- Most syncope in children is neurocardiogenic/vasovagal.
- Situational events that cause a Valsalvalike 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 and transient 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 18.1 Syncope can 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
The pathophysiology of syncope varies with etiology (Table 53–1), but it always results from momentarily inadequate delivery of oxygen and glucose to the brain. Syncope can result from inadequate cardiac output, which can be secondary to obstruction of blood flow, or to an arrhythmia. It can also result from inappropriate autonomic compensation for the normal fall in blood pressure that occurs on rising from a sitting or supine position. Respiratory disturbances, especially hyperventilation that results in hypocapnia and cerebral vasoconstriction, can also cause syncope.1
Table 53-1. Causes of Syncope |Favorite Table|Download (.pdf)
Table 53-1. Causes of Syncope
Reflex syncope (pallid breath-holding spells)
Cardiac mediated syncope
Sick sinus syndrome
Arrhythmogenic right ventricular dysplasia (ARVD)
Idiopathic hypertrophic subaortic stenosis
Coarctation of the aorta
Tetralogy of Fallot
Anomalous origin of the left coronary artery
The first component in the evaluation of a patient with syncope is to determine that momentary loss of consciousness actually occurred. It is common for patients to confuse acute dizziness or vertigo with loss of consciousness. For patients who did indeed lose consciousness, the events antecedent to the syncopal episode are elicited. A prodrome of light-headedness, nausea, dizziness or vision changes, a sudden change in posture, emotional excitement, respiratory difficulty, palpitations, exercise, and ...