What should you know about cardioneurogenic syncope?

A trigger such as prolonged standing, heat, pain, emotional distress or straining can activate a reflex in the nervous system. Heart rate may slow, blood vessels may widen, or both may happen together. Blood pressure then drops briefly and the brain receives less blood flow, causing light-headedness or loss of consciousness.

Warning symptoms can include nausea, sweating, warmth, blurred vision, ringing in the ears or a grey feeling before the faint. Dehydration, anaemia and low blood sugar can make dizziness or collapse more likely, while atrial fibrillation can cause an irregular rhythm; these conditions are different possible explanations and need separate assessment.

Lie down promptly and raise your legs if possible. If lying down is not safe, sit and lower your head. Loosen tight clothing, move away from heat and tell someone nearby. Once fully alert, sip fluids if you can swallow safely. A clinician should review a first, unexplained or repeated faint to confirm the pattern and consider other causes.

Keep a record of triggers, posture, warning symptoms and recovery. Your clinician may discuss hydration, regular meals, gradual position changes and physical counter-pressure techniques. Do not practise a technique that feels unsafe or continue an activity when you feel faint.

Call emergency services for fainting with chest pain, severe breathlessness, sustained palpitations, serious injury, seizure-like activity, one-sided weakness or prolonged confusion. Seek urgent assessment if the faint occurred during exercise, while lying down, or without any warning. Do not give food or drink to someone who is unconscious.

Ask whether your episode fits a reflex pattern, which triggers to avoid, and whether you need an ECG, blood tests or a standing blood-pressure assessment. Discuss safe driving and exercise, how to manage recurrent warning symptoms, and which changes should lead to emergency care.