Atrial fibrillation
Atrial fibrillation (AF) is a common type of heart rhythm disorder (arrhythmia). Normally, your heart beats at a rate of 60 to 100 beats per minute when you are at rest, and all of the heart chambers beat in unison. 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.
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.
Atrial fibrillation can be ‘paroxysmal’, which means that it occurs in recurrent bouts that usually last less than 48 hours; or chronic (ongoing). 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.
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 causes a stroke.
Who is affected by atrial fibrillation?
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. 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. Long-standing high blood pressure, chronic lung disease or an overactive thyroid gland can also put you at a higher risk of AF. 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.
Atrial fibrillation symptoms
You may experience palpitations (an awareness of your heart beating or pounding in your chest) if you have atrial fibrillation. Other atrial fibrillation symptoms include chest pain, dizziness, light-headedness, shortness of breath and fatigue. 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.
Atrial fibrillation diagnosis
Tests
Your doctor can diagnose atrial fibrillation using a simple, painless test called an electrocardiogram (ECG). 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.
However, 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.
Atrial fibrillation treatment
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, and whether you have any underlying 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 (e.g. Flecatab, Tambocor), sotalol (e.g. Solavert, Sotacor) and amiodarone (e.g. Cordarone X, Rithmik).
Medicine that simply slows your heart rate is also effective. Medicines that can be used to control the heart rate include digoxin (e.g. Lanoxin, Sigmaxin), beta-blockers and calcium channel blockers.
Medicines to prevent blood clots
It is likely you will also need to take medicine to prevent your blood from clotting (for example, aspirin or warfarin), to reduce your risk of stroke.
Electrical cardioversion
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 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. For example, 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.
Sometimes, radiofrequency catheter ablation is used. 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 is used to damage the small portion of tissue responsible for the abnormal electrical signals.
Rarely, open heart surgery is 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.
Last Reviewed: 26 January 2010
- 1. Heart Foundation [website]. Atrial fibrillation (published 2008). Available at: http://www.heartfoundation.org.au/Heart_Information/Heart_Conditions/Atrial_Fibrillation/Pages/default.aspx (accessed 2010, Mar 29)
2. Atrial flutter and atrial fibrillation [revised June 2008]. In: eTG complete [Internet]. Melbourne: Therapeutic Guidelines Limited; 2010 Mar (Accessed 2010 Mar 29.) http://www.tg.org.au/
3. eMIMS Prescribing Information, April 2010
4. Mayo Clinic [website]. Atrial fibrillation (updated 2009, Feb 14). Available at: http://www.mayoclinic.com/health/atrial-fibrillation/DS00291 (accessed 2010, Apr 1)
