Atrial fibrillation (AF) is a common type of heart rhythm disorder (arrhythmia), characterised by a rapid and irregular heartbeat.
If you have atrial fibrillation, the electrical signals that control your heartbeat are abnormal. These signals cause the upper chambers of your heart (the atria) to beat chaotically and very quickly. In fact, the atria beat so quickly that the lower heart chambers (the ventricles) can’t quite keep up, and your heart doesn’t beat in the usual, co-ordinated manner. This results in an irregular and rapid heart rate, often ranging from 100 to 180 beats per minute. (Normal heart rate for adults is 60 to 100 beats per minute.)
Atrial fibrillation can be classified as:
- ‘paroxysmal’, which means that it occurs in recurrent bouts that usually resolve without treatment in less than 48 hours;
- persistent, where AF comes on suddenly and lasts for days or weeks without treatment to restore normal heart rhythm; or
- permanent, or chronic, where a normal heart rhythm cannot be achieved and treatment is aimed at controlling the heart rate (number of beats per minute).
It is also possible to have an acute, one-off episode of AF, which may be the result of a particular transient problem such as alcohol intoxication.
Symptoms of atrial fibrillation include:
- palpitations (an awareness of your heart beating or pounding in your chest);
- dizziness or light-headedness;
- shortness of breath (especially on exertion);
- fatigue or weakness; and
- chest pain.
Some people have no symptoms at all, and AF is only detected after a doctor (or another health care worker) notices that your pulse is irregular.
It is possible for otherwise healthy people to have AF — in fact, up to one-third of people with AF have no obvious underlying cause, a condition known as lone atrial fibrillation.
However, there are some known risk factors for AF.
- Age: your risk of having AF increases as you get older — atrial fibrillation affects 5 per cent of people older than 65 years and about 10 per cent of people older than 75 years.
- Heart disease: people who have heart disease or problems with their heart valves are more likely to be affected than those who don’t have these problems.
- Other health conditions, including long-standing high blood pressure, chronic lung disease, an overactive thyroid gland, sleep apnoea and obesity, can increase your risk of AF.
- People with AF have a higher risk of stroke — the risk ranges from less than 1 per cent per year to about 20 per cent per year, depending on your age and other medical conditions.
- People with atrial fibrillation are also at risk of developing heart failure.
How does atrial fibrillation cause stroke?
Because the atria are contracting quickly and abnormally, they don’t pump blood through the heart properly. Blood can then pool in the heart and a blood clot may form. If the clot breaks loose and leaves the heart, it can travel via your blood vessels to other organs in your body. If a clot lodges in a blood vessel that supplies your brain and cuts off the blood supply, it can cause a stroke.
Tests and diagnosis
Your doctor may order any of several tests to diagnose atrial fibrillation.
- ECG (electrocardiogram): This is a simple, painless test. When you have an ECG, small patches connected to wires (electrodes) are placed on your chest to measure the electrical impulses given off by your heart. These electrical impulses are recorded on a piece of paper called an ECG strip. The abnormal pattern of electrical impulses seen in people with AF is easily detected by the ECG.
- Holter monitor test: If you have paroxysmal AF, your heartbeat may be normal at the time the ECG is recorded. To detect paroxysmal AF, you may need to have a Holter monitor test arranged. A Holter monitor (a portable device that you wear under your clothes) continuously records your heart's electrical impulses for at least 24 hours.
- Echocardiogram: While this test – an ultrasound of your heart – is not needed to diagnose AF, an echocardiogram is often recommended to check for heart problems such as leaky valves and to see how well your heart is pumping.
- Blood tests: Your doctor may recommend a number of blood tests, such as thyroid function tests, to check for possible causes of AF.
The treatment for atrial fibrillation varies from person to person depending on a number of factors, including the severity of your symptoms, the cause and duration of your atrial fibrillation, your age and whether you have any underlying or associated health problems. However, in general, the main aims of treatment are to:
- restore your heart’s normal rhythm or control your heart rate; and
- prevent blood clots.
Medicines to control heart rhythm or rate
Your doctor may prescribe medicine to try to restore and maintain the normal, regular rhythm of your heart. Medicines used to control heart rhythm in atrial fibrillation include antiarrhythmics such as:
- flecainide (brand names Flecatab, Tambocor);
- sotalol (brand names Cardol, Solavert, Sotacor); and
- amiodarone (brand names Aratac, Cordarone X, Rithmik).
Medicine that simply slows your heart rate is also effective. Medicines that can be used to control the heart rate include:
- calcium channel blockers; and
- digoxin (brand names include Lanoxin, Sigmaxin).
If medicines are used to treat your AF, the type will depend on several factors, including your age, the type of AF you have, symptoms associated with your AF, other medical conditions and side effects of the different medicines.
Medicines to prevent blood clots
It is likely you will also need to take medicine to prevent your blood from clotting to reduce your risk of stroke. Medicines used include:
- warfarin (brand names Coumadin, Marevan); and
- new oral anticoagulants – dabigatran (Pradaxa), rivaroxaban (Xarelto), apixaban (Eliquis).
Anticoagulants can cause bleeding, so the risk of bleeding needs to be considered before starting these medicines. Your doctor will be able to discuss the risks and benefits of these medicines in the context of your condition and personal risk factors.
Sometimes, the recommended treatment for atrial fibrillation is to use electrical stimulation to convert your heart into a normal rhythm. This procedure is called electrical cardioversion and is performed while you are under sedation or a general anaesthetic.
Invasive treatments for atrial fibrillation
People with atrial fibrillation that has not been effectively treated with medicines or electrical cardioversion may require a more invasive treatment.
- Catheter ablation: in this procedure, a catheter (a long, thin tube) is introduced through the femoral vein in your groin and threaded all the way to the heart, where radiofrequency energy (or heat or cold – cryotherapy) is used to damage the small portion of tissue responsible for the abnormal electrical signals.
- Open heart surgery: this is rarely required. The most common operation performed is known as the maze procedure, where a number of small incisions are made in the atria (upper chambers) of the heart to create a pattern of scar tissue. The scar tissue (which does not carry electrical currents) prevents the abnormal electrical signals that cause atrial fibrillation from travelling through the heart and causing an abnormal heartbeat.
- Pacemaker: a pacemaker (a medical device that helps regulate the heartbeat) may need to be inserted. Pacemakers are placed just under the skin near your collarbone, and a wire connects the pacemaker to your heart.
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3. MayoClinic.com. Atrial fibrillation (updated 18 Mar 2015). http://www.mayoclinic.org/diseases-conditions/atrial-fibrillation/basics/definition/con-20027014 (accessed Apr 2015).