Table 1

Potential causes of syncope3 5 8 12 18–20

Orthostatic hypotensionSyncope
NeurogenicNon-neurogenicNeurocardiogenicCardiac
Causes

  • Associated with autonomic failure disorders

  • Due to extrinsic factors (eg, hypovolaemia, medication use)

  • Associated with emotional stress or pain

  • Arrhythmia

  • Structural cardiac disease

Clinical features

  • BP drop of ≥20 mm Hg systolic or ≥10 mm Hg diastolic on standing

  • Insufficient compensatory HR increase on standing (<15 bpm)

  • BP drop of ≥20 mm Hg systolic or ≥10 mm Hg diastolic on standing

  • Appropriate compensatory HR increase on standing (>15 bpm)

  • Vasodepressor reflex characterised by a sudden drop in BP that may occur after an increase in HR

  • Low cardiac output due to structural or electrical heart abnormalities

  • Occurs during exertion or when supine

  • BP, blood pressure; bpm, beats per minute; HR, heart rate.