OVERVIEW: What every practitioner needs to know

Are you sure your patient has vasovagal syncope? What are the typical findings for this disease?

Syncope is a temporary loss of consciousness and tone. The patient falls to the ground if not supported, with vasodepressor syncope, the episodes are usually of sudden onset and brief. There are many causes of syncope, but the majority of pediatric syncopal episodes are benign. This chapter focuses on vasovagal (or vasodepressor syncope).

The most common symptoms of vasovagal (or vasodepressor syncope) are dizziness, light-headedness, and pallor. The next most common symptoms of vasodepressor syncope are related to autonomic activity and include nausea, perspiration, tachycardia, and anxiety.

The main concerns regarding syncope are:

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1. Establishing the cause and ruling out other pathological causes.

2. Ensuring safety and avoiding injury to self and others with a recurrent episode.

History and Physical Examination

A history that suggests vasovagal syncope should be obtained. Questions asked include:

Did the patient have any preceding symptoms or prodrome? Was the patient standing for a prolonged period of time before the syncopal event? Was the patient standing up quickly after prolonged bed rest? Was there associated pain or symptoms? Was the patient in a warm environment? Was the patient in a crowded room? Was the patient having a blood test or witnessing a blood draw? Was the patient in a stressful academic testing environment or anxious?

Other causes of syncope must be considered and ruled out prior to establishing a diagnosis of vasovagal syncope. These are discussed below.


What was the patient’s activity at the time of syncope? Symptoms with exercise are ominous and are suggestive of other causes of syncope, such as arrhythmias, cardiomyopathy, or left ventricular outflow tract obstruction. Syncope with exercise has to be evaluated completely due to the potential risk of a significant recurrence. Episodes with exercise should be evaluated thoroughly before resuming activity.

Had the patient been fasting? Was there sufficient fluid intake on the day of the event?

The description of the patient’s appearance during the episode by any accompanying witnesses. Was the patient pale and/or diaphoretic? How did the syncopal event develop and what was the description of the event by witnesses? Did the patient slump to the ground or did the patient hurt him or herself in the fall to the ground?

How did the patient recover? Did the patient need a painful stimulus or a sternal rub to wake up? Did the patient require any resuscitation? Was there postictal drowsiness?

Has the patient had any intercurrent illness accompanied by fever or dehydration?

Have there been any previous syncopal episodes?

Are there any other signs or symptoms, such as muscular weakness?

Are there associated symptoms, such as seizure activity or twitching, incontinence, or headaches?

Is there a past medical history that may suggest a metabolic disorder?

Is there a possibility that the patient may be pregnant?

Is there any recent weight loss to suggest thyrotoxicosis, eating disorder, use of stimulants?

Is the patient on any medication? For example, is the patient on stimulants? Is the patient on a diuretic, beta blocker, or a medication that prolongs the QT interval?

Is there a history of drugs or alcohol use?

Is there a past medical history to include congenital heart disease, which may predispose to arrhythmias and/or sudden death?

Is there a family history of familial dysautonomia?

Is there a family history of hypertension? In those families, a low salt diet may be the cause of vasovagal syncope in a child or teenager.

Is there a family history that may suggest a cardiac cause? This should include questioning about any history of cardiac disease, cardiomyopathy, arrhythmias, need for pacemaker or implantable cardiac defibrillators, and sudden or unexplained death. A family history of congenital deafness raises the possibility of prolonged QTc (Jervell Lang Nielson syndrome). A family history of seizures should also be sought.

Physical Examination

It is important to recognize that the physical examination may not reflect any orthostatic changes if the patient is not seen soon after the episode of syncope. The purpose of the physical examination is to evaluate for findings suggestive of orthostasis and intravascular depletion and more importantly, to evaluate for other possible causes of syncope.

Physical examination:

The blood pressure should be obtained in the supine and standing position with the blood pressure taken after the patient has been standing 10 minutes. The blood pressure should be stable after standing for 10 minutes. However in vasodepressor syncope there may be a persistent significant change in blood pressure. A normal cardiac examination and a decrease in blood pressure with an increase in heart rate support the diagnosis of vasodepressor syncope.

An abnormal cardiac examination or atypical features raise the possibility and concern of a cardiac cause, and further evaluation is necessary.

  • Evaluate the point of maximum impulse (PMI) for cardiomegaly.
  • Evaluate for a hyperactive precordium.
  • Evaluate heart sounds and murmurs.
  • Is there any evidence of heart failure such as a third or fourth heart sound, or pulses paradoxus?
  • Is there a carotid bruit?
  • Evaluate four-limb blood pressure and pulses to rule out a coarctation of the aorta.
  • Is there an abnormal second heart sound and/or click that may suggest pulmonary hypertension?

Signs of heart failure such as pulmonary edema, jugular venous distension, or crackles should be noted.

A complete neurological examination should be performed, as neurological disease may present with a syncopal episode. Is there evidence of weakness or asymmetry, signs of upper motor neuron disease, cranial nerve abnormalities, signs of raised intracranial pressure, or evidence to suggest a seizure has occurred, e.g., tongue biting? Are there signs of peripheral neuropathy or signs of exposure to toxins?

Are there needle marks to suggest drug use or raising the possibility of infective endocarditis?

If the patient presents to the emergency room with syncope, are there signs of diabetes mellitus or evidence of insulin administration? Are there signs of trauma from the syncopal episode? Trauma during a syncopal episode cannot be ignored and suggests that the syncope is not benign.

A complete physical and cardiac examination should be performed with an emphasis on: Vital signs, including heart rate for bradycardia or tachycardia, evaluation of possible abnormal rhythm, abnormal temperature to suggest an infectious process, blood pressure and respiratory rate. An increased respiratory rate may suggest a cardiac cause such as poor cardiac output secondary to a cardiomyopathy.

An anxious patient may also have signs suggestive of hyperventilation. The pulse amplitude may be diminished, suggesting poor cardiac output or aortic obstruction or increased, suggesting aortic regurgitation or high output failure.

Oxygen saturation to evaluate for possible hypoxia is recommended.

What other diseases/conditions share some of these symptoms?

Although vasodepressor and orthostatic syncope are the most common causes of syncope, there are many other causes that have to be considered in the differential diagnosis. These include cardiac and non-cardiac syncope.

Cardiac syncope: may be due to congenital or acquired cardiac disease or an arrhythmia. A thorough history may help differentiate the cause of syncope. The cardiac diagnoses that should be ruled out include aortic stenosis, cardiomyopathy, or other obstructive lesions. Arrhythmias should also be considered and ruled out if the history is suspicious or not typical for vasodepressor syncope. Arrhythmias can also be a cause in patients with a history of cardiac surgery. Patients may have other associated symptoms, such as shortness of breath, exercise intolerance, chest pain, or palpitations.

Cardiac causes include:

  • Left ventricular outflow tract or inlet obstruction (aortic stenosis, sub-aortic stenosis, coarctation of the aorta, mitral stenosis, cor triatriatum).
  • Right ventricular outflow tract obstruction (pulmonary stenosis)
  • Cardiomypathy (hypertrophic, restrictive or dilated).
  • Pulmonary hypertension.
  • Sick sinus syndrome
  • Atrial arrhythmias
  • Ventricular arrhythmias
  • Prolonged QT interval
  • Wolff-Parkinson-White syndrome
  • Heart block

Neurological diseases can also present with reported syncope. The patient may have absence seizures or a short epileptic seizure that may be described as a syncopal event. Remember that a seizure may be the presenting finding of a patient with prolonged QTc and arrhythmia, and therefore an electrocardiogram should be performed.

Hypoglycemia and other metabolic disorders or electrolyte abnormalities may also cause syncope and should be considered in the differential. A diabetic patient with hypoglycemia or hyperglycemia can present with loss of consciousness. This is usually not a brief episode and requires therapy. Electrolyte abnormalities may be associated with dehydration and intravascular depletion presenting with orthostatic syncope, but may also cause arrhythmias and more ominous causes of syncope.

As mentioned, although vasodepressor syncope is the most frequent cause of syncope, other causes should be considered in the evaluation, and therefore a thorough history and physical is recommended.

What caused this disease to develop at this time?

Vasodepressor syncope develops as a result of:

Standing, and with the normal physiological response of vascular constriction there is a slight appropriate increase in heart rate. If this does not occur, there is decreased blood pressure and cerebral hypoperfusion that result in syncope. This is a normal protective mechanism. Predisposing factors include decreased fluid intake, dehydration, exposure to warm temperatures, familial dysautonomia.

A stimulus such as a blood draw or watching a blood draw may interrupt the vasomotor pathway. This leads to vasodilation with resultant hypotension and cerebral hypoperfusion.

A family history is seen in about 20% of patients with vasovagal syncope.

What laboratory studies should you request to help confirm the diagnosis? How should you interpret the results?

The clinical features are noted and the description of the symptoms may provide the diagnosis in the majority of patients. Further testing is pursued to evaluate for the possible rare but potentially ominous causes, including the risk for sudden death.

The evaluation will vary depending on the features, and on whether the patient is presenting for examination immediately or soon after an episode, or if the patient presents in clinic at a later time. In all cases, an EKG to evaluate the QTc is essential

In patients who present immediately after an episode, an evaluation should include:

  • Orthostatic blood pressure and heart rate measurement.
  • Electrocardiogram to evaluate the conduction system, the QT interval and for evidence of ventricle hypertrophy or atrial enlargement. The QTc interval should be calculated in every patient presenting with syncope or near syncope.
  • A metabolic evaluation of the glucose level and electrolytes, as this may identify dehydration or hypoglycemia.
  • Pregnancy should be considered in all adolescent females, and a urine HCG should be tested.

In patients who present to clinic for evaluation of a remote episode of syncope, the evaluation should include an electrocardiogram, even when the history is suggestive of vasovagal syncope. If the history is typical and strongly suggests vasovagal syncope and the electrocardiogram is normal, no further testing is usually performed unless symptoms are recurrent.

However, in patients with atypical or concerning features, an abnormal physical examination, recurrence of symptoms , a cardiac family history, or any concerning signs or symptoms, further testing should be performed as appropriate and may include:

  • An echocardiogram to evaluate the cardiac systolic and diastolic function, ventricle hypertrophy and for possible anatomical defects and the coronary anatomy.
  • A 24-hour Holter monitor if the patient has accompanying palpitations or a suspicion of arrhythmias, specifically, if the symptoms occur almost daily.
  • A month-long loop event monitor to evaluate for arrhythmias if the symptoms occur less frequently
  • A stress test if symptoms occur with exertion.
  • Pregnancy test.
  • Neurological evaluation with possible EEG, cerebral MRI or magnetic resonance angiography (MRA).
  • Metabolic evaluation to include electrolytes, glucose and HbA1c.
  • Blood work to evaluate anemia, polycythemia, blood dyscrasia, or toxicity.
  • A tilt table test is performed rarely to produce symptoms and determine the cause of the syncope.
  • Rarely, an implantable loop recorder is used to evaluate for arrhythmias; the use of this has recently increased.
  • Imaging with a cardiac MRI to evaluate for possible arrhythmogenic right ventricular (RV) dysplasia if the patient has a history suggestive of ventricular arrhythmias.
  • Rarely, electrophysiology testing may be recommended to induce an arrhyhmia, especially if symptoms occurred with exercise.

Would imaging studies be helpful? If so, which ones?

If the history is atypical for vasodepressor or vasovagal syncope or there is an abnormal physical finding or family history, further evaluation is recommended. This evaluation should include imaging to evaluate for cardiac or neurological disease and may include: an echocardiogram, a chest x-ray, a cardiac MRI / MRA or a cerebral CT or MRI. This increases the cost of the evaluation but may be necessary as determined by the clinical features of the episode.

If you are able to confirm that the patient has syncope, what treatment should be initiated?

If an episode of syncope is witnessed, the patient should be placed in a Trendelenburg position (elevated leg position). If a seizure is likely, the face should be turned to avoid possible aspiration. Resuscitated measures as appropriate are required.

Evaluation and diagnosis are essential to management. If syncope is caused by an arrhythmia, congenital heart defect, seizure, or a metabolic disease, therapy is directed towards the management of this underlying cause to prevent recurrence.

This section will emphasize management of patients with vasovagal orthostatic syncope. For a patient who presents soon after an episode and has signs of orthostasis, intravenous or oral hydration is recommended. If vasodepressor syncope is a likely diagnosis, treatment is supportive. Increasing fluid with water and electrolyte drinks and liberalizing salt intake is usually sufficient . Caffeine avoidance is recommended. Counseling regarding avoidance of excessive heat and awareness of the prodrome may prevent future episodes.

The majority of patients with first-time syncope do not present for medical attention. The pediatrician may become aware of the episode on routine evaluation after a period of time.

Safety precautions should be recommended and emphasized, such as avoidance of driving, climbing ladders and avoidance of swimming unattended.

If symptoms of vasovagal syncope continue after several weeks of increasing fluid and liberalizing salt intake, medical therapy may be initiated. The first line is usually fludrocortisone acetate that has strong mineralocorticoid properties and leads to sodium retention. Beta blockers are occasionally used to decrease the catecholamine surge; however, if there is bradycardia this may worsen syncope. Side effects in teenagers include fatigue and depression. A peripheral alpha-1 agonist (such as midodrine) may control symptoms; side effects include vasodilation, confusion, dry mouth, and anxiety. A selective serotonin reuptake inhibitor, such as sertraline or paroxetine, has occasionally been used. This is of value in patients with accompanying depression or if other forms of therapy have been unsuccessful.

What are the adverse effects associated with each treatment option?


What are the possible outcomes of vasovagal syncope?

Treatment for vasodepressor syncope with water and electrolyte drinks usually controls the symptoms.

If the diagnosis is vasodepressor syncope, the episodes are usually benign if safety precautions (not driving and not swimming unattended) are followed. After a syncopal episode, the avoidance of driving for six months from an episode is mandated in some states.

The possibility of other causes of syncope should always be considered. If the symptoms persist or the nature of the symptoms change, further evaluation is highly recommended.

What causes this disease and how frequent is it?

Features that support the diagnosis of vasovagal syncope include:

Presence of a prodrome or warning signs

Syncope that occurred while standing or at rest

No injury sustained

Related to emotion, dehydration or hunger

Last less than a minute

Up to 3/1000 teenagers presented for urgent medical attention with syncope. However, syncope occurs much more frequently, with patients not presenting for medical attention. A questionnaire survey of college students reported that 20% of males and 50% of females reported at least one previous episode of syncope.

Vasodepressor syncope is caused by vasodilation and pooling of blood in the venous system. This results in cerebral hypoperfusion and resultant syncope. This tends to occur more frequently in females (females to males 2:1) and in during teenage years (peak incidence in childhood, 15 years). There may be a familial component with a family history of benign or simple fainting. There is a family history of syncope in almost one fifth of patients diagnosed with vasovagal syncope.

How do these pathogens/genes/exposures cause the disease?

There are no known infectious processes that cause vasodepressor syncope; however, a fever with associated dehydration and viral gastroenteritis may predispose a syncopal episode.

Other clinical manifestations that might help with diagnosis and management

Extremely rarely with vasodepressor syncope and profound bradycardia, a pacemaker is required.

What complications might you expect from the disease or treatment of the disease?

Vasovagal syncope usually occurs as an isolated case. If recurrent, symptoms of vasovagal syncope usually resolve by adulthood. The most significant complications of vasovagal syncope are:

  • Misdiagnosis of a more ominous cause
  • Injury occurring as a result of syncope while driving, swimming or climbing.

If the diagnosis of vasodepressor syncope is established, the recommendation for fluid and salt treatment is usually well tolerated and successfully controls symptoms in about 70% of patients. If medical therapy with fludrocortisone, a beta blocker, or alpha agonist is required, complications such as weight gain, fatigue, and dry mouth may be noted.

Rarely, a pacemaker is recommended and requires appropriate follow-up with avoidance of direct trauma.

Are additional laboratory studies available; even some that are not widely available?


How can syncope be prevented?

Symptoms of vasodepressor syncope can be avoided by:

  • Encouraging intake of fluid and salt (especially in warm climates and with exercise).
  • Avoidance of caffeine stimulants end energy drinks.
  • Avoidance of tight clothing
  • Avoidance of hypoglycemia
  • Avoidance of standing up too quickly
  • Awareness and avoidance, where possible, of predisposing situations

What is the evidence?

Batra, AS, Balaji, S. “Management of syncope in pediatric patients”. Curr Treat Options Cardiovascular Med.. vol. 5. 2005. pp. 391-8. In this paper the authors review the frequency of syncope and the underlying causes, noting that 1% to 2 % of children with syncope might have a serious underlying condition. This may result in sudden death; therefore, an evaluation with a thorough history and testing, as appropriate, is recommended.

Brna, P, Camfield, P, Camfield, C. “When are episodes of loss of consciousness life-threatening?”. Paediatr Child Health. vol. 6. 2006. pp. 359-61. In this paper the authors emphasize their points by presenting a case of recurrent loss of consciousness. They review the potential causes and the importance of differentiating benign syncope from epilepsy or the more rare but potentially fatal cardiac causes. The authors emphasize the need for evaluation by a neurologist and cardiologist as appropriate.

Steinberg, LA, Knilans, TK. “Syncope in children: diagnostic tests have a high cost and low yield”. J Pediatr. vol. 146. 2005. pp. 355-8. In this paper the authors discuss the evaluation for syncope and the cost of evaluation per patient. They point out that the evaluation of pediatric syncope has remained expensive, with low diagnostic yield.

Ongoing controversies regarding etiology, diagnosis, treatment

The extent of evaluation remains controversial, and questions are raised whether all patients with a history of vasovagal syncope should have an echocardiogram or electrocardiographic monitoring.

At this time, if the patient’s history is typical with no concerning features and a normal physical examination and electrocardiogram, the diagnosis of vasodepressor syncope can be made clinically. However, if symptoms are atypical, occur with exercise, or are accompanied by chest pain or palpitations, or if there are any other concerning features, further evaluation is recommended.