Vasovagal syncope

Question 1

Define vasovagal syncope

Answer 1

Sudden, temporary, and self-terminating loss of consciousness due to a temporary inadequacy of cerebral nutrient flow, most often due to the fall in systemic arterial pressure

Question 2

Aetiology of vasovagal syncope

Answer 2

A type of neurally mediated reflex syncope (NMRS) = symptomatic hypotension occurs due to result of neural reflex vasodilation and/or bradycardia

Precipitating events: prolonged periods of upright posture, relative dehydration, excessively warm, closed-in environments, or extreme emotions.

Question 3

Risk factors for vasovagal syncope

Answer 3

Prior syncope
Prior history of arrhythmias, MI, HF or cardiomyopathy
Severe aortic stenosis
Prolonged standing
Emotional stress (esp. in warm, crowded environment)
Dehydration/hypovolaemia
Preceding episode of nausea and/or vomiting
Preceding episode of severe pain

Question 4

Symptoms of vasovagal syncope

Answer 4

Suspect if no features to suggest an alternative diagnosis, and the 3 ‘P’s are present:

1. Posture — typically after prolonged standing; less common after sitting. Similar episodes may be prevented by lying down.
2. Provoking factors — fear; pain (somatic or visceral); instrumentation; blood phobia; unpleasant sight, sound or smell; crowded or hot places; dehydration.
3. Progressive prodrome — such as pallor, sweating, and/or nausea or vomiting.

Note: brief myoclonus can occur during uncomplicated vasovagal syncope and is not necessarily diagnostic of epilepsy

Question 5

Investigations for vasovagal syncope

Answer 5

ECG: rule out arrhythmia

FBC: exclude anaemia
Glucose: exclude hypoglycaemia
b-hCG: exclude pregnancy
CK/CK-MB: exclude MI
Troponin: exclude MI
D-Dimer: exclude PE
Cortisol: exclude adrenal insufficiency
U&Es: exclude syncope

Question 6

Management for vasovagal syncope

Answer 6

Patient education
Reassure that prognosis is good
Avoid triggers e.g. stress, dehydration, excessive warmth, upright posture
Early recognition of prodromal symptoms and sit/lie down
Lifestyle modifications:
- Adequate fluid intake (2L/day)
- Salt and electrolyte-rich sports drinks
- Physical counter-pressure manoeuvres e.g. leg and knee crossing, swuatting, hand gripping, arm tensing

Consider Fludrocortisone or Midodrine

Question 7

Complications of vasovagal syncope

Answer 7

Injury
Fracture
Extradural or cerebral haemorrhage secondary to trauma