Syncope
A brief loss of consciousness caused by a temporary fall in blood flow to the brain.
What it means
Syncope is a transient loss of consciousness caused by a temporary reduction in blood supply to the brain, with rapid and complete recovery. Note the three-syllable pronunciation.
The commonest form by far is vasovagal syncope — the ordinary faint, triggered by standing for long periods, heat, pain, the sight of blood or emotional distress, and typically preceded by warmth, nausea and greying vision.
The clinical task is separating harmless faints from cardiac syncope, which is caused by an abnormal heart rhythm or a structural heart problem and carries real risk.
In practice
"Presyncope" describes the feeling of being about to faint without actually losing consciousness.
Distinguishing syncope from a seizure rests on the description — which is why an account from someone who witnessed it is more valuable than any test.
Why it matters
Three features shift a faint from reassuring to concerning, and each warrants prompt cardiology assessment:
- Fainting during exertion rather than after it
- No warning at all before losing consciousness
- A family history of sudden cardiac death under 40
Fainting while lying down, or with chest pain or palpitations beforehand, is also concerning.
Clinically reviewed by Dr Mohammad Zubair Khan, GMC 7563469
Last reviewed
August 30, 2026