The most obvious symptom of atrial fibrillation is heart palpitations – where the heart feels like it's pounding, fluttering or beating irregularly, often for a few seconds or possibly a few minutes.
As well as an irregular heartbeat, your heart may also beat very fast (often considerably higher than 100 beats per minute).
You can work out your heart rate by checking the pulse in your neck or wrist.
Other symptoms you may experience if you have atrial fibrillation include:
The way the heart beats in atrial fibrillation reduces the heart's performance and efficiency.
You should see a GP immediately if you notice a sudden change in your heartbeat and experience chest pain.