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Vasovagal Syncope

Medicine > Cardiovascular

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 adults1.

Pathophysiology

  • Overreaction of the parasympathetic nervous system (vagus nerve) leading to bradycardia (slow heart rate) and vasodilation (widening of the blood vessels).
  • Results in reduced cardiac output 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 🌡️

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 🧪

Investigations

  • Clinical history: Most diagnostic. Collateral history may also help determine possible underlying causes2.
  • 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 🥼

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 standing for long periods.
  • Typically preceded by prodromal symptoms (light headedness, nausea, feeling warm)
  • Education about triggers and early warning signs, in addition to lifestyle advice and compression manoeuvres are important management options.

References

  1. Jeanmonod, R., Sahni, D. and Silberman, M. (2023). Vasovagal Episode. [online] PubMed. Available at: https://www.ncbi.nlm.nih.gov/books/NBK470277/.
  2. National Institute for Health and Care Excellence (2010). Introduction | Transient loss of consciousness (‘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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Cardiovascular