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What is atrial fibrillation?

To understand atrial fibrillation, it’s important to understand the normal heartbeat. Normally, the upper chambers (atria) beat first, about once every second, pushing blood into and “priming” the lower chambers (ventricles). The ventricles, which are thick and muscular and provide essentially all of the pumping action of the heart, then beat to push the blood to the body.

During AF, the atria don’t actually pump blood at all, and so don’t “prime” the ventricles. Instead, the atria “quiver” extremely rapidly and irregularly, causing the ventricles to beat rapidly and irregularly too, often about twice normal. The lack of “priming” and the rapid and irregular beating makes the heart pump less effectively.

Are there different kinds of atrial fibrillation?

Yes, it appears that there are several kinds. We often think of AF as a problem common to older patients with longstanding heart problems such as previous heart attack, leaky valves, and so forth. Sometimes, however, AF is seen in patients with an otherwise normal heart, and this is likely to be a very different kind of AF. In addition, AF is often divided into paroxysmal (comes and goes), persistent (stays until treated with a shock or a medicine), and permanent or chronic (no therapy seems to prevent it) types. These distinctions are made because the implications of these different kinds of AF, as well as the best way to manage AF, depend on type.

What causes atrial fibrillation?

In many cases of AF, no cause can be found. More commonly, it is due to high blood pressure, lung disease, thyroid disease, nerve conditions, alcohol ingestion, excessive stimulants such as caffeine, or heart disease such as leaky valves, congestive heart failure, coronary artery disease, previous heart attack, or inflammation near the heart.

Is atrial fibrillation dangerous? What problems does it cause?

It can certainly be dangerous. The biggest problem is stroke, but that is only one of them:

• Stroke – a blood clot from the heart
• Symptoms – especially palpitations, fatigue, and lack of stamina
• Cardiomyopathy – weakening of the heart muscle

Although AF often occurs without any symptoms at all, it can cause palpitations (a sensation of rapid, irregular, or otherwise abnormal heartbeats), shortness of breath, and lack of stamina or energy. Less commonly, lightheadedness, chest pain, and other symptoms can occur. Continuously elevated heart rates (above 130 beats per minute for weeks or months) can weaken the heart as well and cause Cardiomyopathy; fortunately this is usually reversible and goes away with appropriate treatment of the elevated heart rate. There is some evidence, however, that even if the heart rates are normal, subtle weakening of the heart muscle may still occur if AF persists for years. These three problems – stroke, symptoms, and weakening of the heart if rapid rates are persistent, are the problems associated with AF.

How is atrial fibrillation treated?

Traditional management of AF is directed at reducing symptoms, elevated heart rates, and the risk of stroke, primarily using medications. These proven strategies work for most patients; consequently they do not need catheter ablation or surgery for their AF.

Reducing symptoms, stroke risk, and strain on the heart

Therapy of AF is directed at reducing or eliminating the risk of stroke, symptoms, and cardiomyopathy from persistent rapid heart rate. Treating the underlying cause (such as thyroid disorders or high blood pressure), if one is found, is also very important.

Lone Atrial Fibrillation is AF in patients with an otherwise normal heart, without risk factors for stroke. Unfortunately, only a very small minority of patients with AF have this variety. These patients are treated with aspirin as a mild blood thinner.

Blood thinners are the mainstay of therapy of AF. Because the main problem with AF is stroke, and because a stroke can be so devastating, great efforts are made to try to prevent it. Stroke is the main cause of disability in the US, and the third most common cause of death. Older patients, or those with other heart disease, diabetes, high blood pressure, or a previous stroke are at risk and usually are best off treated with the blood thinner warfarin (Coumadin). Rarely someone has none of these risk factors (“lone AF”); these patients are at low risk of stroke, and may not require blood thinners. Sometimes a patient may not benefit from warfarin, because of a history of falling or bleeding for example, but fortunately that is uncommon. Aspirin is a very mild blood thinner but does not prevent strokes as well as warfarin. A promising and effective new blood thinner (Ximelagatran) caused some problems such as liver trouble and has not been approved by the FDA. No other medications, dietary maneuvers, or herbal products have been shown to prevent strokes.

Medications to keep heart rates down in the normal range are important because symptoms of AF are related to the rapid and irregular beating of the ventricles. Persistently elevated heart rate can weaken the heart as well (cardiomyopathy). Medications such as beta blockers (metoprolol, atenolol, others), calcium channel blockers (verapamil, diltiazem, others) or digoxin are used in an effort to keep heart rates normal.

The combined approach of “Heart Rate Control plus Blood Thinners” has been shown to be the best approach to treating AF for most patients, but other approaches are appropriate in some circumstances; these are described below.

“Pill in the pocket” is the term for taking a single dose of medication (flecainide (Tambocor) or propafenone(Rhythmol)) just when an episode occurs. It is best for patients with infrequent episodes of “persistent” AF – that is, AF that continues until treated, and normal rhythm continues for weeks or months after treatment. For the first trial of this approach, you must be observed in the clinic, emergency room or hospital. If it is effective at that time, and you don't have problems with the medicine, this is a safe and effective way to manage intermittent AF.

Medications to prevent AF: Several medications are available (flecainide (Tambocor), sotalol ( Betapace), dofetilide (Tikosyn), amiodarone (Pacerone)) that can prevent AF in some patients. Although many patients do well with this approach, these medications are only moderately effective and are associated with side effects in some patients.

Cardioversion is a procedure in which an electrical charge resynchronizes the heart so that it beats regularly again. It’s best for those with prolonged continuous (“persistent”, “permanent” or “chronic”) atrial fibrillation. It is performed when a patient is asleep, and most patients do not feel or remember it. It almost always works, but normal rhythm may be maintained only for minutes or hours. In other patients, it may last months or even years. Although one would think that returning to normal rhythm would eliminate the risk of stroke, it has been shown that AF can return without any symptoms, and for that reason blood thinners usually continue to be required. Still, most physicians believe that cardioversion should be considered at least once in patients with persistent AF, and many patients will safely undergo cardioversion many times. It is generally safe and does not hurt the heart. Cardioversion should generally be considered within the first 48 hours or so of the onset of AF if you have not been taking blood thinners (warfarin, Coumadin), as there may be a risk of stroke if you wait longer.

Pacemakers are excellent therapy for slow heart rates, but they don’t do anything for the rapid heart rates usually seen with AF. If heart rate cannot be controlled with medications, it is sometimes best to implant a pacemaker, then eliminate the electrical connection between the upper and lower chambers (“Ablation of AV Node plus Pacemaker”) so that the AF does not cause the lower chambers to beat abnormally. Although the atrial fibrillation (which is in the upper chambers) will still be present, the heart rate (lower chambers) is then controlled by the pacemaker and consequently will be entirely regular and at normal rates. People usually feel better following this, and can often eliminate some of the medications that were used to try to slow down the heart rate. However, because the AF is still present, risk of stroke continues, and blood thinners are needed.

Implantable Cardioverter-Defibrillators (ICDs) have been implanted to allow patients to deliver a shock to terminate atrial fibrillation, but it is uncommon. Usually, these patients also need an ICD for another reason, such as potentially life-threatening arrhythmias from the lower chambers (ventricular tachycardia and ventricular fibrillation).

Advanced therapy of AF refers to procedures intended to permanently cure atrial fibrillation, including the many varieties of the surgical and "catheter maze" procedures. These include procedures involving advancing a catheter into the heart from a vein in the leg in order to cauterize and eliminate the spots from which the AF arises (“Catheter Ablation of AF”), and cardiac surgical procedures in which these areas are cauterized through incisions between the ribs (“Minimally Invasive Surgery of AF” or "mini-maze"). These procedures are appropriate only for a small fraction of all patients with AF, and are beyond the scope of this guide. To learn more, see Curative Procedures for AF.

Recent advancements in understanding and treatment of AF:

Great strides have recently been made in our understanding of AF. Among the things we've learned are that most AF comes from the left upper chamber of the heart (Left Atrium). It usually originates from within or near the areas where the veins bringing oxygenated blood back from the lungs to the heart (“pulmonary veins”) meet the Left Atrium. Nerve fibers connect to the heart in this area as well. Abnormal electrical impulses from these pulmonary veins, or from the nerves to the heart, cause AF in some patients. Better understanding of the pulmonary veins, the nerves to the heart, surgery such as the Maze procedure, and catheter ablation have recently converged to bring us advanced procedures for elimination of AF. Now, advanced therapy for AF involves a multidisciplinary approach, sometimes involving both the electrophysiologist and the surgeon. The goal is to eliminate AF with the very high success rate of the surgical Maze III procedure and the very low complication rate of the catheter ablation procedure. New procedures have been developed and may approach that goal, including Catheter Ablation of AF and the Minimally Invasive Surgical Procedure for AF.

Nerves and the Heart: Most people with AF have it because of some other problem, such as longstanding high blood pressure, or a leaky heart valve. But some people have no apparent reason for AF – so why would they have an arrhythmia? Experiments have shown that excessive nerve activity (the vagal nerves to the heart that usually slow the heart down) can make AF much more likely to occur, and that eliminating these nerves makes AF less likely to occur. Interestingly, many of these nerves are right at the spots that the surgeons cut during the original Maze procedure, and where electrophysiologists cauterize during catheter ablation of AF.

Pulmonary Vein Isolation / Catheter Ablation of AF: This procedure goes by several names, including the Pulmonary Vein Isolation Procedure, Catheter Maze, Pappone Technique, Wide Area Circumferential Ablation, and Catheter Ablation of AF. Catheters are maneuvered from the leg into the left atrium, and ablation of the connections between the Left Atrium and the Pulmonary Veins is performed. The nerves responsible for some AF are near these connections, and many are eliminated at the same time. Because the connections are quite extensive, AF ablation is much more extensive than a standard ablation procedure, and the procedure can be long. Success rate is lower and the potential for complications higher than standard catheter ablation preocedures such as ablation of SVT or atrial flutter, likely due to the large amount of ablation that is required, and the proximity of the pulmonary veins, the esophagus, and other structures. Nevertheless, catheter ablation for AF is successful in many cases, and has been an important part of the management of AF since 1998.

AF: What should you do about it?

Atrial fibrillation needs to be addressed carefully, with special attention to the risk of stroke, which is by far the worst problem. Your primary physician has a great deal of experience with it, and should be consulted first. Your physician will:

• Address potential causes of AF such as high blood pressure
• Recommend lifestyle changes such as limiting intake of alcohol and caffeine
• Estimate your risk of stroke from AF, and start blood thinners if appropriate
• Keep your heart rate in a reasonable range with medications
• Consider cardioversion or other options
• Refer you to a cardiologist or an electrophysiologist (heart rhythm specialist) if you have a particularly difficult or unusual case, or to consider advanced, potentially curative therapy such as catheter ablation or surgery.