II. Definition

  1. Syncope
    1. Rapid onset of transient loss of consciousness
    2. May be associated with a fall
    3. Resolves spontaneously and quickly without intervention
  2. Presyncope
    1. Weakness, Dizziness, light headedness or "graying out" of consciousness without loss of postural tone
    2. Evaluated as Syncope with same risks of adverse event
      1. Grossman (2012) Am J Emerg Med 30(1): 203-6 +PMID:21185670 [PubMed]

III. Background

  1. Up to one third of Syncope cases are idiopathic
  2. Common diagnosis
    1. Occurs in up to 50% of adults, and 75% over age 75
    2. Accounts for up to 3% of ER visits, 6% of admissions
  3. Precautions
    1. Careful history, exam, and ekg should direct limited diagnostics and disposition
    2. Always consider serious cause differential diagnosis (see rule of 15s below)

IV. Pathophysiology

  1. Decreased global cerebral perfusion (usually on standing)

V. Risk Factors

  1. Elderly
  2. Structural heart disease (e.g. Aortic Stenosis)
  3. Congestive Heart Failure
  4. Coronary Artery Disease

VI. Causes: Non-Cardiac Causes (57%)

  1. Reflex Mediated Syncope (no cardiovascular risk, most common)
    1. Vasovagal Syncope (Vasodepressor Syncope)
    2. Situational Syncope
      1. Micturition Syncope or with Defecation
      2. Cough Syncope (or sneezing)
      3. Valsalva (brass instrument playing, weight lifting)
      4. Hyperventilation
    3. Carotid Sinus Syncope
    4. Glossopharyngeal neuralgia (uncommon)
      1. Syncope occurs with swallowing, talking, sneezing
    5. Trigeminal Neuralgia
  2. Medication-related Syncope
    1. Antihypertensive Medications (e.g. Beta Blocker)
    2. Ophthalmic Beta Blockers
    3. Antianginal medications (e.g. Nitroglycerin)
    4. Digitalis
      1. Atrioventricular Block
      2. Ventricular Tachycardia
    5. Antiarrhythmic medications (esp. Type Ia)
    6. Diuretics
      1. Hypokalemia
      2. Hypomagnesemia
      3. Hypovolemia
    7. Adriamycin
    8. Phenothiazines
    9. Tricyclic Antidepressants
  3. Recreational drug use
    1. Alcohol
    2. Ecstasy (MDMA)
    3. Methamphetamine
  4. Orthostatic Syncope (2-24%)
    1. See Orthostatic Hypotension
  5. Neurologic Causes (9% of causes)
    1. Transient Ischemic Attacks: 1-7%
    2. Seizure disorder: 2%

VIII. Causes: Syncope-Plus

X. History: Preceeding or provocative event

  1. Prolonged standing
    1. Vasovagal Syncope
  2. Immediately on standing
    1. Orthostatic Hypotension
  3. While lying supine
    1. Cardiovascular Syncope (higher risk)
  4. With exertion (high risk for serious cause)
    1. See Exertional Syncope
    2. Aortic Stenosis
    3. Coronary Artery Disease or Coronary Artery Abnormalities
    4. Cardiomyopathy (e.g. Hypertrophic Cardiomyopathy, Myocarditis)
    5. Arrhythmia (e.g. ARVD, Long QT Syndrome, WPW Syndrome, Brugada Syndrome)
    6. Miscellaneous Causes (e.g. Heat Stroke, Hypoglycemia, Hyponatremia)
  5. After exertion in an athlete
    1. Vasovagal Syncope
  6. Valsalva (cough, swallowing, urinating or stooling)
    1. Reflex-mediated Syncope
  7. Neck rotation or pressure (e.g. tight collar)
    1. Carotid Sinus Hypersensitivity
  8. Use of arms
    1. Subclavian Steal Syndrome
  9. Stressful event
    1. Vasovagal Syncope

XI. History: Associated symptoms during event

  1. Nausea, chills and sweats
    1. Vasovagal Syncope
  2. Aura
    1. Migraine Headache
    2. Seizure Disorder
  3. No prodromal symptoms (see below)
    1. Cardiovascular Syncope (higher risk)
  4. Slumping
    1. Coronary Artery Disease
    2. Arrhythmia
  5. Kneeling
    1. Orthostatic Hypotension
  6. Brief loss of consciousness
    1. Arrhythmia
  7. Loss of consciousness >5 minutes
    1. Neurologic, metabolic, or infectious cause
  8. Tonic-clonic movements
    1. Seizure disorder
      1. Movements occur before fall and last longer than 30 seconds
      2. Followed by postictal period of confusion
    2. Vasovagal Syncope
      1. Movements occur after fall, and appear as myoclonic jerks
  9. Focal neurologic deficits
    1. TIA or CVA (although LOC requires significant CNS involvement, for which resolution would be delayed)
    2. Todd's Paralysis (Seizure)
  10. Severe Thunderclap Headache
    1. Subarachnoid Hemorrhage
  11. Chest Pain
    1. Coronary Artery Disease
    2. Pulmonary Embolism
    3. Aortic Dissection
  12. Palpitations
    1. Arrhythmia
  13. Incontinence of urine or stool
    1. Seizure Disorder
  14. Severe Abdominal Pain or back pain
    1. Abdominal Aortic Aneurysm
    2. Aortic Dissection
  15. Pelvic Pain or Vaginal Bleeding
    1. Ectopic Pregnancy

XII. Symptoms: Prodromal

  1. Dizziness
  2. Vision Loss
  3. Hearing Loss
  4. Sensation loss
  5. Weakness
  6. Diaphoresis
  7. Palpitations

XIII. Exam

  1. Vital Signs
    1. Temperature
    2. Blood Pressure
    3. Orthostatic Blood Pressure (low yield)
      1. Frequently abnormal in healthy subjects and a majority of the elderly
      2. However, in elderly, Orthostatic Hypotension may alter disposition and management
      3. Evaluate patient for symptoms reproduced on standing (more important than measurements)
  2. General
    1. Pallor
      1. Orthostatic Hypotension due to Anemia
    2. Tongue bitten
      1. Seizure
    3. Ear Exam
    4. Dix-Hallpike Maneuver
  3. Cardiovascular examination
    1. Carotid Bruits
    2. Heart Murmur
      1. Aortic Stenosis
      2. Hypertrophic Cardiomyopathy
    3. Asymmetric pulses
    4. Carotid massage
      1. Avoid in Cerebrovascular Disease or Carotid Bruit!
  4. Neurologic Exam
    1. Post-event Confusion (Seizure Disorder)
    2. Focal neurologic deficit
      1. Perform a careful Neurologic Exam to identify subtle deficits
  5. Red flags suggestive of ongoing active cardiovascular or Syncope-plus cause
    1. Diaphoresis
    2. Tachycardia
    3. Dyspnea
    4. Significant pain
  6. Evaluate for injury related to syncopal fall
    1. See Trauma Evaluation
    2. Exclude head or neck injury
    3. Exclude extremity injury

XIV. Differential Diagnosis: Serious Causes

  1. Arrhythmia
    1. May be mis-diagnosed as Seizure
    2. Wolff-Parkinson-White Syndrome (WPW Syndrome)
    3. Brugada Syndrome
    4. Prolonged QTc >500 ms
    5. Ventricular Tachycardia
  2. Structural heart defects and vascular conditions
    1. Hypertrophic Cardiomyopathy
    2. Aortic Stenosis
  3. Acute catastrophic disorders (Rule of 15s: Each condition has a 15% Incidence as syncopal presentation)
    1. Pulmonary Embolism
    2. Aortic Dissection
    3. Ruptured Abdominal Aortic Aneurysm
    4. Ruptured Ectopic Pregnancy
    5. Subarachnoid Hemorrhage
    6. Acute Coronary Syndrome

XV. Differential Diagnosis: Other causes

  1. Dizziness or Vertigo (no loss of consciousness)
  2. Drop Attacks (No loss of consciousness, no aura)
  3. Seizure Disorder
    1. Not associated with preceding Nausea or diaphoresis
    2. Seizure activity precedes a fall
    3. Postictal period
  4. Muscle Weakness

XVI. Diagnostics: Initial evaluation

  1. Electrocardiogram (EKG)
    1. See Electrocardiogram in Syncope
    2. Obtain in all Syncope patients
      1. However, significant findings in only 5% overall, and 0-3% in those under age 40 years old
    3. Identify VT, Brugada Syndrome, WPW (short PR), Prolonged QTc >500, Hypertrophic Cardiomyopathy, ischemia
    4. May assist in distinguishing Seizure and Syncope
    5. EKG is low yield in syncopal patients under age 40 years old
      1. Sun (2008) Ann Emerg Med 51(3): 240-6 +PMID:17559972 [PubMed]
  2. Basic Chemistry Panel (Serum electrolytes including Glucose)
    1. Low yield in young patients (age <40 years old) without other risk factors
      1. Bedside Glucose alone may be sufficient in these patients
    2. Patients warranting chemistry panel
      1. Patients over age 40 years old
      2. Prolonged QTc (include Serum Magnesium, Serum Calcium, Serum Potassium)
      3. Gastrointestinal losses (Vomiting or Diarrhea)
      4. Diabetes Mellitus
      5. Chronic Kidney Disease
      6. Diuretic use
      7. Dietary restrictions
  3. Hemoglobin or Hematocrit
    1. Obtain for blood loss (e.g. Menorrhagia, GI Bleed), comorbidity (HIV, cancer, Renal Failure) or signs (pallor, weakness)
  4. Pregnancy Test (urine HCG)
    1. Consider in Abdominal Pain, Vaginal Bleeding in patients of child bearing age
  5. Chest XRay
    1. Low yield test (positive in <0.6% of Syncope patients)
    2. Abnormal findings (e.g. mediastinal widening, Pneumonia, Pneumothorax) are unlikely without physical findings
    3. Obtain if Chest Pain, Dyspnea, increased Respiratory Rate or Hypoxia
  6. Fecal Occult Blood Test
    1. Consider in cases of Anemia or associated gastrointestinal symptoms
  7. Troponin I
    1. Associated with a significantly worse outcome if elevated
    2. However Syncope is a rarely due to ACS or Myocardial Infarction (3% of cases)
      1. Arrhythmia is a more likely cause of Syncope
      2. Troponin Is positive in only 1.4% of Syncope patients
      3. Patients with Syncope due to ACS/MI should still appear ill at evaluation
    3. Indications
      1. Chest Pain, Shortness of Breath or other cardiopulmonary symptoms
      2. EKG with ischemic changes
    4. References
      1. Reed (2010) Emerg Med J 27(4): 272-6 +PMID:20385677 [PubMed]
  8. Brain Natriuretic Peptide (BNP)
    1. Non-specific and unlikely to affect management or disposition
    2. Earlier studies demonstrated an association with cardiac cause of Syncope
      1. Tanimoto (2004) Am J Cardiol 93:228-30 [PubMed]
  9. Additional tests to consider
    1. Cardiac stress testing
    2. Event Monitor or Holter Monitor
    3. Echocardiogram
    4. D Dimer or CT chest (if Pulmonary Embolism is suspected)
    5. Imaging related to injuries sustained in a Syncope-related fall

XVII. Imaging: CT Head

  1. Efficacy: Low
    1. Head CT is very low yield in Syncope and not recommended unless indications below
    2. Goyal (2001) Intern Emerg Med 1(2):148-50 [PubMed]
    3. Grossman (2007) Intern Emerg Med 2(1):46-9 +PMID:17551685 [PubMed]
  2. Indications
    1. Trauma above the clavicles
    2. Persistent neurologic deficit
    3. Dizziness
    4. Sudden onset Headache (Thunderclap Headache of Subarachnoid Hemorrhage)
    5. Age over 65 years
    6. Warfarin use
    7. First Seizure

XVIII. Evaluation: Reassuring findings suggestive of neurally-mediated cause

  1. No cardiac history
  2. Chronic history of Syncope
  3. Triggered by specific stimulus
    1. Noxious smell, sound, sight or pain
    2. Prolonged standing, crowded place, heat
    3. Nausea or Vomiting
    4. Post-meal
    5. Rotation of head or tight collar, shaving
    6. Post-exertion

XIX. Management: Hospitalization Indications

  1. Abnormal San Francisco Syncope Rule (CHESS Criteria)
  2. Syncopal episode occurring during Exercise
  3. Family History of sudden death
  4. Severe Orthostatic Hypotension
  5. Abnormal Vital Signs
  6. Hematocrit <30%
  7. Advanced age
  8. Congestive Heart Failure (or other structural heart disease)
  9. Abnormal Electrocardiogram, including Prolonged QTc >500 ms (risk of Torsades de Pointes)
    1. See Electrocardiogram in Syncope
  10. Syncope WITHOUT prodrome
    1. Arrhythmia is more likely if absent prodrome (e.g. vision dimming, light headedness, Nausea, diaphoresis)
  11. Suspected underlying serious cause
    1. Coronary Artery Disease
    2. Cardiac arrhythmia
    3. Cerbebrovascular accident (does not typically result in Syncope, see above)
  12. References
    1. Brignole (2001) Eur Heart 22:1256-306 [PubMed]

XX. Prognosis

  1. See San Francisco Syncope Rule (CHESS Criteria)
    1. Predicts short-term risk of serious outcome
  2. Mortality 10% within 6 months of cardiovascular Syncope
    1. Soteriades (2002) N Engl J Med 347:878-85 [PubMed]

XXI. References

  1. Joshi and Dermark (2016) Crit Dec Emerg Med 30(8):3-12
  2. Orman and Mattu in Herbert (2016) EM:Rap 16(3): 9-11
  3. Kapoor (2000) N Engl J Med 343:1856-62 [PubMed]
  4. Brignole (2001) Eur Heart J 22:1256-306 [PubMed]
  5. Miller (2005) Am Fam Physician 72:1492-500 [PubMed]

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Ontology: Syncope (C0039070)

Definition (MEDLINEPLUS)

Fainting is a temporary loss of consciousness. If you're about to faint, you'll feel dizzy, lightheaded, or nauseous. Your field of vision may "white out" or "black out." Your skin may be cold and clammy. You lose muscle control at the same time, and may fall down.

Fainting usually happens when your blood pressure drops suddenly, causing a decrease in blood flow to your brain. It is more common in older people. Some causes of fainting include

  • Heat or dehydration
  • Emotional distress
  • Standing up too quickly
  • Certain medicines
  • Drop in blood sugar
  • Heart problems

When someone faints, make sure that the airway is clear and check for breathing. The person should stay lying down for 10-15 minutes. Most people recover completely. Fainting is usually nothing to worry about, but it can sometimes be a sign of a serious problem. If you faint, it's important to see your health care provider and find out why it happened.

Definition (NCI) A spontaneous loss of consciousness caused by insufficient blood supply to the brain.
Definition (NCI_CTCAE) A disorder characterized by spontaneous loss of consciousness caused by insufficient blood supply to the brain.
Definition (NCI_FDA) Extremely weak; threatened with syncope.
Definition (NCI_CDISC) Sudden loss of consciousness with loss of postural tone, not related to anesthesia, with spontaneous recovery as reported by patient or observer. A subject may experience syncope when supine. Syncope is often caused by insufficient blood supply to the brain.
Definition (NCI) Extremely weak; threatened with syncope.
Definition (MSH) A transient loss of consciousness and postural tone caused by diminished blood flow to the brain (i.e., BRAIN ISCHEMIA). Presyncope refers to the sensation of lightheadedness and loss of strength that precedes a syncopal event or accompanies an incomplete syncope. (From Adams et al., Principles of Neurology, 6th ed, pp367-9)
Definition (CSP) fainting due to a sudden fall of blood pressure below the level required to maintain oxygenation of brain tissue.
Concepts Sign or Symptom (T184)
MSH D013575
ICD9 780.2
ICD10 R55
SnomedCT 206727002, 206725005, 206731008, 271594007, 271211004, 29423006, 158137001, 158135009, 271785004, 158133002, 139532000, 162263008, 309585006, 272030005
LNC MTHU020851, LA16987-2
English Fainting, Syncope, Syncopes, COLLAPSE TRANSIENT, FAINTNESS, FALLING OUT, Fainted, PASSED OUT, SWOONING, Syncope and collapse NOS, [D]Syncope, [D]Syncope and collapse, [D]Syncope and collapse NOS, A faint, Passed out, [D]Fainting (context-dependent category), [D]Syncope and collapse (context-dependent category), [D]Syncope and collapse NOS (context-dependent category), [D]Fainting, fainting (syncope), syncope, fainting, fainting (symptom), Syncopal attack, Falling out, Swooning, Faint, Syncope [Disease/Finding], attacks syncopal, disorders syncope, fainting episodes, falls out, Attack(s);fainting, collapse syncope, faint, fainted, faints, syncope attack, out pass, pass out, attacks fainting, out passed, syncopes, fainting/syncope, Swoon, syncope fainting, faintness, swoons, out passes, swooning, passed out, syncope collapse, fainting syncope, [D]: [fainting] or [collapse] (disorder), [D]Syncope and collapse NOS (situation), Syncope (finding), [D]: [fainting] or [collapse] (situation), [D]Syncope and collapse (situation), [D]Fainting (situation), Fainting (finding), Fainting [D], Faint symptom, [D]: [fainting] or [collapse], SYNCOPE, FAINT, FAINTING, Syncope and collapse, Syncope symptom, Syncope attack, Syncope (disorder), Syncope and collapse (disorder), Syncope symptom (disorder), Fainting/syncope, attack; syncope, attack; unconsciousness, collapse; general, fainting; fit, fit; fainting, general; collapse, loss of consciousness; attack, syncope; syncope, unconsciousness; attack, Syncope, NOS, Faintness, Collapse fleeting, Collapse transient, fainting attacks, swoon
French SYNCOPE, Collapsus passager, Tendance lipothymique, Syncope et collapsus, Evanouissements, Collapsus transitoire, Chutes fréquentes, Pâmoison, Lipothymie, COLLAPSUS TRANSITOIRE, DECES, ETAT SYNCOPAL, EVANOUISSEMENT, PERTE DE CONNAISSANCE, A perdu connaissance, Syncope, Évanouissement
Portuguese SINCOPE, DESMAIO, Síncope e colapso, Ataque de síncope, Colapso transitório, Esvaimento, Perda de consciência, Desmaiado, Colapso passageiro, COLAPSO TRANSITORIO, DEBILIDADE, DESFALECIMENTO, DESMAIADO, Desmaio, Síncope
Spanish DESVANECIMIENTO, SINCOPE, DESMAYO, Colapso transitorio, Desfallecimiento, Episodio sincopal, Síncope y colapso, Privación de sentido, Alferecía, Pérdida de conocimiento, Desvanecimiento, Colapso fugaz, [D]desvanecimiento (categoría dependiente del contexto), [D]síncope y colapso (categoría dependiente del contexto), [D]síncope y colapso SAI (categoría dependiente del contexto), CAIDA, COLAPSO TRANSITORIO, DESFALLECIMIENTO, desvanecimiento, desvanecimiento (hallazgo), [D]síncope y colapso SAI, [D]desvanecimiento (situación), síncope (hallazgo), [D]síncope y colapso SAI (situación), [D]síncope y colapso (situación), [D]desvanecimiento, [D]síncope y colapso, desmayo, síncope (trastorno), síncope - síntoma (trastorno), síncope - síntoma, síncope y colapso (trastorno), síncope y colapso, síncope, Desmayo, Síncope
German SYNKOPE, ohnmaechtig, Kollaps fluechtig, synkopale Attacke, bewusstlos werden, Synkope und Kollaps, Kollaps voruebergehend, schwummrig, ohnmaechtig werden, Ohnmachtsanfall, BEWUSSTLOSIGKEIT FLUECHTIG, KOLLAPS KURZDAUERND, OHNMACHT, OHNMAECHTIG WERDEN, SCHWAECHEANFALL, Ohnmacht, Synkope
Dutch kortdurende collaps, flauwte, flauw, flauwteaanval, flauwvallen, voorbijgaande collaps, syncope en collaps, uitvallen, flauwgevallen, aanval van syncope, Flauwvallen/syncope, aanval; bewusteloosheid, aanval; syncope, algemeen; collaps, bewusteloosheid; aanval, bewustzijnsverlies; aanval, collaps; algemeen, flauwvallen; toeval, syncope; aanval, toeval; flauwvallen, Syncope en collaps, syncope, Collaps, Flauwvallen, Syncope
Italian Attacco sincopale, Sfaldarsi, Sincope e collasso, Collasso transitorio, Malore, Svenuto, Svenimento, Sincope
Japanese 卒倒, 一過性虚脱, 浮動性めまい感, 失神発作, シッシン, イッカセイキョダツ, ソットウ, シッシンホッサ, フドウセイメマイカン, キゼツ, 脳貧血, 気絶, 失神
Swedish Svimning
Czech synkopa, Tranzientní kolaps, Synkopický záchvat, Omdlívající, Mdloba, Synkopa a kolaps, Synkopa, Výpadek, Upadnout do bezvědomí, Pocit závratě, mdloba
Finnish Pyörtyminen
Russian SINKOPE, OBMOROK, OBMOROK POSTURAL'NYI, POTERIA SOZNANIIA, PREDOBMOROCHNOE SOSTOIANIE, ОБМОРОК, ПОТЕРЯ СОЗНАНИЯ, ОБМОРОК ПОСТУРАЛЬНЫЙ, ПРЕДОБМОРОЧНОЕ СОСТОЯНИЕ, СИНКОПЕ
Korean 실신 및 허탈
Croatian SINKOPA
Polish Zapaść, Omdlenie
Hungarian Ájult, Syncopés roham, Syncope és collapsus, Átmeneti collapsus, Ájulásérzés, Múló collapsus, Syncope, Ájulás, Elájulás, Összeesés
Norwegian Synkope, Besvimelse

Ontology: Presyncope (C0700200)

Definition (NCI) An episode of lightheadedness and dizziness which may precede an episode of syncope.
Definition (NCI_CTCAE) A disorder characterized by an episode of lightheadedness and dizziness which may precede an episode of syncope.
Concepts Sign or Symptom (T184)
MSH D013575
SnomedCT 427461000
English PRE-SYNCOPE, Pre-syncope, Near syncope (disorder), Near syncope, Presyncopes, near syncope, presyncope, pre-syncope, pre syncope, Presyncope
Dutch presyncope, bijna-syncope, Presyncope
French Syncope rattrapée, Malaise, Présyncope, LIPOTHYMIE
German Praesynkope, Beinahe-Synkope, Präsynkope, PRAE-SYNKOPE
Italian Semisincope, Lipotimia, Pre-sincope, Presincope
Portuguese Pré-síncope, Quase síncope, Pré-Síncope, PRE-SINCOPE
Spanish Estado presincopal, casi síncope (trastorno), casi síncope, Presíncope, PRE-SINCOPE
Japanese 失神寸前の状態, シッシンスンゼンノジョウタイ
Czech Presynkopa, Blízko synkopy, presynkopa, presynkopální aura
Hungarian Presyncope, Praesyncope
Norwegian Nærbesvimelse, Presynkope