Heart problems that can cause fainting

Fainting, also called syncope, is a brief loss of consciousness caused by reduced blood flow to the brain. The person usually becomes upright again after lying down, but a fall can cause injury. Heart-related fainting can occur suddenly, sometimes without warning, and should be taken seriously.

A rhythm that is too fast, too slow or irregular may reduce the amount of blood pumped to the brain. Atrial Fibrillation can produce an irregular heartbeat, although fainting has many possible causes and the rhythm must be checked rather than assumed. Problems affecting the heart muscle, valves or the path blood takes out of the heart can also reduce circulation, especially during exertion.

Other causes include dehydration, Hypoglycaemia and Anaemia. Warning sensations such as light-headedness, nausea, warmth, sweating or visual dimming may occur, but a sudden collapse without warning is more concerning for a cardiac cause and needs prompt review.

If someone faints, lay them flat and raise their legs if there is no injury that makes this unsafe. Check breathing, loosen tight clothing and keep them under observation while they recover. Do not give food or drink until they are fully awake, and seek emergency help if they do not regain consciousness promptly or are not breathing normally.

After any unexplained faint, arrange medical assessment, especially if it happened during exercise, while sitting or lying down, or with a racing or irregular heartbeat. Record what happened before the event, the position of the body, warning symptoms, recovery time, injuries and any medicines.

Call emergency services for fainting with chest pain, severe breathlessness, palpitations, seizure-like movements, serious injury, ongoing confusion or repeated collapse. Emergency assessment is also needed when fainting occurs during exertion or when the person has known heart disease or a family history of sudden unexplained death.

Do not drive, climb or operate machinery until a clinician has assessed an unexplained episode. Prompt review can include an examination, blood pressure checks, an electrocardiogram and further rhythm monitoring when appropriate.

Ask: Could this have been caused by a heart rhythm or valve problem? Do I need an electrocardiogram, heart monitoring or an echocardiogram? Could dehydration, low blood sugar or Anaemia have contributed? What activities should I avoid until the cause is clear, and what symptoms should prompt emergency help?