Atrial fibrillation - AF
Atrial fibrillation occurs when electrical impulses in the upper chambers of the heart (atria) begin in multiple sites in a chaotic pattern and are sent rapidly to the heart's lower chambers, causing them to contract irregularly and quickly.
The fibrillation or irregular heartbeat can occur for a few minutes, weeks or can continue for a lifetime. Episodes of atrial fibrillation that are brief or intermittent are termed "paroxysmal" while episodes that last longer are referred to as "persistent."
During atrial fibrillation, the atria do not pump blood as effectively as they normally should. In some cases, blood in the atria, can stagnate and clot. If these clots break up, they may pass into the left ventricle, travel through the blood stream and block a smaller artery. If this happens in the brain, it can cause a stroke. Therefore, diagnosis, careful monitoring and treatment are all important aspects of managing atrial fibrillation.
Symptoms of atrial fibrillation
Symptoms of atrial fibrillation depend on how rapidly the heart is beating. If it remains below 120 beats a minute, there may be no symptoms other than the irregular or increased pulse. If the rate is higher, there may be heart palpitations or discomfort felt in the chest.
Other symptoms may include:
- A feeling of weakness
- Dizziness or faintness
- Shortness of breath
- Chest pain, especially in adults who are older than 65
- Rarely, blood pressure may fall and cause shock. This usually only occurs in individuals who also have severe heart disease.
Causes of atrial fibrillation
Atrial fibrillation can be caused by heart diseases, such as coronary heart disease, high blood pressure, congestive heart failure or abnormalities of the heart valves. They can also be caused by other conditions, such as alcohol abuse, an overactive thyroid gland (hyperthyroidism), or a birth defect affecting the heart. Rheumatic fever (which often leads to damage to heart valves) and high blood pressure cause the atria to enlarge, making atrial fibrillation more likely. The risk of atrial fibrillation and atrial flutter also increase with age.
Treating atrial fibrillation
Paroxysmal AF:
This occurs with AF from time to time. This is usually treated by drugs such as flecanide and beta blockers. Aspirin is also needed. If the AF is troublesome, radiofrequency ablation may be required.
Rate control for permanent AF:
If the AF is persistent or permanent, the speed of the heart rate can be slowed down by medication such as beta blockers, some calcium channel blockers, digoxin and occasionally amiodarone.
Cardioversion:
Some patients with AF may benefit from an electric shock delivered while anaesthetised. This is usually performed when the patient is anticoagulated.
Anticoagulants in AF:
Patients with AF have a risk of stroke. The risk for each patient is calculated and either aspirin or warfarin is recommended. New drugs for this indication are likely to be approved in 2011.