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In 2017, the American College of Cardiology (ACC) / American Heart Association (AHA) Task Force on Clinical Practice Guidelines and the Heart Rhythm Society released their practice guideline on the evaluation and management of patient with syncope (pdf). It is a massive document. Of the 278 pages, the references, appendix, and data supplement combined take up 210 pages. The Admin EM algorithm below is a summary of the guideline contents in regards to the history, physical exam, ecg, and disposition of a patient with syncope. It is intended as a guide for use in the emergency department. The ACC / AHA guidelines go on to further define the types of testing recommended once a disposition has been made.

Admin EM Syncope Algorithm PDF

Syncope is a vast topic. Having reviewed this guideline, what is most impressive is that our common daily practice already includes these numerous considerations for any patient presenting with syncope. There is no new information regarding syncope. However, the creation of the guideline clearly demonstrates the decision-making involved and provides a level of evidence for each decision.

Evidence classification:
  • I recommended; benefit >>>risk
  • IIa reasonable; benefit >>risk
  • IIb may be reasonable; benefit still > risk
  • III (No benefit) not recommended; benefit = risk
  • III (Harm) harmful; risk>benefit
The document takes great care in providing definitions for a multitude of causes of syncope. Notably:
  • Orthostatic Hypotension is divided into 3 categories, all with a required drop in SBP >20 mm Hg or diastolic BP >10mm Hg
    • Initial (immediate) = within 15 sec of position change
    • Classic = within 3 minutes
    • Delayed = onset after 3 minutes
    • Neurogenic = due to dysfunction of the autonomic nervous system
  • Reflex syncope (neurally mediated)
    • Vasovagal
      • May occur with upright posture and may include emotional stress or pain
      • Typically characterized by diaphoresis, warmth, nausea, and pallor
      • Associated with vasodepressor hypotension or inappropriate bradycardia
      • Often followed by fatigue
    • Carotid sinus syndrome – present when a pause of >3 seconds or decrease of SBP >50 mm HG occurs upon stimulation of the carotid sinus
    • Situational syncope – associated with coughing, laughing, swallowing, micturition, or defecation
  • Postural Orthostatic Tachycardia Syndrome (POTS)
    • Frequent symptoms that occur with standing (light-headed, palpitations, tremulousness, weakness, blurred vision, exercise intolerance)
    • Increase in heart rate >30 bpm from supine to standing, often > 120 bpm
    • Absence of orthostatic hypotension
In addition to the algorithm above, the guideline answers some key clinical questions:

1)History and physical examination are key components of the syncope evaluation and should focus on characteristics associated with cardiac and non-cardiac causes: (level1)


  • Age >60
  • Male gender
  • Presence of known ischemic heart disease, structural heart disease, previous arrhythmias, or reduced ventricular function
  • Brief prodrome, such as palpitations, or sudden loss of consciousness without prodrome
  • Syncope during exertion
  • Syncope in the supine position
  • Low number of syncope episodes (1 or 2)
  • Abnormal cardiac examination
  • Family history of inheritable conditions or premature sudden cardiac death (<50 yo)


  • Younger age
  • No known cardiac disease
  • Syncope only in the standing position
  • Positional change from supine or sitting to standing
  • Presence of prodrome: nausea, vomiting, feeling warmth
  • Presence of specific triggers: dehydration, pain, distressful stimulus, medical environment
  • Situational triggers: cough, laugh, micturition, defecation, deglutition
  • Frequent recurrence and prolonged history of syncope with similar characteristics


  • Orthostatic blood pressure and heart rate lying, sitting, and standing, both immediate and after 3 minutes.
  • Heart rate and rhythm
  • Murmurs, Rubs, and Gallops
  • Basic neurological exam

2)Evaluation should include an ECG with special attention to the following: (level 1)

  • Bradyarrhythmia with sinus pauses
  • High grade conduction block
  • Ventricular tachyarrhythmia
  • Wolf-Parkinson-White (WPW)
  • Brugada syndrome
  • Long-QT syndrome
  • Hypertrophic cardiomyopathy (HCM)
  • Arrhythmogenic right ventricular cardiomyopathy (ARVC)

However, the authors note that “prospective studies did not conclude that ECG findings significantly affected subsequent management” and that the “prognostic value of an abnormal ECG in patients with syncope has been questioned”. Lastly, they also explain that the presence of the following conditions “were associated with increased risk of death from all causes in 1 year” in a multicenter, prospective observational study:

  • Atrial fibrillation
  • Intraventricular conduction disturbances
  • Voltage criteria for left ventricular hypertrophy
  • Ventricular pacing

3)Risk assessment of patient with no identifiable cause of syncope is recommended based on the following criteria: (level1)

Note there is significant overlap with questions asked in the history section above. 

Short Term Risk Factors :

  • Male gender
  • Age > 60
  • No prodrome
  • Palpitations preceding syncope
  • Exertional syncope
  • Structural heart disease
  • Heart failure
  • Cerebrovascular disease
  • Family history of sudden cardiac death
  • Trauma
  • Evidence of bleeding
  • Persistent abnormal vital signs
  • Abnormal ECG
  • Positive troponin

Long Term Risk Factors (>30 days)

  • Male gender
  • Age > 60
  • Absence of nausea / vomiting preceding syncopal event
  • Ventricular arrhythmia
  • Cancer
  • Structural heart disease
  • Heart failure
  • Cerebrovascular disease
  • Diabetes mellitus
  • High CHADS-2 score
  • Abnormal ECG
  • Lower GFR

4)Hospital evaluation is recommended for patients with syncope who have a serious medical condition potentially relevant to the cause, such as :  (level 1)

Cardiac Arrhythmic Conditions:

  • Sustained or symptomatic VT
  • Symptomatic conduction system disease or Mobitz II or third-degree heart block
  • Symptomatic bradycardia or sinus pauses not related to neurally mediated syncope
  • Symptomatic SVT
  • Pacemaker/ICD malfunction
  • Inheritable cardiovascular conditions predisposing to arrhythmias

Cardiac or Vascular Nonarrhythmic Conditions:

  • Cardiac ischemia
  • Severe aortic stenosis
  • Cardiac tamponade
  • HCM
  • Severe prosthetic valve dysfunction
  • Pulmonary embolism
  • Aortic dissection
  • Acute HF
  • Moderate-to-severe LV dysfunction

Noncardiac conditions:

  • Severe anemia/gastrointestinal bleeding
  • Major traumatic injury due to syncope
  • Persistent vital sign abnormalities

5)It is reasonable to manage patients with presumptive reflex-mediated syncope (see definitions above) in the outpatient setting or an ED obs unit in the absence of serious medical conditions , listed in item 4 above.  (level 2a)

6)It may be reasonable to manage selected patients with suspected cardiac syncope in the outpatient setting in the absence of serious medical conditions. (level 2b)

7)Targeted laboratory evaluation is reasonable based on history and physical and ECG. (level 2b)

8)Usefulness of BNP and high sensitivity troponin is uncertain. (level 2b)

9)Routine comprehensive lab testing is not useful. (level 3)

10)Transthoracic echocardiography can be useful in patients with syncope suspected of having structural heart disease (level 2a); CT or MRI (level 2b)

11)Routine echocardiography in all patients with syncope if not recommended. (level 3)

12)Exercise stress testing can be useful in patients with exertional syncope/presyncope. This should be performed with caution in a monitored setting with advanced life support available. (level 2a)

13)Cardiac monitoring is determined on the frequency and type of syncope events. (level 1)

14)In ambulatory patients with suspected arrhythmic etiology for syncope, the following external cardiac monitors may be helpful: (level 2a)

  • Holter monitor
  • Transtelephonic monitor
  • External loop recorder
  • Patch recorder
  • Mobile cardiac outpatient telemetry
The exact type is guided by history, symptoms, and availability of device.

15)In select ambulatory patients with suspected arrhythmic syncope, an internal cardiac monitor can be useful. (level 2a)

16)Continuous ECG monitoring is helpful for patients hospitalized for syncope. (level 1)

If you are considering building protocols for inpatient treatment, outpatient treatment, or observation unit care, the recommendations also summarize the evidence for the following conditions.
  • Vasovagal syncope testing and management
  • Tilt table testing indications and populations
  • EEG / Neurological monitoring if seizures are suspected (but not routinely)
  • Carotid imaging (not recommended)
  • Bradycardia treatment
  • SVT treatment
  • Ventricular Arrhythmia patients
  • Brugada syndrome treatment
  • Cardiac sarcoidosis
  • Long-QT syndrome treatment
  • Recurrent vasovagal syncope treatment options
  • Carotid Sinus Syndrome treatment
  • Neurogenic orthostatic hypotension treatment
  • Pediatric syncope testing and treatment
  • Athlete syncope treatment
  • Recommended driving restriction time frames by diagnosis

Emergency physicians may find this portion of the document helpful in discussions with patients regarding potential follow up testing outside the ED.

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