Documented transient third-degree atrioventricular block and asystole in a child with familial dysautonomia.

An 11-year-old boy with familial dysautonomia presented with palpitations. Continuous 24-h Holter monitoring revealed intermittent high-grade atrioventricular block and asystole. The unopposed parasympathetic tone in patients with dysautonomia may make them susceptible to bradycardia and atrioventricular block. We recommend routine 24-h Holter monitoring screening and, when indicated, consideration of pacemaker implantation to reduce the high risk of sudden death phenomena in this patient population.