What is atrial fibrillation?

Atrial fibrillation is a heart condition that causes an irregular and often abnormally fast heart rate. A normal resting heart rate should be regular and between 60 and 100 beats a minute but patients with atrial fibrillation can often have resting heart rates of 100 to 120 beats per minute or even higher in some cases.

Atrial fibrillation is the most common heart rhythm disorder affecting around 1% of the population. While it is rare for young people to develop atrial fibrillation, around 5% of those over the age of 65 and 10% of those over 80 are affected by the condition.

The normal heart rhythm

When beating normally, the muscular walls of the heart tighten and contract to force blood out of the heart and around the body. Then the muscles relax and the heart can fill with blood again and the process is repeated every time the heart beats.

How atrial fibrillation affects the heart

Atrial fibrillation happens when abnormal electrical impulses suddenly start firing in the upper chambers of the heart (atria). This causes the atria to contract erratically and sometimes too fast for the heart muscle to properly relax between contractions – reducing the heart’s performance and efficiency.

The causes of atrial fibrillation are not fully understood and although it isn’t usually life-threatening in itself, in some people it is a serious medical condition that may require urgent treatment. One of the reasons is that it increases the likelihood of developing blood clots within the upper chambers of the heart which may be pumped out to other organs. If these clots block arteries in the other organs, such as the brain, they stop blood and oxygen from being delivered and can cause significant damage, such as a stroke.

Types of atrial fibrillation

Atrial fibrillation can be defined in different ways, depending on the frequency and length of episodes. Paroxysmal atrial fibrillation describes episodes that come and go and usually last less than 7 days in many people they last minutes or hours. Persistent atrial fibrillation episodes last for longer than 7 days with long-standing persistent atrial fibrillation consisting of continuous atrial fibrillation for a year or longer. Permanent atrial fibrillation is where it is accepted that the atrial fibrillation will be there forever and no attempts will be made to get rid of it.

Symptoms of atrial fibrillation

Symptoms of atrial fibrillation include heart palpitations, light-headedness, dizziness, shortness of breath and fatigue. Palpitation means being aware of the heart beat and in atrial fibrillation this is a sensation of fluttering or an irregular, chaotic beating. Other symptoms include chest tightness, a feeling of congestion or just general lethargy.

Complications of atrial fibrillation

Many people with atrial fibrillation are unaware that they have it as it may not cause any symptoms. However, a lack of symptoms does not mean the risk of blood clots and strokes is any less. Patients with atrial fibrillation are 4 to 5 times more likely to suffer a stroke than those without the condition and stroke usually occurs in people who don’t know they have atrial fibrillation and are not on medication for protection.

Also, if the heart rate is very fast all day and night for many weeks it can weaken the heart muscle and cause heart failure, a condition in which your heart can’t circulate enough blood to meet your body’s needs.

This section of the website provides detailed information on the anatomy of the heart, how it is negatively impacted by atrial fibrillation and information on different types of atrial fibrillation and the degree to which each type affects patients.