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This is a clinician-written, evidence-based summary aligned to the 2026 MLA Content Map. It is intended for medical students and junior doctors preparing for the UKMLA. Always cross-reference with NICE guidance, local protocols, and clinical judgement.
The Bottom Line
- Syncope = transient LOC from transient global cerebral hypoperfusion, with rapid onset, short duration, and complete spontaneous recovery
- Three main categories: reflex (vasovagal — commonest), cardiac (arrhythmia, structural — most dangerous), and orthostatic hypotension
- Red flags for cardiac syncope: exertional, during/after exercise, preceded by palpitations, family Hx of SCD, known structural heart disease, abnormal ECG
- All patients: 12-lead ECG + lying and standing BP. High-risk features → admit and monitor. Low-risk vasovagal → reassure
- NICE CG109: structured assessment of TLoC, appropriate use of ambulatory ECG, tilt testing, and implantable loop recorders
Overview
Syncope is a symptom defined as a transient loss of consciousness (TLoC) caused by transient global cerebral hypoperfusion. It is distinguished from other causes of TLoC (epileptic seizures, psychogenic attacks) by its mechanism. The three main pathophysiological categories are: reflex (neurally mediated) syncope — including vasovagal, situational (cough, micturition), and carotid sinus syncope; cardiac syncope — due to arrhythmias (bradycardia, tachycardia) or structural disease (aortic stenosis, HCM, PE); and orthostatic hypotension — from autonomic failure, volume depletion, or drugs. NICE CG109 provides guidance on assessment and diagnosis.
Epidemiology
Syncope affects approximately 40% of people at least once in their lifetime. It accounts for 1–3% of ED attendances and 1–6% of hospital admissions. Vasovagal syncope is by far the commonest cause (>60%), particularly in young people. Cardiac syncope accounts for approximately 10–15% but carries significantly higher morbidity and mortality. Orthostatic hypotension is more common in the elderly, affecting up to 30% of people over 70. Unexplained syncope accounts for up to 20% of cases after initial evaluation.
Clinical Features
Symptoms
Vasovagal: prodrome of lightheadedness, nausea, sweating, visual greying, warmth — triggered by prolonged standing, emotional stress, pain, hot environment
Situational: syncope with coughing, micturition, defaecation, swallowing
Cardiac: sudden onset with no or minimal warning, may occur during exertion, preceded by palpitations
Exertional syncope (aortic stenosis, HCM, pulmonary hypertension)
Syncope while sitting/lying (suggests arrhythmia)
Family history of SCD or channelopathy
Orthostatic: on standing, worse in morning, improved by sitting/lying
Signs
Orthostatic hypotension: SBP drop ≥20 mmHg or DBP drop ≥10 mmHg within 3 min of standing
Ejection systolic murmur (aortic stenosis, HCM)
Bradycardia or irregular pulse
Signs of heart failure
Neurological examination usually normal (focal deficit suggests alternative diagnosis — stroke, TIA)
Investigations
First-line
12-lead ECG (all patients)Look for: arrhythmia, heart block, LBBB, delta wave (WPW), long QT, Brugada pattern, LVH (HCM), signs of old MI. Normal ECG is reassuring
Lying and standing BPOrthostatic hypotension: SBP drop ≥20 or DBP drop ≥10 within 3 min of standing
BloodsFBC (anaemia), glucose, U&Es
Second-line
Ambulatory ECG monitoringIf arrhythmia suspected — duration based on frequency of events: daily → 24h Holter; weekly → 7-day monitor; infrequent → implantable loop recorder
EchocardiographyIf cardiac syncope suspected — assess for structural heart disease (AS, HCM, DCM)
Tilt-table testingConfirm reflex (vasovagal) syncope if diagnosis uncertain — reproduces symptoms with passive tilt to 60–70°
Specialist
Implantable loop recorder (ILR)For recurrent unexplained syncope after initial workup — can monitor for up to 3 years
Electrophysiology studyIf arrhythmic cause suspected and non-invasive testing inconclusive
Carotid sinus massageIf carotid sinus hypersensitivity suspected (syncope associated with head turning, collar pressure) — asystole >3 s or SBP drop >50 mmHg
1
Vasovagal syncope (low-risk)
- Reassurance and education — benign prognosis
- Recognise and avoid triggers; sit/lie down at onset of prodrome
- Counter-pressure manoeuvres (leg crossing, hand grip, squatting) at onset of prodrome
- Adequate fluid and salt intake
- Rarely, fludrocortisone or midodrine if very frequent and debilitating
2
Orthostatic hypotension
- Review medications (antihypertensives, diuretics, alpha-blockers, TCAs)
- Compression stockings, adequate fluid/salt intake
- Stand up slowly, avoid prolonged standing
- Fludrocortisone or midodrine if non-pharmacological measures insufficient
3
Cardiac syncope (high-risk)
- Admit for monitoring if red flags present
- Treat underlying cause: permanent pacemaker for bradycardia/heart block, ICD for VT/VF, AVR for severe AS
- Catheter ablation for arrhythmias
4
DVLA driving advice
- Simple vasovagal faint: no driving restriction
- Unexplained syncope: cease driving until cause identified and treated (Group 1: 6 months; Group 2: 12 months depending on cause)
- Cardiac syncope: cease driving until treated; specific rules for pacemaker/ICD (Group 1: 1 week post-PPM, 6 months post-ICD)
Complications
- Injury: Falls, fractures, head injury, driving accidents
- Sudden cardiac death: If cardiac syncope from VT/VF is the underlying cause
- Reduced quality of life: Recurrent syncope causes anxiety, social isolation, functional impairment
- Misdiagnosis: Cardiac syncope misdiagnosed as epilepsy — may delay life-saving treatment
UKMLA Exam Tips
- 1Young person + prodrome (nausea, sweating, tunnel vision) + trigger (standing, heat, pain) + quick recovery = vasovagal — reassure
- 2Exertional syncope = cardiac until proven otherwise (AS, HCM, PE, arrhythmia)
- 3All syncope patients need a 12-lead ECG + lying/standing BP as minimum workup
- 4Syncope during exercise = cardiac. Syncope AFTER exercise = vasovagal (autonomic)
- 5Orthostatic hypotension: ≥20 SBP or ≥10 DBP drop on standing — always check medications
- 6Do NOT diagnose epilepsy based on brief limb jerking during syncope — anoxic seizures (convulsive syncope) occur in up to 10% of syncope and do not require antiepileptics
practicetest your knowledge on syncopeApply what you've learnt with UKMLA-style questions from the iatroX Q-Bank — cardiovascular and beyond.
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