Neurocardiogenic vasovagal syncope

Neurocardiogenic vasovagal syncope is a reflex faint in which a trigger briefly lowers blood pressure, heart rate or both. It may follow pain, fear, heat, prolonged standing, a needle or straining. Warning symptoms can include nausea, sweating, warmth, dizziness and dimming vision, followed by a short loss of consciousness.

The vagus nerve is part of the automatic system that helps regulate the heart and blood vessels. In a vasovagal episode, the response to a trigger is stronger than needed: blood vessels relax and the heartbeat may slow, reducing blood flow to the brain. Lying down usually helps restore circulation. A clinician may still investigate other causes such as dehydration, anaemia, hypoglycaemia or atrial fibrillation, particularly after a first or unusual event.

Lie flat and raise your legs if you can do so safely. If that is not possible, sit and put your head down. Tense your leg, abdominal and arm muscles or cross your legs while waiting for help, provided this does not delay getting into a safe position. Avoid standing quickly after recovery. Note the trigger and ask a witness to describe your colour, movements and responsiveness.

Call emergency services if the person has chest pain, serious breathing difficulty, a new racing or irregular heartbeat, a severe injury, prolonged confusion, or does not regain normal awareness promptly. Seek urgent review for fainting during exercise, while lying down, without warning, or repeatedly. These features can point beyond a typical vasovagal pattern.

Ask whether your symptoms fit a vasovagal reflex, how to respond to your personal warning signs, whether you need an ECG or blood tests, and which activities should be limited until assessment is complete.