Atrial fibrillation (AF) causes a fast and erratic heartbeat. There are various causes of AF. Medication can slow the heart rate and ease symptoms. Sometimes treatment can restore the heart rhythm back to normal. In addition, a medicine to prevent clots forming is usually advised to reduce the risk of having a stroke.
Understanding a normal heartbeat
The heart has four chambers - two atria and two ventricles. The walls of these chambers are mainly made of special heart muscle. The chambers have to contract (squeeze) in the correct order for the heart to pump blood correctly with each heartbeat.
The sequence of each normal heartbeat is as follows:
What is atrial fibrillation?
If you have atrial fibrillation (AF):
What happens is that the normal controlling timer in the heart is overridden by many random electrical impulses
that fire off from the heart muscle in the atria. The atria then fibrillate. This means that the atria only partially contract - but very rapidly (up to 400 times per minute). Only some of these
impulses pass through to the ventricles in a haphazard way. Therefore, the ventricles contract anywhere between 50 and 180 times a minute, but usually between 140 and 180 times a minute. However, the
ventricles contract in an irregular way and with varying force.
Therefore, if you have AF and feel your pulse, you may count up to 180 beats per minute. Also, the force of each beat can vary, and the pulse feels erratic.
AF is commonly divided into the following types:
Most people with AF have permanent AF.
How common is atrial fibrillation?
It is common, but mainly occurs in older people. Nearly 50,000 cases are diagnosed each year in the UK. It becomes more common with increasing age. About 1 in 200 people aged 50-60 have AF. This rises to around 1 in 10 people aged over 80 years. It is uncommon in younger people unless you have certain heart conditions.
What causes atrial fibrillation?
Causes of AF include the following:
What are the symptoms of atrial fibrillation?
Symptoms often develop quickly, soon after the AF develops. Possible symptoms include:
Breathlessness, dizziness and angina may develop because when the heart beats too fast, it becomes less efficient.
Small amounts of blood pumped faster are not as useful to the body as larger amounts pumped at a slower, normal rate. A reduced output of blood from the heart can lead to blood pooling in the veins
of the lungs, which can lead to these symptoms.
Many people with AF have no symptoms, particularly if their heart rate is not very fast. The AF may then be diagnosed by chance when a doctor or nurse feels your pulse.
Are any tests needed?
What are the possible complications of atrial fibrillation?
An increased risk of having a stroke (or other blood clot problem)
The main complication of AF is an increased risk of having a stroke. AF causes turbulent blood flow in the heart
chambers. This sometimes leads to a small blood clot forming in a heart chamber.
A clot can travel in the blood vessels until it gets stuck in a smaller blood vessel in the brain (or sometimes in another part of the body). Part of the blood supply to the brain may then be cut off, which causes a stroke.
The risk of developing a blood clot and having a stroke varies, depending on various factors. The level of risk can be calculated by your doctor using a set of specific questions. This will help to decide what treatments are required. All people except those at the lowest risk will be offered medication to help prevent clots from forming.
Less common complications of AF include the following:
What are the treatment options for atrial fibrillation?
Treatments that may be considered include:
Each of these are now discussed further.
Rate control treatment
If your heart rate is brought down to normal, your heart becomes efficient again and your symptoms usually improve.
Your pulse may still feel irregular, but not fast.
Several medicines can slow the heart rate down. They include beta-blocker medicines (such as atenolol and propranolol), diltiazem, verapamil and digoxin. These medicines work by interfering with the electrical impulses of the heart. The medicine chosen may depend on factors such as other heart problems that you may have.
In untreated AF, the heart rate may be as fast as 180 beats per minute, although it is more commonly between 120 and 160 beats per minute. The aim of medication is to bring the heart rate back down to normal (ideally, to less than 90 beats per minute when resting).
Treatment is usually successful, but the dose needed can vary from person to person. Also, in some people a combination of medicines may be needed if the heart rate is not brought down low enough with a single medicine.
Rhythm control treatment
Rhythm control means reverting the erratic heartbeat back to a normal regular rhythm. This is called
One method of cardioversion is to give your heart an electric shock. Another method is to use a medicine that may convert the heart rhythm back to a regular beat. Both of these methods have only limited success. For example, after cardioversion, within a year in about half of cases the heart has reverted back to AF.
Cardioversion is more likely to be considered as a possible option in certain situations - for example:
Cardioversion is usually not an option in certain situations - for example:
A newer technique to restore the heart rhythm is called catheter ablation. In this procedure a catheter (a long
thin wire) is passed into the chambers of the heart via a large blood vessel in a leg. The tip of the catheter can destroy tiny sections of heart tissue that may be the source or trigger of the
abnormal electrical impulses. This treatment is only suitable in certain cases and is not a routine treatment. It does not always work and there is a small risk of serious complications.
Your doctor will discuss with you in more detail if you are suitable to have rhythm control treatment and which method of cardioversion would be best for you.
All people with AF (except those with the lowest risk of having a stroke) should be offered anticoagulation treatment. Anticoagulation
means that you take a medicine to reduce the chance of forming a blood clot and having a stroke. Some people call anticoagulation "thinning the blood" although the blood is not actually made any
thinner. The most commonly used anticoagulant medicine has been warfarin, although others have recently been developed. They work by interfering with certain chemicals in the blood to prevent blood
clots forming so easily.
They reduce the risk of stroke by nearly two thirds. In other words, these treatments can prevent about 6 in 10 strokes that would have occurred in people with AF.
As with all treatments, there is a small risk if you take an anticoagulant. The main risk is that a bleeding problem may develop as the blood will not clot so well. For example, some people develop a serious bleeding ulcer in the gut. Warfarin can interact with many different medicines and things in your diet. Some of the newer anticoagulants, such as dabigatran and rivaroxaban, do not have these interactions.
If you take warfarin you will need regular blood tests (INR tests) to check how quickly your blood clots. Blood tests may be needed quite often at first, but should become less often quite quickly. The aim is to get the dose of warfarin just right so your blood does not clot as easily as normal, but not so much as to cause bleeding problems. Dabigatran and rivaroxaban do not need regular blood tests. If you have had trouble getting your INR level just right, your doctor may suggest one of these medicines as an alternative to warfarin.
Aspirin is another medicine that helps to prevent blood clots forming and was used extensively in the past. It is now known that it is not as effective as warfarin, but is just as likely to cause problems. It is only prescribed in AF when oral anticoagulants cannot be used. Aspirin should not be used for people at low risk of having a stroke.
Other treatments may be advised, depending on the need to treat any underlying problems such as angina, heart valve problems, high blood pressure, and overactive thyroid.