Syncope: workup and approach
Transient loss of consciousness with spontaneous full recovery. Distinguish true syncope from seizure, then identify cardiac syncope, which carries the mortality risk.
Presenting complaint
Adult · US guidelines
Draft · awaiting physician review
01Orient
What's new in the evidence
- No new US syncope guideline since 2017; the 2017 ACC/AHA/HRS guideline still applies
- Canadian Syncope Risk Score has been externally validated for 30-day serious outcomes in the ED
- After PESIT (2016) reported PE in 17% of admitted syncope, larger cohorts found PE uncommon; test for PE only when clinically suspected
Differential diagnoses
- Arrhythmia (bradyarrhythmia, VT, heart block)
- Structural heart disease (aortic stenosis, HOCM)
- Pulmonary embolism
- Acute hemorrhage (GI bleed, ruptured AAA, ectopic pregnancy)
- Orthostatic hypotension (volume depletion, medications, autonomic failure)
- Vasovagal (reflex) syncope
- Situational syncope (micturition, cough)
- Seizure (mimic)
- Hypoglycemia (mimic)
02Assess
Risk scores and decision tools
- Canadian Syncope Risk Score
- San Francisco Syncope Rule (lower specificity)
- Orthostatic vital signs
- ECG red flags: Brugada, long QT, pre-excitation, bifascicular block, Mobitz II
Key history questions
- Prodrome (warmth, nausea, tunnel vision) vs none
- Exertional or supine syncope (cardiac red flags)
- Palpitations or chest pain beforehand
- Witness account: duration, jerking, color, tongue biting, post-ictal confusion
- Family history of sudden death under 50
- Medications: antihypertensives, QT-prolonging drugs, diuretics
Examination findings
- Orthostatic vitals (SBP fall of 20 or more, or symptoms)
- Murmur of aortic stenosis or HOCM
- Signs of heart failure
- Rectal exam or stool check if GI bleed suspected
- Injuries from the fall; tongue laceration
- Focal neurological deficits
03Investigate
Initial investigations
- 12-lead ECG: QT, QRS width, heart block, Brugada, pre-excitation, LVH
- Fingerstick glucose
- CBC, BMP, magnesium
- Pregnancy test if of childbearing potential
- Troponin if chest pain or ECG changes
Advanced investigations
- Echocardiogram if murmur, abnormal ECG or suspected structural disease
- Telemetry; outpatient ambulatory ECG monitor
- Tilt-table testing for recurrent unexplained syncope
- EEG or neuroimaging only if seizure or focal deficit suspected
04Treat
Immediate management
- Monitor on telemetry if any cardiac features
- Treat hemorrhage, arrhythmia or hypoglycemia directly
- IV fluids for volume depletion
First-line treatment
- Vasovagal: education, counter-pressure maneuvers, fluids and salt
- Orthostatic: stop or reduce culprit drugs, hydration, compression stockings
- Bradyarrhythmia: stop nodal blockers; pacing per cardiology
Second-line treatment
- Midodrine or fludrocortisone for refractory orthostatic hypotension
- Implantable loop recorder for recurrent unexplained syncope
Specialist referrals
- Cardiology for suspected cardiac syncope
- Neurology if seizure more likely
05Disposition
Admission criteria
- Exertional or supine syncope, or syncope preceded by palpitations
- Abnormal ECG or structural heart disease
- Family history of sudden cardiac death
- Significant injury or hemodynamic instability
- High risk on Canadian Syncope Risk Score
Safe discharge criteria
- Clear vasovagal or orthostatic cause
- Normal ECG and exam, no heart disease
- Recovered fully and ambulating safely
Follow-up timing
- Primary care within 1-2 weeks; cardiology clinic if monitor arranged
Patient instructions
- Sit or lie down at the first warning symptoms
- Check local rules on driving after syncope
- Return for syncope with exertion, chest pain or palpitations
Monitoring
- Telemetry for at least 24 h if cardiac cause suspected
Clinical pearls and pitfalls
- Brief myoclonic jerks are common in syncope and do not imply seizure
- Head CT has low yield without trauma or neurological findings
RefGuidelines and landmark evidence
- GuidelineACC/AHA/HRS – Guideline for the Evaluation and Management of Patients With Syncope (2017)PubMed
- TrialCanadian Syncope Risk Score derivation (Thiruganasambandamoorthy et al., 2016)PubMed
- TrialPESIT: pulmonary embolism among patients hospitalized for syncope (Prandoni et al., 2016)PubMed
- TrialCanadian Syncope Risk Score: multicenter ED validation (2020)PubMed
For education only. Typical adult starting points; confirm doses against renal function, allergies, interactions and your institution's protocols. Not a substitute for clinical judgment or senior review.