Syncope in Adults

Background

• Syncope is a syndrome of transient loss of consciousness secondary to cerebral hypoperfusion characterized by rapid onset, short duration, and complete spontaneous recovery.
• Syncope may be classified into three types: neurally mediated, orthostatic, and cardiac syncope. The most common cause is the neurally-mediated vasovagal syncope and arrhythmias are the most common cause of cardiac syncope, accounting for 10% of all syncopal events.
• The cause of syncope remains unexplained (cryptogenic syncope) in 17%-33% of cases in the emergency department and may require inpatient cardiac workup.

Evaluation

• Obtain a history from the patient and/or witness, including a complete description of the setting of the event, previous episodes, history of heart disease, and recent changes in medication.
• Perform a complete physical exam for all patients with syncope, including:
  • heart rate measurement (Strong recommendation);
  • orthostatic blood pressure and heart rate measurements in all patients. Perform manual intermittent blood pressure and heart rate measurement supine and during active standing for 3 minutes (Strong recommendation).
• Obtain 12-lead electrocardiogram (ECG) for all patients with syncope to evaluate for arrhythmic cause.
• Consider targeted blood testing in patients with a high likelihood of other comorbidities such as severe anemia or electrolyte abnormalities that could contribute to transient loss of consciousness.
• Perform carotid sinus massage in patients > 40 years old with syncope of unknown origin compatible with reflex mechanism after initial evaluation; perform with caution in patients with previous transient ischemic attack, stroke, and known carotid stenosis > 70% (Strong recommendation).
• Consider tilt testing for patients with suspected vasovagal syncope or orthostatic syncope (Weak recommendation).
• Perform additional testing for patients with suspected cardiac syncope including:
  • echocardiography in patients with suspected structural heart disease (Strong recommendation);
  • ECG monitoring using Holter monitor or loop recorder in patients suspected arrhythmic syncope (Strong recommendation);
  • electrophysiological studies for suspected tachycardia in patients with previous myocardial infarction or other scar-related conditions if syncope remains unexplained after noninvasive evaluation (Strong recommendation);
  • exercise testing in patients who develop syncope during or soon after exertion (Strong recommendation).
• Diagnose:
  • Neurally mediated syncope in the absence of heart disease, a history of recurrent syncope, and/or the presence of specific triggers prior to episode:
    • Vasovagal syncope if triggered by pain, fear, or standing and associated with typical progressive prodrome, such as nausea, diaphoresis, tunnel vision, or pale appearance (Strong recommendation);
    • Carotid sinus syncope if carotid sinus massage causes bradycardia suggesting asystole and/or hypotension that reproduces spontaneous symptoms and history features compatible with reflex mechanism of syncope ;
    • Situational syncope if triggered by a specific event, such as defecation, urination, or coughing (Strong recommendation).
  • Orthostatic syncope if episode is related to assuming standing position and documentation of orthostatic hypotension (Strong recommendation).
  • Cardiac syncope:
    • When there is acute cardiac ischemia with or without myocardial infarction (MI) secondary to ischemia (Strong recommendation).
    • Consider a diagnosis of cardiac syncope with the presence of structural heart disease, family history of unexplained sudden death, or when episodes occurred in a supine position, during exercise, or associated with palpitations.

Management

Neurally Mediated Syncope

• Treatment of neurally mediated syncope is based on risk of future syncope episodes and identification of specific mechanism for syncope when possible:
  • if syncope is predictable or occurs at a low frequency, education, reassurance that syncope benign, and avoidance of triggers is usually sufficient;
  • if syncope is unpredictable or occurs at a high frequency, consider specific therapy or delayed treatment (guided by electrocardiogram documentation).
• Explain the diagnosis and assure the patient that the condition is benign. Explain risk of recurrence and avoidance of triggers and situations (Strong recommendation).
• Consider modification or discontinuation of hypotensive drug regimen in patients with vasodepressor syncope (neurally mediated reflex due to vasodepressor), if possible (Weak recommendation).
• Additional treatment for Vasovagal syncope:
  • Consider nonpharmacologic treatments including physical counterpressure maneuvers (isometric muscle contractions) for patients with prodrome and promotion of salt and fluid intake, unless it is contraindicated (Weak recommendation).
  • Consider one or more pharmacological approaches, including midodrine or fludrocortisone in patients with frequent vasovagal syncope (Weak recommendation).
  • Consider cardiac pacing in patients > 40 years old with documented cardioinhibitory response (reflex bradycardia) (Weak recommendation).
  • See Vasovagal syncope for additional information.
• Additional treatment for Carotid sinus syncope:
  • Consider cardiac pacing in patients with carotid sinus syncope that is cardioinhibitory (Weak recommendation).
  • See Carotid Sinus Hypersensitivity and Syncope for additional information.

Orthostatic Syncope

• Consider nonpharmacologic treatment options for patients with orthostatic syncope, including avoidance of carbohydrate-rich meals, limited alcohol intake, adequate hydration, and sodium supplementation and/or wearing lower extremity and abdominal binders, particularly in older patients or patients with pooling issues.
• Consider pharmacological treatment with fludrocortisone, midodrine, droxidopa, or pyridostigmine in patients that do not respond to nonpharmacological treatments.
• See Orthostatic hypotension and orthostatic syncope for additional information.

Cardiac Syncope

• In patients with cardiac syncope due to an arrhythmia, treatment options include cardiac pacing for bradyarrhythmias, and catheter ablation, antiarrhythmic medications, and/or placement of an implantable cardioverter defibrillator (ICD) for tachyarrhythmias.
• For patients with syncope due to structural heart disease, see Syncope secondary to structural heart disease.
• See Treatment of cardiac syncope for additional information.