Topic Editor: Grant E. Fraser, M.D., FRACGP, FACRRM, ASTEM

Review Date: 12/11/2012

Definition

Syncope is a transient loss of consciousness secondary to cerebral hypoperfusion, characterized by quick onset, short length of time, and spontaneous recovery. Some other conditions may mimic syncope, such as a primary neurologic cause, however historical data and physical findings should differentiate such cases.

Description

• Syncope accounts for ~1-3% of all emergency visits and results in up to 6% of admissions
• Syncope is triggered by cerebral hypoperfusion, often linked with the loss of postural tone, and generally succeeded by spontaneous recovery within minutes
• The primary types of syncope include neurally mediated (reflex) syncope, orthostatic syncope, and cardiac syncope. It is quite important to evaluate all syncope patients for other disease processes such as:
  • Acute blood loss (GI tract, trauma, others)
  • Acute coronary syndrome/dysrhythmia
  • Hypoglycemia
  • Pulmonary embolism
  • Seizure
  • Septicemia
  • Stroke (ischemic or hemorrhagic)
  • Vascular dissection
• Patients who have symptoms indicating another disease process should be evaluated for that condition and not considered to have isolated syncope
• In one study, syncope cases in adults were:
  • ~37% Unknown
  • ~21% Vasovagal
  • ~10% Cardiac
  • ~9% Orthostatic
  • ~7% Medication
  • ~5% Seizure
  • ~4% Stroke or TIA
  • ~8% Other (cough, micturition, situational syncope)
• Fatigue, standing for an extended duration, painful stimuli, emotional turmoil, anemia, nausea, dehydration,hyperventilation, and inadequate ventilation are some potential predisposing conditions for syncope

Epidemiology

Incidence/Prevalence

• Based on the data obtained from the Framingham Heart Study(1971–1998),the estimated incidence is 6.2/1,000 person-years
• Syncope is responsible for 1-3% of emergency room visits and upto 6% of hospitalizations

Age

• Prevalence of syncope increases with age from 0.7 % in men aged 35–44 to 5.6% in men aged >75
• Pediatric syncope is a comparatively less common occurrence

Gender

• No clinically significant gender differences have been observed

Risk factors

• Alcoholism
• Aortic stenosis
• Atrial fibrillation
• Diabetes
• High blood pressure
• History of cardiac arrhythmias (brady or tachyarrhythmia's)
• History of myocardial infarction
• History of stroke or transient ischemic attack
• Increasing age
• Insulin therapy
• Interventricular block
• Ischemic heart disease
• Lower body mass index
• Medications:
  
  • Antidepressants/Antipsychotics
  • Antihypertensives
  • Antiarrhythmics
  • Drugs known to prolong the QT interval
• Postprandial hypotension
• PR interval prolongation
• Prior syncopal episode
• Smoking

Etiology

Syncope can be classified into 6 major categories depending upon the etiology

• Cardiac causes
  
  • Arrhythmias
    
    • Atrial tachyarrhythmias (atrial flutter, atrial fibrillation)
    • Atrioventricular (AV) block (second or third degree)
    • Long QT syndrome
    • Pacemaker dysfunction
    • Sick sinus syndrome
    • Supraventricular tachycardia
    • Torsades de pointes
    • Ventricular tachycardia or fibrillation
    • Wolff-Parkinson-White syndrome
  • Organic heart disease
    
    • Aortic dissection
    • Aortic or mitral stenosis
    • Atrial myxoma
    • Myocardial infarction
    • Papillary muscle rupture or dysfunction
    • Prosthetic valve dysfunction
    • Pulmonary hypertension
    • Takayasu's arteritis
  • Low or infective cardiac output (non-arrhythmogenic)
    
    • Cardiac tamponade
    • Congestive heart failure
    • Hypertrophic cardiomyopathy
    • Pulmonary embolism
    • Stress (Takotsubo) cardiomyopathy
• Orthostatic causes
  
  • Autonomic dysfunction
    
    • Primary autonomic dysfunction
      
      • Lewy body dementia
      • Multiple system atrophy
      • Parkinson's disease with autonomic failure
      • Pure autonomic failure (Bradbury-Eggleston syndrome)
    • Secondary autonomic dysfunction
      
      • Amyloidosis
      • Diabetes
      • Spinal cord injuries
      • Uremia
  • Hypovolemia
    
    • Dehydration
    • Diarrhea
    • Hemorrhage
    • Vomiting
  • Medications
    
    • Alcohol
    • Antidepressants
    • Diuretics
    • Phenothiazines
    • Vasodilator drugs
• Neurologic causes
  
  • Migraines
  • Narcolepsy
  • Neuralgia
  • Normal pressure hydrocephalus
  • Seizure
  • Subclavian steal
  • Transient ischemic attack
  • Vertebrobasilar artery disease
• Neuro-autonomic causes
• Vasovagal syncope
  
  • Emotional distress
  • Fear/phobia
  • Instrumentation
  • Pain
  • Orthostatic stress
  • Carotid sinus syncope/hypersensitivity
  • Neck manipulation (e.g.,shaving, tight collars)
  • Occurs in older patients
• Situational syncope
  
  • Coughing or sneezing
  • Defecation
  • Exercise induced
  • Micturition
• Other (e.g.,laughter, playing brass instruments, weight training)
  
  • Postprandial
  • Swallowing
  • Visceral abdominal pain
• Metabolic causes
  
  • Hypoadrenalism
  • Hypoglycemia
  • Hyponatremia
  • Hypothyroidism
  • Hypoxia
• Psychiatric/Pharmacologic causes
  
  • Anxiety
  • Drug abuse/overdose (e.g. heroin)
  • Hyperventilation syndrome
  • Hysteria
  • Major depressive disorder
  • Panic disorder
  • Somatization disorders
    

History

Primary assessment of a patient presenting with transient loss of consciousness should include

• Characteristics and duration of the current episode, including interview of witnesses and patient
• Characteristics, duration, and frequency of previous episodes
• Co-morbid illnesses and medications
• Family and personal history of syncope
• Investigation of symptoms preceding and succeeding the syncopal episode
• Triggering events

Cardiac symptoms

• Chest pain
• Dyspnea
• Palpitations

Common symptoms preceding syncope

• Dizziness
• Fainting with an episode of amnesia
• Fear or apprehension
• Light-headedness
• Palpitations
• Tunnel vision

Neurologic and/or autonomic symptoms

• Anxiety
• Confusion
• Diaphoresis
• Headache
• Nausea
• Sense of warmth
• Skin pallor
• Visual changes (e.g., diplopia)
• Weakness

Physical findings on examination

• A drop of 20/10 mmHg in blood pressure with positional change from the supine to standing is suggestive of orthostatic hypotension
• A 20 mmHg variation in the systolic blood pressure between both arms may indicate subclavianstenosis/steal syndrome or coarctation of the aorta (right being higher than left in coarctation)
• Cardiac findings may include gallop, irregular rhythm, or murmurs
• Baseline neurological findings should be normal in uncomplicated syncope. When abnormal findings are found (focal or general neurological abnormalities), a specific evaluation for this is required. Any neurological deficits following a syncopal episode can be indicative of stroke, structural lesion, or seizure
• Tongue biting or enuresis is generally an indication of seizure
• Hypoglycemia often results in symptoms that mimic syncope. Focal neurological deficits may also occur with hypoglycemia
• A rectal exam may reveal fecal blood (occult or gross) indicative of gastrointestinal (GI) bleeding
• Skin pallor may be due to anemia or hemorrhage
• A pulsatile mass in the abdomen may indicate abdominal aortic aneurysm
• Falls associated with syncope may lead to traumatic injuries such as fractures, dislocations, lacerations,hematomas, and intracranial injury (especially subdural hematomas)

General treatment items

• The primary treatment goals are improved survival outcomes, restriction of physical injuries, and prevention of repeated episodes. The optimal treatment of syncope is based on the underlying etiology
• Neurallymediated syncope (Reflex syncope)
  • It is critically important to educate patients on the mechanism and warning symptoms of syncope (behavior modification) in order to decrease injuries and improve compliance with therapy
  • Non-pharmacological treatment
    • Preventing dehydration, physical counterpressure maneuvers (PCM) during early prodromal stages (lying down with legs elevated), maintaining adequate intravascular volume by means of maintaining adequate oral hydration and salt intake, use of support hose, and physical tilt training
    • Tilt training may be valuable in educating patients but requires continued patient compliance
    • Patients with carotid sinus hypersensitivity may benefit from cardiac pacing
    • Cardiac pacemaker implantation may be valuable in patients with recurrent vasovagal syncope which fails torespond to conventional therapy
  • Pharmacological treatment
    • Midodrine, an alpha-1 receptor agonist,may be used to manage vasovagal syncope that is unresponsive non-pharmacologic measures
    • There is limited evidence to support the effectiveness of beta blockers
• Orthostatic syncope
  • The management of orthostatic syncope includes patient awareness of exacerbating factors, along with non-pharmacologic and drug therapy for correction of hypovolemia and autonomic dysfunction
  • Non-pharmacologic approach:
    • Gradual and cautious positional changes
    • Sufficient hydration and salt intake
    • Maintenance of adequate intravascular volume, generally with adequate oral hydration
    • Abdominal binders and/or support stockings to decrease venous pooling
    • Regular exercise regimen
    • Physical counterpressure maneuvers (PCM)
    • Sleeping in the head-up tilt (HUT) position
  • Pharmacological approach
    • Adjunctive treatment with midodrine or fludrocortisone can effectively improve systolic blood pressure and plasma volume, respectively
• Cardiac syncope
  • Cardiac arrhythmias
    • Cardiac syncope resulting from arrhythmias must receive appropriate evaluation and treatment depending upon the etiology
    • Bradycardia often results in syncope and necessitates a cardiac pacemaker
    • Tachyarrhythmia's are commonly managed with antiarrhythmic drugs, catheter ablation, or use of an implantable cardioverter defibrillator (ICD)
  • Structural heart disease
    • Underlying structural abnormalities which result in syncope, generally require specific treatment
    • Aortic stenosis of high severity generally necessitates surgical treatment
    • Emergency conditions such as myocardial infarction, pulmonary embolism,papillary muscle rupture, and pericardial tamponade should be treated
    • Beta blockers may be useful in improving conditions which result in outflow tract obstruction
• Neurological syncope
  • Treatment of neurologically confirmed stroke includes maintenance of blood pressure and glycemic control, along with treatment of increased intracranial pressure
  • Seizures should be controlled with appropriate oral or IV anticonvulsant drugs
  • Presence of a bilateral carotid artery stenosis necessitates carotid endarterectomy

Medications indicated with specific dose

Caloric agents

• Dextrose
  
  • Adult Dosing
  • Pediatric Dosing

Vasopressors

• Midodrine
  • Adult Dosing
  • Pediatric Dosing

Mineralocorticoids

• Fludrocortisone
  • Adult Dosing
  • Pediatric Dosing

Dietary and activity restrictions

• No specific dietary restrictions are indicated except in patients with heart disease
• Patients with orthostatic hypotension should be advised to maintain a liberal intake of salt, if not contraindicated
• Patients should be advised to refrain from driving until diagnosed and an appropriate treatment initiated. In many states, this is a legal requirement and it is critical to document that such advise was given (some jurisdictions require appropriate form submission)

Disposition

Admission Criteria

• Suspected cardiac syncope cases
• Syncopal in elderly patients
• Patients with cardiovascular disease
• Patients with symptoms concerning for possible non-benign etiology of syncope

Discharge Criteria

• Resolution of hemodynamic instability
• Adequate diagnostic evaluation to determine the cause
• Appropriate management of arrhythmias or seizures
• Appropriate outpatient followup
• Orthostatic syncope secondary to hypovolemia can be appropriately managed in an outpatient setting once treated

Monitoring

• The frequency of follow-up depends on the cause and severity of syncope and whether any drug therapy is needed
• Patients with cardiac causes of syncope, particularly those requiring antiarrhythmic medications, should undergo frequent monitoring and specialist review

Complications

• Syncope related falls are common in older patients and unfortunately can lead to traumatic injuries
• Sudden death can rarely occur in adolescents with recurrent, exercise-induced, or non-neurocardiogenic syncope. Such patients should be reviewed by a pediatric cardiologist prior to being further involved in sports

Prevention

• Vasovagal syncope requires avoidance of precipitating factors, an may also be prevented by self-administered orthostatic training
• It is essential to maintain sufficient hydration and caloric consumption for preventing orthostatic syncope

Prognosis

• Prognosis of syncope is variable, 1-year mortality ranges from 0% for vasovagal syncope to 30% for cardiogenic syncope
• Patients with cardiac syncope have an increased risk of all-cause and cardiovascular mortality
• The prognosis for reflex syncopal conditions in children is excellent; however, it may significantly affect quality of life
• The prognosis for vasovagal syncope is typically benign
• The San Francisco Syncope Rule is an effective tool for identifying patients at high risk of serious outcomes within a week of syncope
• The criteria includes the following items – if any are present – admission is reasonable:
  • Abnormal ECG (e.g. ischemia, AV block, arrhythmia, ischemia)
  • Age >75 years
  • Dyspnea
  • Hematocrit <30%
  • History of congestive heart failure (CHF)
  • Systolic blood pressure <90 mm Hg measured at any time

Associated conditions

Concurrent conditions in women with syncope may include

• Chronic fatigue syndrome
• Gastroparesis
• Interstitial cystitis
• Migraine
• Postural tachycardia syndrome

ICD-9-CM

• 780.2 Syncope and collapse

ICD-10-CM

• R55 Syncope and collapse