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Vasovagal Syncope

Background Knowledge 🧠

Definition

  • A transient loss of consciousness caused by a temporary drop in blood flow to the brain, often due to a reflex of the involuntary nervous system.
  • Most common cause of syncope in adults.

Pathophysiology

  • Overreaction of the parasympathetic nervous system (vagus nerve) leading to bradycardia (slow heart rate) and vasodilationΒ (widening of the blood vessels).
  • Results in reduced cardiac outputΒ and transient cerebral hypoperfusion.

Triggers

  • Emotional distress: Fear, severe pain, distressing sights.
  • Standing for long periods.
  • Heat exposure.
  • Physical factors: Coughing, urination, swallowing.
  • After exercise.

 

Clinical Features πŸŒ‘️

Clinical Presentation

  • Prodromal symptoms:
    • Light-headedness
    • Nausea
    • Feeling warm
    • Pallor
    • Visual“blackout”
    • Sweating
  • Transient loss of consciousness (often less than a minute).
  • Recovery is typically rapid but may be associated with transient confusion.

Investigations πŸ§ͺ

Investigations

  • Clinical history: Most diagnostic. Collateral history can help determine possible underlying causes.
  • ECG: To rule out cardiac causes.
  • Orthostatic blood pressure measurements.
  • Tilt table test: Diagnostic in some cases.
  • Holter monitor (ambulatory ECG monitor): If episodic or suspicion of arrhythmia.

Management πŸ₯Ό

Management

  • Educate about triggers and early warning signs.
  • Counterpressure manoeuvres: Leg crossing, handgrip, arm tensing.
  • Increased salt and fluid intake.
  • Avoid prolonged standing, especially in hot environments.
  • Gradual physical training.
  • Pharmacological: Beta-blockers, fludrocortisone, SSRIs – used in recurrent cases.

Complications

  • Generally benign but has the potential for injury due to falls.
  • Recurrent episodes are common.

Key Points

  • Inappropriate reflex of the parasympathetic nervous system can cause a temporary drop in blood flow to the brain, resulting in a transient loss of consciousness.
  • Common triggers include emotional distress and standingΒ for long periods.
  • Typically preceded by prodromal symptoms (light headedness, nausea, feeling warm)

References

Jeanmonod, R., Sahni, D. and Silberman, M. (2023). Vasovagal Episode. [online] PubMed. Available at: https://www.ncbi.nlm.nih.gov/books/NBK470277/.

National Institute for Health and Care Excellence (2010). Introduction | Transient loss of consciousness (β€˜blackouts’) in over 16s | Guidance | NICE. [online] www.nice.org.uk. Available at: https://www.nice.org.uk/guidance/cg109/chapter/Introduction.

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