Asystole during outbursts of laughing in a child with Angelman syndrome.

A girl with Angelman syndrome had recurrent episodes of ventricular asystole and syncope caused by severe vagal hypertonia during outbursts of laughing. After intravenous administration of atropine, laughing no longer induced asystole or syncope. The vast majority of patients with Angelman syndrome have seizures. Since hypoxia associated with asystole can provoke convulsions, we suggest electrocardiographic evaluation of Angelman patients with symptomatic bradycardia, loss of consciousness, or convulsions related to laughing.