For pediatric patients patients see syncope (peds)


  • Transient loss of postural tone and consciousness due to cerebral hypoperfusion
  • Syncope and pre-syncope assessed similarly
  • Important considerations:
    • Is this true syncope or something else (eg, stroke, seizure, head injury)?
    • If this is true syncope, is there a clear life-threatening cause?
    • If this is true syncope and the cause is not clear, is the patient at high risk for serious outcome?

Risk Factors for Serious Cause

  • Exertion preceding the event
    • Note that syncope during exertion much more concerning than syncope after exertion
  • No preceding symptoms
    • Concerning for cardiac dysrhythmia
  • History of cardiac disease in the patient
  • Family history of sudden death, deafness, or cardiac disease
    • Consider unexplained deaths and deaths due to single vehicle accidents
  • Recurrent episodes
  • Recumbent episode
  • Prolonged loss of consciousness
  • Associated chest pain, shortness of breath or palpitations
  • Use of medications that can alter cardiac conduction

Clinical Features

Physical Exam

Clinical Features by Cause

  • Cardiovascular-mediated syncope
    • Usually occurs without warning (absence of prodrome)
    • History of structural heart disease
    • Family history of sudden cardiac death
    • Syncope during exertion
    • Chest pain or palpitations associated with syncope
    • Abnormal ECG
  • Neurally mediated syncope
    • Trigger event (fear/pain, prolonged standing, warm environment)
    • Prodrome of nausea/vomiting, tunnel vision, lightheadedness, diaphoresis, warmth [1]
    • Associated with head movement or pressure on neck
  • Orthostatic hypotension-mediated syncope
    • After standing up
    • Change in medications

Differential Diagnosis

Syncope Causes



ACEP only recommends ECG and H&P as must haves

  • ECG
    • Perform on every patient, unless trigger clearly identified (i.e. following blood draw) and no risk factors
  • Urine pregnancy

Consider based on history/symptoms
  • CBC (or POC hemoglobin) & chemistry (or POC glucose)
  • Troponin
    • Not recommended to rule out AMI in patients with isolated syncope[2]
    • Elevated troponin predicts adverse cardiac outcome in syncope[3]
    • May be useful for risk stratification
  • CXR
  • Orthostatics (symptomatic)
  • Guaiac
  • CT scan of head is not recommended in asymptomatic, insignificant trauma with normal neurologic examination
  • Does PE need to be worked up?
    • NEJM paper by Prandoni[4] showed that 7.14% of patients admitted for syncope had a pulmonary embolism and of the cohort that were not low risk with a negative d-dimer, the risk was as high as 17.3%
    • 2018 systematic reviewed [5] showed 0.8% of admitted ED pts with syncope had PE
    • Also supported by 2019 study showing prevalence of 2.3% in undifferentiated patients admitted with syncope[6].
    • Both of these two studies refute the findings of the PESIT study listed first
  • Bedside US
    • PSL view may show thickened ventricular septum
    • High sensitivity to rule out AAA



  • Treat underlying cause, if known (~50% of patients do not have a firm diagnosis)



  • Abnormal ECG
  • CHF
  • Suspicion of structural heart disease
    • Ischemic, dysrhythmic, obstructive, valvular
  • HCT <30
  • Shortness of Breath
  • Hypotension(SBP <90)
  • Family history of sudden cardiac death
  • Advanced age
  • Evidence of hemorrhage (occult blood)
  • Syncope without prodrome
  • Exertional syncope in younger patients without an obvious benign cause


  • None of the above findings (esp if age <45)
  • No events on telemetry after period of observation (2-4 hours in the ED)
  • Consider referral for holter or til-table test
  • Instruct to avoid precipitating factors, such as extreme heat, dehydration, postexertional standing, alcohol and certain medications

Additional Risk Stratification Tools for Selecting Low-Risk patients for Discharge

Canadian Syncope Risk Score[12] MDCalc

Category No Yes
Predisposition to vasovagal symptoms (triggered by being in a warm crowded place, prolonged standing, fear, emotion, or pain) 0 -1
Heart disease history (CAD, afib, flutter, CHF, valvular disease) 0 1
SBP < 90 or > 180mmHg 0 2
Elevated troponin 0 2
Abnormal QRS axis 0 1
QRS > 130ms 0 1
Corrected QT interval >480ms 0 2
Vasovagal syncope (based on clinical impression 0 -2
Cardiac Syncope (based on clinical impression) 0 2
  • Score < 0 associated with < 2% risk of serious adverse event at 30 days.
  • Externally validated per data presented at SAEM 2018 and only 0.3% 30 day adverse events for very low risk patients in 2020 Jama study [13]

San Francisco Syncope Rule

  • 1.4% of patients who are rule-negative will have a 7-day serious outcome
  • 10% of patients meeting the below criteria will have a 7-day serious outcome
Criteria (CHESS Pneumonic)[14]


  • Performed poorly on external validation[15]
  • External validation of San Francisco Syncope Rule showed sensitivity 90% but only specificity of 33% [16]

External Links

See Also


  1. Romme JJCM, van Dijk N, Boer KR, et al. Influence of age and gender on the occurrence and presentation of reflex syncope. Clin Auton Res. 2008;18(3):127-133
  2. Reed MJ, Newby DE, Coull AJ, et al. Diagnostic and prognostic utility of troponin estimation in patients presenting with syncope: a prospective cohort study. Emerg Med J. 2010; 27(4):272-276
  3. Reed MJ, Mills NL, Weir CJ. Sensitive troponin assay predicts outcome in syncope. Emerg Med J. 2012;29(12):1001- 1003
  4. Prandoni P, Lensing AW, Prins MH, Ciammaichella M, Perlati M, Mumoli N, Bucherini E, Visonà A, Bova C, Imberti D, Campostrini S, Barbar S; PESIT Investigators. Prevalence of Pulmonary Embolism among Patients Hospitalized for Syncope. N Engl J Med. 2016 Oct 20;375(16):1524-1531. PubMed PMID: 27797317.
  5. Prevalence Of Pulmonary Embolism In Patients Presenting With Syncope: A Systematic Review And Meta-Analysis Oqab, Z., et al, Am J Emerg Med 36(4):551, April 2018
  6. Prevalence of pulmonary embolism in patients with syncope Badertscher P, du Fay de Lavallaz J, Hammerer-Lercher A, et al. J Am Coll Cardiol. 2019;74(6):744-754.
  7. D’Ascenzo F, Biondi-Zoccai G, Reed M, et al. Incidence, etiology and predictors of adverse outcomes in 43,315 patients presenting to the emergency department with syncope: an international meta-analysis. Int J Cardiol. 2013;167(1)57-62
  8. Quinn J, McDermott D. Electrocardiogram findings in emergency department patients with syncope. Acad Emerg Med. 2011;18(7):714-718
  9. Thiruganasambandamoorthy V, Hess EP, Turko E, et al. Defining abnormal electrocardiography in adult emergency department syncope patients: the Ottawa Electrocardiographic Criteria. CJEM. 2012;14(4):248-258
  10. Sud S, Klein GJ, Skanes AC, et al. Predicting the cause of syncope from clinical history in patients undergoing prolonged monitoring. Heart Rhythm. 2009;6(2):238-243
  11. Huff JS, Decker WW, Quinn JV et al. Clinical policy: critical issues in the evaluation and management of adult patients presenting to the emergency department with syncope. Ann Emerg Med. 2007;49(4):431-444
  12. Thiruganasambandamoorthy, V et al. Development of the Canadian Syncope Risk Score to predict serious adverse events after emergency department assessment of syncope. CMAJ. 2016 Sep 6;188(12):E289-E298.
  13. Multicenter Emergency Department Validation of the Canadian Syncope Risk Score. JAMA Intern Med. 2020 Mar 23.
  14. Quinn J, McDermott D, Stiell I, Kohn M, Wells G. Prospective validation of the San Francisco Syncope Rule to predict patients with serious outcomes. Ann Emerg Med. 2006 May;47(5):448-54. PubMed PMID: 16631985.
  15. Birnbaum A, Esses D, Bijur P, Wollowitz A, Gallagher EJ. Failure to validate the San Francisco Syncope Rule in an independent emergency department population. Ann Emerg Med. 2008;52(2):151-9.
  16. Thiruganasambandamoorthy et al, External validation of the San Francisco Syncope Rule in the Canadian setting. Ann Emerg Med. 2010 May;55(5):464-72. doi: 10.1016