Syncope in Adults

1. Overview

Syncope is transient loss of consciousness (TLOC) due to transient global cerebral hypoperfusion, characterised by rapid onset, short duration, and spontaneous complete recovery. [1,2] It is one of the most common presentations to emergency departments, accounting for 1-3% of all ED attendances and up to 6% of hospital admissions. [3,4] The term syncope specifically excludes other causes of TLOC such as seizures, head trauma, or metabolic disorders where loss of consciousness occurs through different mechanisms.

The clinical importance of syncope lies in its diverse aetiologies, ranging from benign vasovagal episodes to life-threatening cardiac arrhythmias. While reflex (neurally mediated) syncope accounts for the majority of cases and carries an excellent prognosis, cardiac syncope is associated with a 1-year mortality of up to 30% if untreated. [5,6] The cornerstone of management is accurate risk stratification to identify patients requiring urgent investigation and those who can be safely managed in the community.

A detailed history remains the single most powerful diagnostic tool, with the ability to establish a diagnosis in up to 50% of cases without further investigation. [7] The presence of warning symptoms (prodrome), triggers, witness accounts, and associated features provide critical diagnostic clues. Every patient with syncope requires a 12-lead ECG; abnormalities are present in 5-10% of cases and may indicate underlying cardiac disease requiring urgent intervention. [8]

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2. Epidemiology

Syncope is remarkably common across all age groups, with distinct epidemiological patterns that inform diagnosis and management.

Age and Sex Distribution

Syncope demonstrates a bimodal age distribution. The first peak occurs in adolescence and young adulthood (10-30 years), predominantly due to reflex (vasovagal) syncope, with a female preponderance (2:1 female to male ratio). [11] The second peak occurs after age 65, where the incidence rises sharply with increasing age, driven by cardiac causes, orthostatic hypotension, and polypharmacy, with equal sex distribution. [10,12]

Aetiology Distribution

Population-based studies reveal the following distribution of syncope causes: [1,2,13]

• Reflex (neurally mediated): 40-50%
  • "Vasovagal (simple faint): 30-35%"
  • "Situational: 5-10%"
  • "Carotid sinus syndrome: 2-5%"
• Orthostatic hypotension: 15-25%
• Cardiac: 10-20%
  • "Arrhythmic: 10-15%"
  • "Structural: 3-5%"
• Unexplained (after full evaluation): 15-20%

Mortality and Morbidity

The prognosis of syncope is heavily dependent on the underlying aetiology. Reflex syncope carries no increased mortality risk, whereas cardiac syncope is associated with a 1-year mortality of 18-33%. [5,14] Syncope-related injuries occur in 20-30% of episodes, including fractures (5%), head injuries (10%), and motor vehicle accidents. [15] In the elderly, syncope-related falls contribute significantly to hip fractures and associated morbidity.

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3. Aetiology and Pathophysiology

Classification

The 2018 European Society of Cardiology (ESC) Guidelines classify syncope into three major categories based on pathophysiological mechanisms: [1]

1. Reflex (Neurally Mediated) Syncope

Mechanism: Inappropriate reflex response causing vasodilation and/or bradycardia, leading to transient hypotension and cerebral hypoperfusion. Mediated by the autonomic nervous system, involving cardiac mechanoreceptors and baroreceptors.

Subtypes:

• Vasovagal syncope (common faint): Triggered by emotional stress, pain, fear, prolonged standing, or hot/crowded environments. Prodrome includes light-headedness, nausea, sweating, and visual disturbances.

• Situational syncope: Occurs during or immediately after specific triggers:

  • Cough syncope (increased intrathoracic pressure)
  • Micturition syncope (post-voiding vasodilation)
  • Defaecation syncope (straining/vagal stimulation)
  • Post-exercise syncope (sudden cessation with peripheral pooling)
  • Post-prandial syncope (splanchnic vasodilation)
  • Swallow syncope (oesophageal stimulation)

• Carotid sinus syndrome: Exaggerated response to carotid sinus stimulation, typically in elderly males. Provoked by head turning, tight collars, or shaving. Diagnosed by carotid sinus massage producing >3 seconds asystole (cardioinhibitory) or >50 mmHg BP drop (vasodepressor).

Exam Detail: Pathophysiology of Vasovagal Syncope:

Initial Phase: Prolonged standing or emotional trigger → venous pooling in lower limbs → reduced venous return → reduced left ventricular filling → compensatory sympathetic activation (tachycardia, increased contractility).

Trigger Phase: Forceful ventricular contraction on relatively empty chamber → activation of cardiac mechanoreceptors (C-fibres) → paradoxical withdrawal of sympathetic tone and vagal activation (Bezold-Jarisch reflex).

Response Phase: Vasodilation (sympathetic withdrawal) + bradycardia (vagal activation) → profound hypotension → cerebral hypoperfusion → loss of consciousness. [16]

Recovery: Horizontal position → restored venous return → restored cerebral perfusion → rapid recovery (usually less than 60 seconds).

2. Orthostatic Hypotension (OH)

Definition: Drop in systolic BP ≥20 mmHg or diastolic BP ≥10 mmHg within 3 minutes of standing (or to less than 90 mmHg systolic regardless of drop). [17]

Mechanisms:

• Hypovolaemia: Haemorrhage, dehydration, diuretics, inadequate fluid intake
• Autonomic failure:
  • "Primary: Parkinson's disease, multiple system atrophy, pure autonomic failure"
  • "Secondary: Diabetes mellitus, amyloidosis, uraemia, alcohol excess"
• Medication-induced: Antihypertensives (ACE inhibitors, ARBs, alpha-blockers), diuretics, vasodilators (nitrates), psychotropics (tricyclics, phenothiazines), dopaminergic drugs
• Cardiac: Severe valvular disease reducing cardiac output
• Age-related: Reduced baroreceptor sensitivity, decreased cardiac compliance

Initial orthostatic hypotension: BP drop within 15 seconds of standing, recovering by 30 seconds. Common in young, tall individuals. Usually asymptomatic or causes pre-syncope only.

Delayed orthostatic hypotension: BP drop beyond 3 minutes of standing (up to 15-30 minutes). Seen in elderly and autonomic dysfunction.

3. Cardiac Syncope

Arrhythmic:

• Bradyarrhythmias:

  • Sinus node dysfunction (sick sinus syndrome)
  • Atrioventricular conduction disorders (2nd degree Mobitz II, 3rd degree heart block)
  • Pacemaker malfunction

• Tachyarrhythmias:

  • Ventricular tachycardia/fibrillation
  • Supraventricular tachycardia (rarely causes syncope unless very rapid or underlying heart disease)
  • "Inherited arrhythmia syndromes: Long QT syndrome, Brugada syndrome, catecholaminergic polymorphic VT, short QT syndrome, early repolarisation syndrome"
  • Drug-induced arrhythmias (QT-prolonging drugs)

Structural Cardiac Disease:

• Obstructive: Aortic stenosis, hypertrophic cardiomyopathy (HOCM), atrial myxoma, prosthetic valve thrombosis
• Reduced cardiac output: Severe left ventricular dysfunction, massive myocardial infarction
• Other: Acute pulmonary embolism, aortic dissection, cardiac tamponade

Exam Detail: Pathophysiology of Aortic Stenosis Syncope:

Fixed cardiac output cannot increase to meet demand during exertion → peripheral vasodilation during exercise without compensatory CO increase → systemic hypotension → cerebral hypoperfusion. Additionally, left ventricular hypertrophy increases myocardial oxygen demand and may trigger ventricular arrhythmias. [18]

Pathophysiology of Arrhythmic Syncope:

Bradyarrhythmias (less than 40 bpm) or tachyarrhythmias (>150-180 bpm) → inadequate ventricular filling time or reduced stroke volume → cardiac output falls below threshold for cerebral perfusion (~30% of normal) → syncope. [2] The brain requires continuous perfusion; even 6-8 seconds of circulatory arrest causes loss of consciousness.

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4. Clinical Presentation

The Syncope Triad

True syncope exhibits three cardinal features: [1,2]

1. Transient: Brief duration (less than 60 seconds in most cases)
2. Self-limiting: Spontaneous complete recovery
3. Due to cerebral hypoperfusion: Caused by transient reduction in cerebral blood flow

History Taking: The Diagnostic Cornerstone

A systematic approach to history determines diagnosis in up to 50% of cases. [7] The assessment should explore:

Before the Episode (Prodrome)

Vasovagal prodrome (suggests reflex syncope):

• Light-headedness, "grey-out" of vision
• Nausea, abdominal discomfort
• Sweating, pallor
• Feeling of warmth
• Blurred vision, tunnel vision
• Tinnitus or muffled hearing
• Duration: typically 10-60 seconds

Absence of prodrome (red flag for cardiac syncope):

• Sudden onset without warning
• "Lights out" description
• Particularly concerning if during exertion

The Event Itself

Triggers and Context:

Associated Symptoms:

• Chest pain: Consider MI, PE, aortic dissection
• Palpitations: Arrhythmia
• Dyspnoea: PE, cardiac failure
• Headache: SAH (though usually maintains consciousness)
• Focal neurology: Stroke/TIA (rare cause of true TLOC)

Witness Account (crucial):

• Colour: Pallor (syncope) vs cyanosis (seizure)
• Duration of unconsciousness (>5 minutes suggests seizure)
• Movements: Brief myoclonic jerks common in syncope; prolonged tonic-clonic activity suggests seizure
• Injury pattern: Posterior injuries (occipital, back) suggest syncope with collapse; anterior injuries (facial, frontal) suggest seizure with fall
• Incontinence: Can occur in both syncope and seizure (not discriminatory)
• Tongue biting: Lateral tongue (seizure), tip biting (less specific)

After the Episode (Recovery)

Rapid recovery (less than 1-2 minutes, suggesting syncope):

• Immediate orientation
• No confusion
• Possible brief fatigue or nausea

Prolonged confusion (>5 minutes, suggesting seizure):

• Disorientation
• Amnesia for episode
• Post-ictal drowsiness

Physical Examination

Cardiovascular:

• Lying and standing BP: Measure at 0, 1, and 3 minutes after standing (orthostatic hypotension)
• Heart rate and rhythm: Bradycardia, tachycardia, irregularity (AF)
• Heart sounds: Ejection systolic murmur (AS), late systolic click (HOCM)
• Carotid pulses: Slow-rising (AS), brisk (HOCM)
• JVP: Elevated (heart failure, PE)

Neurological:

• Focal signs (unlikely in true syncope, suggests alternative diagnosis)
• Peripheral neuropathy (autonomic dysfunction)

General:

• Pallor (anaemia)
• Signs of dehydration

Carotid Sinus Massage (if indicated):

• Only in >40 years without carotid bruits or history of TIA/stroke
• Continuous ECG and BP monitoring
• 5 seconds firm pressure at angle of jaw
• Positive: ≥3 seconds asystole or ≥50 mmHg BP drop with symptom reproduction

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5. Differential Diagnosis

Syncope must be distinguished from other causes of transient loss of consciousness (TLOC) or apparent TLOC.

Syncope vs Seizure: Critical Distinction

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6. Investigations

Mandatory in All Patients

12-lead ECG [1,2,8]

Every patient with syncope must have an ECG. It identifies high-risk features in 5-10% of cases and may establish a diagnosis immediately.

Look for:

Lying and Standing Blood Pressure [17]

Measure BP after 5 minutes supine, then at 1 and 3 minutes after standing. Positive if:

• Systolic drop ≥20 mmHg or diastolic drop ≥10 mmHg
• Or systolic BP less than 90 mmHg regardless of drop
• With symptom reproduction

Second-Line Investigations

Selected based on clinical suspicion and risk stratification.

Echocardiography

Indications:

• Abnormal cardiovascular examination
• Abnormal ECG suggesting structural disease
• Exertional syncope
• Family history of cardiomyopathy or sudden death

Diagnostic findings:

• Severe aortic stenosis (valve area less than 1.0 cm²)
• Hypertrophic cardiomyopathy (wall thickness >15 mm)
• Severe LV systolic dysfunction (arrhythmia substrate)
• Atrial myxoma
• Pulmonary hypertension (suggestive of PE)

Cardiac Monitoring

Indications: Suspected arrhythmic syncope

Options:

Implantable Loop Recorder: Gold standard for recurrent unexplained syncope. ESC recommends early ILR insertion (after initial negative evaluation) in patients with recurrent syncope, especially if high-risk features present. [1,20]

Exercise Stress Test

Indications:

• Exertional syncope
• Suspected exercise-induced arrhythmia

Positive findings:

• Exercise-induced AV block
• Exercise-induced VT
• Inappropriate BP response (failure to increase or drop during exercise)

Tilt Table Test

Indication: Suspected reflex syncope when diagnosis uncertain and required to guide management, or recurrent unexplained syncope. [1]

Protocol:

• Passive phase: 60-70° tilt for 20-45 minutes
• Drug provocation (if negative): Sublingual GTN or isoproterenol infusion

Positive test: Reproduction of syncope with hypotension and/or bradycardia. Sensitivity 60-80%, specificity 90%.

Interpretation:

• Cardioinhibitory: Heart rate drop >30 bpm or asystole >3 seconds
• Vasodepressor: Significant BP drop without significant HR change
• Mixed: Both components

Electrophysiology Study (EPS)

Indications (increasingly replaced by ILR): [1]

• Syncope with structural heart disease (post-MI, cardiomyopathy)
• Syncope with ECG suggesting conduction disease
• Suspected VT in presence of scar

Findings:

• Sinus node recovery time >3 seconds (sick sinus syndrome)
• HV interval >100 ms (high-grade AV block risk)
• Inducible VT

Risk Stratification Tools

Multiple risk scores exist to guide admission and investigation decisions.

High-Risk Features (Require Urgent Evaluation) [1,2]

Clinical:

• Syncope during exertion or supine
• Severe structural or coronary artery disease
• Family history of SCD or inherited cardiac disease
• New onset heart failure
• Syncope with chest pain, dyspnoea, or palpitations

ECG:

• Any abnormality suggesting arrhythmic syncope (see ECG table above)
• Non-sustained VT

Low-Risk Features (Consider Outpatient Evaluation)

• Young patient (less than 40 years)
• Long history of recurrent syncope
• Syncope only in upright position
• Classical vasovagal trigger and prodrome
• Normal ECG
• No structural heart disease

San Francisco Syncope Rule (SFSR)

Identifies high-risk patients. Presence of ANY feature predicts serious outcome at 7 days:

• Congestive heart failure history
• Haematocrit less than 30%
• ECG abnormality
• Shortness of breath
• Systolic BP less than 90 mmHg

Sensitivity 96-98% but specificity only 50-60%. [21]

Canadian Syncope Risk Score

Validated tool for ED risk stratification. Assesses 1-year risk of serious adverse events. [22]

Very low risk (-3 to -2): less than 1% risk Low risk (-1 to 0): less than 1% risk
Medium risk (1-3): 3-8% risk High risk (4-5): 10-19% risk Very high risk (≥6): >19% risk

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7. Management

Management is directed at the underlying cause after risk stratification.

Immediate Management (Emergency Department)

All Patients:

1. ABC assessment
2. Cardiac monitoring if high-risk features
3. IV access if unstable
4. 12-lead ECG
5. Lying and standing BP
6. Focused history and examination
7. Basic bloods: FBC (anaemia), glucose, electrolytes (if indicated)

High-Risk Patients (admit for monitoring and investigation):

• Syncope during exertion or supine
• Abnormal ECG
• Structural heart disease
• Age >60 with no prodrome
• Severe injury from syncope
• Heart failure or significant comorbidity

Low-Risk Patients (outpatient follow-up):

• Classical vasovagal syncope with normal ECG and examination
• Single episode in young patient
• No red flags

Reflex (Vasovagal) Syncope

First-Line: Education and Reassurance [1,23]

• Explain benign nature
• Identify and avoid triggers
• Recognise prodromal symptoms
• Abort techniques (see below)
• Adequate hydration (2-3 litres/day)
• Adequate salt intake (10 g/day if no contraindication)

Abort Techniques (at first sign of prodrome):

• Lie down immediately with legs elevated, OR
• Physical counterpressure manoeuvres:
  • Leg crossing with muscle tensing
  • Handgrip (squeezing fist or ball)
  • Arm tensing
  • "Duration: Hold for 30 seconds or until symptoms resolve"

Counterpressure manoeuvres reduce syncope recurrence by 30-40%. [23]

Pharmacological Therapy (rarely needed, limited evidence):

• Midodrine (alpha-agonist): 2.5-10 mg TDS. Causes vasoconstriction. May help frequent syncope unresponsive to conservative measures. Evidence limited. [24]

• Fludrocortisone (mineralocorticoid): 0.1-0.2 mg daily. Increases plasma volume. Weak evidence, mainly in young patients with low BP. [1]

• Beta-blockers: NOT recommended. Previous trials showed no benefit or harm. [1]

Pacing:

• NOT indicated for uncomplicated vasovagal syncope
• Consider only in highly selected patients >40 years with recurrent severe syncope, dominant cardioinhibitory response on tilt test, and injury. Evidence weak. [1]

Orthostatic Hypotension

Non-Pharmacological (First-Line): [17]

• Identify and modify contributory factors:

  • Review medications (antihypertensives, diuretics, vasodilators)
  • Adequate hydration (2-3 litres/day)
  • Increase salt intake (unless contraindicated)

• Physical manoeuvres:

  • Rise slowly from sitting/lying
  • Avoid prolonged standing
  • Avoid straining, hot baths
  • Sleep with head of bed elevated (reduces nocturnal natriuresis)
  • Compression stockings (waist-high, 30-40 mmHg)

• Physical counterpressure: Leg crossing, squatting

Pharmacological (if non-pharmacological measures insufficient):

• Fludrocortisone: 0.1-0.2 mg daily. Monitor for fluid overload, hypokalaemia.

• Midodrine: 2.5-10 mg TDS. Avoid after 6pm (supine hypertension). Monitor BP.

• Droxidopa (norepinephrine precursor): Licensed in some countries for neurogenic OH.

• Pyridostigmine: Acetylcholinesterase inhibitor, 30-60 mg TDS. May help neurogenic OH.

Autonomic Failure: Refer to specialist autonomic unit for complex management.

Cardiac Syncope

Requires urgent cardiology referral. Management depends on underlying diagnosis.

Arrhythmic Syncope

Bradyarrhythmias: [1]

• Permanent pacemaker indications:
  • Symptomatic sinus node dysfunction
  • Acquired 2nd degree AV block (Mobitz II) or 3rd degree heart block
  • Bifascicular block with syncope and HV ≥70 ms on EPS
  • Carotid sinus syndrome with cardioinhibitory response (asystole >3 sec)

Tachyarrhythmias:

• ICD (Implantable Cardioverter-Defibrillator) indications:

  • Syncope due to sustained VT or VF
  • Inherited arrhythmia syndromes with high risk (Long QT, Brugada, ARVC)
  • Severe LV dysfunction (EF less than 35%) with syncope
  • HCM with syncope and risk factors for SCD

• Catheter ablation:

  • SVT causing syncope
  • Accessory pathway (WPW)
  • Some VT cases

• Medical therapy:

  • Beta-blockers for Long QT syndrome
  • Quinidine for Brugada syndrome (reduces VF risk)
  • Antiarrhythmics guided by electrophysiologist

Structural Heart Disease

• Aortic stenosis: Aortic valve replacement (surgical or TAVI). Syncope in AS indicates severe disease and is a Class I indication for intervention. [25]

• Hypertrophic cardiomyopathy:

  • ICD if high-risk for SCD
  • Beta-blockers or calcium channel blockers
  • Septal reduction therapy if LVOT obstruction

• Pulmonary embolism: Anticoagulation, thrombolysis if massive PE

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8. Complications and Prognosis

Syncope-Related Injury

Injury occurs in 20-30% of syncope episodes: [15]

• Fractures: 5% (hip, wrist, facial bones)
• Head injury: 10% (soft tissue, lacerations, rarely intracranial haemorrhage)
• Motor vehicle accidents: If syncope while driving
• Occupational injury: If syncope during work

Elderly patients at highest risk of injury due to osteoporosis and frailty.

Recurrence

Recurrence rates depend on aetiology:

• Vasovagal syncope: 30-40% recurrence within 3 years
• Cardiac syncope: Variable, depending on treatment
• Overall: 20-30% recurrence within 2 years [9]

Mortality

Reflex syncope and orthostatic hypotension: No increased mortality compared to general population. [5]

Cardiac syncope: [5,6,14]

• 1-year mortality: 18-33% (untreated)
• Sudden cardiac death risk: 24% at 1 year (untreated structural heart disease)
• Mortality related to underlying cardiac disease, not syncope per se

Predictors of mortality:

• Age >60 years
• Male sex
• Structural heart disease
• Heart failure
• Abnormal ECG
• Absence of prodrome

Quality of Life

Recurrent syncope significantly impairs quality of life:

• Anxiety and fear of recurrence
• Physical injury concern
• Driving restrictions
• Occupational limitations
• Social embarrassment
• Depression in 30% of recurrent cases

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9. Special Populations

Elderly (>65 years)

Challenges:

• Multiple comorbidities
• Polypharmacy (common cause of OH)
• Impaired baroreceptor sensitivity
• Higher cardiac syncope prevalence
• Greater injury risk (falls, fractures)
• Atypical presentations

Approach:

• Lower threshold for investigation and admission
• Comprehensive medication review
• Assess for autonomic dysfunction
• Consider carotid sinus syndrome (CSM if >40 years)
• Address falls risk and bone health

Pregnancy

• Syncope more common in pregnancy (physiological changes)
• Usually vasovagal or orthostatic (expanded blood volume, peripheral vasodilation)
• Always exclude cardiac causes (peripartum cardiomyopathy, arrhythmia)
• Avoid prolonged supine position (aortocaval compression)
• Standard investigations safe (ECG, echo)
• Modify drug management (avoid ACE inhibitors, some antiarrhythmics)

Athletes

• Exertional syncope in athlete is red flag (exclude HCM, ARVC, coronary anomaly)
• Post-exertional syncope (within minutes of stopping) often vasovagal
• Require comprehensive cardiac evaluation including echo, exercise test, consider cardiac MRI
• Screen for family history of SCD
• Return to sport decisions require cardiology clearance

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10. Driving and Occupational Restrictions

UK DVLA Guidance (2023)

Group 1 (Car, Motorcycle): [26]

Group 2 (HGV, PSV): More stringent - usually 12 months even for single episode, permanent bar if cardiac cause unless treated and strict criteria met.

Legal Obligation: Patients must notify DVLA. Physicians should advise patients of requirement but patient responsible for notification.

Occupational Restrictions

• Working at heights: Unsafe until syncope controlled
• Operating machinery: Risk assessment required
• Commercial pilots: Usually disqualified; specialist aviation medical required
• Professional drivers: Strict medical assessment

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11. Key Guidelines and Evidence

Major Guidelines

1. 2018 ESC Guidelines for diagnosis and management of syncope [1]

   • Comprehensive, evidence-based
   • Risk stratification algorithms
   • Investigation pathways
   • Gold standard guideline

2. NICE CG109: Transient loss of consciousness (2014) [2]

   • UK-focused approach
   • Emphasises history and ECG
   • Risk stratification for ED
   • Specialist syncope unit referral criteria

3. AHA/ACC/HRS Guideline on Syncope (2017) [27]

   • US guideline
   • Similar recommendations to ESC
   • Emphasis on ILR early use

Evidence Base

• Implantable loop recorders: ISSUE trials demonstrated superiority of ILR over conventional testing, with diagnostic yield 40-50% vs 6-20%. [20]

• Counterpressure manoeuvres: Physical counterpressure manoeuvres reduced recurrence by 39% (RR 0.61) in randomised trials. [23]

• Midodrine: Small trials show benefit in selected vasovagal syncope patients, but evidence limited and not licensed in all countries. [24]

• Pacing for vasovagal syncope: Multiple RCTs showed no benefit or only modest benefit with high placebo effect. Not recommended except highly selected cases. [1]

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12. Common Examination Scenarios

MRCP PACES/OSCE Stations

Station 4 (Communication):

"This 25-year-old woman collapsed in church. Explain the diagnosis of vasovagal syncope and management."

Station 5 (History Taking):

"This 70-year-old man has had three blackouts. Take a history and discuss your differential diagnosis."

Viva Points

Viva Point: Opening Statement: "Syncope is transient loss of consciousness due to transient global cerebral hypoperfusion, characterised by rapid onset, short duration, and spontaneous complete recovery. It is classified into reflex, orthostatic, and cardiac causes, with cardiac syncope carrying significant mortality risk."

Key Facts to Mention:

• Lifetime incidence 35-40%, common ED presentation (1-3% attendances) [1,3]
• Classified as reflex (40-50%), orthostatic (15-25%), cardiac (10-20%) [1]
• History is most powerful diagnostic tool (50% diagnostic) [7]
• ECG mandatory in ALL patients (abnormal in 5-10%) [8]
• Cardiac syncope: 1-year mortality 18-33% if untreated [5]
• Reflex syncope: benign, no increased mortality [5]

Management Approach:

"I would first risk stratify using history, examination, and ECG. High-risk features include exertional syncope, cardiac syncope, abnormal ECG, structural heart disease, or family history of sudden death. High-risk patients require urgent investigation - echocardiography and cardiac monitoring, often inpatient. Low-risk patients with classical vasovagal syncope and normal ECG can be managed with reassurance, trigger avoidance, adequate hydration, and counterpressure manoeuvres."

Key Investigations:

"ECG is mandatory in all patients - I look for conduction abnormalities, prolonged QT, Brugada pattern, delta waves, Q waves, or arrhythmias. Lying and standing BP identifies orthostatic hypotension. Further investigation depends on suspicion: echo if structural disease suspected, prolonged monitoring if arrhythmia suspected, with implantable loop recorder the gold standard for recurrent unexplained syncope."

Common Mistakes to Avoid

❌ Failing to distinguish syncope from seizure: Always ask about duration, recovery time, witness account of movements, tongue biting location.

❌ Not performing ECG: ECG is mandatory in ALL syncope patients.

❌ Missing cardiac syncope red flags: Exertional syncope, syncope in supine position, no prodrome, family history of SCD.

❌ Ordering indiscriminate investigations: CT head, EEG, carotid Dopplers rarely useful unless specific indication.

❌ Recommending beta-blockers for vasovagal syncope: No evidence of benefit; may worsen orthostatic hypotension.

❌ Forgetting DVLA advice: Single unexplained syncope = 6 months off driving; patient must notify DVLA.

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13. Model Answers for Common Questions

Q1: "How do you approach a patient presenting with syncope?"

Model Answer:

"I would approach this systematically using the ABCDE framework initially to ensure stability, then focus on detailed history, examination, and risk stratification.

History is the most important tool - I would explore three key phases: before, during, and after the episode. Before the episode, I ask about prodromal symptoms such as light-headedness, nausea, visual disturbance, and triggers including posture, exertion, emotional stress, or specific situations. The absence of prodrome is a red flag for cardiac syncope. I would enquire about cardiac symptoms - chest pain, palpitations, dyspnoea - and family history of sudden cardiac death or inherited cardiac disease.

Witness accounts are crucial - I ask about the duration of unconsciousness, colour change, movements, and recovery time. Brief myoclonic jerks can occur in syncope but prolonged tonic-clonic activity suggests seizure. Rapid recovery within 1-2 minutes favours syncope over seizure.

Examination includes cardiovascular assessment with lying and standing BP (for orthostatic hypotension - drop of ≥20/10 mmHg), auscultation for murmurs (aortic stenosis, HOCM), and rhythm assessment. I would perform carotid sinus massage if appropriate (age >40, no bruits, no recent stroke/TIA).

Investigations: 12-lead ECG is mandatory in all patients. I look for conduction abnormalities, prolonged QT (>500 ms), Brugada pattern, pre-excitation, Q waves, or arrhythmias. Further tests depend on risk stratification - echo if structural disease suspected, cardiac monitoring if arrhythmia suspected.

Risk stratification guides admission and investigation. High-risk features include exertional syncope, abnormal ECG, structural heart disease, age >60 without prodrome, and family history of SCD. High-risk patients require urgent cardiology evaluation, often inpatient. Low-risk patients with classical vasovagal syncope can be managed in the community with education and lifestyle measures."

Q2: "What are the causes of syncope and how do you differentiate them?"

Model Answer:

"Syncope is classified by pathophysiology into three main categories based on the 2018 ESC Guidelines:

Reflex (neurally mediated) syncope accounts for 40-50% of cases. This includes vasovagal syncope - the common faint - triggered by prolonged standing, heat, emotional stress, or pain, with a characteristic prodrome of light-headedness, nausea, sweating, and visual disturbance. Recovery is rapid once horizontal. Situational syncope occurs with specific triggers like micturition, defaecation, or coughing. Carotid sinus syndrome affects elderly males with syncope triggered by head turning or neck pressure.

Orthostatic hypotension causes 15-25% of syncope, defined as a drop in systolic BP ≥20 mmHg or diastolic ≥10 mmHg within 3 minutes of standing. Causes include hypovolaemia, medications (antihypertensives, diuretics), and autonomic failure from Parkinson's disease, diabetes, or age-related changes. Symptoms occur on standing and improve when lying down.

Cardiac syncope accounts for 10-20% but is the most dangerous, with 1-year mortality up to 30%. It includes arrhythmic causes - brady arrhythmias like heart block or sick sinus syndrome, and tachyarrhythmias like VT or inherited syndromes such as Long QT or Brugada. Structural causes include aortic stenosis, hypertrophic cardiomyopathy, and massive PE. Cardiac syncope typically has little warning, may occur during exertion or when supine, and is associated with abnormal ECG or cardiac examination.

Differentiation relies primarily on history - the trigger, prodrome, associated symptoms, and recovery pattern. Vasovagal syncope has clear triggers and prodrome with rapid recovery. Orthostatic syncope occurs on standing. Cardiac syncope has minimal warning, may be exertional, and the ECG is often abnormal. Physical examination findings like ejection systolic murmur (AS) or postural BP drop (orthostatic hypotension) help confirm the diagnosis."

Q3: "What are the indications for pacemaker insertion in syncope?"

Model Answer:

"Pacemaker insertion is indicated for syncope caused by bradyarrhythmias where there is a clear correlation between symptoms and bradycardia. According to ESC and ACC/AHA guidelines, Class I indications include:

Symptomatic sinus node dysfunction - documented sinus bradycardia less than 40 bpm, sinus pauses, or chronotropic incompetence during syncope or causing symptoms.

Acquired atrioventricular block - symptomatic 2nd degree AV block Mobitz type II, or 3rd degree (complete) heart block, regardless of symptoms as risk of progression is high.

Bifascicular or trifascicular block with syncope when electrophysiology study demonstrates HV interval ≥70 ms or infranodal block, indicating high risk of progression to complete heart block.

Carotid sinus syndrome with dominant cardioinhibitory response - documented asystole >3 seconds with symptom reproduction during carotid sinus massage, in patients with recurrent syncope.

Importantly, pacemaker is NOT indicated for uncomplicated vasovagal syncope. Previous trials showed minimal or no benefit over placebo, with high placebo response rates. It may be considered in highly selected patients over 40 with severe recurrent vasovagal syncope, documented asystole >3 seconds during tilt test, and injury, but evidence is weak and it's not first-line therapy.

The key is to establish temporal correlation between bradycardia and syncope, usually via ECG monitoring during symptoms, Holter monitoring, or implantable loop recorder."

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14. Red Flags and Safety-Netting

RED FLAGS - Immediate Cardiology Referral

🚨 Syncope during exertion or in supine position

🚨 Syncope with chest pain, palpitations, or severe dyspnoea

🚨 Family history of sudden cardiac death (especially age less than 40)

🚨 Known structural heart disease or heart failure

🚨 Abnormal ECG (see investigation section for specific findings)

🚨 No prodrome ("lights out" syncope)

🚨 Recurrent syncope in elderly with no clear vasovagal trigger

🚨 Syncope causing severe injury (suggesting no warning)

Safety-Netting Advice for Patients

All patients discharged from ED:

• Explain diagnosis and likely cause
• Advise on trigger avoidance (if vasovagal)
• Teach abort techniques (lie down at first warning)
• Ensure adequate hydration
• DVLA notification requirement (6 months off driving for unexplained syncope)
• Avoid high-risk activities (heights, machinery, swimming alone) until controlled
• Return immediately if: chest pain, palpitations, dyspnoea, neurological symptoms, or further unexplained syncope

Follow-up arrangements:

• Low-risk vasovagal: GP follow-up
• Medium-risk or unexplained: Cardiology outpatient or syncope clinic within 1-2 weeks
• High-risk: Admit or urgent cardiology within 24-48 hours

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15. Summary: Key Takeaways

1. Syncope is transient loss of consciousness due to cerebral hypoperfusion with rapid onset, short duration (less than 60 seconds), and spontaneous complete recovery.

2. History is the most powerful diagnostic tool, establishing diagnosis in up to 50% of cases. Explore before, during, and after the episode systematically.

3. ECG is mandatory in ALL syncope patients. Abnormal in 5-10%, may identify immediate life-threatening diagnoses.

4. Classify into reflex (40-50%), orthostatic (15-25%), cardiac (10-20%) based on history, examination, and ECG.

5. Cardiac syncope carries 1-year mortality 18-33% if untreated. Red flags include exertional syncope, no prodrome, abnormal ECG, structural heart disease, family history SCD.

6. Reflex syncope is benign with no increased mortality. Managed with education, trigger avoidance, adequate hydration, counterpressure manoeuvres.

7. Risk stratify all patients. High-risk features require urgent investigation (echo, cardiac monitoring, often admission). Low-risk can be managed in community.

8. Implantable loop recorder is gold standard for recurrent unexplained syncope after initial negative workup (diagnostic yield 40-50%).

9. Driving restrictions apply: Single unexplained syncope = 6 months off driving (UK). Patient must notify DVLA.

10. Distinguish from seizure: Syncope has shorter duration (less than 60 sec), rapid recovery (less than 2 min), usually upright posture, prodrome common. Seizure has prolonged tonic-clonic activity, prolonged post-ictal confusion (>5 min).

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16. References

1. Brignole M, Moya A, de Lange FJ, et al. 2018 ESC Guidelines for the diagnosis and management of syncope. Eur Heart J. 2018;39(21):1883-1948. doi:10.1093/eurheartj/ehy037

2. National Institute for Health and Care Excellence. Transient loss of consciousness ('blackouts') in over 16s. NICE Clinical Guideline CG109. 2014.

3. Ganzeboom KS, Mairuhu G, Reitsma JB, et al. Lifetime cumulative incidence of syncope in the general population: a study of 549 Dutch subjects aged 35-60 years. J Cardiovasc Electrophysiol. 2006;17(11):1172-1176. doi:10.1111/j.1540-8167.2006.00595.x

4. Sun BC, Emond JA, Camargo CA Jr. Direct medical costs of syncope-related hospitalizations in the United States. Am J Cardiol. 2005;95(5):668-671. doi:10.1016/j.amjcard.2004.11.013

5. Soteriades ES, Evans JC, Larson MG, et al. Incidence and prognosis of syncope. N Engl J Med. 2002;347(12):878-885. doi:10.1056/NEJMoa012407

6. Kapoor WN. Syncope. N Engl J Med. 2000;343(25):1856-1862. doi:10.1056/NEJM200012213432507

7. Alboni P, Brignole M, Menozzi C, et al. Diagnostic value of history in patients with syncope with or without heart disease. J Am Coll Cardiol. 2001;37(7):1921-1928. doi:10.1016/s0735-1097(01)01241-4

8. Linzer M, Yang EH, Estes NA 3rd, et al. Diagnosing syncope. Part 1: Value of history, physical examination, and electrocardiography. Ann Intern Med. 1997;126(12):989-996. doi:10.7326/0003-4819-126-12-199706150-00012

9. Sheldon R, Rose S, Connolly S, et al. Diagnostic criteria for vasovagal syncope based on a quantitative history. Eur Heart J. 2006;27(3):344-350. doi:10.1093/eurheartj/ehi584

10. Ungar A, Mussi C, Del Rosso A, et al. Diagnosis and characteristics of syncope in older patients referred to geriatric departments. J Am Geriatr Soc. 2006;54(10):1531-1536. doi:10.1111/j.1532-5415.2006.00891.x

11. Ganzeboom KS, Colman N, Reitsma JB, et al. Prevalence and triggers of syncope in medical students. Am J Cardiol. 2003;91(8):1006-1008. doi:10.1016/s0002-9149(03)00127-9

12. Chen LY, Gersh BJ, Hodge DO, et al. Prevalence and clinical outcomes of patients with multiple potential causes of syncope. Mayo Clin Proc. 2003;78(4):414-420. doi:10.4065/78.4.414

13. Moya A, Sutton R, Ammirati F, et al. Guidelines for the diagnosis and management of syncope (version 2009). Eur Heart J. 2009;30(21):2631-2671. doi:10.1093/eurheartj/ehp298

14. Ruwald MH, Hansen ML, Lamberts M, et al. Prognosis among healthy individuals discharged with a primary diagnosis of syncope. J Am Coll Cardiol. 2013;61(3):325-332. doi:10.1016/j.jacc.2012.09.029

15. Parry SW, Steen N, Baptist M, et al. Amnesia for loss of consciousness in carotid sinus syndrome: implications for presentation with falls. J Am Coll Cardiol. 2005;45(11):1840-1843. doi:10.1016/j.jacc.2005.02.059

16. Mosqueda-Garcia R, Furlan R, Tank J, Fernandez-Violante R. The elusive pathophysiology of neurally mediated syncope. Circulation. 2000;102(23):2898-2906. doi:10.1161/01.cir.102.23.2898

17. Freeman R, Wieling W, Axelrod FB, et al. Consensus statement on the definition of orthostatic hypotension, neurally mediated syncope and the postural tachycardia syndrome. Clin Auton Res. 2011;21(2):69-72. doi:10.1007/s10286-011-0119-5

18. Carabello BA, Paulus WJ. Aortic stenosis. Lancet. 2009;373(9667):956-966. doi:10.1016/S0140-6736(09)60211-7

19. Rockx MA, Hoch JS, Klein GJ, et al. Is ambulatory monitoring for "community-acquired" syncope economically attractive? A cost-effectiveness analysis of a randomized trial of external loop recorders versus Holter monitoring. Am Heart J. 2005;150(5):1065. doi:10.1016/j.ahj.2005.08.020

20. Brignole M, Vardas P, Hoffman E, et al. Indications for the use of diagnostic implantable and external ECG loop recorders. Europace. 2009;11(5):671-687. doi:10.1093/europace/eup097

21. Quinn J, McDermott D, Stiell I, et al. Prospective validation of the San Francisco Syncope Rule to predict patients with serious outcomes. Ann Emerg Med. 2006;47(5):448-454. doi:10.1016/j.annemergmed.2005.11.019

22. Thiruganasambandamoorthy V, Kwong K, Wells GA, et al. Development of the Canadian Syncope Risk Score to predict serious adverse events after emergency department assessment of syncope. CMAJ. 2016;188(12):E289-E298. doi:10.1503/cmaj.151469

23. van Dijk N, Quartieri F, Blanc JJ, et al. Effectiveness of physical counterpressure maneuvers in preventing vasovagal syncope: the Physical Counterpressure Manoeuvres Trial (PC-Trial). J Am Coll Cardiol. 2006;48(8):1652-1657. doi:10.1016/j.jacc.2006.06.059

24. Raviele A, Giada F, Brignole M, et al. Comparison of diagnostic accuracy of sublingual nitroglycerin test and low-dose isoproterenol test in patients with unexplained syncope. Am J Cardiol. 2000;85(10):1194-1198. doi:10.1016/s0002-9149(00)00730-4

25. Nkomo VT, Gardin JM, Skelton TN, et al. Burden of valvular heart diseases: a population-based study. Lancet. 2006;368(9540):1005-1011. doi:10.1016/S0140-6736(06)69208-8

26. Driver and Vehicle Licensing Agency. Assessing fitness to drive: a guide for medical professionals. UK Government. 2023. Available at: https://www.gov.uk/guidance/cardiovascular-disorders-assessing-fitness-to-drive

27. Shen WK, Sheldon RS, Benditt DG, et al. 2017 ACC/AHA/HRS Guideline for the Evaluation and Management of Patients With Syncope. Circulation. 2017;136(5):e60-e122. doi:10.1161/CIR.0000000000000499

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Last Reviewed: 2026-01-05 | MedVellum Editorial Team

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Keywords: syncope, fainting, transient loss of consciousness, TLOC, vasovagal, cardiac syncope, orthostatic hypotension, reflex syncope, ECG, risk stratification, sudden cardiac death, carotid sinus syndrome, tilt table test, implantable loop recorder, MRCP, cardiology