Chapter 51: Syncope

High-Yield Facts

• Most syncope in children is neurocardiogenic/vasovagal.

• Situational events that cause a Valsalva-like maneuver can cause syncope.

• Prolonged QT syndrome is an uncommon but important cause of syncope in children.

• A head upright tilt-table test may diagnose neurocardiogenic syncope in selected cases.

Syncope refers to a sudden, brief loss of consciousness and postural tone. Although in the pediatric age group it accounts for less than 1% of emergency department visits, 15% to 50% of children will have experienced a syncopal episode by age 18 years.¹ The etiology of syncope in children is generally benign. Syncope can, however, be a manifestation of serious underlying pathology and always warrants careful evaluation. Unlike the adult population, in which syncope often results from malignant cardiac arrhythmias, in the pediatric population it is more often secondary to neurally mediated causes and is therefore discussed in the section on neurologic emergencies.¹ An extensive workup for syncope is usually unnecessary. All children presenting to the ED with syncope should have a detailed history, physical examination, and electrocardiogram (ECG) performed.

Pathophysiology

The pathophysiology of syncope varies with etiology (Table 51-1), but it always results from momentarily inadequate delivery of oxygen and glucose to the brain. Syncope can result from dangerous causes such as inadequate cardiac output, which can be secondary to obstruction of blood flow, or to an arrhythmia. It can also result from more benign events such as inappropriate autonomic compensation for the normal fall in blood pressure that occurs on rising from a sitting or supine position. Metabolic causes such as hypoglycemia should also be considered especially in at-risk patients (e.g., diabetes). Respiratory disturbances, especially hyperventilation that results in hypocapnia and cerebral vasoconstriction, can also cause syncope.¹

History