Some people with atrial fibrillation, particularly older people, do not have any symptoms.

The irregularity in heart rhythm is often only discovered during routine tests or investigations for another condition.

Typically, a cardioversion (where the heart is given a controlled electric shock to restore normal rhythm) is carried out.

At this point, many people feel much better and realise they had not been feeling normal.

People often attribute tiredness and feeling lethargic to ageing, but once normal rhythm is restored, they realise these symptoms were caused by atrial fibrillation.

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 our your heart rate by checking your pulse in your neck or wrist.

Other symptoms you may experience if you have atrial fibrillation include:

• tiredness and being less able to exercise
• breathlessness
• feeling faint or lightheaded
• chest pain

The way the heart beats in atrial fibrillation reduces the heart's performance and efficiency.

This can lead to low blood pressure (hypotension) and heart failure.

See a GP or call 111 if:

• you have chest pain that comes and goes
• you have chest pain that goes away quickly but you're still worried
• you notice a sudden change in your heartbeat
• your heart rate is consistently lower than 60 or above 100 (particularly if you're experiencing other symptoms of atrial fibrillation, such as dizziness and shortness of breath)

It's important to get medical advice to make sure it's nothing serious.

Call 999 if:

An electrocardiogram (ECG) can be used to confirm a diagnosis of atrial fibrillation. An ECG is a test that records the rhythm and electrical activity of your heart.

Read more about how atrial fibrillation is diagnosed