Atrial Fibrillation (AF) March, 2013

Transcription

1 Atrial Fibrillation (AF) March, 2013 This handout is meant to help with discussions about the condition, and it is not a complete discussion of AF. We hope it will complement your appointment with one of our physicians. Questions during your office visit or afterwards are encouraged. Please feel free to call back or send to [email protected]

2 Atrial Fibrillation (AF) Overview This is a cardiac rhythm abnormality which results from abnormal impulse formation in the 2 upper cardiac chambers, the atria. The primary problem is that rapid and ineffective beating of the heart causes poor pump function of these chambers. An uncontrolled heart rate will also compromise function of the lower cardiac chambers, the ventricles. Having less blood pumped to the body causes symptoms and AF can also lead to blood clot formation in the atria. Treatment is directed towards slowing the heart rate and, in many cases, restoring a normal rhythm. Medical treatment can also reduce the risk of stroke. In some cases, drug treatment slows the heart down too much (usually when the heart has returned to a normal rhythm). In those cases (this is called tachycardia-bradycardia syndrome ), pacemaker insertion will allow continued use of drugs, potentially allowing the arrhythmia to be controlled. Drugs do not always work and catheter ablation is an option for some individuals. At present, catheter ablation is not considered a first line treatment. Evaluation Testing looking for coexistent heart and lung disease is done. Thyroid testing is very appropriate. Knowing the duration of the AF is also very helpful. A cardiac ultrasound study (echocardiogram) will help to diagnose coexistent heart and lung disease. It will also help to determine risk of stroke and whether carrying out steps to restore a normal rhythm is reasonable. Ambulatory recording of the heart rhythm will help to determine how well-controlled the heart rate is over the course of the day. Treatment The risk of stroke is assessed. Older individuals are at higher risk of stroke. Having other medical conditions like high blood pressure, congestive heart or diabetes, and various structural cardiac abnormalities all predict stroke, as does having previously had a stroke. Drug treatment will be used if there is a significant risk of stroke. While aspirin can be used, individuals who are at high risk should be treated with other, more potent drugs. Drugs to control heart rate are usually needed, and often need to be adjusted over time. For many people, restoring a normal rhythm can greatly reduce symptoms. It is appropriate to use anti-arrhythmic drugs (AAD) and other therapies to restore a normal rhythm when someone is symptomatic and usually when the AF is of recent onset. After being started on a medicine to prevent stroke, then an AAD will be given. If this fails to convert, then shocking the heart (cardioversion) to restore a normal rhythm is usually carried out. Cardioversion is done at a hospital with an anesthesia specialist present to give medication. Most often it is done on an outpatient basis. While cardioversion is highly effective, it does not ensure that one will stay in a normal rhythm afterwards.

3 Common Questions What happens if atrial fibrillation is untreated? Over time the heart can enlarge and the risk of stroke then increases. Some individuals will go from having AF intermittently to having it continually. What treatment is available? Drugs can be used to control the rate, to reduce the likelihood of stroke and to convert the heart rhythm to normal. A pacemaker will prevent slow heart beating while an individual is taking antiarrhythmic drugs. Infrequently, the rate support will reduce the amount of AF but pacemakers are not an effective therapy alone. Catheter ablation or surgery entails using a physical modality to treat AF. Is atrial fibrillation life threatening? AF can cause stroke and congestive heart failure, and there is a small increased risk of dying as well in addition to this. How well do drugs work? Drugs work extremely well to prevent stroke. If an individual does not have severe symptoms, then simply preventing stroke may, in fact, be enough. It is more difficult to maintain a normal rhythm. Trials of drugs to maintain a normal rhythm have shown at least one third of patience have return of AF within a year. Factors that make it more likely that AF will not be suppressed include how long someone has been in AF before treatment, having other heart disease, having an enlarged left atrium, having an untreated sleep disorder and having an overactive thyroid. What causes atrial fibrillation? Although there is a long list of causes, most cases of AF are result from high blood pressure, chronic lung disease, or obesity and associated sleep disorders. Why might I need to stay on blood thinning medicine after things are done to restore a normal rhythm? The main reason is that treatment is not uniformly successful and individuals sometimes don t know when they go back into AF. So the first presenting symptom then could be a stroke. Conversely over time, if someone is maintaining a normal rhythm, stopping blood thinners or using aspirin is a consideration. Is cardioversion safe? This procedure was first done in the early 1960 s. It is clear that delivery of an accurately timed shock is safe. The procedure carries a small risk of stroke, but pretreatment with blood thinners is very effective in preventing stroke as a result of cardioversion. What is ablation? It is well known that AF is usually caused by abnormal electrical activity in the veins returning blood to the heart from the lungs. So procedures can be done to electrically disconnect these veins from the heart. Previously this was done by burning around the veins using a small catheter which delivers electricity to the back of the left atrium. More recently a balloon catheter has become available which freezes those areas. Ablation is not done as a first line treatment because it carries some risk. Also, individuals who have other kinds of heart disease may need drug treatment otherwise and often drugs can be used which treat both conditions.

4 How will I know I m in AF? Everyone feels this arrhythmia differently and some have no symptoms. Common symptoms include breathlessness, palpitation, chest pain and fatigue. Following medical treatment, the arrhythmia will usually be slower and less symptomatic so it may be harder to detect. Should I exercise? Many patients have other forms of cardiovascular disease that will clearly be helped by exercise. It s not clear that regular exercise will help to prevent AF, but an individual with AF can exercise safely. What if I have thyroid disease? This arrhythmia occurs with an overactive thyroid. Hyperthyroidism is not common, but it s important to diagnose it if an individual has AF. Correcting the hyperthyroidism will probably cure the arrhythmia, while treating an individual with undiagnosed hyperthyroidism may be ineffectual. What if I have no symptoms? First of all, absence of symptoms doesn't mean there should be no treatment as there can still be a high risk of stroke. Beyond that, having a high heart rate for a long time can cause the heart to weekend. So treatment to prevent stroke and control heart rate is still needed. What if I have sleep apnea? Again, while not one of the most common causes of AF, sleep apnea is an important thing to diagnose. Effective treatment of sleep apnea will greatly improve outcomes and not treating it effectively will make it much harder to control AF. Why can't I just take aspirin? ASA has been shown to be less effective than warfarin and, in some groups, it is not at all effective. If there is a high risk of stroke, you need a more effective blood thinner. What about new medicines like Pradaxa, Eliquis and Xarelto that can replace warfarin? These medicines have been shown to be better than warfarin in terms of preventing stroke. There's also no need for a blood test, diet is not an issue and there are fewer significant drug interactions. Disadvantages are cost and not having an easy way to reverse the drug effect. If you are already on warfarin and doing well, it is certainly reasonable to continue it. Can stress cause AF? The simple answer to this is no. Individuals clearly have a propensity to have AF episodes and evaluation usually finds a physical cause for the arrhythmia. In so much as not getting enough sleep (or having disturbed sleep) contributes to AF then of course stress can result in poor sleep which in turn is detrimental in individuals with AF. Does anti-arrhythmic drug therapy alone eliminate the risk of stroke? Again the best answer is no. Ablation also does not eliminate the risk of stroke, and other factors must be considered. But if you are unable to take blood thinners, then treatment with anti-arrhythmic drugs, which will at least reduce the risk of stroke, is an option.

5 Definitions Arrhythmia- an abnormal heart rhythm. This can mean, practically speaking, a fast or slow sequence of heart beats, an irregular sequence of heart beats, or a combination. Anti-arrhythmic drugs- a group of medicines which are used to slow the heart down, eliminate abnormal beating, or both. Atrial fibrillation- a common and specific arrhythmia which involves fast and irregular beating of the upper cardiac chambers. Cardioversion- using electrical energy to correct an abnormal heart rhythm. Usually the energy (a precisely timed shock) is applied to the outside of the chest. Cryoablation- treating arrhythmias by freezing the heart. This can be done with a catheter or with a baloon that is inflated in the heart. Normal rhythm (also sinus rhythm)- the usual electrical sequence in a normal, healthy heart. This is based on normal movement, with a defined sequence, of electrical impulses through the heart. Radiofrequency Catheter ablation- delivering energy to the inside of the heart using a catheter. Electricity passes through heart tissue and resistive heating damages the cells in the path of the catheter.