AUTHOR AND EDITOR INFORMATION

Section 1 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• References

INTRODUCTION

Section 2 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• References

Background

Syncope is a term used to describe the loss of consciousness from temporary disruption of cerebral oxygenation. This is typically due to the interruption of blood flow to the brain, and the loss of consciousness usually lasts for less than 30 seconds. In lay terms, fainting is the equivalent descriptive term.

Patients who complain of dizziness, light-headedness, passing out, and/or blacking out must be questioned carefully to determine whether a true syncopal event has occurred. Other spells (eg, seizure, transient ischemic attack, cataplexy) may be similar, and a careful history often can clarify the condition and guide further evaluation and care. Syncope is a symptom of either cardiac or hemodynamic dysfunction and not a disease (or diagnosis).

Pathophysiology

The causes of syncope are many (see Causes). The 3 most important broad categories are the following: (1) decreased cardiac output secondary to intrinsic cardiac disease or clinically significant blood or volume loss; (2) decreased peripheral vascular resistance and/or venous return; and (3) clinically significant cerebrovascular disease that leads to compromise of cerebral perfusion. Regardless of the cause, all of these categories share a common factor, namely, disruption of adequate cerebral oxygenation resulting in a transient alteration of consciousness.

Frequency

United States

Syncope is common. However, exact rates are difficult to cite because of the many potential causes and varying history of the symptoms. Syncope accounts for 1-6% of admissions to hospitals and 3% of visits to emergency departments.

Mortality/Morbidity

• In cases of syncope, morbidity parallels the cause. If an individual has had a simple case of fainting precipitated by specific circumstances and without sequelae, extensive workup may not be necessary. However, if the symptoms are recurrent or without clear provocation, cardiac, autonomic, or peripheral vascular dysfunction must be investigated and treated to prevent further events.
• Patients may have physical injuries due to a fall, depending on how quickly the symptoms occur and the individual. For example, injuries are most likely in physically frail or elderly people.
• Depending on the etiology, syncope may be a sign of serious underlying cardiovascular or cerebrovascular disease. A cardiac etiology is associated with more serious disease and carries a 20-30% mortality rate at 1 year. The mortality risk in noncardiac causes and idiopathic cases is approximately 5%.

Age

Syncope can occur in any age group, but the etiology varies by age. A young individual may have a syncopal attack with blood loss, dehydration, or hypoglycemia. Although these problems can occur in older individuals, additional medical problems could potentiate syncope. These problems may include congestive heart failure, autonomic instability, valvular heart disease, and cerebrovascular disease.

CLINICAL

Section 3 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• References

History

Regardless of the cause, patients with syncope present in a similar fashion. Vertigo is not a typical symptom of syncope. By definition, vertigo requires a sensation of spinning or movement that may indicate a cerebellar or vestibular problem. When patients use the term dizziness, the physician should thoroughly question the patient to clarify the symptom. The word dizzy or dizziness is ambiguous, and people can have vastly different meanings.

• At the start of an episode, an individual feels a sense of uneasiness, progressing to unsteadiness, facial pallor, and perspiration; the vision can become darkened concentrically.
• • During this time, nausea and vomiting can occur.
  • Sighing can occur (an attempt to catch one's breath) because the person can have a feeling of shortness of breath.
  • All these symptoms occur in the presyncope stage and usually last for less than 1 minute before loss of consciousness occurs.
• In cases of cardiac or carotid sinus syncope, the loss of consciousness can be rapid with little prodrome.
• If the individual assumes a supine position during the presyncopal stage, syncope is often avoided because cerebral perfusion is restored. However, an attempt to rise too quickly may lead to another presyncopal episode.
• The degree of altered consciousness varies from a static, dazed feeling to complete unconsciousness.
• If unconsciousness lasts for more than 15-20 seconds, simple body and extremity jerks can be seen. This condition is termed convulsive syncope.
• • It should not be confused with seizures.
  • Unlike those associated with a seizure, the jerking motions are single and nonrhythmic.
• During the syncopal period, the patient's systolic BP can be expected to be less than 60-80 mm Hg, and the patient's pulse may be thready.
• • Sphincteral tone is typically maintained.
  • Tongue biting of the type often noted with a generalized convulsion does not occur.
  • Once the patient is in the supine position, brain oxygenation is restored, and the patient regains consciousness.
  • The patient can usually recall the presyncopal symptoms that are critical to the diagnosis.
• Falling may cause injury if the individual cannot protect himself. This is of particular concern in the elderly in whom the incidence of falls is already high.
• Pulmonary embolism should be considered in the differential diagnosis, especially in the elderly

Physical

Because syncope is, by definition, a transient event, the general physical findings on initial presentation are usually normal. However, the following abnormalities can be noted:

• Carotid bruits can indicate clinically significant cerebrovascular disease and an increased risk of stroke.
• Abnormal heart sounds and/or an irregular heart rhythm might indicate a risk of decreased cardiac output.
• Poor BP regulation may be present. Bedside testing of BP and heart rate with postural changes is imperative in the workup for syncope.
• • The patient's vital signs are assessed while he or she is supine and reassessed while the patient is standing.
  • If the systolic pressure decreases by more than 15 mm Hg, orthostatic hypotension can be diagnosed.
  • The heart rate is also measured. An increase is considered clinically significant if it is greater than 20 bpm while the patient is standing.
• Peripheral neuropathy also suggests defective peripheral vascular tone caused by an autonomic neuropathy.
• • Neuropathy should be assessed by means of careful sensory and deep tendon reflex examination.
  • Abnormalities in light touch, vibration and proprioception, and pin-prick sensation and absent or sluggish deep tendon reflexes should be noted.

Causes

Syncope has many potential causes. The cause of syncope is commonly misdiagnosed.

• Neurogenically mediated syncope: This can occur sporadically. However, familial dysautonomia with wild-type and mutations in IKBKAP mRNA.
• • Vasodepressor or vasovagal causes
    • These are common etiologies in young people and are frequently associated with a precipitating circumstance, such as intense pain, emotion (eg, fear), the sight of blood, or having blood drawn.
    • The pathophysiology involves a sudden drop in peripheral vascular resistance and resultant hypotension coupled with bradycardia. The increased sympathetic activity induces perspiration, gastrointestinal (GI) motility, and occasionally vomiting.
    • Although the terms vasodepressor and vasovagal often are used synonymously, they indicate the involvement of different systems, with the latter referring to increased vagus-nerve efferent output with resulting bradycardia.
    • The term neurocardiogenic syncope suggests the hemodynamic stimulation of left ventricular mechanoreceptors, which can precipitate events leading to hypotension. This entity may be a separate mechanism for syncope.
  • Carotid sinus syncope
    • This results when the stretch receptors are activated and cause reflex hypotension (as opposed to only bradycardia).
    • The history is notable for the patient wearing a tight shirt collar and turning his or her head. Although carotid massage can reproduce the symptoms, carotid sonography must be performed first to rule out stenosis of the contralateral carotid, which indicates unilateral anterior blood supply to both hemispheres.
    • Carotid massage is contraindicated if plaque is present because it may theoretically liberate plaque debris and cause subsequent stroke.
  • Glossopharyngeal neuralgia
    • This is more common in men than in women and in those older than 40 years than in those younger, but is less common than trigeminal neuralgia.
    • Glossopharyngeal neuralgia is characterized by repeated, stabbing pain in the base of the tongue, tonsillar area, or pharyngeal area on 1 side of the throat. The pain can radiate to the angle of the jaw or ear.
    • These symptoms are due to involvement of the glossopharyngeal nerve. Because this cranial nerve can influence BP or heart rate, some patients may have cardiovascular symptoms, such as syncope.
  • Brugada syndrome
    • Patients can present with syncope.
    • Brugada syndrome is inherited in a dominant fashion and linked to mutations in SCN5A on chromosome 3.
    • On clinical evaluation, the heart is structurally normal but electrographic abnormalities may be present.
    • Sudden cardiac death is due to dysrhythmias.
    • The clinic features of Brugada syndrome can also be acquired by using drugs that can interfere with the ionic currents in the conduction system of the heart.
  • Micturition syncope: This is more common in older men than in other groups. It most often occurs at night when the patient stands up to urinate.
• Cough syncope: This typically occurs in individuals with chronic obstructive pulmonary disease and usually follows a protracted bout of coughing.
• Valsalva maneuver: A Valsalva maneuver (eg, as in straining to urinate) increases thoracic pressure and decreases venous return to the heart.
• Postprandial syncope: This occurs in the elderly and is thought to be due to increase blood flow to the GI vasculature and an inability to compensate hemodynamically.
• Impaired postural reflexes
• • These reflexes primarily include postural reflexes impaired by incompetence of the sympathetic nervous system, and they can be centrally or peripherally mediated. Centrally mediated findings are a feature of Parkinson disease, multisystem atrophy, Shy-Drager syndrome, and striatonigral degeneration. Although the most obvious symptoms involve abnormal motor control, the autonomic nervous system also can be involved severely. Postural BP regulation is typically defective, resulting in presyncope or syncope. The patient may have spinal disease or injury that affects the autonomic transmission of information. A stroke of the medulla or hypothalamus involving the relay nuclei that mediate autonomic activity may also be a cause.
• Peripherally mediated findings are due to baroreceptor dysfunction and can be seen with peripheral neuropathies (eg, diabetes, amyloid, alcohol-related, Guillain-Barré syndrome), pure autonomic failure, and effects of drugs (eg, antihypertensives, tricyclics, phenothiazines, levodopa). The prognosis for patients with pure autonomic failure is more favorable than that of patients with multiple system atrophy.
• Hemodynamic findings: Changes result from insufficient cardiac output or insufficient blood volume.
• • Hypovolemia
    • Hemorrhage
    • Dehydration (eg, diuretics, inadequate intake, gastroenteritis)
  • Insufficient cardiac output
    • Aortic stenosis
    • Hypertrophic subaortic stenosis
    • Cardiac tamponade
    • Prosthetic valve failure
    • Arrhythmias (eg, atrial fibrillation, complete atrioventricular block, sick sinus syndrome, sinus bradycardia, tachyarrhythmias, familial long-QT syndrome)
    • Myocardial infarction
    • Congestive heart failure
    • Pulmonary hypertension
• Systemic conditions
  • Hypoglycemia
  • Anemia
  • Hypoxia
• Transient ischemic attack (uncommon)
  • Severe vertebrobasilar stenosis
  • Bilateral severe carotid stenosis
• Subarachnoid hemorrhage
  • Sudden, severe headache almost always heralds a ruptured aneurysm before any loss of consciousness occurs.
  • Although unconsciousness can be sudden, this is not a true syncopal event because of the longer duration.
• Other: Adverse effects of prescribed or over-the-counter medications can cause syncope and are often overlooked.

DIFFERENTIALS

Section 4 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• References

Other Problems to be Considered

Hysteria
Other psychiatric diseases
Brainstem syndromes
Marijuana use

WORKUP

Section 5 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• References

Lab Studies

• ECG should be performed in all patients to evaluate for current or past cardiac disease (eg, myocardial infarction, arrhythmia, conduction disturbances).
• Complete electrolyte and chemistry panels are needed to evaluate for any contributing metabolic disorder (eg, hypoglycemia, dehydration).
• A CBC should be ordered to rule out anemia.

Imaging Studies

• Emergency CT scan of the brain is indicated if intracranial hemorrhage is suspected or if a structural or destructive lesion is suspected.
• If subarachnoid hemorrhage is suspected and if CT findings are negative, lumbar puncture is indicated.
• MRI of the brain is recommended to evaluate for acute ischemic stroke or to further evaluate a structural or mass lesion.
• MR angiography (MRA) of the brain is recommended to evaluate the carotid and intracranial circulation.
• MRI of the spinal cord may also be appropriate.

Other Tests

• Additional testing may be performed depending on the history and physical examination findings.
• • Prolonged cardiac monitoring, such as inpatient telemetry or Holter monitoring, should be considered if cardiac disease is suspected.
  • If monitoring is needed for longer than 24 hours then ambulatory continuous-loop recording permits monitoring for days to weeks.
  • Routine EEG is used to investigate a possible seizure disorder.
  • Prolonged ambulatory EEG or inpatient video-EEG monitoring may be indicated if the patient's history indicates a strong possibility of epilepsy.
  • Transthoracic and/or transesophageal echocardiography is ordered to evaluate cardiac output and valvular or wall-motion abnormalities.
  • Tilt-table testing may be needed to evaluate orthostatic hypotension. Tilt-table testing is an accurate method of assessing changes in BP and pulse with changes in position. The table is actually a bed that can be pivoted from a supine position to a standing position to enable precision measurements of BP and pulse in both. Tilt-table testing is generally available only in the cardiology departments of tertiary care centers or in autonomic testing laboratories of a neurology department.
• Appropriate consultation should precede some of these additional tests.

TREATMENT

Section 6 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• References

Medical Care

• Medical care depends on the etiology of the syncope.
• If a serious cardiac or neurologic illness is suspected, admission to the hospital, where diagnostic testing can be performed in a monitored setting, may be warranted. This is particularly true if a patient presents to the emergency department.
• If a patient is examined in an outpatient setting and if his or her history suggests a remote event, the workup may not be urgent and might be completed in an outpatient setting.

Consultations

Consultation with a specialist may be appropriate.

• A neurologist may be consulted in the following cases:
• • Seizures suspected
  • Abnormal EEG
  • Neurologic abnormalities on examination
  • Abnormal brain MRI or CT scan
• Consultation with a cardiologist should be considered when cardiac abnormalities are found during physical examination, ECG, or other testing.

Diet

• In cases of chronic orthostatic hypotension, altering the diet by adding salt to encourage volume expansion may be helpful.

Activity

• Patients often recall particular activities that cause the symptoms (and therefore learn to avoid them).
• Patients should avoid warm environments, use of alcohol, excessive fatigue, or hunger, which can precipitate a syncopal episode.
• Patients should avoid rising out of bed or a chair too quickly.

MEDICATION

Section 7 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• References

Pharmacotherapy is indicated when presyncope or syncope is recurrent and refractory to nonpharmacologic treatment. The choice of medication depends on the cause and the severity of the orthostatic hypotension in particular. Various medications for associated comorbidities, such as diabetes, hypertension, and cardiac abnormalities, may indirectly improve some symptoms of syncope.

Drug Category: Corticosteroids

These agents have anti-inflammatory properties and cause profound and varied metabolic effects.

Drug Category: Alpha-adrenergic agonists

These agents improve the patient's hemodynamic status by increasing myocardial contractility and heart rate, increasing cardiac output. They also increase peripheral resistance by causing vasoconstriction. Increased cardiac output and increased peripheral resistance lead to increased BP.

FOLLOW-UP

Section 8 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• References

Patient Education

• For excellent patient education resources, visit eMedicine's Brain and Nervous System and Statins Center. Also, see eMedicine's patient education articles Fainting, Atorvastatin (Lipitor), Pravastatin (Pravachol), and Simvastatin (Zocor).

REFERENCES

Section 9 of 9

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• References

• Adams RD, Victor M, Ropper AH. Faintness and syncope. In: Adams RD, Victor M, Ropper AH, eds. Principles of Neurology. New York, NY: McGraw-Hill;. 1997:367-79.
• Axelrod FB, Goldberg JD, Rolnitzky L, et al. Fludrocortisone in patients with familial dysautonomia--assessing effect on clinical parameters and gene expression. Clin Auton Res. Aug 2005;15(4):284-91. [Medline].
• Claydon VE, Hainsworth R. Salt supplementation improves orthostatic cerebral and peripheral vascular control in patients with syncope. Hypertension. Apr 2004;43(4):809-13. [Medline].
• Drislane FW, Feske S. Transient events. In: Samuels MA, Feske S, et al, eds. Office Practice of Neurology. New York, NY: Churchill-Livingstone;. 1996: 111-4.
• Eagle KA, Black HR, Cook EF, Goldman L. Evaluation of prognostic classifications for patients with syncope. Am J Med. Oct 1985;79(4):455-60. [Medline].
• Farrehi PM, Santinga JT, Eagle KA. Syncope: diagnosis of cardiac and noncardiac causes. Geriatrics. Nov 1995;50(11):24-30. [Medline].
• Farwell DJ, Freemantle N, Sulke N. The clinical impact of implantable loop recorders in patients with syncope. Eur Heart J. Feb 2006;27(3):351-6. [Medline].
• Gould PA, Krahn AD, Klein GJ, et al. Investigating syncope: a review. Curr Opin Cardiol. Jan 2006;21(1):34-41. [Medline].
• Jiménez D, Diaz G, Valle M, et al. [Prognostic value of syncope in the presentation of pulmonary embolism]. Arch Bronconeumol. Jul 2005;41(7):385-8. [Medline].
• Kapoor W, Snustad D, Peterson J, et al. Syncope in the elderly. Am J Med. Mar 1986;80(3):419-28. [Medline].
• Kapoor WN, Karpf M, Wieand S, et al. A prospective evaluation and follow-up of patients with syncope. N Engl J Med. Jul 28 1983;309(4):197-204. [Medline].
• Kokturk N, Oguzulgen IK, Demir N, et al. Differences in clinical presentation of pulmonary embolism in older vs younger patients. Circ J. Aug 2005;69(8):981-6. [Medline].
• Lipsitz LA, Wei JY, Rowe JW. Syncope in an elderly, institutionalised population: prevalence, incidence, and associated risk. Q J Med. Apr 1985;55(216):45-54. [Medline].
• Mabuchi N, Hirayama M, Koike Y, et al. Progression and prognosis in pure autonomic failure (PAF): comparison with multiple system atrophy. J Neurol Neurosurg Psychiatry. Jul 2005;76(7):947-52. [Medline].
• Medical Economics. Physician's Desk Reference. 53rd ed. Montvale, NJ: Medical Economics;. 1999.
• Pérez Riera AR, Antzelevitch C, Schapacknik E, et al. Is there an overlap between Brugada syndrome and arrhythmogenic right ventricular cardiomyopathy/dysplasia?. J Electrocardiol. Jul 2005;38(3):260-3. [Medline].

Article Last Updated: Nov 2, 2006