Pediatric emergency medicine trisk 378

the outflow of the left ventricle, creating a functional obstruction. In addition,
anterior motion of the mitral valve into the left ventricle during systole further
compromises outflow. Patients may present with dyspnea, exercise intolerance,
angina, syncope, or sudden death.
Adult congenital heart disease survivors are at risk for syncope because of the
underlying cardiac condition and/or previous palliative/corrective surgeries.
These patients can present with heart failure, arrhythmias, or pulmonary
hypertension. It is important to exclude atrial arrhythmias in patients with
syncope and congenital heart conditions or surgeries associated with a risk of
atrial rhythm abnormalities (e.g., tetralogy of Fallot, Ebstein anomaly, and the
Mustard, Senning, and Fontan procedures).

Other Arrhythmias
Supraventricular tachycardia is the most common symptomatic pediatric
tachyarrhythmia, and syncope can theoretically result from compromised cardiac
output, though such presentations are rarely seen. First-degree heart block may be
an incidental finding in patients with syncope. However, second- and third-degree
heart block need further investigation. Search for evidence of myocarditis,
cardiomyopathy, or congenital heart disease when such arrhythmias are observed.
Conduction disturbances are common after cardiac surgery. Patients who have
undergone correction of tetralogy of Fallot, aortic stenosis, and transposition of
the great arteries may be particularly prone to syncope. Ventricular arrhythmias
may occur as a consequence of surgeries involving incision to the ventricles.
Rarely, direct blunt trauma to the chest (commotio cordis) may cause ventricular
arrhythmias leading to syncope or sudden death.

OTHER CONDITIONS AND THOSE THAT MIMIC SYNCOPE
There are several other conditions that may cause or mimic syncope. The most
frequent of these are seizures and migraine. The rest are less frequent but still
important conditions.

Hypoglycemia
Low blood sugar is usually associated with feelings of weakness, diaphoresis,
lightheadedness, and confusion that can mimic presyncope. Infants may present
with lethargy or jitteriness. Diagnosis is rapidly established by obtaining a blood
glucose level.

Epilepsy


It may be difficult to differentiate an epileptic seizure from the convulsions or
posturing that may follow a brief but severe cerebral hypoxic event caused by
vasovagal syncope. An important distinguishing feature is that in the latter, the
patient usually displays a normal orientation after the syncopal event compared to
the more prolonged postictal confusion and lethargy that usually follows a typical
generalized epileptic seizure. Nausea and sweating are also more common with
syncope. Incontinence and fall-induced trauma may be observed in both
conditions and are not discriminatory. A distant stare may precede an atonic
seizure but is not typical of vasovagal syncope. The prodromal symptoms of
vasovagal syncope differ from the aura that may precede a seizure in some
patients. Prolonged clonic seizure activity after the patient is recumbent is not
expected in a syncopal event.

Narcolepsy
Cataplexy, muscle weakness, and collapse in a patient with narcolepsy may
mimic syncope. However, in these patients there are more likely to be disorders
of the sleep–wake cycle, symptoms of daytime somnolence, and sometimes
hallucinations.

Vertebrobasilar Migraine or Transient Ischemic Attacks
In such migraines, symptoms such as tinnitus, vertigo or other aura, and occipital

headache may be observed. However, this constellation of symptoms is not
specific. In vertebrobasilar migraine, as in vertebrobasilar arterial insufficiency
causing transient ischemic attacks, loss of consciousness may be observed.

Psychogenic Causes of Syncope
Hyperventilation and conversion disorder can lead to syncopal events. These
conditions are relatively common in adolescence. Hyperventilation may occur as
part of a panic disorder. Patients may complain of chest tightness, breathlessness,
lightheadedness, palpitations, and dizziness. Syncope-like symptoms due to
conversion disorder occur in the presence of an audience and are not associated
with injury. Episodes tend to last longer than the typical vasovagal syncope and
are not posture dependent. Neurologic and autonomic manifestations are usually
absent.

Orthostatic Intolerance
Syncope attributable to orthostatic hypotension occurs upon assuming an upright
posture (i.e., orthostasis) due to a drop in BP. It is defined as a drop in systolic BP
of ≥20 mm Hg or diastolic BP of ≥10 mm Hg with assumption of an upright


posture. Symptoms of orthostatic hypotension consist of lightheadedness,
syncope or presyncope, vision changes, headaches, palpitations, tremulousness,
and diaphoresis and are ameliorated by recumbent position. The causes include
volume depletion (e.g., hemorrhage or dehydration), febrile illness, pregnancy,
anemia, eating disorders, and use of medications such as diuretics, vasodilators,
or calcium channel blockers. Symptoms typically abate upon treatment of the
primary cause. In some patients, recurrent orthostatic symptoms may occur in the
absence of true orthostatic hypotension, and may be associated with an excessive
increase in heart rate during upright positioning. This condition is known as
postural orthostatic tachycardia syndrome (POTS). It is a clinical syndrome

usually characterized by (1) frequent symptoms that occur with standing, such as
lightheadedness, blurred vision, palpitations, tremor, generalized weakness,
exercise intolerance, and fatigue; (2) an increase in heart rate of ≥30 beats per
minute (bpm) when moving from a recumbent to a standing position (or ≥40 bpm
in individuals 12 to 19 years of age); and (3) the absence of orthostatic
hypotension (as defined by >20 mm Hg drop in systolic BP). There are two forms
of POTS, and both forms are observed more often in females than males. In the
first and more common type, persistent tachycardia, associated with fatigue,
exercise intolerance, and palpitations, is present while the patient assumes an
upright position. This condition may occur after a viral illness, trauma, or surgery.
The second or central form of POTS is often associated with migraines, tremor,
and excessive sweating. Presyncope is a more common symptom than syncope in
patients with POTS; however, POTS and vasovagal syncope are not mutually
exclusive. The clinician should make careful use of the history and physical
examination to distinguish between patients with suspected POTS and those with
other disorders. The anxiety and somatic hypervigilance sometimes attributed to
patients with POTS may be associated with other disorders such as migraine or
mood disorders. Similarly, fatigue and weakness could be signs of another
systemic illness.

Dysautonomia
In rare cases, a child may exhibit an inadequate vasoconstriction in response to
postural changes that would normally demand sympathetic nervous system
activation. In such patients, the heart rate may not increase appropriately with
standing, and BP may be labile, leading to syncope.

Drugs and Toxins
Medications that decrease cardiac output, such as barbiturates and tricyclic
antidepressants, may cause syncope. Recreational drugs such as cocaine, alcohol,

inhalants, and opiates may cause a loss of consciousness, though not true
syncope. Carbon monoxide is an important environmental toxin to consider in
applicable clinical scenarios.

CLINICAL EVALUATION
In children who present with syncope, the history usually offers key information
to assist the clinician in making the diagnosis. However, objective findings are
often absent, which can pose a challenge. An orderly approach to the evaluation
of pediatric syncope is essential and consists of a meticulous history and physical
examination, a 12-lead ECG, and the use of additional testing only in selected
patients ( Fig. 76.1 ). Extensive testing is usually unnecessary.
Determine the sequence of events leading up to the syncopal event and the
position of the patient’s body just before the syncope. It may be necessary to
obtain information from eyewitnesses, as the patient may not recollect all aspects
of the event. Search for precipitating factors, such as exercise, loud noise or a
startle response, rapid postural changes, anxiety or emotional stress, trauma,
dehydration, medication intake, or recreational drug use. Exertion-related
syncope suggests a cardiac cause. Sudden loud sounds or arousal may precipitate
syncope in patients with long QT interval syndromes. In situational syncope,
some specific activities such as stretching, arising suddenly from a recumbent
position, swallowing, coughing, hair brushing, voiding, or defecation may be
associated with loss of consciousness.