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 requiring treatment are referred to as "persistent."
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 and Risk Factors 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 another 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.