About This Page
This is a clinician-written, evidence-based guide aligned to the MCC Examination Objectives. It is structured by clinical presentation — the way the MCCQE tests and the way patients actually present. Management reflects current Canadian guidelines (CMA, CFPC, CPS). Always cross-reference with institutional protocols and clinical judgment.
The Bottom Line
- Three categories: reflex/vasovagal (~60%), orthostatic (~15%), cardiac (~15%) — cardiac is most dangerous
- History is the single most important diagnostic tool — triggers, prodrome, witnesses, position, exertional, family Hx of sudden death
- All syncope patients need: detailed history, orthostatic vitals, 12-lead ECG. Echo if cardiac cause suspected
- Canadian Syncope Risk Score (validated in Canadian EDs): risk-stratifies for 30-day serious adverse events to guide admission vs discharge
- Red flags for cardiac syncope: exertional, no prodrome, abnormal ECG, structural heart disease, family Hx of SCD, older patient
Approach to the Presentation
Syncope accounts for ~1-3% of ED visits and up to 6% of hospital admissions in Canada. The challenge is distinguishing the ~15% with dangerous cardiac causes from the ~60% with benign vasovagal episodes. The Canadian Syncope Risk Score (Thiruganasambandamoorthy et al., CMAJ 2020) was developed and validated in Canadian emergency departments to predict 30-day serious adverse events and guide disposition. A structured approach starts with: (1) detailed history from patient AND witnesses; (2) orthostatic vitals; (3) 12-lead ECG; (4) focused cardiac and neurological examination. Neuroimaging (CT head) is NOT routine for syncope and should only be done if there are features suggesting a primary neurological event (focal deficits, prolonged confusion, head trauma).
Differential Diagnosis
| diagnosis | likelihood | key features | distinguishing test |
|---|---|---|---|
| Ventricular Tachycardia / Fibrillation | must-not-miss | Sudden onset without prodrome, structural heart disease (prior MI, HFrEF), family Hx of SCD. May present as cardiac arrest | ECG: wide QRS tachycardia, prior MI (Q waves), long QT, Brugada pattern. Telemetry monitoring |
| High-grade AV Block / Sinus Node Dysfunction | must-not-miss | Sudden syncope without prodrome (Stokes-Adams), elderly, on AV-nodal blocking drugs (beta-blockers, CCBs, digoxin) | ECG: Mobitz II, complete heart block, sinus pauses >3 sec |
| Aortic Stenosis / HCM / Pulmonary HTN | must-not-miss | Exertional syncope (inability to augment CO). Characteristic murmurs on exam | Echocardiogram: AVA <1.0 cm2 (severe AS), septal hypertrophy (HCM), elevated RVSP (pulmonary HTN) |
| Pulmonary Embolism | must-not-miss | Syncope + dyspnea + tachycardia + risk factors for VTE. Massive PE can present as syncope from acute RV failure | CTPA, D-dimer if low-moderate probability |
| Vasovagal Syncope | common | Prodrome (warmth, nausea, diaphoresis, tunnel vision), triggered by prolonged standing, pain, emotional stress, warm crowded environments. Rapid recovery | Clinical diagnosis from history. Tilt-table if recurrent and unclear |
| Orthostatic Hypotension | common | Occurs on standing. Medications (antihypertensives, diuretics, alpha-blockers), volume depletion, autonomic neuropathy (diabetes, Parkinson) | Orthostatic vitals: SBP drop >=20 or DBP >=10 within 3 min of standing |
| Situational Syncope | common | Triggered by specific action: cough (tussive), micturition, defecation, swallowing. Mechanism: vagal-mediated | History of consistent trigger + typical vasovagal features |
| Carotid Sinus Hypersensitivity | less common | Elderly men, syncope with head turning, tight collar, shaving. Cardioinhibitory (bradycardia) or vasodepressor (hypotension) type | Carotid sinus massage under monitoring (contraindicated if carotid bruit) |
| Seizure (mimics syncope) | less common | Prolonged LOC (>5 min), tonic-clonic movements during LOC (not just myoclonic jerks), tongue biting (lateral), post-ictal confusion, urinary incontinence | EEG, clinical history. Lateral tongue bite is most specific for seizure |
Red Flags & Key History
Symptoms
Exertional syncope — suggests structural cardiac disease (AS, HCM, pulmonary HTN) or arrhythmia
Syncope without prodrome (sudden LOC) — suggests arrhythmia
Family history of sudden cardiac death at young age — channelopathy or HCM
Associated chest pain or dyspnea — suggests ACS or PE
Syncope while supine or sitting — suggests arrhythmia (vasovagal is almost always upright)
Prodrome of warmth, nausea, diaphoresis, tunnel vision — typical vasovagal (generally benign)
Situational trigger (cough, micturition, defecation) — situational syncope (benign)
Signs
Orthostatic hypotension (SBP drop >=20 or DBP >=10 within 3 min of standing)
New or previously undetected cardiac murmur
Abnormal ECG (any abnormality: AV block, bundle branch block, long QT, WPW, Q waves)
Focal neurological deficit — suggests stroke, NOT simple syncope
Prolonged post-event confusion >5 min — consider seizure rather than syncope
Approach to Investigation
First-line
12-lead ECGMandatory for ALL syncope. Abnormal in ~5% (diagnostic) and ~10% (suggestive). Look for: AV block, long QT, Brugada (coved ST V1-V3), WPW (short PR + delta wave), Q waves (prior MI), LVH (HCM/AS), epsilon waves (ARVC), AF
Orthostatic vitalsBP and HR lying, then standing at 1 and 3 minutes. SBP drop >=20 or DBP >=10 or symptoms with standing = positive
Blood glucoseRule out hypoglycemia as cause of altered consciousness
CBCIf anemia or acute blood loss suspected
Second-line
Canadian Syncope Risk ScoreValidated in Canadian EDs for 30-day risk of serious adverse events. Components: clinical evaluation (predisposition to vasovagal, heart disease, any SBP <90, troponin elevation) + ECG findings (abnormal QRS axis, QTc >480, type II 2nd/3rd degree AV block). Score -3 to +11. Very low risk (<=0): <1% 30-day event rate — consider discharge. Higher scores: admission + monitoring
EchocardiogramIf cardiac syncope suspected: assess LVEF, valvular disease, HCM, RVSP. NOT routine for clearly vasovagal syncope
Continuous ECG monitoringTelemetry inpatient if high-risk. Holter (24-48h) or event monitor (2-4 weeks) outpatient for recurrent unexplained syncope. Implantable loop recorder for infrequent episodes
Specialist
Tilt-table testingFor recurrent syncope suspected vasovagal when history alone is not diagnostic
EP studyIf arrhythmic cause suspected with non-diagnostic ambulatory monitoring in a patient with structural heart disease
Management Principles
Canadian Syncope Risk Score (CMAJ 2020) + CCS Syncope Position Statement1
Vasovagal syncope
- Education and reassurance (excellent prognosis)
- Avoid triggers; counterpressure manoeuvres (leg crossing + tensing at prodrome onset)
- Adequate hydration and salt intake
- Midodrine or fludrocortisone for recurrent refractory cases
2
Orthostatic syncope
- Review and reduce offending medications (diuretics, antihypertensives, alpha-blockers)
- Rise slowly, compression stockings, adequate fluid/salt intake
- Midodrine or droxidopa for neurogenic orthostatic hypotension
3
Cardiac syncope
- Treat specific cause: pacemaker for high-grade AV block/SSS, ICD for VT/VF, AVR for severe AS, septal reduction for obstructive HCM
- See specific condition management for details
4
Disposition using Canadian Syncope Risk Score
- Score <=0 (very low risk, <1% 30-day events): consider safe discharge with outpatient follow-up
- Score 1-3 (low-moderate risk): clinical judgment — many can be discharged with close follow-up + ambulatory monitoring
- Score >=4 (high risk): admission for telemetry monitoring and further investigation
- Always arrange appropriate follow-up regardless of disposition
MCCQE1 Exam Tips
- 1The Canadian Syncope Risk Score is a made-in-Canada tool — expect it to be tested. Know the risk stratification approach: score <=0 = low risk, safe for discharge
- 2ECG is the single most important investigation after history. An abnormal ECG in a syncope patient = red flag requiring further workup
- 3Exertional syncope = cardiac until proven otherwise: AS, HCM, pulmonary HTN, arrhythmia
- 4CT head is NOT routine for syncope — only if head trauma, focal neuro deficit, or prolonged confusion suggesting a primary neurological event
- 5Lateral tongue bite is the most specific physical finding for seizure over syncope
- 6Vasovagal syncope: prodrome + trigger + rapid recovery. If the question gives you this classic picture, the answer is reassurance + education, not extensive cardiac workup
- 7Orthostatic vitals: check in EVERY syncope patient. Many medications cause orthostatic hypotension — always review the med list
practicetest your knowledge on syncope & pre-syncopeApply what you've learnt with MCCQE1-style questions from the iatroX Q-Bank — cardiovascular and beyond.
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