Atrial Fibrillation
What is Atrial Fibrillation?
What is Atrial Fibrillation?
Atrial fibrillation is a common disorder in which the heartbeat is irregular. A normal heartbeat occurs as follows: first, an electrical impulse is generated in the sino-atrial, or SA node, a specialized region of pacemaker cells in the chamber of the heart called the atrium. This impulse spreads in an orderly path through the heart--first through the atria, then to another pacemaking region known as the atrioventricular, or AV node, and finally to the ventricles. The result of this organized pathway of electrical transmission is a coordinated heartbeat: the atria contract first, followed by the ventricles, and blood is effectively pumped out into the body. This is called sinus rhythm, and the resultant heart’s pumping can be heard or felt as a regular heartbeat.
In atrial fibrillation, electrical impulses are generated randomly throughout the atria rather than in the SA node alone. As these impulses spread throughout the atria, the atria quiver, or “fibrillate,” (hence the name), instead of contracting in a coordinated fashion. Furthermore, these irregular electrical impulses bombard the AV node chaotically and are conducted through to the ventricles, resulting in an irregular heart beat. Depending on how quickly impulses are conducted to the ventricles, the heart rate that ensues can be very fast.
Atrial fibrillation is important to recognize and treat, not only because it causes symptoms, but because it is associated with strokes. As the atria contract irregularly, blood can pool and form clots within the heart. If these clots dislodge and travel through the circulation to the brain, they can block crucial blood flow and result in transient ischemic attacks and strokes. If you have atrial fibrillation, it is important to discuss this with your doctor and decide if you are someone who would benefit from treatment to prevent strokes.
Key points:
1. Atrial fibrillation is characterized by an irregular heartbeat.
2. Atrial fibrillation is caused by abnormal electrical conduction through the atria of the heart.
3. Atrial fibrillation is associated with risk of strokes.
What are the Symptoms?
Atrial fibrillation causes a variety of symptoms. Some people notice a sensation of palpitations or a rapid heart rate. Others may just feel fatigued and weak. If your heart rate is very fast, you may experience shortness of breath, chest pain, dizziness, light-headedness, or even fainting. Many people do not feel any symptoms at all, and the irregular heartbeat is only discovered on a routine physical exam. You may be able to take your pulse and notice that the heartbeat is irregular.
Key points:
1. Atrial fibrillation causes a variety of symptoms, from none at all to shortness of breath, chest pain, light-headedness and fainting.
2. The faster the heart rate, the more severe the symptoms may be.
Risk Factors
Atrial fibrillation is more likely to develop if you have underlying heart problems, such as coronary artery disease, structural or valvular heart problems, or high blood pressure. This may be because the normal structure of the heart is distorted, which favors the abnormal electrical conduction characterizing atrial fibrillation. Atrial fibrillation is also associated with alcoholism, hyperthyroidism, lung disease and obstructive sleep apnea. Interestingly, atrial fibrillation can be seen when there does not seem to be any underlying abnormalities. This is called “lone” atrial fibrillation.
Atrial fibrillation is more common in older individuals. One study showed that 3.8% of people older than 60 had atrial fibrillation, and 9% of those older than 80 did. It is also more common in men, and also more prevalent in whites compared to African-Americans.
Key points:
1. Atrial fibrillation is associated with underlying heart disease, high blood pressure, alcoholism and hyperthyroidism.
2. Atrial fibrillation is more common with advanced age.
How is it Diagnosed?
If you or your doctor suspects atrial fibrillation, you should have a 12 lead electrocardiogram to confirm the diagnosis. It is also customary to check a chest x-ray, echocardiogram, and various blood tests. Your doctor may want you to wear a Holter monitor or a loop monitor to assess your heart’s activity over a period of time. If you have severe symptoms, your doctor may recommend that you be hospitalized for monitoring and treatment.
Key points:
1. Diagnosis includes a 12 lead electrocardiogram (ECG).
2. Other tests may include x-rays, echocardiogram, blood work and a device known as a Holter, or loop, monitor.
What are the Treatments
The approach to treating atrial fibrillation has several parts. First, your doctor will evaluate whether it is important that your heart be restored to a normal heart rhythm. In many people, atrial fibrillation does not cause any severe consequences, and restoration of a normal heart rhythm may not be necessary. However, if you are experiencing severe symptoms or have underlying heart problems, your doctor may recommend treatments designed to return the heart to a normal rhythm. Cardioversion uses an electrical current to stimulate the heart back to a normal rhythm. Alternatively, various drugs can be used to restore sinus rhythm (or a normal heart rhythm), such as propafenone, amiodarone or ibutilide.
Second, your doctor will make sure that your heart rate is in a healthy range. If the atrial fibrillation is causing your heart to beat too fast, you may need to take a medication designed to slow down the heart. Atenolol, me-toprolol, dil-tiazem and digoxin are medications that are commonly prescribed.
Finally, you and your doctor will need to decide if you would benefit from anticoagulation, which means taking blood-thinning medication aimed at preventing strokes. If you are younger than 60 and otherwise healthy, a daily aspirin may be adequate for blood-thinning and stroke prevention. However, if you are older than 60 and have other medical problems or have had previous blood clots, your doctor will likely recommend a medication called warfarin. Warfarin is an effective blood-thinner that lowers the risk of strokes, but needs close monitoring, as it can cause serious bleeding. You will need frequent blood tests of the INR, or internal normalized ratio (a measure of anticoagulation) while you are on this medication. The goal INR should be between 2.0 and 3.0 in order to reduce the risk of stroke while limiting the chance of bleeding.
For atrial fibrillation that does not respond to other treatments, various surgical approaches can be tried. These treatments are either done in open surgery or via minimally invasive surgical techniques. These approaches target the areas of the heart thought to be responsible for the abnormal electrical activity and attempt to damage these regions using incisions or energy sources such as radiofrequency, laser, cryothermy and microwaves. These methods are sometimes helpful in treating atrial fibrillation.
Key points:
1. Treatment of atrial fibrillation has 3 parts: 1. Deciding whether sinus rhythm needs to be restored, 2. Controlling heart rate, and 3. Using anticoagulation to prevent strokes.
3. If you are on warfarin for anticoagulation, you will need frequent blood tests to make sure the anticoagulation is adequate while reducing chance of bleeding complications.
What are the Complications
The complications of atrial fibrillation include transient ischemic attacks (TIAs) and strokes. AS MENTIONED EARLIER, THIS IS CAUSED BY BLOOD CLOTS THAT CAN FORM IN THE HEART DUE TO ATRIAL FIBRILLATION. THESE CLOTS CAN SOMETIMES MOVE THROUGH THE BLOOD VESSELS INTO THE BRAIN. Also, if the heart rate is too fast, the ability of the heart to pump blood effectively is impaired. This strain on the heart can result in heart failure, heart attacks, and structural changes to the heart.
Key points:
1. Complications include TIA, stroke and various heart problems.
Tips for Patients
In summary, atrial fibrillation is a disorder where the heart beats irregularly, You may notice a sensation of palpitations, or feel short of breath, light-headed, or fatigued. Some people do not notice any symptoms at all. Atrial fibrillation is more common in older individuals and in people with heart problems. If you have atrial fibrillation, it is important to discuss it with your doctor, since atrial fibrillation can lead to strokes and TIAs, and it can also cause further heart problems. Your doctor will discuss treatments for atrial fibrillation with you, which include taking a blood thinner to prevent strokes, using medicines or electrical cardioversion to restore the heart to a normal rhythm, or taking medications to keep the heart from beating too fast.
1. In atrial fibrillation, the heart beat is irregular.
2. It is important to get treatment for atrial fibrillation because it can lead to strokes and further heart problems.
3. There are a variety of treatments for atrial fibrillation, including taking a blood thinner to prevent strokes, using medicines or electrical cardioversion to restore the heart to a normal rhythm, and taking medications to keep the heart from beating too fast.
References:
1. Page R. Newly diagnosed atrial fibrillation. New Engl J Med 2004;351(23): 2408-2416.
2. Falk R. Medical progress: Atrial fibrillation. New Engl J Med 2001;344(14): 1067-1078.
3. http://www.americanheart.org/presenter.jhtml?identifier=4682
4. http://www.emedicine.com/med/topic184.htm
Copyright 2008-9, MD Kiosk
