Syncope, or fainting, is the abrupt loss of consciousness and postural tone resulting from transient global cerebral hypoperfusion, followed by complete spontaneous recovery.¹ In children, this process is usually benign, but it can be a symptom of serious cardiac, neurologic, or metabolic pathology. Assessing syncope in children is complicated by the variability of symptoms and lack of a gold standard for diagnosis. The primary goal of the emergency physician is to differentiate children with benign syncope from those with serious disease.

Syncope is a presenting symptom in 1% to 3% of pediatric emergency visits^2,3 and 6% of hospital admissions⁴ and is more common in adolescents than in younger children. Between 15% and 25% of adolescents experience at least one episode of syncope.⁵ Only 10% to 15% of patients evaluated in the pediatric ED for syncope are ultimately diagnosed with a serious illness.⁶ About 80% of pediatric fainting is neurocardiogenic (previously known as vasovagal) syncope. Neurologic disorders, mostly seizures, account for about 10% of episodes, and 2% to 3% are due to cardiac pathology.^6,7

Neurocardiogenic syncope, or neurally mediated syncope, is a mix of vasodepressor syncope (due to vasodilation) and cardioinhibitory syncope (due to vagal stimulation). Neurocardiogenic syncope can be triggered by a variety of conditions in which a reduction in venous return enhances vagal tone causing hypotension, bradycardia, and reduced cerebral perfusion. Recovery of consciousness occurs over 1 to 5 minutes, but symptoms of nausea and fatigue can last for several hours.

Cardiac syncope occurs when there is an interruption of cardiac output due to an intrinsic cardiac abnormality. These causes are divided into tachydysrhythmia, bradydysrhythmia, outflow obstruction, and myocardial dysfunction.

Any event that causes sufficient cerebral hypoperfusion can lead to sudden death. The most common causes are seizures, cardiac diseases, and metabolic diseases. Little is known about the most common dysrhythmias that cause sudden death in children, because such cardiopulmonary arrests are unwitnessed. In children, bradycardic or asystolic arrests are thought to be most common, especially in infants <1 year, but ventricular fibrillation is also seen in older children, although at much lower rates than in adults.⁸

Syncope is characterized by the sudden onset of falling with a brief episode of loss of consciousness. Other associated symptoms or signs are usually related to the cause for the syncopal event. Two thirds of children experience a prodrome of light-headedness or dizziness before the event,⁵ and vertigo is uncommon. Involuntary motor movements, related to cerebral hypoxia, occur with all types of syncopal events but are more common with seizures. A careful history can usually differentiate tonic-clonic movements associated with seizures from the myoclonus of cerebral hypoxia, by their onset after loss of consciousness, less rhythmic nature, and shorter duration.

RISK FACTORS FOR A SERIOUS CAUSE OF SYNCOPE

Risk factors are outlined in Table 127-1. Events that may mimic syncope in children are listed in Table 127-2.

Exertion before a syncopal event increases the suspicion of structural heart disease, specifically cardiac outflow obstruction. Conditions such as aortic stenosis, hypertrophic obstructive cardiomyopathy, and other vascular or valvular anomalies may cause cardiac outflow obstruction.

Prior to age 6, syncope is much more likely to be associated with seizures, breath-holding spells, and cardiac arrhythmia.¹ Preexisting cardiac disease heightens suspicion of ventricular arrhythmias as a cause of syncope. Bradyarrhythmias secondary to ischemia, overmedication, or pacemaker malfunction also cause syncope. A history of heart murmur, or discovery of one on exam, may indicate undiagnosed congenital heart disease.

Several familial inherited syndromes are associated with syncope and sudden death. Romano-Ward syndrome is an autosomal dominant syndrome associated with prolonged QT interval and ventricular arrhythmias; Jervell and Lange-Nielsen syndrome is an autosomal recessive syndrome associated with prolonged QT interval, deafness, and ventricular arrhythmias. The presence of a family history of dysrhythmias should prompt a more thorough investigation.

When more than one episode of syncope has occurred, the presence of ongoing cardiac disease producing a low-flow state must be considered. Illnesses associated with valvular insufficiency, congestive heart failure and diastolic dysfunction, or recurrent supraventricular tachycardia or atrial fibrillation causing rate-dependent hypoperfusion should be considered, even in children. Recurrence also raises the probability of a neurologic cause (i.e., seizures).

Episodes that occur when the patient is supine can suggest ventricular arrhythmias or seizures, which are unrelated to activity.

An extended period of loss of consciousness is worrisome and can be a sign of hypotension resulting from cardiac disease that causes prolonged cerebral hypoperfusion. Alternatively, prolonged loss of consciousness, lasting for hours, is often seen with pseudosyncope or pseudoseizures in adolescent females.⁹ Syncope in association with chest pain may result from acute myocardial infarction or aortic dissection, whereas preceding palpitations should raise suspicion for possible arrhythmia.

Antidysrhythmic medications, blood pressure agents, tricyclic antidepressants, amphetamines, and cocaine are all agents that can precipitate electrical conduction disturbances. Many common medications can prolong QT interval and predispose to syncope (see Table 127-5).

No clinical or historical features can reliably exclude all serious causes of syncope.⁷ Certain elements in the history increase the likelihood of a potentially serious cause (Table 127-1), and a careful history taking and physical examination are necessary. Many of the diseases that cause syncope also cause sudden death in children. A syncopal event can be the presenting symptom of these more serious illnesses. Up to 25% of children who die suddenly have a history of at least one prior syncopal event.¹⁰ Syncope is a very common event, however, and a syncopal event by itself is not associated with an increased risk of sudden death unless certain features are present (Table 127-1).⁵

HISTORY

Obtain a history focused on hydration status, last meal, environmental conditions, activity preceding the syncopal event, and the use of drugs and medications. Note the position the child was in when syncope occurred, because recumbent positioning is less consistent with neurocardiogenic syncope. Be sure to include interviews with any family members, friends, or witnesses who were with the child just before the event. A history of syncope during exertion or exercise increases the likelihood of a serious cause. A prodrome of warmth, nausea, light-headedness, and a visual gray-out or tunneling of vision is indicative of benign neurocardiogenic syncope. The sequence and timing of motor movements and postural positioning help to differentiate primary seizures from syncope. Loss of consciousness occurs with the onset of movements in seizures, but loss of consciousness precedes movements in most cases of true syncope. Inquire about past history such as previous syncopal events, cardiac disease, diabetes, seizures, medication or drug use, and psychiatric or psychological problems. Ask about a family history of structural cardiac disease, dysrhythmias, sudden death, migraines, or seizures. Take statements by the witnesses that the patient appeared dead and required CPR seriously and characterize the duration of pulselessness and the degree of intervention required. Whenever CPR has been performed, even if by an inexperienced layperson, consider the event resuscitation from sudden death and evaluate comprehensively.

PHYSICAL EXAMINATION

Complete cardiovascular, neurologic, and pulmonary examinations are crucial, but the findings are normal in the vast majority of children with syncope, regardless of the seriousness of the cause. Perform a neurologic examination including deep tendon reflex, gait, and coordination testing. Examine the cardiovascular system including blood pressure, resting heart rate, oxygen saturation, and respiratory rate. Assess pulse quality in all extremities. Measure blood pressure and heart rate with positional changes (orthostatic vital signs), especially if syncope occurred during positional change. Auscultate the heart to identify any murmurs, abnormalities in rhythm, and variations or abnormalities in heart sounds. Any abnormal findings in the cardiovascular assessment require an in-depth cardiac evaluation.

LABORATORY EVALUATION

Obtain an ECG in all children with syncope.¹¹ However, abnormalities on the ECG may not correlate with the syncopal event, and some patients with an arrhythmic cause of syncope have normal ECGs.³ See the section “ECG Interpretation in Infants and Children” at the end of chapter for detailed discussion.

A detailed history, physical exam, and ECG have a 96% sensitivity for detecting cardiac syncope.¹² Selection of other laboratory tests should be guided by clinical suspicion (e.g., a hemoglobin measurement for a patient with possible anemia or a glucose measurement for a patient with diabetes). Routine laboratory studies are not needed in a child with a clear episode of vasovagal syncope. For patients with an atypical presentation or worrisome associated symptoms, a serum chemistry panel, hematocrit, thyroid function tests, and chest radiograph may be performed in the ED if indicated by history. For example, hyperthryroidism predisposes children to supraventricular tachycardia, so thyroid function tests are appropriate when supraventricular tachycardia is considered. In adolescents, consider serum alcohol level and a urine drug screen to rule out illicit drug use (most commonly cocaine and amphetamines).

Obtain an echocardiogram for those with known cardiac disease, abnormal heart sounds, abnormal cardiac murmurs, evidence of cardiac chamber enlargement, or repolarization abnormalities on ECG, or other features that suggest myocardial dysfunction. If an echocardiogram cannot be obtained in the ED, then consider admission for inpatient evaluation.

EEG has very low diagnostic yield in syncope and is not needed routinely.¹³ The clinical utility of other tests, such as stress tests, tilt-Table tests, electrophysiologic studies, and cardiac catheterization, usually is determined by the pediatric cardiologist and is beyond the scope of this chapter.

Children resuscitated from sudden death must undergo a complete evaluation unless a clear cause for the arrest is apparent. The diagnostic possibilities are extensive, so laboratory and radiographic studies should be directed by clinical and historical information. For all such patients, obtain a serum chemistry panel, cardiac enzymes, a CBC, serum alcohol level, urine drug screen, thyroid function tests, chest radiograph, and ECG. Look for complications resulting from the arrest, such as hypothermia, acidosis, rhabdomyolysis, and cerebral edema or hypoxia. Inpatient evaluation can include an echocardiogram, cardiac catheterization, stress test, and electrophysiologic testing as directed by the pediatric cardiologist.

Most children experiencing syncope have recovered fully by the time they arrive at the ED.^5,6 Continued altered level of consciousness should prompt an evaluation for continued neurologic, cardiovascular, or psychological derangements. Treatment should be tailored to current symptoms. Correct compromised oxygenation, ventilation, or circulation. Apply a cardiac monitor to document any transient dysrhythmias while gathering the history and physical findings. Manage ongoing cardiac dysrhythmias or seizures as appropriate (see chapters 109, “Resuscitation of Children” and 135, “Seizures in Infants and Children”). Most patients, however, have no treaTable dysrhythmias in the ED.

Treatment is targeted to specific identified causes of the syncopal event; 80% of the time, this will be neurocardiogenic syncope, and treatment for these patients includes reassurance, increasing water (1.5 to 2.5 L/d or until urine consistently clear) and salt intake (2 to 5 g/d), and isometric counter-pressure maneuvers. There is little evidence to support the use of compression devices.

A child who had a syncopal event can present a challenging disposition decision, although in the majority of patients, the condition is benign.

Admit any child with a dysrhythmia documented by prehospital providers or on the ECG in the ED. Children who have any of the risk factors listed in Table 127-1 should be seen by a pediatric cardiologist, either in the ED or in follow-up. Patients with a normal ECG but a history suspicious for dysrhythmia are candidates for outpatient ambulatory cardiac monitoring. Identified causes of syncope should be treated as appropriate in the ED, and admission to the hospital should be directed by the need for further evaluation or therapy. All children admitted for an evaluation of syncope should be placed on a cardiorespiratory monitor.

If, after appropriately thorough history taking, physical examination, and ECG, no concerning features are elicited, the child may be discharged to home with close follow-up by the child’s primary physician. Because neurally mediated syncope accounts for up to 80% of the cases of syncope in children, most children without cardiac risk factors or exercise-induced symptoms may be safely evaluated as outpatients.

SUDDEN DEATH

Sudden unexpected death includes many causes, such as a seizure, asthma, or toxic ingestion, whereas sudden cardiac death includes just those events that directly relate to cardiovascular dysfunction. Sudden unexpected death in children occurs in 7.5 cases per 100,000 children overall with a much higher rate of 96 per 100,000 in children less than 1 year old.¹⁴ Sudden cardiac death rates range from 0.8 to 6.2 per 100,000.^10,15 These numbers are approximate because there is no centralized registry of these cases. Excluding trauma, sudden cardiac death is the most common cause of sports-related death in young athletes, accounting for about 100 deaths per year in the United States.¹⁶ The greatest risk for sudden cardiac death is in patients with congenital or acquired structural cardiac disease, including those with congenital heart disease who have undergone corrective surgery. The most frequent causes of sudden cardiac death in children are listed in Table 127-3.¹⁷ Hypertrophic cardiomyopathy and congenital artery anomalies are the most common causes of sudden cardiac death in adolescents without known cardiac disease.¹⁶

Sudden cardiac death is usually an unexpected, unwitnessed, terminal event.

Survival from an out-of-hospital cardiac arrest is very unlikely, with reported rates from 2.5% to 5%.^18,19 Any surviving patients must undergo rapid stabilization, and any identified conditions must be quickly treated, following the principles of pediatric advanced life support (see chapter 109). Avoid use of class Ia agents such as procainamide and quinidine for the treatment of wide QRS complex tachydysrhythmias if long QT syndrome is suspected, because these medications act by prolonging the QT interval; use class Ib drugs, such as phenytoin or amiodarone, instead (see chapter 109).