Occult arrhythmias as the etiology of unexplained syncope in children with structurally normal hearts.

We evaluated six children for syncope of unknown etiology between March, 1983, and March, 1984. All had undergone previous neurologic evaluation which was normal. Cardiac examination, chest roentgenograms, and two-dimensional echocardiograms were also normal in all of the patients. Abnormal noninvasive findings in five patients included Mobitz type II atrioventricular (AV) block (one patient), sinus bradycardia (three patients), and supraventricular tachycardia (one patient). Four patients had one or more abnormal findings at invasive electrophysiologic study including evidence of sinus node dysfunction (three patients), AV node dysfunction (three patients), and distal His-Purkinje system disease (two patients). All children had a normal right heart hemodynamic catheterization. We conclude that arrhythmias are an important cause of syncope in some children with an otherwise normal heart when neurologic causes have been excluded.