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
[Outline]
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)
[Outline]
Laboratory diagnosis is generally of little value in syncope. Laboratory investigations should be guided by history and physical findings. In general, electrolytes, renal function, and hemogloblin are sufficient general screening. Additional focused testing may be indicated in selected cases.
Blood test findings
- A Complete blood count (CBC) may be useful for evaluation of anemia and for infection (increased WBC's)
- Assessment of Serum electrolytes and fluid status is important in cases of syncope
- Serum drug levels may be appropriate in cases where toxicity is suspected
- Elevated cardiac biomarkers (Troponin T, Troponin I, Pro brain natriuretic peptide) may be present in patients presenting witha history of chest pain prior to syncope; and thus being consistent with a cardiogenic etiology. Sepsis, pulmonary embolism, and other causes may result in abnormal cardiac biomarkers
- Women of childbearing age should be assessed for pregnancy (β-HCG)
Radiographic findings
- Echocardiography
- Echocardiography is useful in highly selected cases, where a structural cardiopulmonary cause of syncope such as hypertrophic cardiomyopathy, aortic stenosis, papillary muscle rupture, pericardial tamponade,or pulmonary embolism is suspected
- Computed tomography (CT)/magnetic resonance imaging (MRI)
- A CT or MRI scan of the head is rarely indicated in syncope. When patients have focal neurological deficits following or preceding syncope, which are concerning for stroke, transient ischemic attack, or seizure; such testing is indicated
- Chest or abdominal CT with IV contrast (if renally insufficient, with no contrast)should identify ruptured aortic aneurysm or dissection
Other diagnostic test findings
- Exercise stress testing
- Exercise stress testing is valuable in identifying cardiac causes of syncope such as coronary artery disease and exercise-induced cardiac arrhythmias. Lack of a significant increase in systolic blood pressure during stress testing may be indicative of structural heart conditions
- It is important to note that such testing is not highly sensitive in high risk patients. Angiography or CT coronary angiogram may be indicated
- Tilttable test
- A tilt table test can be a valuable outpatient evaluation for confirming autonomic dysfunction and revealing orthostatic hypotension. The patient is tilted on the table at an angle of 70–80 degrees for a period of 30–45 minutes. Vital parameters are then recorded placing the patient in various positions. Evidence of hypotension and significant bradycardia or asystole signify a positive result
- Tilttable testing +/-isoproterenol infusion is a provocative test for evaluating vasovagal syncope. Such testing may be pursued in cases where there is an inconclusive diagnosis in a patient with syncope
- Electrocardiogram (ECG)
- A 12-lead ECG exam is indicated in all patients presenting with syncope. A careful evaluation of the ECG by an experienced emergency physician, internist or cardiologist is essential
- Abnormal ECG features ranging from AV block, to arrhythmia, or ischemic findings may increase concern about the underlying etiology of the syncopal episode
- An ECG may help identify certain arrhythmic conditions such as Brugada syndrome, Wellens syndrome (symmetric deeply inverted T waves in V2/V3 or Biphasic T Waves in V2/V3) indicative of LAD critical stenosis, and Wolff-Parkinson-White syndrome
- Electrophysiological testing
- Electrophysiological testing is indicated in patients with intermittent or sporadic syncopal episodes due to suspected arrhythmia
- Patients with frequent syncopal episodes may be evaluated with a Holter monitor or external loop recorder which allows continuous ambulatory ECG monitoring
- Implantable loop recorders (ILR) are preferable in patients presenting with infrequent episodes or if conventional cardiac testing yields inclusive results
- Electroencephalography (EEG)
- EEG is indicated when seizures or other neurological conditions are a probable cause
- Carotid sinus massage
- Carotid sinus massage is a useful bedside test used to identify patients with suspected carotid sinus hypersensitivity
- The test is contraindicated in patients with suspected carotid artery
[Outline]
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
Vasopressors
Mineralocorticoids
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
[Outline]
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
[Outline]
