What is atrial fibrillation?
Atrial fibrillation is a condition where the heart beats irregularly. The heartbeat is outside its usual rhythm and is often faster than normal. Atrial fibrillation can be 'intermittent' (heartbeat is sometimes irregular) or 'permanent' (heartbeat is always irregular).
Because of the irregular heartbeat, the heart cannot pump blood through the heart with the usual force. This can cause blood to pool in one of the chambers of the heart (the left atrium).
When blood pools, it can form a clot which can travel through the blood vessels to another place in the body. This is dangerous, as a clot can block the blood supply to the brain and cause a stroke. Clots can also travel to other areas of the body (e.g. the lungs) and cause other life-threatening problems (e.g. a pulmonary embolism).