Normally, the heart beat begins at the sinoatrial (SA) node, located in your right atrium. When the SA node fires, electrical activity spreads through the right and left atria, causing them to contract. The impulses travel to the AV (atrioventricular) node, which is the bridge that allows the impulses to go from the atria to the ventricles. The impulse then travels through the walls of the ventricles, causing them to contract. This forces blood out of the heart to the lungs and body.

The heart's regular pattern of electrical impulses causes the heart to fill with blood and contract in a normal fashion. The normal heart beats in the same constant rhythm about 60 to 100 times per minute at rest.

What is atrial fibrillation?

Atrial fibrillation

Atrial fibrillation (AF) is one of the most common irregular heart rhythms. It affects more than 2.2 million people in the United States, and more than 160,000 new cases of atrial fibrillation are diagnosed each year.

When you have AF, many impulses begin and spread through the atria. The resulting rhythm is disorganized, rapid and irregular. Because the impulses are traveling through the atria in a disorderly fashion, the atria are not able to contract in a regular rhythm.

The rate of impulses through the atria can range from 300 to 600 beats per minute. Luckily, the AV node limits the number of impulses it allows to travel to the ventricles. The resulting heart beat is irregular, ranging from about 50 to 150 beats per minute.

An ECG recording of atrial fibrillation

What causes AF?

In at least 10 percent of cases, no underlying heart disease is found. In these cases, AF may be related to alcohol, excessive caffeine use, stress, some drugs, electrolyte or metabolic imbalances, or severe infections. In some cases, no cause may be found.

The risk of AF increases with age, especially after 60 years of age.

Symptoms of AF may include one or more of the following:

• heart palpitations – a sudden pounding, fluttering or racing feeling in your chest
• lack of energy or feeling over-tired
• dizziness – feeling lightheaded or faint
• chest discomfort – pain, pressure or discomfort in the chest
• shortness of breath – having difficulty breathing while doing normal activities or at rest

Some people have AF without any symptoms at all.

Is AF dangerous?

Many people live for years with atrial fibrillation without problems. For many years, AF was thought as a harmless annoyance. However, now it is known that chronic atrial fibrillation can result in future problems:

• Because the atria are beating rapidly and irregularly, blood does not flow through them as quickly. This makes the blood more likely to clot. If the clot is pumped out of the heart, it can travel to the brain, resulting in a stroke. People with atrial fibrillation are five to seven times more likely to have a stroke than the general population. Clots can also travel to other parts of the body (kidneys, heart, intestines), causing damage.
• Atrial fibrillation can also decrease the heart's pumping ability by as much as 20 to 30 percent. Atrial fibrillation, combined with a fast heart rate over a long period of time, can result in heart failure.
• Chronic atrial fibrillation is associated with an increased risk of death.

How is AF diagnosed?

• Atrial fibrillation is diagnosed by four tests:
  • ECG (electrocardiogram)
  • Holter monitor
  • Event monitor
  • Transtelephonic monitor

These monitoring devices help the doctor learn if you are having irregular heart beats, what kind they are, how long they last and what may cause them Click here to learn more about diagnostic tests.

How is AF treated?

The purpose of AF treatment is to:

• Restore normal heart rhythm
• Control the heart rate
• Prevent clots and decrease the risk of stroke

Many options are available to treat AF. These include medications, lifestyle changes, and many procedures such as cardioversion, ablation therapy, device therapy and surgery. The choice of treatment for you is based on your heart rhythm and symptoms.

Medications

Different medications are prescribed to manage atrial fibrillation, depending on the overall treatment goal:

• Restore normal heart rhythm: Many medications are available to restore and maintain a normal heart rhythm. These drugs (called antiarrhythmic drugs) include Quinidex (quinidine), Pronestyl (procainamide), Norpace (disopyramine), Toprol, Lopressor, Tambocor, Rythmol (propafenone), Betapace (sotalol), Tikosyn, and Cordarone. You may have to stay in the hospital when you first start using these drugs so that your heart rhythm can be carefully monitored. These medications are effective 30 to 60 percent of the time, but may lose their effectiveness over time. Many have potentially serious side effects and everyone reacts to the medications differently. You may need to try several medications so your doctor can find the best one for you.
• Control heart rate: Control of your heart rate can be obtained using Lanoxin (digoxin) or two other groups of medications that control heart rate, called beta-blockers and calcium channel blockers.
• Prevent clots and stroke: Anticoagulant or antiplatelet therapy drugs (called blood-thinners), such as Coumadin (warfarin), are prescribed to reduce the risk of clots forming or stroke. Coumadin reduces the risk of stroke by 60 - 80 percent in people with AF. When Coumadin is used, regular blood tests are required to assure that the blood is thinned at a safe and affective level. Some people may be treated with aspirin instead of Coumadin.

Check the drug search to find out more about your medications. It is important to know:

• the names of your medications
• what they are for
• how often and at what times to take them

Lifestyle changes

If you notice your irregular heart rhythm occurs more often with certain activities, you should avoid them.

• If you smoke, stop.
• Limit your intake of alcohol. Ask your doctor for specific alcohol guidelines.
• Limit or stop using caffeine. Some people are sensitive to caffeine and may notice more symptoms when using caffeinated products (such as tea, coffee, colas and some over-the-counter medications).
• Beware of stimulants used in cough and cold medications. Some of these types of medications contain ingredients that promote irregular heart rhythms. Read the label and ask your doctor or pharmacist what type of cold medication is best for you.

Procedures

When medications do not work to correct or control AF, a procedure may be necessary:

• Electrical cardioversion

If drugs are not able to control a persistent irregular heart rhythm (such as, AF), cardioversion may be required. After administration of a short-acting anesthesia, an electrical shock is delivered to your chest wall to synchronize the heart and restore a normal rhythm.

• Catheter ablation

  Ablation therapy is an option for people who cannot tolerate medications or when medications fail to maintain the normal heart rhythm.

  Two types of ablation can be performed. Both are performed by an electrophysiologist (doctor who specializes in treating heart rhythm conditions):

  Ablation of the AV node: During an ablation, soft wires (catheters) are inserted through the veins (usually in the groin), and guided to the heart. High-frequency electrical energy is delivered through the catheter to destroy the AV node. This energy "disconnects" the pathway between the atria and ventricles. Because the ablation causes the heart rate to become very slow, a permanent pacemaker must be implanted to maintain an adequate heart rate. Ablation of the AV node combined with a pacemaker implant does improve symptoms of AF. However, AF does continue, so blood-thinners are still needed to reduce the risk of stroke.

  Pulmonary vein isolation: Special catheters are inserted through the veins to the heart. A needle is then used to guide the catheters to the left atrium. Catheters are used deliver energy ("ablation"), and to"map," or look for the electrical impulses that fire abnormally, causing AF. Energy is delivered from one catheter into the area of the atria that connects to the pulmonary vein, producing a circular scar. The scar will then block any impulses from firing within the pulmonary vein, thus prevent AF from occurring. The process is repeated with all pulmonary veins. The goal is to isolate, rather than ablate, the area responsible for triggering atrial fibrillation. Click here to learn more about pulmonary vein isolation.

• Device Therapy

  ICD: An implantable cardioverter-defibrillator (ICD) is a device designed to provide a person with the option to treat atrial fibrillation symptoms themselves. When the symptoms of AF occur, the person can turn on the device and treat the AF when appropriate and convenient. Alternatively, the device can be set to operate automatically. The ICD can be programmed to identify when a person is having an episode of atrial fibrillation. When it occurs, the device delivers therapy to convert AF to a normal heart rhythm.

  Permanent Pacemaker: A pacemaker is a device that sends small electrical impulses to the heart muscle to maintain a suitable heart rate. Pacemakers are implanted after ablation of the AV node, or are implanted in people with AF who have a slow heart rate. The pacemaker has a pulse generator (that houses the battery and a tiny computer) and leads (wires) that send impulses from the pulse generator to the heart muscle, as well as sense the heart’s electrical activity. Newer pacemakers have many sophisticated features that are designed to help with the management of arrhythmias and to optimize heart-rate-related function as much as possible.

• Heart surgery

  The maze procedure

  Patients with chronic AF not alleviated by medication, procedures, or have other conditions requiring heart surgery, are candidates for surgical treatment of atrial fibrillation.

  The Maze procedure is a successful surgery in which a series of precise incisions are made in the right and left atria to confine the electrical impulses to defined pathways to reach the AV node. Click here to learn more about the Maze Procedure

The Partial Maze procedure uses a similar approach as that of the Maze procedure, however the incisions are made only in the left atrium.

Some patients may have atrial fibrillation combined with other heart problems (such as valve or coronary artery disease), requiring surgery. In these cases, the surgeon may combine surgical treatment of AF with other surgical therapies to correct the atrial fibrillation and the coexisting heart problem.

Surgical pulmonary vein isolation is a modification of the maze procedure, in which the surgeon uses alternative energy sources instead of incisions to create lesions.

Cleveland Clinic heart surgeons are using techniques that allows use of minimally invasive surgery along with the microwave technology to complete the treatment. Click here for more information about surgical treatment of atrial fibrillation.

Sources:

• CHIRP. (1999) Atrial Fibrillation. Cleveland, Ohio: Cleveland Clinic Foundation.
• Gillinov, M.A. Treating Atrial Fibrillation Surgically, Cleveland Clinic Foundation Health Talk
• Natale, A. Atrial Fibrillation: How to Keep a Steady Rhythm, Cleveland Clinic Foundation Health Talk
• Prystowsky E, , Katz A. (1998). Atrial Fibrillation, In Topol E. (Ed.), Textbook of Cardiovascular Medicine (pp.1661-1693). Philadelphia: Lipincott-Raven.