Syncope
Red flags
- Syncope during exertion -> structural cardiac disease (aortic stenosis, HOCM) - do not miss
- Syncope with chest pain, palpitations preceding, or no prodrome (sudden collapse) -> cardiac/arrhythmic cause
- Family history of sudden cardiac death <40 years, or known channelopathy/cardiomyopathy
- Abnormal ECG - long/short QT, Brugada pattern, WPW, high-grade block, evidence of prior MI
- Syncope while supine or seated - reduces likelihood of simple vasovagal/orthostatic cause
- Injury sustained (suggests no/brief prodrome - higher-risk mechanism)
Differential by mechanism
Reflex (neurally mediated) - commonest overall
- Vasovagal - prolonged standing, emotional trigger, pain, prodrome of nausea/warmth/visual greying
- Situational - micturition, defecation, cough, swallow
- Carotid sinus hypersensitivity - older adults, head-turning/tight collar trigger
Orthostatic
- Volume depletion, autonomic failure (Parkinson's/MSA, diabetic autonomic neuropathy), drug-induced (antihypertensives, diuretics)
Cardiac (highest-risk category)
- Arrhythmic: bradyarrhythmia (sick sinus, high-grade AV block), tachyarrhythmia (VT, SVT with rapid rate), channelopathy (long QT, Brugada)
- Structural: aortic stenosis, HOCM, PE, cardiac tamponade, acute MI
Not true syncope (mimics)
- Seizure (post-ictal confusion, tongue biting, longer duration, incontinence more typical though not exclusive to seizure)
- Hypoglycaemia
- Psychogenic pseudosyncope
- Vertebrobasilar TIA (rare true cause of LOC, usually with other brainstem signs)
Focused history
- Before: posture, activity (exertional vs rest), triggers, prodrome (nausea/warmth/visual greying = reflex; palpitations = arrhythmic; none = higher risk)
- During: witnessed account - duration of LOC, myoclonic jerks (can occur in syncope too, brief), tongue biting (lateral suggests seizure), incontinence
- After: rapid, full recovery (typical syncope) vs prolonged confusion (seizure, or prolonged cerebral hypoperfusion)
- Cardiac history, family history of sudden death, medication review (QT-prolonging drugs, antihypertensives)
- Frequency and recurrence pattern
Focused examination
- Lying-to-standing BP (1 and 3 minutes)
- Cardiovascular exam - murmurs (AS, HOCM), irregular pulse, signs of heart failure
- 12-lead ECG in every patient - the single most important bedside test
- Carotid sinus massage (with monitoring) if carotid sinus hypersensitivity suspected and no contraindication (carotid bruit, recent stroke/MI)
- Neurological exam if seizure/TIA mimic considered
Investigation strategy
- ECG - all patients; look for conduction disease, QT interval, ischaemia, pre-excitation, Brugada pattern
- Bloods - FBE, UEC, glucose; troponin/D-dimer if cardiac/PE suspected clinically
- Echocardiogram if structural heart disease suspected or abnormal ECG/exam
- Ambulatory ECG monitoring (Holter, external/implantable loop recorder) if arrhythmic cause suspected but not captured - duration matched to symptom frequency
- Tilt-table testing - reflex syncope diagnosis in atypical/recurrent cases where diagnosis remains unclear
- Electrophysiology study in selected high-risk structural heart disease patients
- CT brain/EEG not routinely indicated unless a seizure mimic is genuinely suspected - low yield in typical syncope
Management
A. Risk stratification drives disposition - the central organising decision
- Low-risk features (typical reflex syncope, normal ECG, no structural heart disease, no red flags): safe for outpatient work-up
- High-risk features (red flags above, abnormal ECG, known structural/ischaemic heart disease, family history of sudden death): admit for cardiac monitoring and urgent work-up
B. Reflex/vasovagal syncope
- Education and reassurance, avoid triggers, adequate hydration/salt intake
- Physical counter-pressure manoeuvres (leg crossing, hand grip) at prodrome onset
- Review and reduce hypotensive medications
- Fludrocortisone or midodrine in refractory cases (specialist-guided)
C. Orthostatic syncope
- Deprescribe causative drugs, treat volume depletion, manage as for orthostatic hypotension (see Geriatric medicine note)
D. Cardiac syncope
- Arrhythmic: pacemaker (bradyarrhythmia/high-grade block), ICD (high-risk structural disease/channelopathy/documented VT), antiarrhythmic therapy or ablation as appropriate
- Structural: treat underlying lesion (e.g. valve replacement for severe symptomatic AS)
E. Driving and safety
- Apply jurisdictional driving restrictions based on cause and recurrence risk (commercial vs private licence rules differ)
- Safety-net advice on injury prevention during prodrome
Traps
- Missing exertional syncope as a red flag for structural heart disease
- Failing to obtain an ECG in every syncope presentation
- Over-investigating clearly typical reflex syncope with tilt-table/EPS when history alone is diagnostic
- Under-investigating syncope with red flags because "they look well now"
- Confusing brief myoclonic jerks during syncope with a primary seizure disorder
- Not addressing driving legality/safety before discharge
Talk track
Get an ECG on everyone, then risk-stratify: reflex/orthostatic syncope with a normal ECG and no structural heart disease is safe for outpatient work-up, while exertional syncope, an abnormal ECG, known structural heart disease, or a family history of sudden death needs admission and monitoring. History (prodrome, trigger, recovery speed) does most of the diagnostic work; investigations (Holter, tilt-table, echo) are chosen to match the suspected mechanism rather than ordered as a panel.
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