Syncope

Question 1

What is syncope?

Answer 1

Syncope is a sudden, brief loss of consciousness associated with loss of postural tone from which recovery is spontaneous

Question 2

What percentage of children are likely to experience an episode of syncope by end of adolescense?

Answer 2

Up to 15 percent

Question 3

What are the causes of syncope in children and adolescents?

Answer 3

Question 4

What two broad categories of pathology account for cardiac causes of syncope?

Answer 4

Life-threatening cardiac conditions cause syncope as the result of an abrupt decrease in cardiac output, either from an arrhythmia or related to structural heart disease

Question 5

How might syncope occur with regards to primary electrical disturbances and structural pathology?

Answer 5

• Primary electrical disturbances can occur in patients with structurally normal hearts. These arrhythmias may be related to exogenous factors (ie, a metabolic disturbance or drug ingestion) or an inherited electrophysiologic abnormality (ie, congenital long QT syndrome).
• Arrhythmias may result from structural heart disease, such as myocarditis or repaired congenital heart disease.
• Aortic stenosis and hypertrophic cardiomyopathy (HCM) and the resulting left ventricular outflow tract obstruction and compromised systemic blood flow, particularly during exercise, can cause syncope

Question 6

Which is more common - primary electrical disturbances vs. structural heart disease, as a cause of syncope?

Answer 6

structural heart lesions

Question 7

What is Long QT syndrome

Answer 7

• Disorder of myocardial repolarization characterized by prolongation of QT interval on ECG and increased risk of sudden death due to potential to degenerate into polymorphic ventricular tachycardia
• Long QT syndrome may be acquired or congenital.

Question 8

What drug therapy or electrolyte disturbance might cause acquired long QT?

Answer 8

Patients with eating disorders may have prolongation of the QT interval, as well as other ECG abnormalities. These changes typically normalize during nutritional rehabilitation.

Question 9

What two clinical phenotypes of congenital long QT are there?

Answer 9

• more common autosomal dominant form, the Romano-Ward syndrome, has a purely cardiac phenotype.
• The autosomal recessive form, the Jervell and Lange-Nielsen syndrome, is associated with LQTS and sensorineural deafness and a more malignant clinical course.
• Causes of acquired LQTS (ie, drugs, hypokalemia, and hypomagnesemia) can also precipitate ventricular arrhythmia in patients with congenital LQTS.

Question 10

What is Brugada syndrome?

Answer 10

• Patients with Brugada syndrome (BS) have a characteristic pattern on electrocardiogram (ECG) and an increased risk of sudden death.
• Sudden cardiac death may be the first and only clinical event in BS, occurring in as many as one-third of patients.
• Arrhythmic events generally occur between ages 22 and 65, although cases in children as young as three years of age have been reported
• Arrhythmic events in children with BS are uncommon, but may be more likely during febrile episodes

Question 11

What ECG findings to you expect in Brugada syndrome?

Answer 11

Typical ECG findings include pseudo-right bundle branch block and persistent ST segment elevation in leads V1 to V3. ECG changes may be transient in some patients.

Question 12

What drugs can induce a Brugada-like ECG?

Answer 12

Question 13

What is Catecholaminergic polymorphic VT?

Answer 13

• Children with catecholaminergic polymorphic ventricular tachycardia (VT) may present during childhood or adolescence with syncope as the result of VT or ventricular fibrillation (VF) induced by emotional or physical stress.
• Familial and sporadic cases occur and several genetic patterns have been described.
• Arrhythmias typically cannot be induced at electrophysiologic study but can be provoked by exercise testing or IV catecholamine infusion.

Question 14

Describe congenital short QT syndrome

Answer 14

3 genetic mutations have been described. Correct QT (QTc) in this syndrome is <0.3s. Congenital short QT is much less common than long QT syndrome

Question 15

What structural heart diseases can be associated with sudden cardiac death?

Answer 15

Repaired defects such as TOF, aortic stenosis, and transposition of great arteries are associated with sudden cardiac death

Children with CHD, including those who have had surgical palliation or correction are at increased risk for malignant arrhythmias

Question 16

What is hypertrophic cardiomyopathy?

Answer 16

Relatively common AD disorder (1 in 500 in the general population) that is characterized by asymmetric hypertrophy of the left ventricle. Patients may experience exertional syncope. HCM is the most common cause of sudden death during exercise

Question 17

What mechnism/s results in inadequate cardiac output in hypertrophic cardiomyopathy?

Answer 17

left ventricular outflow obstruction, ischemia during exertion, and arrhythmia

Question 18

How might coronary artery abnormalities present with syncope or sudden cardiac death?

Answer 18

Congenital abnormalities in the origin of the coronary arteries may present as syncope or sudden death in teenagers and young adults. An abnormally located coronary artery (as an example, between the aorta and pulmonary artery) may become compressed during exercise, resulting in myocardial ischemia and syncope or sudden death

Question 19

In what ages does arrhythmogenic RV cardiomyopathy typically present?

Answer 19

Presentation is most common between the ages of 10 and 50, with a mean age at diagnosis of approximately 30 years

Question 20

What is heat syncope?

Answer 20

• occurs when an athlete is unable to stand or walk due to lightheadedness or syncope. This form of syncope usually occurs immediately after completing a race or workout and is commonly observed at distance running events.
• cause: abrupt decrease in venous return once that athlete completes the event. Given the typical degree of vasodilatation seen with prolonged exertion, the sudden loss of the pressure exerted by the skeletal muscles on the vasculature leads to a precipitous decline in venous return, as well as postural tone, causing the athlete to collapse

Question 21

What is heat stroke?

Answer 21

Heat stroke may also cause collapse in association with progressive altered mental status, seizures, or coma. Heat stroke is differentiated from other causes of syncope by an elevated core temperature, tachypnea, tachycardia with hypotension, nausea, vomiting, and diarrhea

Question 22

Can anaphylaxis cause syncope?

Answer 22

Yes. Anaphylaxis can occasionally involve syncope and loss of consciousness, and patients or caregivers sometime overlook or forget the more subtle, earlier symptoms, such as flushing, itching, hives, cough and bronchospasm, or abdominal cramping. In addition, these less dramatic symptoms may have resolved by the time the patient is evaluated

Question 23

How often is vasovagal syncope the cause of syncope in the emergency department in children?

Answer 23

Vasovagal syncope (also known as neurocardiogenic, reflex, or situational syncope, and common fainting) is the most common cause of syncope among children, accounting for 50 percent or more of cases presenting to the emergency department

Question 24

What are the typical clinical features of vasovagal syncope?

Answer 24

Typical clinical features are a precipitating event and a prodrome.

●Precipitating events include standing or stress (physical or emotional), although reflex precipitants (such as swallowing, hair grooming, and micturition) have been reported.

●Patients typically describe a prodrome, which may include lightheadedness, dizziness, visual changes (decrease acuity, tunnel vision, or double vision), nausea, pallor, and diaphoresis.

Question 25

What is the underlying mechanism behind vasovagal syncope?

Answer 25

exaggeration of reflex-mediated alterations in vasomotor tone and heart rate normally responsible for maintaining blood pressure

Question 26

What are breath holding spells?

Answer 26

Breath holding spells typically occur in children 6 months to 24 months of age and are triggered by an emotional insult, such as pain, anger, or fear

Question 27

What are the two main types of breath holding spells?

Answer 27

The spells may be cyanotic or pallid. The cyanotic variety begins with breath holding, followed by cyanosis and loss of consciousness. In a pallid spell, loss of consciousness occurs before breath holding. Brief posturing or tonic-clonic motor activity may occur with either cyanotic or pallid spells

Question 28

What is the typical clinical course of breath holding spells?

Answer 28

generally benign. Spells typically stop by five years of age. Some children go on to develop vasovagal syncope. Breath holding spells may represent a variation of vasovagal (neurocardiogenic) syncope. Autonomic dysfunction appears to play a role in both cyanotic and pallid breath holding spells

Question 29

What is orthostatic hypotension? How does orthostatic hypotension occur?

Answer 29

Syncope that occurs with postural change may be related to an abrupt drop in blood pressure. Orthostatic hypotension can result from volume depletion (hemorrhage or dehydration), pregnancy (venous pooling), anemia, anorexia nervosa, and medications that alter vasomotor tone and heart rate such as calcium channel blockers, vasodilators, phenothiazines, and diuretics.

Question 30

What toxins might cause syncope?

Answer 30

Intoxication may present as syncope, either from decreased cardiac output (barbiturates, tricyclic antidepressants, and phenothiazines) or sudden loss of consciousness (cocaine, alcohol, marijuana, inhalants, and opiates). Some of these agents (such as tricyclic antidepressants and cocaine) may also cause life-threatening syncope.

Severe carbon monoxide poisoning can cause syncope as the result of QT prolongation. Other clinical features (such as history of exposure, headache, and nausea) may suggest carbon monoxide poisoning

Question 31

How might hypoglycaemia present as syncope?

Answer 31

Hypoglycemia is frequently cited as a cause of syncope; however, outside of the insulin-dependent diabetic it is an uncommon cause of syncope. Before the onset of syncope, patients with hypoglycemia frequently report feeling weak, hungry, and sweaty. As blood glucose continues to fall they may exhibit agitation, confusion, and finally altered mental status

Question 32

What are two non-life threatening arrhythmias that can cause syncope? (not ventricular origin)

Answer 32

Supraventricular tachycardia – Syncope is an unusual presentation of supraventricular tachycardia. Accessory pathway mediated tachycardia and atrioventricular nodal reentry tachycardia are relatively common arrhythmias, but rarely present with syncope.

Bradycardia – In children, syncope caused by isolated bradycardia is unusual. Causes of symptomatic bradycardia in children are corrective surgery for congenital heart disease, hypervagotonia, hypothyroidism, and medications (such as beta adrenergic blockers)

Question 33

What is POTS? In what percentage of POTS patients does syncope occur in?

Answer 33

Postural tachycardia syndrome (POTS) – POTS is defined as a form of orthostatic intolerance characterized by an excessive increase in heart rate (>40 bpm over baseline in children and adolescents and >30 bpm or to >120 bpm in adults) that occurs on standing without arterial hypotension. POTS is a common disorder among teenage girls that typically manifests as palpitations, anxiety, dizziness, and tremulousness. However, syncope may occur in up to 40 percent of patients.

Question 34

What are some conditions that can mimic syncope?

Answer 34

Seizures

Migraine syndrome

Hysteria/conversion disorder

Hyperventilation

Itnention strangulation activities (e.g. the choking game)

Narcolepsy

Question 35

How do seizures differ from syncope?

Answer 35

A seizure typically includes loss of consciousness and postural tone. However, seizures usually last longer than syncopal episodes and include features such as an aura, prolonged tonic clonic activity, and/or the presence of a postictal phase

Question 36

How might a migraine syndrome differ from syncope? How do basilar migraines present?

Answer 36

Migraine syndromes, particularly basilar migraines, may present with symptoms that are similar to syncope such as loss of conscious, ataxia, or vertigo. Loss of consciousness is usually longer than several seconds. In addition, patients generally have other neurologic symptoms, as well as headache and nausea

Question 37

How does hysteria/conversion disorder differ from syncope?

Answer 37

Hysteria/conversion disorder is most common in adolescent patients. These events typically occur in the presence of an audience, lack hemodynamic (heart rate, blood pressure) or autonomic (sweating, pallor) changes, may be prolonged, and rarely result in injury. Patients typically describe the event in a calm indifferent manner. They may disclose details of the event that indicate no loss of consciousness.

Question 38

How does narcolepsy differ from syncope?

Answer 38

Patients with narcolepsy may have cataplexy, emotionally-triggered muscle weakness with collapse that may mimic syncope. However, they also have other features that indicate a disorder of sleep-wake control such as chronic daytime sleepiness, hypnagogic hallucinations (vivid, often frightening visual, tactile, or auditory hallucinations occurring as the patient falls asleep), or sleep paralysis (inability to move for one or two minutes immediately after awakening.

Question 39

What are the broad categories of causes of syncope? How often do each of these occur as a cause of syncope?

Answer 39

• Syncope is a symptom that can be classified according to the underlying cause: autonomic (eg, vasovagal [neurocardiogenic], situational, and orthostatic syndromes)
• cardiac
• metabolic
• or a condition that mimics syncope.
• autonomic forms comprise up to 80 percent of cases.
• Neurologic etiologies, such as seizures or migraine headaches, are present in up to 20 percent of patients.
• Life-threatening conditions such as hypoglycemia, heat illness, anaphylaxis, cardiac arrhythmia, or structural cardiac disease are relatively rare but occur frequently enough (1 to 2 percent of children) to warrant diagnostic consideration.

Question 40

What are key findings that suggest possible cardiac syncope in children and adolescents?

Answer 40

Question 41

What are key aspects of preceding events or precipitating factors in syncope evaluation?

Answer 41

• Exercise: Syncope during physical exertion is concerning for cardiac cause. If occurs after exertion it can be cardiac, but vasovagal syncope is also common
• Acute arousal or loud noise: Some triggers are associated with specific primary electrical disturbances. As an example, for patients with long QT syndrome, the triggers for the most common genotypes are acute arousal (or startle) and auditory stimuli (ie, a fire alarm)
• Postural changes: Children with a vasovagal cause of syncope typically have been upright (prolonged standing or taking a hot shower) or changed position (eg, went quickly from lying or sitting to standing) just prior to the event
• Pain or emotional stress: A trigger (such as pain [eg, blood draw or intramuscular injection] or emotional stress) may be the precipitant in some cases of vasovagal syncope. However, rarely, children with familial catecholaminergic polymorphic ventricular tachycardia can also develop arrhythmias in association with emotional or physical stress

Question 42

What are key history features in terms of description of event when evaluating paediatric syncope?

Answer 42

• Palpitations or chest pain prior to or during a syncopal event are concerning for a cardiac etiology. These symptoms occasionally occur with vasovagal syncope as well.
• Loss of consciousness followed by abnormal motor activity (ie, tonic clonic movement or posturing) can occur at the end of a syncopal event, and most often correlates with neurocardiac syncope although arrhythmia should also be suspected. The duration of such activity is usually brief, and recovery is rapid.
• Motor activity that starts at the beginning of the event and is followed by a prolonged recovery time is more consistent with a seizure.
• Patients with orthostatic hypotension or vasovagal syncope may report that symptoms recurred when they tried to sit up immediately after the initial syncopal event.
• Children with vasovagal (neurocardiogenic) syncope frequently report prodromal symptoms that include dizziness, lightheadedness, sweating, nausea, weakness, and visual changes (blurred vision, tunnel vision, slow visual loss).
• Children with vasovagal syncope may experience fatigue for hours after the event.

Question 43

What features on past medical history are concerning for cardiac cause of syncope?

Answer 43

• CHD (corrected or uncorrected)
• Acquired heart disease with residual cardiac dysfunction
  
  • Kawasaki
  • RHD
  • Myocarditis
• Arrhythmia

Question 44

What are concerning features on family history when evaluating syncope?

Answer 44

A family history in parents, siblings, grandparents or other first or second degree relatives of any of the following increases the concern for a cardiac etiology:

●Early cardiac death (<50 years of age)

●Sudden deaths including unexplained accidents involving a single motor vehicle or drowning

●Known arrhythmia (eg, long or short QT syndromes or Brugada syndrome)

●Familial cardiomyopathy

A family history of vasovagal syncope may be present in up to 90 percent of children with this condition and can be reassuring if no other red flag clinical findings are present

Question 45

What are characteristic findings in aortic stenosis on exam?

Answer 45

systolic ejection murmur and ejection click

Question 46

What are characteristic findings in patients with coarctation?

Answer 46

In patients with coarctation, a difference in upper and lower extremity systolic blood pressures 20 mmHg or more (arm >leg) may be present and may also be suggested by a difference in pulse intensity between radial or brachial and femoral pulses. Thus, in patients with systemic hypertension or with findings suggesting aortic stenosis (sometimes associated with coarctation), four extremity blood pressures should be measured

Question 47

What are some characteristic exam findings of hypertrophic cardiomyopathy?

Answer 47

In patients with hypertrophic cardiomyopathy, maneuvers that affect the degree of obstruction cause a change in murmur intensity.

• An increase in intensity, due to enhancement of obstruction, is seen with the assumption of an upright posture from a squatting, sitting, or supine position, or with the Valsalva maneuver, during the more forceful contraction that follows the compensatory pause after a premature ventricular complex/contraction
• A decrease in intensity, due to attenuation of obstruction, is heard after going from a standing to a sitting or squatting position, with sustained gripping of the hand, and following passive elevation of the legs.
• The classic murmur of hypertrophic cardiomyopathy is an outflow murmur that decreases in intensity with increased venous return to the heart (during a Valsalva maneuver or squatting).

Question 48

What are some characteristic findings of heart failure on examination?

Answer 48

Signs of heart failure (ie, rales, a gallop, and/or hepatomegaly) are consistent with cardiac disease.

Question 49

What are key ECG findings which should be noted in syncope patients?

Answer 49

In patients with syncope, incidental findings occur in approximately 10 percent of ECGs and abnormal findings caused by important cardiac pathology are seen in <1 percent of cases.

ECG findings that should be noted include:

●Nonsinus rhythms, excessive bradycardia, atrioventricular block, and abnormal age-appropriate intervals of the cardiac cycle (hand calculated)

●Signs of myocardial injury

●A corrected QT interval (hand calculated: QTc = QT interval ÷ √RR interval [in sec]), with attention to T wave morphology

●Findings suggestive of Brugada syndrome, including pseudo-right bundle branch block (RBBB) and persistent ST segment elevation in leads V1 to V3

●Delta wave or other findings suggestive of ventricular preexcitation (Wolff-Parkinson-White syndrome)

●Several abnormalities, most notably epsilon waves, may be present in patients with arrhythmogenic right ventricular cardiomyopathy (ARVC)

●Findings indicative of hypertrophic cardiomyopathy including left axis deviation; prominent abnormal Q waves, especially inferior leads (II, III, aVF); left atrial or bilateral atrial enlargement, especially with left ventricular hypertrophy; and/or deeply inverted T waves (“giant negative T waves”) in the mid-precordial leads (V2 through V4)

●Ventricular hypertrophy and strain patterns suggesting heart failure

Question 50

What are some laboratory tests which may be useful in evaluation of syncope?

Answer 50

●Rapid blood glucose determination for children who present immediately after the episode

●Hematocrit for children who are at risk for anemia, including menstruating females

●Urine pregnancy tests in post menarcheal females

●Urine toxicology screens for drugs of abuse in patients with altered metal status

Question 51

What studies (other than blood tests) may be warranted in syncope evaluation?

Answer 51

TTE - strongly suspect cardiac cause

Ambulatory ECG - low yield for children and adolescents with isolated syncope but may be useful in syncopal pediatric patients with palpitations, frequent syncopal episodes, or exertional syncope

Exercise ECG or stress testing - potentially helpful to elicit characteristic changes in QT intervals in patients with long QT syndrome or arrhythmias in those with catecholaminergic polymorphic ventricular tachycardia

Tilt table testing - POTS and vasovagal syncope

Neuroimaging - unusual child or adolescent with syncope and focal neurologic deficits, persistently altered mental status, or a significant head injury as the result of the syncopal episode

EEG - appropriate for patients with syncope accompanied by prolonged loss of consciousness, seizure activity, and a postictal phase. However, epilepsy is a rare cause of syncope

Question 52

What are some ECG features of LVH?

Answer 52

Question 53

What abnormal ECG findings should be looked for in syncope evaluation?

Answer 53

●A prolonged QT interval is consistent with the diagnosis of acquired or congenital long QT syndrome

●A short QT interval (QTc ≤0.30 sec) suggests congenital short QT syndrome.

●Findings suggestive of Brugada syndrome, including pseudo-RBBB and persistent ST segment elevation in leads V1 to V3

●Findings suggestive of preexcitation syndrome indicate the diagnosis of Wolff-Parkinson-White syndrome

●Several abnormalities, most notably epsilon waves, may be present in patients with ARVC. ARVC is a progressive disorder, however, and these findings may not be present in young patients.

Other diagnoses that may be suggested by ECG findings include the following:

●Signs of left ventricular hypertrophy or strain are consistent with hypertrophic cardiomyopathy

●Right ventricular hypertrophy can occur with tetralogy of Fallot or primary pulmonary hypertension

●A pattern of myocardial injury may be seen with congenital coronary artery abnormalities.

●Bradyarrhythmias such as complete AV block can be identified on ECG

Question 54

What abrnormal cardiac exam findings are red flags in syncope evaluation?

Answer 54

Children with known congenital heart disease may have abnormalities consistent with their diagnosis and/or surgical repair. Findings such as a systolic ejection murmur with ejection click (valvar aortic stenosis) or an outflow murmur that decreases in intensity with increased venous return to the heart during squatting or a Valsalva maneuver (hypertrophic cardiomyopathy) may indicate undiagnosed structural heart disease

Question 55

Vasovagal syncope is typically diagnosed by presence of consistent clinical features and the exclusion of other causes, including:

Answer 55

●Abnormalities identified by laboratory tests that may explain syncope include hypoglycemia, pregnancy, and anemia.

●Orthostatic hypotension is the likely etiology for syncope in patients with postural changes in heart rate and blood pressure and a normal ECG. The underlying cause of these changes (such as volume depletion or medications) must be identified and treated.

Although orthostatic hypotension has also been associated with long QT syndrome, the ECG is abnormal in the vast majority of cases.

●A toxic exposure may be suggested by history (such as symptoms among other household members with carbon monoxide poisoning), blood or exhaled ethanol level, or a rapid urine toxicologic screen for drugs of abuse.

●A history of an abnormal respiratory pattern prior to the syncopal episode suggests hyperventilation or breath holding as the etiology.

• Patients with hyperventilation are frequently adolescents experiencing some type of emotional stress. They may describe additional symptoms such as chest pain, lightheadedness, paresthesias, and visual disturbances.
• Breath holding spells occur in younger children (typically 6 to 24 months of age). Loss of consciousness develops in association with breath holding. A cardiac evaluation is indicated for children with a family history of syncope or sudden death or with episodes that are prolonged, frequent, or precipitated by startle or other nontraumatic stimuli.

●Patients with syncope related to hysteria (somatization disorder) or a conversion disorder are commonly seen in adolescents. Expected physiologic signs (such as sweating, pallor, or changes in heart rate and blood pressure) are often absent. In addition, patients may disclose details of the event that indicate no loss of consciousness and generally suffer no injury during collapse.

●Patients who engage in the choking game purposely attempt self-strangulation or allow strangulation by another person with the hands or a ligature to produce a euphoric state caused by cerebral hypoxia. The plan is to release the pressure just before loss of consciousness, but failure to do so can result in death, particularly when the game is played alone using ligatures.

●In the emergency evaluation of a child with syncope, a diagnosis of vasovagal (neurocardiogenic) syncope is typically a diagnosis of exclusion for patients with consistent clinical features (such as precipitating events and a prodrome). Children with concerning manifestations such as absence of a significant prodrome, associated palpitations or chest pain, or a family history of syncope or sudden death may require further cardiac evaluation.