AF Tutorial
What is Atrial Fibrillation?
Atrial fibrillation (AF) is the most common irregular heart rhythm in the United States. AF is a condition where the upper chambers of the heart (atria) beat at rapid rates in an irregular rhythAF Tutorialm. Instead of the impulse traveling in an orderly fashion through the heart, many impulses begin and spread through the atria and compete for a chance to travel through the AV node (a structure that connects the upper and lower chambers of the heart).
The AV node limits the number of impulses it allows to travel to the ventricles. In the ECG illustration below the atria (small waves) are beating 3-4 times as fast as the ventricles (spikes). The resulting heart beat is irregular, ranging from about 50 to 150 beats per minute with periods of rapid and slow heart beat.
An ECG Recording of Atrial Fibrillation
For more information on AF, symptoms, diagnosis and treatment options:
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What causes Atrial Fibrillation?
The most common causes of Atrial Fibrillation are:
- Hypertension (high blood pressure)
- Coronary artery disease
- Heart valve disease
- Heart surgery
- Chronic lung disease
- Heart failure
- Cardiomyopathy
- Congenital heart disease
- Pulmonary embolism
Less common causes of Atrial Fibrillation include hyperthyroidism, pericarditis and viral infections.
In at least ten percent of cases, no underlying heart disease is found. In these cases, AF may be related to alcohol or excessive caffeine use, stress, certain drugs, electrolyte or metabolic imbalances, or severe infections. In some cases, no cause can be found. Of note, the risk of AF increases with age, particularly after age 60.
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What are the dangers of Atrial Fibrillation?
Many people live for years with atrial fibrillation without problems. However, chronic atrial fibrillation can result in future heart problems and increase your risk of other adverse events. 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 a 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 (such as the kidneys, heart, or intestines), causing damage.
Atrial fibrillation can decrease the heart's pumping ability by as much as 20 to 25 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.
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Where can I get more information on AF?
There are many good web-sites for obtaining information on atrial fibrillation. All three AFIC academic partner institutions have sites Web sites:
Books: Atrial Fibrillation : My Heart, the Doctors, and Me. by E. A. Butler
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What are the current treatment objectives for Atrial Fibrillation?
The treatment goals for atrial fibrillation include restoring a normal heart rhythm (sinus rhythm), controlling heart rate, and preventing blood clots to reduce the risk of stroke.
Many treatment options are available for atrial fibrillation. These include medications, lifestyle changes, catheter based procedures, device implantation, and surgery. The choice of treatment is based on a patient’s heart rhythm and symptoms.
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What are some of the specifics regarding treatment options for Atrial Fibrillation?
Lifestyle changes
There are some changes you can make to improve your heart health.
- If you notice your irregular heart rhythm occurs more often with certain activities, you should avoid them.
- Quit smoking.
- Limit your intake of alcohol. Moderation is the key. 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.
Medications
Typically medications are used as the first treatment option for AF patients. The medications may include:
- Rhythm control medications (also known as antiarrhythmic drugs). These medications help return the heart to its normal sinus rhythm or maintain normal sinus rhythm.
- Rate control medications (to slow the heart rate). These medications slow the rate at which impulses travel from the upper chambers of the heart to the lower chambers.
- Medications to prevent blood clots and reduce the risk of stroke. These medications make it more difficult for your blood to clot.
Procedures
When medications do not effectively correct or control AF, or when medications are not tolerated, a procedure may be necessary such as electrical cardioversion, catheter ablation, pulmonary vein isolation, or ablation of the AV node.
- Electrical cardioversion:
If medications are not able to control a persistent irregular heart rhythm (such as AF), cardioversion may be required. Cardioversion frequently restores a normal rhythm, although its effect may not be permanent. After a short-acting anesthesia is given, an electrical shock is delivered to your chest wall to synchronize the heartbeat and restore a normal rhythm.
- Catheter ablation:
Catheter ablation therapy is an option for people who cannot tolerate medications or when medications fail to maintain a normal heart rhythm. Two types of ablation can be performed including pulmonary vein antrum isolation or ablation of the AV node. Both procedures are performed by an electrophysiologist (a doctor who specializes in treating heart rhythm conditions).
- Pulmonary vein antrum isolation: Research has shown that almost all atrial fibrillation signals come from the four pulmonary veins. During this procedure, special catheters are inserted into the heart. Two catheters are inserted into the right atrium and two into the left atrium. An intracardiac echocardiogram is used to visualize the left atrium during the procedure. One catheter in the left atrium is used to map or locate the abnormal impulses coming from the pulmonary veins. The other catheter is used to deliver the radiofrequency energy to ablate, or create lesions outside the pulmonary veins. The procedure is repeated for all four pulmonary veins. The lesions heal and within 4 to 8 weeks, form a circular scar around the pulmonary veins. The scar blocks any impulses firing from within the pulmonary veins, thereby "disconnecting" the pathway of the abnormal rhythm and eliminating the triggers for atrial fibrillation.
- Ablation of the AV node (rarely used): During an ablation, catheters are inserted through the veins (usually in the groin) and guided to the heart. Radiofrequency energy is delivered through the catheter to sever or modify the AV node. The end result is a permanent, very slow heart rate because the electrical impulses from the top chamber of the heart cannot travel down to the lower chamber. Therefore, the patient needs a permanent pacemaker to maintain an adequate heart rate. This procedure improves atrial fibrillation symptoms, but does not cure the condition. An anticoagulant medication is prescribed to reduce the risk of stroke following the procedure. Due to better treatment alternatives, AV node ablation is rarely used to treat atrial fibrillation.
- Implantable Device Therapy:
- Implantable atrial defibrillator: The implantable defibrillator is a device used to treat AF symptoms. When the symptoms of AF occur, the person or physician can turn on the device and treat the AF when appropriate and convenient. Alternatively, the device can be set to operate automatically. The atrial defibrillator can be programmed to identify when a person is having an episode of atrial fibrillation. When AF occurs, the device delivers low-dose therapy to convert AF to a normal heart rhythm. This procedure improves atrial fibrillation symptoms, but does not cure the condition.
- 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 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, designed to help with the management of arrhythmias and to optimize heart rate-related function as much as possible. This procedure improves atrial fibrillation symptoms, but does not cure the condition.
- Surgical treatment
Patients with chronic AF not relieved by medication or procedures, or patients who have other conditions requiring heart surgery, are potential candidates for surgical treatment of atrial fibrillation. During the Maze procedure, 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. Surgical Pulmonary vein isolation is a modification of the Maze procedure in which the surgeon uses energy sources, instead of incisions, to create lesions. The possible energy sources used during surgical pulmonary vein isolation include: radiofrequency, cryothermy, microwave and laser. The goal of all four energy sources is to produce lesions and ultimately scar tissue to block the abnormal electrical impulses from being conducted through the heart and promote the normal conduction of impulses through the proper pathway. Many of these approaches can be performed with minimally invasive (endoscopic or "keyhole") surgical techniques.
Energy sources used during surgical pulmonary vein isolation:
- Radiofrequency Ablation: A special radiofrequency energy catheter is used to heat the tissue and produce lesions on the heart similar to the lesions of the Maze procedure. There are a variety of surgical techniques related to the type of catheter used, the dose of energy, and the types of lesions created.
- Cryothermy: (also called cryoablation) Very cold temperatures are transmitted through a probe (called a cryoprobe) to create lesions. This technique is used commonly during arrhythmia surgery to replace the incisions made during the Cox Maze procedure.
- Microwave Technology: A special wand-like catheter is used to direct microwave energy to create several lesions on the heart. The lesions block the conduction of abnormal electrical beats and restore a normal heartbeat.
- Laser: Lasers rapidly create the lesions or lines of conduction block. Laser technology offers promise for the development of additional minimally invasive approaches.
** FAQs adapted form CCF Heart Center website and the 2005 Wright Centers of Innovation and the Biomedical Research and Technology Transfer Partnership Award to Cleveland Clinic for the ‘Atrial Fibrillation Innovation Center’
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