SYNCOPE 

Syncope is a transient loss of consciousness (TLOC) due to global cerebral hypoperfusion, characterized by:

• Rapid onset
• Short duration
• Spontaneous complete recovery

1️⃣ Pathophysiology of Syncope

Cerebral perfusion stops when:

• SBP < 60 mmHg OR
• Cerebral perfusion pressure falls abruptly

Brain tolerance to hypoperfusion:

• LOC within 6–8 seconds
• Myoclonic jerks may occur (convulsive syncope)

Causes by Age 

Young	Elderly
Vasovagal	Orthostatic
HCM	Carotid sinus
Long QT	AV block
SVT	Aortic stenosis

2️⃣ Classification of Syncope

Category	Mechanism	Examples
Reflex (Neurally mediated)	Autonomic reflex → vasodilation ± bradycardia	Vasovagal, situational, carotid sinus
Orthostatic hypotension	Failure of BP compensation on standing	Volume depletion, autonomic failure
Cardiac syncope	Arrhythmia or structural heart disease	VT, AS, HCM
Cerebrovascular (rare)	Vertebrobasilar insufficiency	Subclavian steal

• Exertional syncope = cardiac until proven otherwise
• Normal ECG does NOT rule out arrhythmia

3️⃣ Reflex (Neurally Mediated) Syncope

1. Vasovagal Syncope (Most common)
2. Mechanism

Bezold-Jarisch reflex:
↓ Venous return → hypercontractile LV
→ Paradoxical vagal activation
→ Bradycardia + vasodilation

Triggers

• Prolonged standing
• Pain
• Emotional stress
• Heat
• Sight of blood

Prodrome 

• Nausea
• Sweating
• Pallor
• Yawning
• Blurred vision
• “Feeling warm”

Recovery

• Rapid
• No postictal confusion

B. Situational Syncope

Trigger-specific:

• Micturition
• Defecation
• Cough
• Swallowing

Mechanism:↑ Vagal tone

C. Carotid Sinus Syncope

Usually elderly males.

Trigger:

• Tight collar
• Head turning
• Shaving

Diagnosis:
Carotid sinus massage →Pause >3 sec OR SBP drop >50 mmHg

⚠ Contraindicated in carotid bruit / recent TIA

4️⃣ Orthostatic Hypotension

Defined as:
↓ SBP ≥20 mmHg OR
↓ DBP ≥10 mmHg within 3 minutes of standing

Causes

A. Volume depletion

• Diuretics
• Dehydration
• GI bleed

B. Autonomic failure

• Diabetes
• Parkinson’s disease
• Amyloidosis
• Alcohol neuropathy

C. Drugs

• Alpha blockers
• Nitrates
• Antidepressants

Neurogenic vs Non-neurogenic Clue 

If heart rate does NOT rise appropriately → neurogenic cause.

5️⃣ Cardiac Syncope 

A. Arrhythmias

Bradyarrhythmias

• Complete heart block
• Sick sinus syndrome

Tachyarrhythmias

• Ventricular tachycardia
• SVT with poor filling

Clinical features 

• Syncope during exertion
• No prodrome
• Palpitations before event
• Structural heart disease

B. Structural Causes

1️⃣ Aortic stenosis

Classic triad:

• Angina
• Syncope
• Dyspnea

Mechanism:Fixed cardiac output → unable to increase during exertion.

2️⃣ Hypertrophic cardiomyopathy

Syncope in young patient
Murmur ↑ with Valsalva
Risk of sudden death

3️⃣ Pulmonary embolism

Syncope + dyspnea + tachycardia

6️⃣ Syncope vs Seizure 

Feature	Syncope	Seizure
Prodrome	Nausea, sweating	Aura
Jerks	Few (<10)	Many (>20)
Tongue bite	Rare	Lateral tongue
Post-event confusion	None	Present
Incontinence	Rare	Common
Recovery	Rapid	Slow

⚠ Convulsive syncope exists.

7️⃣ Initial Assessment 

1. History (MOST IMPORTANT)

• Circumstances
• Posture
• Prodrome
• Palpitations
• Family history sudden death
• Drug history

2. Examination

• Orthostatic BP
• Murmurs
• Neurological exam

3. ECG (MANDATORY)

Look for:

• Long QT
• Brugada pattern
• AV block
• Pre-excitation
• VT

8️⃣ Risk Stratification (Admission vs Discharge)

High-Risk Features

• Structural heart disease
• Abnormal ECG
• Syncope during exertion
• Syncope while supine
• Family history sudden death
• Severe anaemia
• Persistent hypotension

These patients → Admit

Low Risk

• Typical vasovagal
• Normal ECG
• Normal heart
• Clear trigger

These patients → Reassure

9️⃣ Investigations (Targeted – Not Blanket Testing)

Test	Indication
ECG	All patients
Echo	Murmur / cardiac suspicion
Holter	Recurrent unexplained syncope
Tilt table	Suspected vasovagal
Implantable loop recorder	Infrequent unexplained syncope
CT brain	Only if focal deficit

⚠ Brain imaging rarely needed.

🔟 Management

Reflex Syncope

• Education
• Avoid triggers
• Hydration
• Counter-pressure maneuvers
• Midodrine (selected cases)

Orthostatic Hypotension

• Stop offending drugs
• Compression stockings
• Fludrocortisone
• Midodrine

Arrhythmia

• Pacemaker (AV block)
• ICD (VT)
• Antiarrhythmics

Structural

• Valve replacement (AS)
• Septal reduction (HCM)