Atrial fibrillation (AF) is a heart condition that causes an irregular heartbeat and raises your risk of a serious stroke. Find out more about symptoms of AF, how it’s diagnosed and reducing your risk of a stroke with AF.

For printable or accessible versions of the information on this page, see the resources section.

On this page

How can atrial fibrillation cause a stroke?
Who can get AF?
Atrial fibrillation symptoms
What happens to the heartbeat in atrial fibrillation?

How can atrial fibrillation cause a stroke?

Normally, blood flows into the heart and gets fully pumped out every time the heart beats. But in AF, blood can pool inside the heart. A clot can form in the blood and then travel to the brain, causing a stroke.

AF can make you five times more likely to have a stroke. Strokes due to AF tend to be more serious, with more damage to the brain and worse long-term effects If you’re diagnosed with AF, you’ll have an individual stroke risk assessment to make sure you get the right treatment and advice for you.

Who can get AF?

There are different types of heart rhythm problem (arrhythmia). Atrial fibrillation is the most common. Around 1.4 million people in the UK have AF.

AF can happen to anyone, including people who are otherwise fit and well. It usually affects adults and your risk goes up with age. It’s more common in people with conditions such as heart disease, high blood pressure, diabetes, obesity, sleep apnoea or overactive thyroid. It’s also more common in smokers.

Atrial fibrillation symptoms

Atrial fibrillation often has no symptoms. Because of this, you might only find out you have AF during a routine medical check-up or after a stroke.

AF sometimes has symptoms including palpitations (feeling as if your heart is fluttering, thumping or skipping a beat).

Other AF symptoms include tiredness, feeling breathless or faint, or having chest pain.

If you are having symptoms or notice an abnormal pulse, contact your GP or call 111.
If you are having worrying symptoms such as chest pains, severe shortness of breath or passing out, call 999.

What happens to the heartbeat in atrial fibrillation?

Your heart is a powerful pump. Its job is to keep the blood constantly moving around your body, bringing vital oxygen to your cells and organs.

The heart is designed to contract (beat) regularly, pumping blood around the body. Your heart contracts when specialised ‘pacemaker cells’ in the heart send out electrical impulses. The pacemaker cells set the speed and rhythm of your heartbeat.

In AF, the electrical impulses that set your heartbeat are disrupted. The heartbeat can become irregular and may be extremely fast.

Your heart has four chambers:

Left and right atria.
Left and right ventricles.

Specialised cells send electrical impulses to set your heartbeat. These cells are known as the pacemaker, or sinoatrial node. They can adapt to your body’s oxygen needs, speeding up if you move around or slowing down when you rest.

Resources

This guide explains how AF is diagnosed and treated, and treatments to reduce your risk of a stroke. It also lists sources of support and information.