Atrial fibrillation (AF) is an abnormal heart rhythm that affects the top chambers of the heart (the atria) making them fibrillate or contract in a fast and random manner. Many people are completely unaware that they are in atrial fibrillation, but some people feel the irregularity as palpitations or a fast heart rate, and some feel breathless.
AF is the commonest heart rhythm problem and becomes increasingly frequent with age. It occurs in about 10% of people over 80 years of age, and is much more likely if you have an underlying cardiac problem such as high blood pressure, a previous heart attack or heart muscle problem, but it is not uncommon for people to experience atrial fibrillation with a completely normal heart.
In some people atrial fibrillation comes and goes (paroxysmal AF), lasting minutes, hours or days at a time, and in others it continues long term (persistent AF), unless it reverts to normal (sinus) rhythm after treatment.
There are two key points to consider when treating atrial fibrillation. Firstly, AF can increase the risk of a stroke. This is because the blood does not flow normally in the atria when the heart is in atrial fibrillation, and this results in stagnant areas of blood flow, which can result in blood clots within the heart. If these blood clots form and are carried into the brain, they can cause a stroke. The risk of a stroke caused by AF is calculated using the CHADS2VASc score, which uses many of the same factors that are already risk factors for stroke in patients without AF, such as increasing age, high blood pressure and diabetes. The CHADS2VASc score is calculated from 0 to 9, with 9 representing the highest risk of stroke (15% per year). Treatment with blood thinners (anticoagulants) is recommended for people at increased risk of stroke. These drugs help to prevent blood clots forming within the heart and thereby reduce the risk of stroke. However, because the blood is thinner than usual there is a small increase in risk of bleeding. The decision as to whether or not you take blood thinners should be based on a discussion around the potential risks and benefits of treatment and your views of what you consider most important.
Once the risk of stroke has been adressed, any further treatment of AF is purely directed at symptoms. So if you do not have any symptoms, in most situations, no further treatment is required. Similarly if the symptoms you have are mild and not obtrusive, there is no mandate for you to have any further treatment. However, if you do not feel you can put up with the symptoms caused by atrial fibrillation, there are a variety of treatment options.
Firstly, if the AF is making your heart rate fast (often over 100 beats per minute even at rest), then slowing it down with a betablocker, such as bisoprolol, may be all that is needed to alleviate symptoms.
If you continue to have symptoms, such as breathlessnes on exertion, despite a well controlled heart rate (usually < 90 beats per minute at rest) and without evidence of very high heart rates on exertion, we might consider trying to get your heart back into normal (sinus) rhythm. This will usually be done when you have been on anticoagulants for at least 4 weeks (to minmise the risk of stroke), and can be done with drugs or with an electric shock to reset the heart rhythm (DC cardioversion), which is performed under a short anaesthetic. It is worth pointing out that there is a high chance of AF recurring after Cardioversion, and while some people can go for years without any more AF, some will find they are back in AF within a few weeks. Unfortunately, even if Cardioversion is successful, in most situations this is not a reason to stop taking anticoagulant medication, because of the risk of further AF in the future.
Often people who go into and out of atrial fibrillation (paroxysmal AF) are the most symptomatic, because they can have slow heart rates when in normal rhythm, and fast heart rates when in AF. Depending on the frequency and duration of atrial fibrillation there are various options for treatment.
If symptoms are infrequent and brief, no treatment may be required. If symptoms are infrequent but can last more than 45-60minutes, it may be appropriate to take a tablet at the onset of AF to try to encourage the heart to go back into a normal rhythm. Tablets usually take the best part of an hour, at least, to get into the system, so this approach is not useful for shorter episodes. Drugs used for this ‘pill-in-the-pocket’ strategy include bisoprolol, sotalol and flecainide. It is usually trial and error to see what medication works best for you and at what dose.
If your symptoms are more frequent or shorter-lived, you might consider taking a regular medication to try to stop the AF happening in the first place. Again bisoprolol, sotalol and flecainide are the most commonly used drugs, and often we will build of the doses of one drug and then switch to another if it does not seem to be helpful. If these drugs do not work, we will sometimes discuss trying dronedarone or amiodarone with you. These are the most effective drugs for treating AF, but are not used first line as they have a number of side effects that you need to be aware of.
For all types of atrial fibrillation, if medication and/or cardioversion do not successfully control symptoms, we may consider AF ablation. This is a complex procedure that involves burning the inside wall of the heart using a catheter inserted into the heart from a hole in the vein in the leg. This procedure carries a 1:1000 risk of death and a 1-2% risk of major complications, including stroke (0.5-1%) or major bleeding. The success rate of AF ablation depends on a variety of factors. In the best situations there is a 70% success rate after 1 procedure, and a success rate of up to 95% after 3 procedures. However, if your heart is abnormal (heart failure, valve problems, heart muscle disease) or you are in persistent atrial fibrillation, the success rates you can expect will be lower than this.
If you are on anticoagulants or are at low risk of stroke from AF, then AF is very rarely dangerous, and even if you have symptoms from it you do not need to panic, and often sitting down and trying to relax can help slow down the heart rate and help alleviate the symptoms somewhat until the heart returns to normal rhythm. However, if you are feeling very unwell, particularly if you lose consciousness, develop chest pain or are unable to breathe, you should dial 999 and come to the nearest Emergency Department.