When to worry about fainting with atrial fibrillation

Fainting is a common presentation of Atrial Fibrillation. A fast, slow, or irregular rhythm can briefly reduce blood flow to the brain. Medicines, dehydration, blood loss, or another heart problem may also contribute. A brief blackout is different from feeling light-headed, but both deserve attention when atrial fibrillation is known.

Lie flat and raise the legs if there is no injury or breathing problem. Do not drive, climb, or stay alone until you have been assessed. Record what you felt before the episode, how long recovery took, your pulse if available, and any missed or recently changed medicines. Do not take an extra heart medicine dose unless a clinician has instructed you.

Call emergency services if fainting comes with chest pain, severe breathlessness, confusion, weakness on one side, trouble speaking, a sustained very fast heartbeat, serious injury, or failure to wake promptly. Seek same-day medical advice for a first episode, repeated episodes, fainting during exertion, or an episode after a medication change.

Ask whether your rhythm, blood pressure, medicines, or hydration could have contributed, and whether you need an ECG, heart monitoring, blood tests, or a medication review. Ask what pulse or symptom changes should prompt emergency help.