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Syncope

Red flags

The only question that matters: is this cardiac? Cardiac syncope ~30% 1-yr mortality; reflex syncope ~0%

History red flags

Exertional syncope (during, not after) - AS, HOCM, anomalous coronary, PAH
Supine or seated onset
No prodrome / sudden onset ("like a switch")
Preceded by palpitations or chest pain
Family history of SCD <40yr or inherited cardiac disease
Known structural heart disease or prior MI

ECG red flags

Any bifascicular block, QRS >=120 ms, Mobitz II or 3rd degree AV block
Sinus brady <40 awake, or pauses >3 s
Pre-excitation (short PR + delta wave)
QTc >460 ms (long) or <340 ms (short)
Brugada type 1 coved ST elevation V1-V2
Epsilon wave / T inversion V1-V3 (ARVC)
Q waves, LVH, ventricular ectopy

Examination / context red flags

Systolic murmur (AS, HOCM)
Hypotension (SBP <90), unexplained anaemia
Syncope causing injury or occurring while driving
Syncope in a known HF / low EF patient

Differential by mechanism

1. Reflex (neurally mediated) - ~60%

Mechanism: inappropriate vagal surge +/- sympathetic withdrawal -> cardioinhibition, vasodepression, or both

Vasovagal - emotional or orthostatic trigger, long prodrome (nausea, warmth, tunnel vision), pallor, slow recovery
Situational - cough, micturition, defecation, swallow, post-exercise, laughing
Carotid sinus syndrome - shaving, head-turning, tight collars. M>F, age >40

2. Orthostatic hypotension - ~15%

Fall in SBP >=20 or DBP >=10 within 3 min of standing

Drug-induced (commonest) - antihypertensives, alpha blockers, nitrates, diuretics, TCAs, antipsychotics, EtOH
Volume depletion - haemorrhage, vomiting, diarrhoea, Addison's
Primary autonomic failure - MSA, PD, Lewy body, pure autonomic failure
Secondary autonomic failure - diabetes, amyloid, uraemia, spinal injury, B12
Delayed OH (>3 min) is missed by a standard 3-min stand

3. Cardiac - ~15% (the lethal group)

Arrhythmic
- Brady: sinus node disease, AV block, pacemaker failure
- Tachy: VT (structural or channelopathy), SVT with rapid conduction, torsades, pre-excited AF
Structural / obstructive
- AS, HOCM, prosthetic valve thrombosis, myxoma, tamponade, PE, PAH, aortic dissection, ACS
- Fixed cardiac output + exercise vasodilation -> exertional syncope

Not syncope - the pseudo-syncopes

Feature	Points away from syncope
Prolonged (>5 min) LOC	Seizure, hypoglycaemia, psychogenic
Confusion >5 min after	Post-ictal
Focal neurology	Stroke/TIA, seizure
Eyes closed throughout	Psychogenic pseudosyncope
Falls with no LOC	Mechanical fall, drop attack, cataplexy

Brief myoclonic jerks are COMMON in reflex syncope and do NOT mean seizure - convulsive syncope
Tongue bite: lateral = seizure; tip = syncope

Focused history

Eyewitness account is the single highest-yield item - phone them.

Before

Position (supine / seated / standing), activity (exertion vs post-exertion), trigger
Prodrome: duration, nausea, sweating, visual greying, palpitations, chest pain, aura
Time since last meal, standing time, heat, dehydration, pain, venepuncture

During (witness)

Duration of LOC (syncope is seconds; >1 min suspect other)
Colour: pallor = syncope; cyanosis/flushing = seizure
Movements: timing (jerks AFTER collapse = syncope; before = seizure), symmetry
Incontinence (non-discriminating), tongue biting, eyes open/closed

After

Time to full orientation (immediate = syncope, minutes = seizure)
Injury, retrograde amnesia, residual nausea/fatigue

Background

Prior episodes - number, over what period, stereotyped?
Cardiac history: MI, HF, EF, valve disease, devices
Drugs - new or dose-changed; QT-prolonging; antihypertensives
Family history of SCD, drowning, unexplained MVA, epilepsy before 40
Occupation and driving (determines disclosure obligations)

Focused examination

Lying and standing BP at 0, 1, 3 min (add 5-10 min if delayed OH suspected)
BP both arms (dissection), pulse character
- Slow-rising, low-volume pulse + late-peaking ESM + soft/absent A2 = severe AS
Precordium - murmurs, dynamic manoeuvres (HOCM murmur inc with Valsalva/standing)
JVP - inc in tamponade, PE, PAH
Signs of HF, anaemia, PR for melaena
Neurological exam incl. cerebellar and autonomic features
Carotid sinus massage if age >40 and unexplained syncope
- 5-10 s sequential pressure, supine and upright, ECG+BP monitoring
- Positive: asystole >3 s (cardioinhibitory) or SBP fall >50 mmHg (vasodepressor) and symptoms reproduced
- Contraindicated: carotid bruit, TIA/stroke or MI within 3 months

Investigation strategy

Everyone

12-lead ECG - the only universal test
Lying/standing BP
Targeted bloods only: FBE (anaemia/bleed), UEC, glucose, beta-hCG
- Troponin and D-dimer only if the history suggests ACS or PE - not reflexively

Then stratify

Assessment	Action
Clear reflex/situational + normal ECG + normal heart	No further testing. Reassure, discharge
Orthostatic	Medication review, volume, autonomic assessment
Structural suspected	TTE
Arrhythmia suspected	Rhythm monitoring proportional to frequency
High risk	Admit / monitored bed

Rhythm monitoring - match the tool to event frequency

Inpatient telemetry - high-risk, daily-to-weekly events
Holter 24-48 h - only if episodes near-daily (low yield otherwise)
External loop / patch 2-4 weeks - weekly-to-monthly
Implantable loop recorder (ILR) - infrequent, unexplained, recurrent; highest diagnostic yield, use it earlier rather than after a long testing cascade

Selected

Exercise stress test - exertional syncope (also for exercise-induced AV block and CPVT)
EPS - syncope with bifascicular block or prior MI when non-invasive testing negative
Tilt-table - suspected reflex syncope where diagnosis unclear, or suspected psychogenic pseudosyncope
- Does not diagnose; demonstrates susceptibility. Confirms the mechanism, not the cause

Tilt response	Finding	Pacing helps?
Cardioinhibitory	Asystole / marked bradycardia	Yes
Vasodepressor	HR rises, BP falls	No
Mixed	Both HR and BP fall	Partial
POTS	HR inc >30 (>40 if <20yr) without BP fall	No
OH pattern	Immediate progressive BP fall	No

CT/MRI brain, carotid Dopplers, EEG: not indicated in syncope unless focal neurology or witnessed seizure
- Ordering them is the commonest wasted workup

Management

A. Reflex syncope - education first

Explain benign prognosis; identify and avoid triggers
Counter-pressure manoeuvres at prodrome - leg crossing + tensing, handgrip, arm tensing
Liberal salt and fluid (avoid if HTN/HF)
Deprescribe vasoactive drugs - the single most effective intervention
Refractory only:
- Midodrine (alpha agonist) - young, vasodepressor-dominant
- Fludrocortisone - POST trial: benefit marginal
- Dual-chamber pacing with closed-loop stimulation - Class I in severe recurrent reflex syncope, age >40, with documented spontaneous or tilt-induced asystolic pause
  - Useless for vasodepressor syncope

B. Orthostatic hypotension

Withdraw the offending drug; rehydrate
Slow position change, compression stockings, raise bed head
Midodrine, fludrocortisone; droxidopa in neurogenic OH
Treat supine hypertension separately - do not dose at night

C. Cardiac syncope - treat the cause

Bradyarrhythmia -> permanent pacemaker
VT with structural disease / low EF -> ICD (+ treat ischaemia, optimise GDMT)
SVT / AVNRT / accessory pathway -> ablation
AS -> SAVR/TAVI (syncope in AS = symptomatic severe AS, ~2-3 yr survival untreated)
HOCM -> risk score, ICD if high risk
Channelopathy -> beta blocker +/- ICD, genetic counselling, drug-avoidance list

Driving

Must counsel and document; patient has the reporting obligation in most states
Cardiogenic syncope: at least 4 weeks off private driving, 3 months commercial (Austroads)
Longer where an ICD is implanted or cause untreated

Traps

Exertional syncope is cardiac until proven otherwise - never discharge it as vasovagal
Myoclonic jerking does not make it a seizure
A single normal ECG does not exclude an arrhythmia; a normal ECG does make cardiac syncope much less likely
Holter for monthly episodes is guaranteed to be negative - go to ILR
Head CT, EEG and carotid Dopplers have essentially no role in undifferentiated syncope
"Vasovagal" in a 75-year-old with a prior MI is a diagnosis of exclusion, not of convenience
Orthostatic hypotension and a cardiac cause can coexist - finding one does not stop the search
Syncope during shaving/head turning: think carotid sinus, but also exclude AS
Pulmonary embolism presents as syncope in ~1 in 6 first-episode syncope admissions - ask about pleuritic pain, dyspnoea, DVT risk
Prodrome does not exclude arrhythmia; a brief prodrome of palpitations is a red flag
Prolonged QT can be intermittent and drug-dependent - review the full medication list including recent antiemetics and antibiotics

Talk track

"This was syncope - transient loss of consciousness from global cerebral hypoperfusion, with rapid onset, short duration and spontaneous complete recovery."
"My task is to place it in one of three buckets - reflex, orthostatic, or cardiac - because only the third carries mortality."
"The features that point me toward/away from cardiac are ..." (name exertional onset, absent prodrome, palpitations, structural disease, family SCD, and the ECG)
"My immediate investigations are an ECG, lying and standing blood pressure and a focused set of bloods. I would specifically not request brain imaging or an EEG here."
"Risk stratification determines disposition: this patient is high/low risk because ..., so I would admit for monitoring / discharge with outpatient follow-up."
"If the episodes are infrequent and remain unexplained after that, I would move to an implantable loop recorder rather than repeat Holters."
"I would address driving explicitly and document the advice given."
"The definitive treatment depends on mechanism - pacing only helps the cardioinhibitory form, which is why establishing mechanism matters before implanting anything."

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