When the upper chambers of the heart (atria) do not pump efficiently, as in atrial fibrillation, there's a risk of blood clots forming.
These blood clots may move into the lower chambers of the heart (ventricles) and get pumped into the blood supply to the lungs or the general blood circulation.
Clots in the general circulation can block arteries in the brain, causing a stroke.
Atrial fibrillation increases the risk of a stroke by around 4 to 5 times.
If your atrial fibrillation is persistent, it may start to weaken your heart. In extreme cases, it can lead to heart failure, as your heart is unable to pump blood around your body efficiently.