence suggesting autosomal dominant inheritance was found in 21 of 28 normally hearing patients in Group 1 and in 2 of 11 patients in Group 2. Syncopes were definitely stress-induced in 22 patients in Group 1 and in all 11 patients in Group 2. Of 23 patients in Group 1 in whom an electrocardiogram was obtained during physical exercise, only one showed severe ventricular dysrhythmia. In contrast, all eleven patients in Group 2 developed severe ventricular dysrhythmia with exercise. Treatment with beta-blocking medication prevented further syncopes in 15 of 19 patients with several previous attacks in Group 1 and in 3 of 5 patients of Group 2. Four of the 29 patients in Group 1 died suddenly and one more remained apallic after an attack. Of the 11 patients in Group 2, four died suddenly and one retains severe cerebral damage after resuscitation from ventricular fibrillation. We conclude that, besides the group of patients with the long QT-syndrome, there may be a distinct group of patients with a consistently normal QT-interval and severe ventricular dysrhythmia with exercise. Patients of both groups are threatened by sudden death and are improved by treatment with beta-blocking medication.