[Tachycardia and syncope in a 15-year-old teenager].

Patients with highly symptomatic tachycardia may suffer significantly; in addition to a standardized rule-out of structural heart disease, secondary causes need to be excluded. Disorders such as inappropriate sinus tachycardia and postural tachycardia syndrome are caused by cardiac autonomic dysregulation which may be part of a rare underlying noncardiac disease.