Vagally mediated atrial fibrillation in a young man.

Atrial fibrillation may be provoked by either vagal or sympathetic stimulation. Sympathetic effects are common in middle-aged and elderly patients with underlying heart disease. However, in the young, non-diseased heart, vagal influences are more likely to predominate. Recognition of vagally mediated atrial fibrillation in young adults as a unique clinical entity has diagnostic and therapeutic implications.