Atrial fibrillation

About atrial fibrillation

Your heart is a muscular pump, responsible for delivering blood to the rest of your body. When your heart doesn’t beat in a normal way, it can’t do this as efficiently.
Atrial fibrillation mostly occurs in older people, affecting about seven in 100 people over the age of 65, although it can happen in younger people as well.

What happens in atrial fibrillation?

Your heartbeat is controlled by electrical signals (impulses), which travel through the heart making it contract. The signals travel from the atria (the upper chambers of the heart) to the ventricles (the lower chambers) through an area called the atrioventricular (AV) node. The AV node helps to synchronise the pumping action of the atria and ventricles.
Atrial fibrillation occurs when the electrical signals in the atria become disorganised, overriding the heart’s normal rate and rhythm. This causes the atria to contract irregularly or ‘fibrillate’.
There are three main types of atrial fibrillation:

• paroxysmal – it happens over seconds, minutes or up to 48 hours and the heart returns to a normal rhythm by itself or with treatment
• persistent – it requires electrical cardioversion to correct the rhythm
• permanent – even electrical cardioversion fails to restore the rhythm

Complications

Atrial fibrillation can cause a stroke and/or heart attack. This is because your blood isn’t flowing properly through your heart, so a blood clot can form. If a clot forms, it can block blood supply in your heart and cause a heart attack, or travel to your brain and cause a stroke. Because of this, people with atrial fibrillation are five times more likely to have a stroke than people without the condition.
If you have atrial fibrillation, you may need anticoagulant medicine (such as aspirin or warfarin) to prevent a clot forming.

Causes of atrial fibrillation

Many conditions that affect the heart or blood circulation can cause atrial fibrillation, including:

• high blood pressure
• heart valve disease
• heart muscle disease (cardiomyopathy)
• coronary heart disease
• congenital heart disease (problems of the heart since birth)
• inflammation of the heart (pericarditis)
• thyroid diseases
• lung cancer and chest infections
• a blood clot on the lung (pulmonary embolism)

Certain factors can also trigger temporary, reversible atrial fibrillation, including:

• alcohol
• being overweight
• caffeine
• certain medicines or drugs
• emotional or physical stress
• surgical procedures

Many people develop atrial fibrillation without having any underlying cause or risk factor. This is called lone atrial fibrillation.