Tuesday, November 28, 2023


Practice Essentials

Syncope is defined as a transient, self-limited loss of consciousness
with an inability to maintain postural tone that is followed by spontaneous recovery. This definition excludes seizures, coma, shock, or other states of altered consciousness. Although most causes of syncope are benign, this symptom presages a life-threatening event in a small subset of patients.

Signs and symptoms

History and physical examination are the most specific and sensitive ways of evaluating syncope. These measures, along with 12-lead electrocardiography (ECG), were the only current level A recommendations listed in the 2007 American College of Emergency Physicians (ACEP) Clinical Policy on Syncope.

A detailed account of the event must be obtained from the patient, including the following:

Precipitating factors

Activity the patient was involved in before the event

Position the patient was in when the event occurred

The following questions should be asked:

Was loss of consciousness complete?

Was loss of consciousness with rapid onset and short duration?

Was recovery spontaneous, complete, and without sequelae?

Was postural tone lost?

If the answers are positive, syncope is highly likely; if 1 or more are negative, other forms of loss of consciousness should be considered.

Presyncopal symptoms reported may include the following:

Prior faintness, dizziness, or light-headedness (70% of cases of true syncope)

Prior vertigo, weakness, diaphoresis, epigastric discomfort, nausea, blurred or faded vision, pallor, or paresthesias

Red flag symptoms – Exertional onset, chest pain, dyspnea, low back pain, palpitations,
severe headache, focal neurologic deficits, diplopia, ataxia, or dysarthria

Other information that should be obtained includes the following:

Detailed account of the event from any available witnesses (eg, whether patient experienced postevent confusion)

Patient’s medication history

Patient’s personal or familial medical history of cardiac disease

A complete physical examination is required, with particular attention to the following:

Analysis of vital signs

Measurement of the glucose level by rapid fingerstick

Detailed cardiopulmonary examination

Detailed neurologic examination

Assessment for signs of trauma

Stool guaiac examination (if appropriate, based on the patient’s history)

See Presentation for more detail.


No specific laboratory testing has sufficient power to be absolutely indicated for evaluation of syncope. Tests may not be necessary and can be tailored to any signs or symptoms that raise concern for a specific underlying illness. Research-based and consensus guideline recommendations are as follows:

Serum glucose

Complete blood count

Serum electrolytes

Cardiac enzymes

Total creatine kinase


Imaging studies that may be helpful include the following:

Chest radiography – May serve to identify pneumonia, congestive heart failure (CHF), lung mass, effusion, or widened mediastinum

Computed tomography (CT) of the head (noncontrast) – Has a low diagnostic yield in syncope but may be clinically indicated in patients with new neurologic deficits or in patients with head trauma secondary to syncope

CT of the chest and abdomen – Indicated only in select cases (eg, suspected aortic dissection, ruptured abdominal aortic aneurysm, or pulmonary embolism [PE])

Magnetic resonance imaging (MRI) of the brain and magnetic resonance arteriography (MRA) – May be required in select cases to evaluate vertebrobasilar vasculature

Ventilation-perfusion (V/Q) scanning – Appropriate for suspected PE

Echocardiography – The test of choice for evaluating suspected mechanical cardiac causes of syncope

A standard 12-lead ECG is a level A recommendation in the 2007 ACEP consensus guidelines for syncope.
The following considerations are relevant:

Normal ECG findings are a good prognostic sign

ECG can be diagnostic for acute myocardial infarction or myocardial ischemia and can provide objective evidence of preexisting cardiac disease or dysrhythmia

Bradycardia, sinus pauses, nonsustained ventricular tachycardia and sustained ventricular tachycardia, and atrioventricular conduction defects are truly diagnostic only when they coincide with symptoms

Loop recorders have a higher diagnostic yield than Holter monitor evaluation, with a marginal cost savings

Ambulatory monitoring appears to have a higher negative than positive diagnostic yield

Other diagnostic tests and procedures include the following:

Head-up tilt-table test – Useful for confirming autonomic dysfunction and can generally be safely arranged on an outpatient basis

Electroencephalography (EEG) – Can be performed at the discretion of a neurologist if seizure is considered a likely alternative diagnosis

Stress test – A cardiac stress test is appropriate for patients in whom cardiac syncope is suspected and who have risk factors for coronary atherosclerosis

Carotid sinus massage (to diagnose carotid sinus syncope)

See Workup for more detail.


Prehospital management of syncope may require the following:

Intravenous access

Oxygen administration

Advanced airway techniques

Glucose administration

Pharmacologic circulatory support

Pharmacologic or mechanical restraints

Defibrillation or temporary pacing

Advanced triage decisions, such as direct transport to multispecialty tertiary care centers, may be required in select cases.

In patients brought to the emergency department with a presumptive diagnosis of syncope, appropriate initial interventions may include the following:

IV access, oxygen administration, and cardiac monitoring

ECG and rapid blood glucose evaluation

The treatment choice for syncope depends on the cause or precipitant of the syncope, as follows:

Situational syncope – Patient education regarding the condition

Orthostatic syncope – Patient education; additional therapy in the form of thromboembolic disease (TED) stockings, mineralocorticoids, and other drugs (eg, midodrine); elimination of drugs associated with hypotension; intentional oral fluid consumption

Cardiac arrhythmic syncope – Antiarrhythmic drugs or pacemaker placement

Cardiac mechanical syncope – Beta blockade; if valvular disease is present, surgical correction

See Treatment and Medication for more detail.

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