EXECUTIVE SUMMARY
- When children present with transient loss of consciousness (LOC), a careful history and physical exam should be obtained and performed, considering a wide range of causes to include syncope mimics.
- Children younger than the age of 6 years are less likely to have the most common cause of benign syncope, vasovagal syncope (VVS), and are more likely to have had a seizure, breath-holding spell, or arrhythmia.
- Subclavian steal resulting from lesions in the subclavian artery and causing retrograde vertebral flow can give rise to transient LOC. This should be considered when syncope occurs in the setting of arm exercise, and on physical exam, patients may have significant blood pressure (BP) differences between the two arms. Those with surgical history of Blalock-Taussig shunt are at increased risk for subsequent subclavian steal.
- In one systematic review of pediatric syncope patients, more than 50% of syncope ultimately were attributed to vasovagal etiologies. It is common for children to have a family history of VVS.
- Postural orthostatic tachycardia syndrome (POTS) is not a diagnosis that will be made definitively in the emergency department (ED), since diagnostic criteria include at least six months of symptoms. Signs of this diagnosis in the ED include sustained increase in heart rate (HR) greater than 30 beats per minute higher than baseline (without corresponding BP decrease meeting criteria for orthostatic hypotension) within 10 minutes of standing, or such change in HR found during heads-up tilt test. The prevalence of POTS is believed to be 0.2% overall. POTS is mostly diagnosed in people aged 15-25 years. Many patients with POTS also experience reflex syncope.
- Historical features raising concern for cardiac etiologies include syncope during or immediately after exertion, with mid-activity being most concerning for cardiac syncope. Lack of prodrome, prodrome including chest pain or palpitations, triggering events to include swimming or water on the face, loud noises, strong emotions, and startle are commonly associated with cardiac syncope.
- Long QT syndrome can be congenital (typically autosomal dominant) or acquired and leads to sudden cardiac death via prolonged ventricular repolarization, which predisposes patients to ventricular arrhythmias. For those pediatric patients with either cardiac arrest or syncope, QTc more than 460 ms is sufficient for diagnosis. Meanwhile, in asymptomatic children, QTc more than 480 ms is diagnostic.
- In 2014, the American College of Cardiology created appropriate use criteria for echocardiogram in pediatric syncope: In those with no known heart disease, echocardiogram is warranted if there is an abnormal ECG, concerning family history, exertional syncope, or unexplained post-exertional syncope.
Syncope is a frightening event for a child’s family. Fortunately, the majority of etiologies are benign. However, there are rare, potentially life-threatening causes of cardiac diseases that cannot be missed. The authors review and present a balanced approach to a child with syncope.
— Ann M. Dietrich, MD, FAAP, FACEP, Editor
By Margaret Driscoll, MD, and Daniel Migliaccio, MD, FPD, FAAEM
Introduction
The word syncope comes from the Greek “synkoptein,” meaning “to cut short.”1 Syncope commonly is defined as a sudden, brief loss of consciousness (LOC) and tone that self-resolves.2,3 In the emergency department (ED), syncope as a chief complaint also encompasses a wide range of LOC causes with various presenting signs and symptoms. Syncope accounts for approximately 1% of all pediatric ED visits and roughly 125 of every 100,000 children seeking medical care.1,4,5 Nearly 15% of children experience syncope by the age of 20 years.6
A vast majority of syncopal events are benign and do not require extensive workup, diagnostic studies, or specialty follow-up. There often is diagnostic uncertainty as to the exact cause of an LOC episode.3 This uncertainty must be weighed against suspicion for dangerous causes. Syncope in the pediatric patient could be the first and only sign of serious underlying pathology. Witnesses of these events may be alarmed by LOC, which can appear dangerous, and those presenting with syncope are more likely to present via emergency medical services (EMS).4 Particularly in pediatrics, anxiety in the face of diagnostic uncertainty can result in inconsistent application of diagnostic tests. Overall, in one study, 4% of syncope cases were attributed to cardiac etiologies.3 When considering the morbidity and mortality of underlying cardiac issues, failure to consider and identify cardiac syncope would result in an unacceptable miss rate. However, unwarranted fear of rare etiologies may drive costly, low-yield, and excessive testing.
There are many causes of LOC, as outlined in Figures 1 and 2. When children present with transient LOC, a careful history and physical exam should be obtained and performed, considering a wide range of causes to include syncope mimics. A deep understanding of the etiologies of LOC can save children and caregivers unnecessary concern and the health system the cost and resources of low-yield additional evaluation. In one study, interpretation by physicians of LOC histories had surprisingly low agreement, suggesting that physician misinterpretation of the history plays a substantial role.7
Figure 1. Syncope-Based Causes of Loss of Consciousness |
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VVS: vasovagal syncope; OH: orthostatic hypotension; POTS: postural orthostatic tachycardia syndrome |
Figure 2. Non-Syncope-Based Causes of Loss of Consciousness |
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Before the age of 10 years, and especially below the age of 6 years, patients are less likely to have the most common cause of benign syncope, vasovagal syncope (VVS).8,9 Thus, those at young ages presenting with possible syncope are more likely to have had a seizure, breath-holding spell, or arrhythmia.10 VVS occurs disproportionately in females, with up to 70% of cases occurring in females.11 Shorter height and heavier weight correlate with higher general risk of syncope.12 It is estimated that between 50% and 80% of syncope in pediatric patients is from benign, reflex causes.3,13 This review will present both the common causes of syncope as well as frequently encountered syncope mimics and discuss appropriate ED syncope workup and management.
Alternate Causes of LOC
Seizure
Historical elements suggestive of seizure include prior personal or family history of seizure disorders. Reported prodromal déjà vu sensation or unpleasant smell or taste may represent seizure aura. Prolonged LOC duration as well as prolonged recovery with confusion are more suggestive of seizure than of syncope.14
Duration of LOC more suggestive of syncope (accounting for possible eyewitness overestimation) is around five minutes.14 When the reported duration of LOC exceeds five minutes, ED physicians should pay careful attention to any further features suggestive of seizure. Eye or head deviation, psychomotor slowing, or movements observed prior to LOC also are highly suggestive of seizure.6 Myoclonic jerks can be observed in syncope. However, these occur after LOC, are short-lived — with usually less than ten jerks — and typically are not clearly rhythmic or high-amplitude.6,14
Atonic seizures and syncope may appear alike to witnesses, but patients will not report prodrome prior to the LOC in atonic seizure. Automatisms, such as mouth smacking or hand wringing, as well as lateral eye deviation also increase suspicion of seizure.6 Open eyes, urinary incontinence, fatigue, amnesia to the event, vertical eye deviation, and sleep following LOC are not helpful elements in discrimination between seizure and syncope because they can be seen in either etiology.14
On physical exam, lateral tongue bite is very specific for seizure, while anterior tongue bite is not.14 Any patient arriving not at their mental status baseline also should be promptly evaluated with a high concern for possible postictal state vs. ongoing seizure activity. Evidence of focal neurologic abnormality, aphasia, or hemiparesis following LOC is suggestive of seizure with resultant Todd’s paralysis.6 The Calgary Syncope Seizure Score was created for differentiating between syncope and seizure in adults, but when applied to children with a slight modification for better application, it resulted in a sensitivity and specificity of 92% and 96%, respectively.15 However, the utility of such scores has not yet been validated. ED physicians should be very cautious with patients presenting with seizure vs. syncope with a history of “therapy-resistant” or difficult-to-treat epilepsy.15 Antiepileptic medications can manipulate ion channels and cause worsening cardiac function in patients with underlying cardiac disease.16 While recurrent seizures are possible in this population, careful attention should be paid to the eyewitness account and any deviation from typical seizure semiology, if available.
The Evaluation of Guidelines in Syncope Study (EGSYS) score was developed for differentiation of cardiac vs. noncardiac causes of syncope in adults (see Table 1 for the application to children). When applied to children, one study found that half of children presenting with scores indicating high likelihood of cardiac syncope were found to have channelopathy after being misdiagnosed for years with epilepsy that had been unresponsive to treatment.17
Table 1. The Evaluation of Guidelines in Syncope Study (EGSYS) Scores |
|
| Clinical Variable | Points |
Palpitations |
4 |
Abnormal ECG*/heart disease** |
3 |
Effort syncope |
3 |
Syncope in supine position |
2 |
Neurovegetative prodromes*** |
-1 |
Preciptating and predisposing factors**** |
-1 |
ECG: electrocardiogram Note: A total score of 3 or more implies an increased risk of cardiac syncope. * Abnormal ECG was defined as any of the following: bradycardia less than 40 beats/min, repetitive sinoatrial blocks, sinus pauses greater than 3 seconds, ST changes > 1 mm elevation or depression, QT prolongation 440 ms or more, ventricular tachycardia, atrioventricular block (Mobitz 2, second- or third-degree atrioventricular block, alternating left and right bundle branch block), sick sinus syndrome, ventricular and rapid paroxysmal supraventricular arrhythmias, or sinus pauses and pacemaker malfunction. ** Heart disease was defined as congestive heart failure or any form of structural heart disease, including ischemic disease, valvular dysfunction, cardiomyopathy, and congential heart disease. *** Neurovegetative prodromes: nausea, vomiting, abdominal discomfort, feeling of cold, sweating, aura, pain in neck or shoulders, blurred vision, and dizziness **** Precipitating and predisposing factors: position (supine, sitting, or standing); activity (rest, change in posture, during or after exercise, during or immediately after urination, defecation, cough, or swallowing); predisposing factors (e.g., crowded or warm places, prolonged standing, postprandial period); and precipitating events (e.g., fear, intense pain, neck movements) Reprinted with permission from Környei L, Szabó A, Róth G, et al. Frequency of syncope as a presenting symptom in channelopathies diagnosed in childhood. can the multivariable EGSYS score unmask these children? Eur J Pediatr 2021;180:1553-1559. |
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Breath-Holding Spells
Breath-holding spells are a common nonepileptic disorder of childhood, peaking at around 2 years of age.16 Guidelines recommend calling them VVS in infants because previous terms, including reflex anoxic seizures or reflex asystolic syncope, may raise inaccurate concerns for epilepsy or an underlying cardiac issue.14 Parents often will describe a trigger, such as anger, surprise, startle, or injury, prior to the event.16 Seizures typically are not triggered by anger or injury. The prototypical breath-holding child will otherwise be healthy, at mental status baseline, and developmentally meeting all milestones. Breath-holding spells are rare before the age of 6 months and will last around one minute in total.16 There are two types of breath-holding spell defined by the appearance of the child during the event: cyanotic and pallid. Cyanotic spells tend to begin with a loud cry in response to the inciting stimulus, then the child will become apneic and, thus, cyanotic. Parents may report jerking or rhythmic limb movements, loss of tone, followed by deep inspirations and return of normal coloration and responsiveness.1
The pallid spell type makes the term “breath-holding spell” a misnomer, since these events are not necessarily related to halted respirations.14 Parents typically will describe no cry, but LOC and unresponsiveness, then loss of tone and pale coloration.16 Parents also may describe abnormal, stiff, backward-arching tone during the event.15 If monitoring during the event is obtained, there often will be bradycardia or asystole noted. However, if a breath-holding spell has occurred, there are no further testing or treatments indicated other than reassurance. Children frequently will have no additional episodes after 8 years of age, but these episodes may rarely continue into the teenage years.1,18 Those with breath-holding spells in early childhood may be predisposed to VVS as they age.19
Other Neurological and Neurovascular Etiologies
It is important to consider and elicit concomitant vertigo, ataxia, headache, nystagmus, and hearing loss in association with events because these can increase clinical suspicion for etiologies such as vertebrobasilar insufficiency. Subclavian steal resulting from lesions in the subclavian artery and causing retrograde vertebral flow can give rise to transient LOC.19 This should be considered when syncope occurs in the setting of arm exercise, and on physical exam, patients may have significant blood pressure (BP) differences between the two arms. Those with surgical history of Blalock-Taussig shunt are at increased risk for subsequent subclavian steal.20 In addition, children with a history or recent symptoms suggestive of Ménière’s or vestibular disorders could have vertiginous drop attacks, mediated by the vestibulospinal reflex as part of their presentation. Concomitant headache, dysarthria, ataxia, and paresthesias may clue the clinician into a possible diagnosis of basilar migraine.19
In addition, any acute increase in intracerebral pressure can lead to LOC. This, of course, should be considered in children with a history of hydrocephalus or corrective surgical interventions for it. One important consideration would be acute or first presentation of hydrocephalus with a history of protracted nausea and vomiting, fatigue, and irritability as prodromal symptoms. On physical examination, these children may have eye movement abnormalities or other signs of increased intracranial pressure, such as papilledema. The lesion resulting in hydrocephalus could be a posterior fossa tumor obstructing the cerebral aqueduct, a colloid cyst that is positional with intermittent obstruction of cerebrospinal fluid outflow, or Chiari malformation with intermittent fourth ventricular involvement.19
Cataplexy
While VVS can be brought on by unpleasant stimuli, such as needles or the sight of blood, cataplexy often is triggered by positive emotional stimuli or surprise.6 Another point of caution is that loss of tone or LOC triggered by similar episodes or loud noises also can be an indication of possible long QT syndrome.19 Most commonly, children with narcolepsy type I (defined by the presence of cataplexy) will have cataplexy after a funny stimulus and laughter. They may stick out their tongue, have facial and eyelid weakness, or make abnormal facial expressions as part of their cataplexy.21 Parents or witnesses will report sudden loss of muscle tone in response to this trigger, although less severe cataplexy can consist only of eyelid weakness and may not result in complete loss of tone. Patients often will report awareness of a sudden sense of overwhelming fatigue. This syndrome often is in association with narcolepsy, although it can occur in isolation.6 Care should be taken when suspecting cataplexy to be mindful of a history of chronic sleepiness, hallucinations, sleep paralysis, or problems maintaining sleep. Patients should be referred for polysomnography and sleep latency testing and told to keep a log of cataplexy, symptoms, and sleep.21
Nonaccidental or Accidental Trauma
Syncope is nontraumatic in etiology. When diagnosing syncope, it is very important to differentiate syncope causing a fall and a fall causing LOC. LOC after traumatic head injury is an indication for intracranial hemorrhages. For unwitnessed events, prodrome or activity in which the child was engaged can provide clues to the physician indicating a syncopal origin of fall. A careful physical exam should be performed to identify any other signs of trauma. If the event was unwitnessed or the story is incongruent with physical exam findings, a full skin exam should be performed for any signs of nonaccidental trauma. Additionally, syncope can arise from hypoxia or occlusion of the carotid arteries in nonlethal strangulation episodes. These also can arise in accidental situations, such as in a “choking game.”6
Metabolic/Toxicologic Causes
Multiple metabolic and toxicologic syndromes should be considered when evaluating an individual with transient LOC. Any child not at baseline should be evaluated for any signs of bleeding or dehydration. Multiple electrolyte disturbances also may manifest in altered level of consciousness.19 Those reporting persistent autonomic symptoms, such as sweating, tremor, nervousness, and hunger, may benefit from evaluation for hypoglycemia, which is most common in the setting of poor intake, low weight, or insulin-dependent diabetes.19,22 When considering the classic causes of VVS, such as hot, crowded environments, it also is imperative to measure temperature and consider concurrent heat-related illness.
A full physical exam and social history also may demonstrate signs of inhalant use, which would raise suspicion for aborted ventricular tachycardia. Rash to the philtrum or EMS report of a patient being found near commonly abused substances such as paints, varnishes, glues, lighter fluids, or aerosol cans are important signs. In these settings, sympathomimetics should be avoided, and beta-blockers should be considered for treatment of tachyarrhythmias.16
Other Organic Illnesses
Syncope also could present as a manifestation of other illnesses. LOC can result from hypotension from any cause, including anaphylaxis, adrenal insufficiency, sepsis, hypoperfusion, or ectopic pregnancy, or from heart block caused by rheumatic fever, myocarditis, Lyme disease, or endocarditis.6 Although rare in pediatric populations, pulmonary embolism should be considered, especially in patients with obesity, indwelling catheters, congenital heart disease, nephrotic syndrome, total parenteral nutrition, or patients who are on oral contraceptives.
There are no validated pulmonary embolism decision tools in the pediatric population, but this diagnosis should be considered in children with syncope who are found to have tachycardia, hypoxia, dyspnea, or leg swelling.16 Systemic illnesses affecting the heart also can cause syncope as part of the presentation. In children, for example, sarcoidosis is far more likely to affect the heart and can lead to syncope in the setting of arrhythmias. With systemic illnesses such as these, there usually are other physical signs. In the example of sarcoidosis, these may include rash, arthritis, uveitis, and lymphadenopathy.23 Neuromuscular dystrophies also can result in bradyarrhythmia or atrioventricular blocks, and myocarditis can result in ventricular tachycardia.1
Types and Pathophysiology of Syncope
The final common pathway of syncope is believed to be transient global cerebral hypoperfusion.8 The visual prodrome often described by patients is casued by retinal hypoperfusion.15 LOC can result from just six to eight seconds of cerebral hypoperfusion.11
Reflex or Neurally Mediated
There are many confusing terms used to refer to benign causes of syncope. For the purposes of this article, vasovagal, situational, orthostatic hypotension, and postural orthostatic tachycardia syndrome (POTS) are categories of reflex or neurally mediated syncope. Multiple sources also refer to “neurocardiogenic syncope,” a term used in place of reflex syncope. However, this term no longer should be used because the reflex does not begin in the heart, and it can confuse the picture between benign causes and cardiac causes of syncope.11,15
Vasovagal
The pathophysiology of VVS is not fully elucidated in adults or children. However, there are several leading theories regarding the reasons it occurs. Physiological compensatory mechanisms exist to maintain cerebral perfusion in a standing position, where up to 70% of blood volume is below the heart.11 Upon standing, there is a drop in cardiac output from reduction in central blood volume and increased venous pooling below the diaphragm, with approximately 10 mL/kg of volume being displaced.20 This decreased blood return to the heart is sensed by arterial baroreceptors and counteracted by increased systemic vascular resistance caused by vasocontraction in skeletal muscle, increased sympathetic tone.11
In those who experience VVS, it is thought that cardioinhibitory mechanoreceptors, triggered by low filling of the left ventricle, cause increased parasympathetic activity and paradoxical bradycardia.20 Possibly these mechanoreceptors exist to vasodilate the coronary arteries and ensure coronary perfusion during times of low cardiac output.11,24
In VVS, the uncoordinated response of the heart and body to the decreased BP results in decreased perfusion to the brain until LOC. Then, LOC results in supine positioning and the reestablishment of homeostasis.25
By the same token, prolonged standing can result in vasodilation and bradycardia from suppression of the sympathetic nervous system.26 Vagal output from painful or frightening stimuli predisposes to VVS.27 As children age, the heart is more sensitive to adrenergic stimulation, and pressure receptors become more sensitive, increasing the risk of syncope with age.28 Asystole can be observed during reflex syncope and is not a cardiac emergency. There is no evidence of poor prognosis when asystole happens to be observed in the absence of other concerning historical or exam features.14
As such, any child who describes syncope in the setting of going from sitting or lying to standing, or standing for prolonged periods prior to syncope, is likely to have experienced VVS. In one systematic review of pediatric syncope patients, more than 50% of syncope ultimately were attributed to vasovagal etiologies.3 It is common for children to have a family history of VVS.24
The 2017 American College of Cardiology/American Heart Association (ACC/AHC) guideline described VVS as: “1) may occur with upright posture (standing or seated) or with exposure to emotional stress, pain, or medical settings; 2) typically is characterized by diaphoresis, warmth, nausea and pallor; 3) is associated with vasodepressor hypotension and/or inappropriate bradycardia; and 4) often is followed by fatigue.”2 One confusing factor can be that if patients are not put into a supine position, but are instead pulled into a chair or upright, this can prolong recovery and make clinicians concerned for prolonged recovery time.2
Situational
Micturition syncope is thought to be caused by rapid bladder decompression, which decreases total peripheral resistance and reduced venous return to the heart. Cough syncope commonly is associated with asthma and paroxysms of coughing.9 Parents often will note facial plethora or pallor before LOC.11 An increase in intrapleural pressure decreases venous return and cardiac output. Other situational syncope precipitants include laughing, defecation, swallowing, and the “fainting lark” game wherein children hyperventilate then stand and perform a Valsalva maneuver.1,11
Orthostatic Hypotension
Orthostatic hypotension is defined in adult populations as a systolic BP drop of at least 20 mmHg and/or a diastolic BP drop of at least 10 mmHg from baseline or a drop in systolic BP lower than 90 mmHg within three minutes of standing.11,29 In general, this definition has been used for adolescents as well.30 The pathophysiology of orthostatic hypotension is related to poor intake, fluid losses, or drug-induced vasodilation interfering with the compensatory mechanisms for positional changes described earlier.11,27 Delayed orthostatic hypotension occurs more than three minutes after standing.11 It is believed to be rare in children, and when it is found, it is likely to be related to illnesses, vasoactive medications, and type I diabetes.14
Postural Orthostatic Tachycardia Syndrome
POTS is not a diagnosis that will be made definitively in the ED, since diagnostic criteria include at least six months of symptoms.11 Signs of this diagnosis in the ED include sustained increase in heart rate (HR) greater than 30 beats per minute higher than baseline (without corresponding BP decrease meeting criteria for orthostatic hypotension) within 10 minutes of standing, or such change in HR found during heads-up tilt test.11,31 The prevalence of POTS is believed to be 0.2% overall.25 POTS is mostly diagnosed in people aged 15-25 years.32 Many patients with POTS also experience reflex syncope.11 Those with POTS have a lower resting HR and diastolic BP than their counterparts.32 Like VVS, POTS is hypothesized to arise from failure, discoordination, or dysfunction of arterial baroreceptor reflex to position changes.25
Patients with POTS seem to have a slower arterial baroreceptor reflex compared to their counterparts without the condition, although impaired sympathetic vasoconstriction, excessive cardiac sympathetic response, volume dysregulation, and physical deconditioning also have been proposed as possible mechanisms.25 Confusingly, 25% of healthy and symptom-free adolescents meet the definition of POTS.30 Expert consensus does recognize greater HR variation in patients aged 12-19 years and changes the cutoff for POTS in this age group to an increase in HR of more than 40 beats per minute.29
Overall, diagnosis of POTS is difficult in pediatric patients, given the lack of clear age-related cutoffs between expected and pathologic HR changes. In one systematic review including more than 3,700 pediatric patients with syncope, POTS was attributed as cause of syncope in 13%.3 Historical features raising concern for POTS include frequent presyncopal or syncopal symptoms as well as exaggerated tachycardia in response to orthostasis. The Canadian Cardiovascular Society and Canadian Pediatric Association position statement on approach to syncope notes that the modified Calgary score can be helpful for differentiating POTS from cardiac syncope.19
Cardiac Causes
Cardiac syncope occurs when decreased cardiac output lowers cerebral perfusion. This can occur because of obstructive lesions that inhibit forward flow of blood, general cardiac dysfunction, and arrhythmias.20 Children tolerate supraventricular tachycardias well enough that LOC tends to occur only with an extremely high HR, when cerebral blood flow is decreased because of decreased cardiac output.9,14 Notably, if LOC is ended with resuscitation, this is called aborted cardiac death and is not syncope, since syncope requires a spontaneous return to baseline.14
Historical features raising concern for cardiac etiologies include syncope during or immediately after exertion, with mid-activity being most concerning for cardiac syncope.14,24 Lack of prodrome, prodrome including chest pain or palpitations, triggering events to include swimming or water on the face, loud noises, strong emotions, and startle are commonly associated with cardiac syncope.14,16,19,24 In the end, even most exercise-related syncope is not cardiac in origin.9
A family history including sudden cardiac death (SCD), unexplained death, implantable cardiac defibrillator or pacemaker placement, congenital deafness, or channelopathy should be sought.16,24 Past medical history of cardiac disease or surgery is a red flag, and the medication list should be reviewed for QT-prolonging medications.16,24 Physical exam findings of dysmorphic or marfanoid features or hypermobility can raise concern for connective tissue disorders that increase the risk of cardiac involvement.8
An abnormal cardiac exam, including a murmur or findings associated with heart failure, should raise concern. In a retrospective analysis of 332 syncopal children, EGSYS scores greater than or equal to 3 had a sensitivity for identifying cardiac causes of 84.3%. The score contains six predictors: abnormal electrocardiogram (ECG) and/or structural heart disease, palpitations, syncope during effort, syncope in supine position, precipitating or predisposing factors, and lack of autonomic neurovegetative prodromes.33
Without Structural Defects
Brugada syndrome is an autosomal dominant disorder affecting cardiac sodium channels, which can lead to SCD. There are three types, which are differentiated by ECG findings, although many patients will have ECG findings only during a drug challenge.16 Fever can precipitate cardiac events in patients with Brugada syndrome.14 Patients with Brugada pattern on ECG should be referred to cardiology for consideration of an implantable cardiac defibrillator.16
Long QT syndrome can be congenital (typically autosomal dominant) or acquired and leads to SCD via prolonged ventricular repolarization, which predisposes patients to ventricular arrhythmias. For those pediatric patients with either cardiac arrest or syncope, QTc more than 460 ms is sufficient for diagnosis. Meanwhile, in asymptomatic children, QTc more than 480 ms is diagnostic.16
A normal QTc does not preclude a diagnosis of long QT syndrome, since 25% of patients with long QT syndrome mutation have a normal QTc on ECG.34 Family history is very important, and long QT syndrome can go along with congenital deafness. Penetrance appears to be higher in females. Triggers for syncope or SCD can include swimming, cold water on the face, or startle events. Patients are treated with beta-blockers and/or an implantable defibrillator.14,16 Acquired long QT syndrome can be related to medication use and usually occurs when a combination of multiple QT-prolonging medications is used. Most of the commonly implicated drugs are psychiatric, although antibiotics and multiple other classes of medications can have this effect.16 A useful list of QTc-prolonging medications can be found at https://crediblemeds.org/healthcare-providers/.
Short QT syndrome is a rare syndrome with shortened QTc interval, although an exact definition of an abnormally low QT value is debatable. This may occur in hypercalcemia from any cause. This abnormality can give rise to ventricular tachycardias and SCD.16
Wolff-Parkinson-White (WPW) is an accessory conduction pathway in the heart that, when part of WPW syndrome, can result in tachycardia. ECG findings will include a widened QRS complex, short PR interval, and slurred upstroke or “delta wave” reflective of preexcitation in the accessory pathway. The WPW pattern is present in approximately 0.2% of the population, and less than 0.1% of these patients will have SCD.16
Arrhythmogenic right ventricular cardiomyopathy (or dysplasia) is an autosomal dominant progressive condition that results in fibrofatty replacement of myocardium and resultant predisposition to ventricular tachycardia. Key ECG findings are numerous but include inverted T waves (beyond 14 years of age) or epsilon waves in the right precordial leads.16 Syncope during excitement can raise concern for this.14
Catecholaminergic polymorphic ventricular tachycardia is an inherited disorder that predisposes to adrenergic induction of polymorphic ventricular tachycardia because of defects in intracellular calcium handling. Baseline ECG is normal. Triggering events for syncopal episodes will include exercise or emotional stress. Treatment includes beta-blockade and defibrillator implantation.34
Myocardial infarction can occur in the pediatric population and should be considered in the combination of ECG with ischemic features and concerning history. Features that increase concern for myocardial infarction are chest pain, family history of early myocardial infarction or cardiac disease, or a history of Kawasaki disease. Lesions that can cause ischemia in pediatric patients include anomalous coronary artery origins or congenital or acquired cardiomyopathies.16,20
Nonobstructive Structural Defects
Pulmonary hypertension is a rare but important to consider cause of syncope in children. In a child with congenital heart disease, pulmonary hypertension should be considered in any presentation with syncope. Even in those without a history of diagnosed cardiac disease, reports of exercise intolerance, chest pain, or dyspnea should raise concern for this diagnosis.16
In a retrospective review from a children’s hospital, there was an average of more than nine months between first presentation and ultimate diagnosis of pulmonary hypertension, and all patients who were diagnosed with pulmonary hypertension had a history of at least one presentation to the ED with syncope.35 Loud P2 on physical exam was present in 68% of these children, and a majority reported dyspnea on exertion.35 The mean age of presentation was 8.5 years, emphasizing the point that syncope at younger ages is more concerning for cardiac etiologies.35 An ECG may show signs of right ventricular hypertrophy: a large R wave with upright T wave in V1 with rightward axis.36
Repaired or unrepaired congenital heart disease should be considered a source of cardiac syncope until proven otherwise.20 Coarctation of the aorta, anomalous coronary arteries, tetralogy of Fallot, and transposition of the great arteries can be causes of hypoxia or arrhythmia giving rise to syncope, and postoperative scarring to the heart can be arrhythmogenic.14
Obstructive Structural Defects
Hypertrophic obstructive cardiomyopathy (HOCM) is a disorder of left ventricular outflow obstruction by a hypertrophied intraventricular septum. It is the most common cause of SCD in young athletes. The risk of SCD in HOCM increases with episodes of syncope.16 On physical exam, the murmur of HOCM is a mid-systolic crescendo decrescendo heard at the left sternal border. It increases in intensity with Valsalva or any maneuver that augments afterload and worsens outflow obstruction. ECG findings may have deep, narrow “dagger” Q waves in the inferior and lateral leads and may show evidence of left ventricular hypertrophy.16
Aortic stenosis causes decreased blood flow to the aorta and poor cardiac perfusion. It is commonly caused in pediatrics by congenital bicuspid valves and is the most common valvular abnormality. The murmur is a harsh crescendo-decrescendo systolic murmur at times in conjunction with an ejection click, paradoxically split S2, or S4 gallop.16 Pulmonary stenosis or atresia, coarctation of the aorta, or any other defect leading to obstructive or restrictive physiology also may lead to cardiac syncope.18,20
Psychiatric Etiologies
There is no one finding in the ED that definitively will diagnose an episode of syncope as psychiatric in origin. The clinical picture can be complicated; in a prospective case control study, pediatric patients with VVS had significantly higher rates of depression, generalized anxiety, social anxiety, separation anxiety, and conversion disorder.26 Psychogenic or functional LOC often is divided into pseudosyncope or conversion disorder, factitious, somatization, panic with hyperventilation, and psychogenic nonepileptic seizures.6,14
Some factors that can raise concern for psychiatric etiologies include prolonged episodes without other concerning cardiac or neurological findings, strong psychiatric history, and multiple attacks per day.8 When eyes are closed during attacks or lids flutter during attacks, psychiatric etiologies should be considered.8,14
Lack of recovery despite supine positioning, episodes occurring in emotional situations, as well as known failure to be reproduced on ambulatory ECG or electroencephalogram (EEG) will point toward this diagnosis.9,18 At times, patients report remembering the event (lack of true LOC) and may exhibit indifference to these events.19
When syncope results from panic and hyperventilation, hypocapnia leads to cerebral vasoconstriction.9 Patients may report a prodrome of significant anxiety, tingling in the extremities, tachypnea, and numbness.9,19 In a study by Zhang et al, syncope duration of greater than 30 minutes, upright posture, and short QT dispersion (difference between longest and shortest QT on ECG) increased the likelihood of pseudosyncope.15,37
In a retrospective case-control study, pseudosyncope was more likely in patients with at least two attacks per day, longer than nine-minute duration, and onset without upright posture.38 Tilt table testing has been proposed as one method of differentiating between psychiatric and reflex syncope because it allows for detection of cardiac and BP changes during episodes; BP and HR are likely to be high rather than low in psychogenic LOC.14,33
ED Approach to Syncope in Pediatrics
The initial evaluation of patients arriving with a chief concern of syncope should begin with an assessment of whether the child is stable. Any child not at their mental status baseline should be evaluated promptly. A full set of vital signs should be obtained quickly, and physical exam findings, including a thorough exam of volume status, cardiac auscultation, and neurological exam, are critical. Febrile temperatures should prompt consideration of sepsis, febrile seizure, or heat-related illnesses as well as the search for physical exam or historical elements to raise concern for less common considerations such as Kawasaki disease, rheumatic fever, or endocarditis. Point-of-care glucose should be rapidly obtained in patients who are not at baseline.
If there are vital sign abnormalities or signs of instability, appropriate resuscitative measures should be pursued. Evaluation should include a thorough history of events and activities leading up to the event, the event itself, and prodromal and recovery descriptions. See Table 2 for key questions to ask when gathering a history. See Table 3 for red and green flags that may be elicited on history and physical examination. In addition, a history of medications, medical history, and history of migraine or seizures are relevant.
Table 2. Syncope History: Key Questions to Ask |
Prodrome
|
Table 3. Red and Green Flags on History and Physical Examination |
||
| Examination | Red Flags for Cardiac Syncope | Green Flags for Cardiac Syncope |
Hydration status |
Signs of heart failure, fluid overload |
Missed meals, poor hydration, recent illness |
Trigger |
Emotion, loud noise, water on the face, startle |
Painful or frightening stimuli, warm ambient temperature |
Activity |
Mid-or postexertional, swimming |
Prolonged standing |
Medical history |
Prior cardiac surgery, arrhythmia, cardiac problem |
History of VVS, breath-holding spells |
Prodrome |
None, palpitations, chest pain |
Warmth, nausea, light-headedness, vision changes |
Position |
Supine |
Upright |
Family history |
SCD, arrhythmia, channelopathy, deafness, ICD or pacemaker placement, connective tissue disorder |
VVS |
Physical exam |
Murmur, sternotomy scar, marfanoid features, hypermobility |
|
Recovery |
With chest compressions |
|
VVS: vasovagal syncope; SCD: sudden cardiac death; ICD: implantable cardioverter defibrillator Adapted from Sanatani S, Chau V, Fournier A, et al. Canadian Cardiovascular Society and Canadian Pediatric Cardiology Association Position statement on the approach to syncope in the pediatric patient. Can J Cardiol 2017;33:189-198. |
||
Electrocardiography
The 2017 ACC/AHA guideline recommendation includes obtaining an ECG in all pediatric patients presenting with syncope.2 In a study by Ritter et al, exercise-induced syncope, family history, and abnormal physical exam, in combination with abnormal ECG, had a 96% sensitivity in identifying cardiac causes of syncope.10 Despite this, there is a large variation among pediatric ED clinicians in their evaluation of syncope. A large survey of American pediatric ED physicians’ practice patterns demonstrated that only 58.1% of physicians obtained an ECG on evaluation of syncopal patients.4 By contrast, prior to the introduction of a guideline for clinicians at Boston Children’s Hospital, 92% of clinicians obtained an ECG.39
Borderline ECG findings are common, with up to 15% of normal children having QTc values in the borderline range.40 This creates anxiety for both clinicians and families who are understandably distressed regarding possible dangerous etiologies. In addition, a small study outlined that only 26% of ECGs obtained for patients with LOC in a pediatric ED had documented interpretations.41 In another study including 754 patients with ECG, only 87% of ECGs had a documented interpretation.22
Interestingly, the Canadian Cardiovascular Society and Canadian Pediatric Cardiology Association guidelines recommend only obtaining ECGs if the history does not suggest vasovagal etiology or there is a lack of prodrome, exertional syncope, syncope triggered by loud noise or startle, family history of SCD or heart disease, abnormal cardiac exam, or new medications with cardiac side effects.19
ECG is a relatively low-cost intervention, but on a population level, it is not cost-effective. In one study, only 1% of patients had ECG findings in the absence of other red flag physical and historical features, and only one ECG was of diagnostic utility for cause of syncope.19 In a retrospective study, 0.39% of children had cardiac causes of syncope, and none of these had a lack of other risk factors on history and physical examination.42
The diagnostic yield of ECGs overall is estimated to be less than 0.5%, and they have a high false-positive rate.16 One-third of ECGs with long QTc intervals in the ED in one study had normalized on follow-up, calling into question the utility of ECGs obtained acutely following LOC for diagnosis of long QT syndrome.19
In one retrospective study of pediatric ED ECGs obtained for any reason, those without a cardiac medical history and with normal age-adjusted vital signs very rarely had abnormal ECGs, although the baseline rate of abnormal ECGs was relatively high at 17%.43
In a survey of Canadian ED physicians presented with a clinical vignette of typical VVS, 51% of respondents would order an ECG. A clinical vignette of higher-risk syncope prompted all ED physicians to order an ECG and 94% to request cardiology consultation.40 Those who obtained an ECG in the low-risk vignette frequently cited medicolegal concerns, and only half indicated that their reasoning was to help rule out a cardiac cause.40
Development of clinical criteria for pediatric patients in whom an ECG is not necessary could represent an opportunity for cost savings, reduction in ED length of stay, and reduced resource use from the perspective of unnecessary cardiology consultation or referral. Those with false-positive abnormal ECGs understandably will experience avoidable stress. ECGs in those meeting criteria for benign syncope had abnormalities only 0.6% of the time in another study.22 The cost at one institution for an ECG was $325.22
Findings on ECG to raise concern for increased risk of SCD and requiring further diagnostic evaluation were put forth in 2012 by the American Medical Society for Sports Medicine.44 These were intended to be a screening tool for outpatient clinicians evaluating athletes, but they outline important findings that warrant further evaluation.
Orthostatic Vital Signs
The utility of obtaining orthostatic vital signs in the ED is not clear in pediatrics or adults.14,45 In a prospective study of 223 patients aged 16 years and older, recurrence of syncope was not related to orthostatic hypotension.46 In another pediatric study of healthy adolescents, more than 33% had orthostatic symptoms.30 Expert consensus does recognize greater HR variation in patients aged 12-19 years.29 Initial orthostatic hypotension is very common in adolescents and, in one review, is defined as a decrease in systolic BP of > 40 mmHg and/or diastolic BP > 20 mmHg within 15 seconds of standing.14
Because of a lack of clearly established reference ranges in pediatric age ranges, it is difficult to know what specific orthostatic vital sign changes would be relevant to the evaluation of syncope and constitute “true positive” changes increasing the chance of orthostatic etiologies. With orthostatic changes being prevalent in euvolemic and normal children with no history of syncope, it is difficult to conceptualize what positive orthostatic vital signs would add to the clinical picture. As Schunk et al put it, “The presence or absence of positive orthostatic vital signs should not be the sole driver of diagnostic and disposition decisions.”16
At the same time, the Canadian Cardiovascular Society position statement does recommend obtaining orthostatic vital signs, stating that it adds information regarding hydration and dysautonomia to clinical evaluation.19 In fact, in a survey of Canadian ED physicians presented with both high- and low-risk clinical vignettes, 42% of physicians requested orthostatic vital signs as part of evaluation in both cases.40
Electroencephalogram and Neuroimaging
If neurological causes, such as acute hydrocephalus, are suspected, intracranial imaging should be obtained emergently to evaluate for obstructive lesions and confirm hydrocephalus. These children warrant urgent neuroimaging, as transient cerebrospinal fluid pressure increases can become fatal if not relieved.6 When there is a concern for head trauma on history or physical exam in those meeting Pediatric Emergency Care Applied Research Network criteria for intracranial imaging, emergent computed tomography (CT) imaging should be obtained. Most well-appearing children who have sustained a syncopal episode will not meet criteria for imaging, even in the setting of their LOC, and at most will require observation in the ED for any worsening clinical findings.
Children younger than 2 years of age with reported LOC of less than five seconds and no other concerning findings require no imaging. Regardless of duration, isolated LOC in children older than 3 months has a risk of < 1% of clinically important brain injury.47 In one study of national data over five years, more than 25% of patients received a CT or magnetic resonance imaging as part of their workup.4 Clinically significant head injuries from syncope alone are rare, but a high clinical suspicion should be maintained. In patients with intact cranial nerve, perform fundoscopic and vestibular testing where indicated. Head and brain imaging rarely is necessary.6
When concern is high for seizure, especially ongoing epileptic activity, appropriate treatment with benzodiazepines and escalating therapies should be initiated as soon as possible. When continued seizure activity is suspected, EEG must be sought.1 In the patient arriving at baseline or with return to baseline after suspected postictal state, in consultation with neurology, EEG may be done on an expedited outpatient basis. EEG has a very low positive yield when patients do not have prolonged lethargy or LOC.9
Echocardiography
Echocardiograms can identify structural cardiac abnormalities that may have given rise to syncopal events. It follows that if the cardiac abnormality is not structural in nature, echocardiography will not be elucidative for the cause and should not be pursued.2 When there is high suspicion for obstructive lesions, pulmonary hypertension, and congenital heart disease, or a history of cardiac surgery, echocardiography should be part of the evaluation.9 In 2014, ACC created appropriate use criteria for echocardiogram in pediatric syncope: In those with no known heart disease, echocardiogram is warranted if there is an abnormal ECG, concerning family history, exertional syncope, or unexplained post-exertional syncope.49 In a single-center retrospective study of a tertiary pediatric center, these criteria performed well, with no echocardiograms deemed “rarely appropriate” revealing abnormalities.51
Echocardiography generally is low-yield, and in a retrospective review of more than 480 patients, only two cases had findings related to syncope. In those two cases, ECG was noted to be abnormal as well.10 In one study of more than 400 patients who were evaluated by cardiology for syncope and underwent both echocardiography and Holter monitoring, only one patient had findings related to the cause of syncope.48 One clinical guideline for pediatric cardiologists limited additional cardiology testing to those with an abnormal ECG, abnormal cardiac exam, family history of cardiomyopathy or SCD, history suggestive of acute myocarditis, exertional syncope, or suspected central nervous system disease and resulted in no negative impact on patient outcomes.50
Tilt Table Testing
Tilt table testing often is performed by obtaining baseline BP and ECG, then tilting a patient 60 degrees head upward for up to 45 minutes or until symptoms arise. If any symptoms or syncope occur, the patient is put back into a supine position. If not, medications such as nitroglycerine or isoproterenol can be given and HR, BP, and ECG recorded until symptoms occur.11,12 In adult populations, orthostasis has been defined as sustained 20 mmHg or 10 mmHg drop in systolic or diastolic BP, respectively, within three minutes of tilt to at least 60 degrees on a tilt table.29
This methodology frequently is described as possibly helpful in the setting of recurrent syncope. The goal is to provoke symptoms and correlate them with cardiac rate and rhythm and BP response to changes in position.9 The protocol varies, limiting its reproducibility, yield, and sensitivity and specificity.9,18 However, around 25% of adolescents with no history of syncope will syncopize during a tilt test.9 One study suggests the use of tilt testing in children who have repeated syncope with normal or nondiagnostic EEG and lack a response to antiepileptic drugs, which can be helpful as well for possible psychogenic syncope.19,52 In adults, reproducibility of tilt table testing is low — 62%.9
Ambulatory ECG Monitoring
Patients with frequent episodes or concerning histories may benefit from ambulatory ECG monitoring, which can increase the possibility of correlating arrhythmias with syncopal symptoms. When patients experience symptoms on ambulatory monitoring that do not correlate with arrhythmia, this likely excludes arrhythmic causes for syncope.9 Young children with exertional syncope who are unable to undergo stress testing on a treadmill may benefit from monitoring during active play.19
There are many options for ambulatory monitoring. A Holter monitor records for short periods, frequently 24 hours. A loop recorder offers the opportunity for longer monitoring if patients can activate the monitor when they have symptoms, while a non-looping recorder may be used when patients are unable to trigger the device. An implantable loop recorder can be used for much longer periods.9,53
The choice of methodology often is dictated by the frequency of symptoms, and longer-term monitoring often is sought out when there is recurrent, otherwise unexplained syncope or palpitations.19 However, these studies are low-yield, with 79% of patients having only brief or no arrhythmias found.53
Stress Testing
If the syncopal event was associated with exercise, a stress test often is performed on an outpatient basis to monitor BP and ECG during exertion, with the goal of reproducing symptoms and monitoring for corresponding arrhythmia.9 Cardiology referral from the ED for exertional syncope may query the need for outpatient stress testing.
Laboratory Studies
Per ACC/AHA guidelines, there are no blood tests that are indicated routinely in syncope.2 When laboratory tests such as glucose, complete blood count (CBC), and basic metabolic panel are obtained in adults, they lead to a cause of syncope in only 3% of patients, including (and mostly owing to) those who have had seizures.53 Patients with syncopal episodes often are seen hours after recovery to baseline and are very unlikely to have glucose or electrolyte abnormalities.9 There is a dearth of data to establish the role of laboratory studies in pediatrics. In one study introducing a pediatric ED syncope practice guideline, laboratory testing was discouraged, and rates of obtaining tests dropped from 36% to 16% without an increase in subsequent further medical care or diagnostic testing.54 In a similar study at Boston Children’s Hospital, a guideline decreased the odds ratio of obtaining CBC, electrolytes, and point-of-care glucose with no observed increase in missed serious cardiac or neurologic diagnoses on follow-up.39 In a retrospective review of 969 children with syncope, only 0.3% of children had hypoglycemia.42
One syncope protocol introduced at a university pediatric ED suggested laboratory studies “as indicated,” and no electrolyte abnormalities or hypoglycemia were observed.55 All of these studies excluded children who were not previously healthy, who had observed seizure activity, or who were not well-appearing. Thus, in pediatric patients presenting with syncope not meeting those criteria, consideration of laboratory studies should be guided by the clinical situation.
If the presentation is thought to be orthostatic hypotension arising from dehydration, intravenous fluids and measurement of electrolytes should be considered. If substance use or intoxication is suspected as a component of the presentation, a toxicology screen should be considered.21 Serum or urine human chorionic gonadotropin generally is advisable in post-pubertal females to exclude pregnancy.21 In a study introducing a syncope pathway at Boston Children’s Hospital, a pregnancy test was encouraged as part of initial evaluation along with ECG.39
Disposition and Management
Most patients presenting with syncope will be appropriate for outpatient follow-up. Patients being discharged home after apparent reflex syncope should be counseled and educated regarding the likely mechanism, and reassurance should be given to patients and family regarding the lack of the need for additional testing. It is important to provide effective counseling and reassurance because syncope can decrease quality of life to a similar degree as asthma, end-stage renal disease, and obesity.6 Parents and patients should be encouraged to identify precipitating factors and avoid them; increase water and salt intake; and, if experiencing a prodrome, to perform counterpressure maneuvers, such as sitting, lying down, squatting, crossing legs, or squeezing items in the hand.11 Avoiding hot, crowded conditions and prolonged standing can be key, if these were precipitating factors.19
When prolonged standing is unavoidable, patients can bolus water and salt intake prior to these events.14 A meta-analysis of pediatric randomized controlled trials showed increased water and salt intake did help prevent VVS.56 Orthostatic training may reduce VVS, although evidence is weak.11,21 Patients with suspected reflex syncope can be counseled to slow transitions between lying, sitting, and standing.14 Counseling should include that patients with classic reflex syncope are in the “fortunate majority” of syncope patients who are not at increased risk for mortality.27
When reflex syncope is recurrent and refractory to the strategies discussed earlier after six months, some medications can be considered, although there are no Food and Drug Administration-approved medications for reflex syncope.1 Parents should be counseled to record attacks to increase clinicians’ ability to evaluate the etiology of the attacks. There are no prospective long-term studies. However, the only predictor of recurrence is syncope frequency, and it is reasonable for those with frequent VVS to follow up with their primary doctors routinely.19 Medications that can be considered include midodrine (2.5 mg twice daily) and fludrocortisone (0.1 mg daily), both of which have some evidence of safety and efficacy in children.11,19 The current first-line medication is midodrine, and efficacy has been reported for serotonin-agonists, such as sertraline.9,20 No agent has been shown to have a consistent benefit in clinical trials.8 Other medications have weak evidence, and there are no randomized placebo-controlled trials in pediatrics regarding the use of beta-blockers.11
Those who are at high risk for cardiac causes of syncope, or in whom a cause of cardiac syncope has been identified, should be admitted to the hospital for cardiac monitoring, expedited evaluation, and treatment of the cause. This should be considered especially in those with known structural heart disease, symptoms suggestive of arrhythmia or ischemia, or markedly abnormal ECG findings.53 In some cases, such as borderline ECG, it can be reasonable to discharge the patient with close outpatient cardiology follow-up as well as patient and parent agreement to avoid triggering stimuli and adhere to activity restriction from exertion and exercise until cleared by cardiology. Those believed to be at intermediate risk by the physician may benefit from observation or syncope unit evaluation, where available.57
Conclusion
Multiple ultimate diagnoses are possible when patients arrive at the ED with a chief concern of syncope. ED evaluation of syncope represents an important opportunity for diagnosis of dangerous causes before significant morbidity or mortality results. Physicians must be well-versed with a multitude of possible causes and become experts in interpreting histories. Very few patients who present with syncope are at increased risk of morbidity or SCD. The episode in question should be described fully if able. It is important to consider non-syncopal causes of LOC when gathering this history.
When true syncope is confirmed by the history, it is prudent to obtain an ECG and urine pregnancy test in postmenarchal females. In one retrospective review of 226 pediatric syncope patients, no ancillary test, including EEG, CT, blood tests, echocardiography, and 24-hour Holter monitor diagnosed the cause of syncope.13 Typically, a thorough history and exam are all that is needed to determine whether any other tests are needed. Implementation of a guideline regarding evaluation of pediatric syncope in the ED can result in decreased visits to the ED as well as statistically significant reduction in costly and unhelpful tests, as well as length of stay.39,50
Margaret Driscoll, MD, works with the Department of Emergency Medicine, University of North Carolina at Chapel Hill
Daniel Migliaccio, MD, FPD, FAAEM is a clinical associate professor, division director of emergency ultrasound, ultrasound fellowship director, Department of Emergency Medicine, University of North Carolina at Chapel Hill
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Syncope is a frightening event for a child’s family. Fortunately, the majority of etiologies are benign. However, there are rare, potentially life-threatening causes of cardiac diseases that cannot be missed. The authors review and present a balanced approach to a child with syncope.
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