Overview
Syncope Evaluation
Quick Reference
Critical Alerts
- Cardiac syncope is life-threatening: Arrhythmia, structural heart disease, PE
- High-risk features require admission: Cardiac findings, abnormal ECG, older age
- Vasovagal is most common but diagnosis of exclusion
- ECG is essential for all patients: May reveal cause
- Orthostatic vitals must be measured: Common cause
- Unexplained syncope with cardiac risk factors = Workup
High-Risk Features (San Francisco Syncope Rule, Canadian Syncope Risk Score)
| Feature | Concern |
|---|---|
| Abnormal ECG | Arrhythmia |
| History of CHF | Cardiac cause |
| Hematocrit <30% | Bleeding |
| Shortness of breath | PE, cardiac |
| Systolic BP <90 | Hemodynamic instability |
| Older age (>0) | Higher cardiac risk |
| Syncope during exertion | Structural heart disease |
| Syncope while supine | Arrhythmia |
| Family history SCD | Channelopathy |
| Prior heart disease | Cardiac cause |
Emergency Treatments
| Condition | Treatment |
|---|---|
| Vasovagal | Reassurance, education, hydration |
| Orthostatic hypotension | IV fluids, review medications |
| Cardiac arrhythmia | Treat arrhythmia (pacing, cardioversion, drugs) |
| PE | Anticoagulation, ± thrombolytics |
| AAA (ruptured) | Emergent surgery |
| Hypoglycemia | Glucose |
Definition
Overview
Syncope is transient loss of consciousness (TLOC) due to global cerebral hypoperfusion with rapid onset, short duration, and spontaneous complete recovery. The ED challenge is identifying patients with high-risk (cardiac) causes who require admission and workup from those with benign (vasovagal, orthostatic) causes who can be safely discharged.
Classification
By Mechanism:
| Type | Mechanism | Examples |
|---|---|---|
| Reflex (neurally mediated) | Inappropriate reflex causing vasodilation/bradycardia | Vasovagal, situational, carotid sinus |
| Orthostatic | Autonomic failure or volume depletion | Dehydration, meds, autonomic neuropathy |
| Cardiac | Arrhythmia or structural heart disease | VT, bradycardia, AS, HOCM, PE |
Epidemiology
- Lifetime prevalence: 30-40%
- 1-3% of ED visits; 1-6% of hospital admissions
- Reflex syncope: 50-60% of cases
- Cardiac syncope: 10-20% (higher mortality)
- Unknown cause: 10-40%
Etiology
Reflex (Neurally Mediated):
| Type | Trigger |
|---|---|
| Vasovagal | Prolonged standing, pain, emotional stress |
| Situational | Cough, micturition, defecation, swallowing |
| Carotid sinus | Pressure on carotid sinus (shaving, collar) |
Orthostatic:
| Cause | Examples |
|---|---|
| Hypovolemia | Dehydration, hemorrhage |
| Medications | Antihypertensives, diuretics, α-blockers |
| Autonomic dysfunction | Diabetes, Parkinson's |
Cardiac:
| Cause | Examples |
|---|---|
| Arrhythmia | VT, SVT, bradycardia, sick sinus, complete heart block |
| Structural | Aortic stenosis, HOCM, myxoma, tamponade |
| Vascular | PE, aortic dissection |
Pathophysiology
Mechanism
- Reduction in cerebral blood flow: >6-8 seconds → LOC
- Global cerebral hypoperfusion: Causes syncope
- Horizontal position: Blood returns to brain → Recovery
Reflex Syncope (Vasovagal)
- Trigger → Vagal activation
- Bradycardia + Vasodilation
- Decreased cerebral perfusion → Syncope
Cardiac Syncope
- Arrhythmia → Inadequate cardiac output
- Structural disease → Fixed cardiac output
- Pulmonary embolism → Obstructed RV outflow
Clinical Presentation
Symptoms
Before Syncope (Prodrome):
| Finding | Suggests |
|---|---|
| Lightheadedness, warmth, diaphoresis, nausea | Vasovagal |
| No warning (sudden LOC) | Cardiac arrhythmia |
| Palpitations | Arrhythmia |
| Chest pain | ACS, PE, aortic dissection |
| Dyspnea | PE, cardiac |
| Triggered by standing | Orthostatic |
During Syncope:
| Finding | Significance |
|---|---|
| Brief duration (<1-2 min) | Typical |
| Pallor | Common |
| Brief myoclonic jerks | Can occur (not seizure) |
After Syncope:
| Finding | Significance |
|---|---|
| Rapid recovery | Typical syncope |
| Prolonged confusion | Suggests seizure |
| Incontinence, tongue bite | More suggestive of seizure |
History
Key Questions:
Physical Examination
| Assessment | Findings |
|---|---|
| Vital signs | Orthostatic hypotension (SBP drop ≥20 or DBP drop ≥10) |
| Cardiovascular | Murmur (AS, HOCM), irregular rhythm, JVD (CHF, PE) |
| Neurological | Focal deficits (suggests stroke, not syncope) |
| Skin | Pallor, diaphoresis |
| Rectal exam | GI bleeding (if suspected) |
Exactly what happened? (Witness account if possible)
Common presentation.
Prodrome symptoms?
Common presentation.
Triggers (standing, pain, emotional stress, exertion)?
Common presentation.
Position at onset (supine = concerning)?
Common presentation.
Palpitations?
Common presentation.
Chest pain or dyspnea?
Common presentation.
Duration of LOC?
Common presentation.
Post-event confusion?
Common presentation.
Prior syncope episodes?
Common presentation.
Family history of sudden death?
Common presentation.
Cardiac history (CHF, MI, arrhythmia)?
Common presentation.
Medications (especially new or changed)?
Common presentation.
Red Flags
High-Risk Features
| Finding | Concern |
|---|---|
| Syncope during exertion | Aortic stenosis, HOCM, arrhythmia |
| Syncope while supine | Arrhythmia |
| No prodrome | Arrhythmia |
| Palpitations before syncope | Arrhythmia |
| Family history sudden death | Channelopathy, HOCM |
| Known heart disease | Cardiac cause |
| Abnormal ECG | Arrhythmia |
| Chest pain | ACS, PE, dissection |
| Dyspnea | PE, cardiac |
| Systolic BP <90 | Hemodynamic instability |
| Severe anemia | Hemorrhage |
Differential Diagnosis
Not Syncope (Distinguish From)
| Diagnosis | Features |
|---|---|
| Seizure | Prolonged postictal confusion, tongue bite (lateral), incontinence, tonic-clonic movements |
| Hypoglycemia | Low glucose, recovery with glucose |
| Stroke/TIA | Focal deficits, not rapid full recovery |
| Psychogenic pseudosyncope | Eyes closed, prolonged, no injury, psychiatric history |
| Drop attack | Falls without LOC |
Diagnostic Approach
Essential for All
| Test | Purpose |
|---|---|
| ECG | Arrhythmia, ischemia, prolonged QT, Brugada, WPW |
| Orthostatic vitals | Orthostatic hypotension |
| Glucose | Hypoglycemia |
Based on Clinical Suspicion
| Test | Indication |
|---|---|
| CBC | Anemia, hemorrhage suspected |
| Troponin | Chest pain, ischemia concern |
| BNP | CHF suspected |
| D-dimer / CTA | PE suspected |
| BMP | Electrolytes, renal function |
| Pregnancy test | Women of childbearing age |
Advanced Testing (Usually Inpatient or Outpatient)
| Test | Indication |
|---|---|
| Echocardiogram | Structural heart disease |
| Telemetry/Holter | Arrhythmia detection |
| Tilt table test | Recurrent unexplained syncope |
| Electrophysiology study | High-risk with negative workup |
| Implantable loop recorder | Recurrent syncope, outpatient |
Risk Stratification
San Francisco Syncope Rule (SFSR)
Admit if any present:
- C: CHF history
- H: Hematocrit <30%
- E: Abnormal ECG
- S: Shortness of breath
- S: Systolic BP <90
Canadian Syncope Risk Score (CSRS)
- Predisposition to vasovagal: -1
- Heart disease history: +1
- SBP <90 or >180: +2
- Elevated troponin: +2
- Abnormal QRS axis: +1
- QRS >130 ms: +1
- Corrected QT >480 ms: +2
- ED diagnosis of cardiac syncope: +2
- ED diagnosis of vasovagal syncope: -2
Score ≥1 = Higher risk → Consider admission
Treatment
Principles
- Risk stratify: Identify high-risk patients
- Treat underlying cause: If identified
- Supportive care: IV fluids if orthostatic
- Admission for high-risk: Monitoring, further workup
- Education for low-risk: Avoid triggers, hydration
Specific Treatments
Vasovagal (Low Risk):
| Intervention | Details |
|---|---|
| Reassurance | Benign cause |
| Avoid triggers | Prolonged standing, heat, dehydration |
| Counterpressure maneuvers | Leg crossing, muscle tensing |
| Hydration and salt intake | Increase fluid volume |
Orthostatic Hypotension:
| Intervention | Details |
|---|---|
| IV fluids | If dehydrated |
| Review medications | Reduce or stop offending agents |
| Compression stockings | Increase venous return |
| Midodrine | For refractory cases |
Cardiac Arrhythmia:
| Arrhythmia | Treatment |
|---|---|
| Bradycardia/Heart block | Atropine, pacing |
| VT | Cardioversion, antiarrhythmics, ICD |
| Long QT, Brugada | Cardiology, ICD |
Structural Heart Disease:
| Condition | Treatment |
|---|---|
| Aortic stenosis | Avoid vasodilators, AVR |
| HOCM | Beta-blockers, avoid dehydration |
| PE | Anticoagulation |
Disposition
Discharge Criteria (Low Risk)
- Clear vasovagal or situational etiology
- No high-risk features
- Normal ECG
- Normal orthostatic vitals
- No structural heart disease
- No family history of sudden death
- Reliable follow-up
Admission Criteria
- Any high-risk feature
- Abnormal ECG (new or concerning)
- Known cardiac disease
- Syncope during exertion or supine
- Concern for PE, GI bleed, or aortic pathology
- No clear etiology with risk factors
Referral
| Indication | Referral |
|---|---|
| Cardiac syncope | Cardiology |
| Recurrent unexplained | Cardiology or EP |
| Structural heart disease | Cardiology |
Patient Education
Condition Explanation
- "Syncope is fainting caused by temporary reduced blood flow to the brain."
- "The most common cause is a reflex reaction where your blood pressure drops temporarily."
- "We've ruled out serious heart problems."
Prevention
- Stay hydrated
- Avoid prolonged standing
- If you feel faint, sit or lie down immediately
- Avoid triggers (heat, alcohol, large meals)
- Don't skip meals
Warning Signs to Return
- Chest pain
- Shortness of breath
- Palpitations
- Another fainting episode
- Fainting during exercise
Special Populations
Elderly
- Higher risk of cardiac cause
- More likely to have injury from fall
- Lower threshold for admission
Athletes
- Syncope during exertion is concerning
- Screen for HOCM, long QT, ARVC
- Cardiology referral
Pregnant Women
- Increased blood volume but decreased SVR
- Consider ectopic pregnancy if abdominal pain
- Pulmonary embolism risk
Quality Metrics
Performance Indicators
| Metric | Target | Rationale |
|---|---|---|
| ECG performed | 100% | Essential for all |
| Orthostatic vitals | >0% | Common cause |
| High-risk features documented | 100% | Risk stratification |
| Discharge low-risk only | >0% | Safety |
Documentation Requirements
- Witness account if available
- Prodrome, triggers
- Exertional or positional
- Duration of LOC
- Post-event recovery
- ECG interpretation
- Orthostatic vitals
- Risk stratification
- Disposition rationale
Key Clinical Pearls
Diagnostic Pearls
- Sudden LOC without prodrome = Arrhythmia: High risk
- Exertional syncope = Structural heart disease or arrhythmia
- Supine syncope = Arrhythmia
- Vasovagal has clear trigger and prodrome: Diagnosis of exclusion
- ECG is essential: Prolonged QT, Brugada, WPW, heart block
- Orthostatic drop ≥20 systolic or ≥10 diastolic
Treatment Pearls
- Low-risk vasovagal = Reassurance and education
- Treat dehydration: IV fluids
- Stop offending medications: If orthostatic
- Cardiac syncope needs admission: Monitoring, workup
- Don't delay treatment for arrhythmia: Cardioversion, pacing
Disposition Pearls
- High-risk = Admit for monitoring: Echo, telemetry
- Low-risk can be discharged: With clear follow-up
- Elderly and cardiac history = Lower threshold to admit
- Recurrent unexplained = Cardiology/EP referral
References
- Brignole M, et al. 2018 ESC Guidelines for the diagnosis and management of syncope. Eur Heart J. 2018;39(21):1883-1948.
- Shen WK, et al. 2017 ACC/AHA/HRS Guideline for the Evaluation and Management of Patients With Syncope. J Am Coll Cardiol. 2017;70(5):e39-e110.
- Quinn JV, et al. Derivation of the San Francisco Syncope Rule. Ann Emerg Med. 2004;43(2):224-232.
- Thiruganasambandamoorthy V, et al. Development and validation of the Canadian Syncope Risk Score. CMAJ. 2016;188(12):E289-E298.
- Sheldon RS, et al. Diagnostic criteria for vasovagal syncope. J Cardiovasc Electrophysiol. 2006;17(1):76-81.
- Kapoor WN. Syncope. N Engl J Med. 2000;343(25):1856-1862.
- Task Force for the Diagnosis and Management of Syncope. Eur Heart J. 2009.
- UpToDate. Approach to the adult patient with syncope in the emergency department. 2024.