Syncope is a transient loss of consciousness, associated with an inability to maintain postural tone, followed by rapid and spontaneous recovery with the absence of clinical features specific for another form of transient loss of consciousness such as an epileptic seizure.¹ 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.² 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 this section on neurologic emergencies.² 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.

The pathophysiology of syncope varies with etiology (Table 52-1), 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.²

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. With a good history, it is often discovered that many patients had a near-syncopal event versus true syncope. It is unclear whether this should impact the workup. For patients who did indeed lose consciousness, the events antecedent to the syncopal episode are elicited. A prodrome of lightheadedness, nausea, dizziness or vision changes, a sudden change in posture, emotional excitement, respiratory difficulty, palpitations, exercise, and any history of trauma are essential information. An association with exertion, palpitations, chest pain, and shortness of breath should be queried, as this increases one’s suspicion for a cardiac etiology. Past history of syncope is sought, as is any history of medication or drug ingestion that would explain a precipitous fall in blood pressure. Patients are queried carefully about any history of congenital heart disease, any family history of heart disease, or family history of sudden death in children or young adults.^3,4 Medical conditions that put patients at risk for metabolic derangement, such as diabetes mellitus or insipidus, should also be sought.

An important consideration in any patient with a history of loss of consciousness is the possibility that the patient may have suffered a seizure. In contrast to syncope, seizures are usually accompanied by some form of muscle twitching or convulsions and are usually followed by a postictal phase, during which the patient has confusion, disorientation, or other mental status changes, usually lasting more than 5 minutes.⁵ Convulsions are unusual during syncopal episodes except during very severe events, or with reflex anoxic seizures, and patients generally have normal mental status upon recovery from the episode.^3,6

The physical examination focuses upon establishing the hemodynamic stability of the patient. Particular attention is paid to vital signs, especially to pulse and orthostatic blood pressure. A positive test is a decrease in systolic blood pressure by 20 mmHg or an increase in heart rate (20 beats per minute [bpm]), ongoing from lying to sitting or sitting to standing. However, if the patient has recurrent symptoms the test is considered positive.⁷

For all patients, a careful cardiac examination is indicated. The regularity of the pulse is noted, as is the quality of the peripheral pulses. The heart is auscultated carefully to detect the presence of a murmur that may indicate congenital heart disease, especially aortic stenosis (systolic ejection murmur and ejection click). The presence of gallops, rubs, thrills, or carotid bruits is noted. The quality and presence of all peripheral pulses are evaluated. Diminished pulses should prompt blood pressure measurements in all extremities to check for coarctation of the aorta.⁷

The patient’s mental status is carefully evaluated, and an age-appropriate neurologic examination is performed. Any abnormalities should be noted and considered for further evaluation.

The selection of laboratory studies of use in evaluation of the syncope patient is largely guided by the history and physical examination (Fig. 52-1). For a patient with a history of fasting or diabetes, measurement of blood glucose is indicated. In the presence of pallor or a history of blood loss, hemoglobin measurement is obtained. Electrolyte abnormalities are uncommon but if an arrhythmia is suspected, then serum potassium, calcium, and magnesium are measured. Other studies including arterial blood gas, toxicology screening, and pregnancy testing may be indicated in certain clinical scenarios.⁷

For all patients with a history of syncope, a 12-lead ECG is indicated. This provides information concerning potential conduction defects or arrhythmias. Special attention is paid to determination of the corrected QT interval (QT_c), since prolonged QT syndromes as well as a short QT_c are causes of syncope in children. Other abnormalities to note include bradyarrhythmias, AV block, delta waves (preexcitation/Wolff–Parkinson–White [WPW]), epsilon waves (ARVD), and ST segment elevation in V₁–V₃ (Brugada syndrome), and left ventricular hypertrophy or strain patterns (hypertrophic cardiomyopathy). If abnormalities are seen or if a cardiac abnormality is strongly suspected, further evaluation will include a 24-hour ambulatory (Holter) monitor or continuous loop event monitoring and cardiology consultation.^5,7