Fainting

Fainting (Syncope)

Introduction

Fainting, medically termed syncope, is a sudden, brief loss of consciousness and postural tone due to transient global cerebral hypoperfusion (reduced blood flow to the brain). Recovery is usually spontaneous and complete within seconds to minutes. While fainting is often benign, it can also indicate life-threatening cardiovascular, neurological, or metabolic disorders.

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Pathophysiology

The brain requires a constant supply of oxygen and glucose, delivered via adequate cerebral blood flow. A reduction of 20% or more in cerebral perfusion for only a few seconds can result in syncope. Causes include:

• Decreased cardiac output (arrhythmias, structural heart disease).

• Peripheral vasodilation (vasovagal response, orthostatic hypotension).

• Impaired vascular resistance or autonomic failure.

• Neurological conditions affecting consciousness regulation.

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Types and Causes of Syncope

1. Neurally Mediated Syncope (Most Common)

• Vasovagal syncope (“common faint”): Triggered by pain, fear, prolonged standing, or emotional stress.

• Situational syncope: Associated with urination (micturition syncope), defecation, swallowing, or coughing.

• Carotid sinus hypersensitivity: Exaggerated vagal response to carotid sinus stimulation (e.g., turning the neck, wearing tight collars).

2. Orthostatic Hypotension

• Defined as a drop in systolic BP ≥20 mmHg or diastolic BP ≥10 mmHg within 3 minutes of standing.

• Causes:

  • Hypovolemia (dehydration, blood loss).

  • Medications (antihypertensives, diuretics, vasodilators, antidepressants).

  • Autonomic dysfunction (Parkinson’s disease, diabetic neuropathy).

3. Cardiac Syncope (Potentially Life-Threatening)

• Arrhythmias: Bradycardia, tachycardia, AV block, ventricular tachycardia.

• Structural heart disease: Aortic stenosis, hypertrophic cardiomyopathy, pulmonary embolism, myocardial infarction.

4. Neurological Causes

• Seizures (convulsive syncope vs epilepsy).

• Transient ischemic attack (especially vertebrobasilar).

• Subarachnoid hemorrhage (rare but serious).

5. Metabolic and Other Causes

• Hypoglycemia.

• Hypoxemia.

• Hyperventilation.

• Severe anemia.

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Clinical Features

• Prodrome (warning signs): Dizziness, lightheadedness, sweating, blurred vision, nausea, palpitations.

• Event: Sudden collapse, loss of consciousness lasting seconds to 1–2 minutes.

• Recovery: Rapid and complete return to baseline, often with fatigue or mild confusion (but not prolonged as in seizures).

Red flag features suggesting serious cause:

• Syncope during exertion or supine.

• Palpitations at onset.

• Family history of sudden cardiac death.

• Abnormal ECG.

• Injury during fainting.

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Diagnostic Evaluation

1. History and Examination

• Circumstances, triggers, prodromal symptoms, duration, recovery.

• Past medical history (cardiac, metabolic, neurological).

• Medications.

• Family history of arrhythmias or sudden death.

2. Investigations

• Vital signs and orthostatic BP measurement.

• Electrocardiogram (ECG).

• Echocardiography if structural heart disease suspected.

• Holter monitor / event recorder for arrhythmias.

• Tilt-table test for suspected vasovagal syncope.

• Blood glucose, CBC, electrolytes.

• Neurological imaging (CT/MRI) if seizure or stroke suspected.

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Management

1. Acute Episode

• Lay the patient flat, elevate legs to improve cerebral perfusion.

• Ensure airway, breathing, circulation (ABC).

• Recovery usually within 1–2 minutes.

2. Non-Pharmacological Management

• Avoid triggers: dehydration, prolonged standing, sudden posture changes.

• Increase hydration and salt intake (unless contraindicated).

• Physical counter-pressure maneuvers: leg crossing, hand gripping, squatting when prodrome occurs.

• Compression stockings: For orthostatic hypotension.

3. Pharmacological Treatment (For recurrent or severe cases)

a) Vasovagal / Neurally Mediated Syncope

• Fludrocortisone: 0.1 mg orally once daily; increases blood volume.

• Midodrine: 2.5–10 mg orally three times daily; alpha-agonist that increases vascular tone.

• Beta-blockers (e.g., Metoprolol 25–100 mg daily): Occasionally used, but evidence is mixed.

b) Orthostatic Hypotension

• Midodrine: As above.

• Droxidopa: 100–600 mg orally three times daily; for neurogenic orthostatic hypotension.

• Fludrocortisone: As above.

c) Cardiac Syncope

• Antiarrhythmic agents:

  • Amiodarone: 200–400 mg daily for tachyarrhythmias.

  • Flecainide: 50–150 mg twice daily (in selected arrhythmias).

• Beta-blockers: For arrhythmias and hypertrophic cardiomyopathy.

• Anticoagulants / antiplatelets: If syncope secondary to embolic disease.

• Surgical interventions: Pacemaker, implantable cardioverter-defibrillator (ICD), valve replacement, revascularization if indicated.

d) Neurological Causes

• Antiepileptic drugs: Valproate, Lamotrigine, or Levetiracetam if seizures confirmed.

• Stroke management: Antiplatelets (Aspirin 75–150 mg daily, Clopidogrel 75 mg daily), anticoagulation for atrial fibrillation.

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Prognosis

• Vasovagal syncope: Benign, but recurrent episodes may affect quality of life.

• Orthostatic syncope: Manageable with lifestyle and medications; prognosis depends on underlying cause.

• Cardiac syncope: Carries the highest risk of sudden death; requires urgent and definitive management.

• Neurological causes: Prognosis depends on underlying disease (stroke, epilepsy).

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Prevention

• Maintain adequate hydration and salt intake.

• Rise slowly from sitting or lying positions.

• Avoid prolonged standing, especially in hot environments.

• Adhere to prescribed medications and monitor for drug-induced hypotension.

• Regular follow-up with a cardiologist or neurologist if recurrent or unexplained syncope occurs.