DefinitionAtrial fibrillation is an abnormal heart rhythm. The heart's electrical system normally sends regularly spaced signals. These signals tell the heart muscle to contract or beat. The heart has two upper chambers called atria. It also has two lower chambers called ventricles. Each signal starts in the atria and travels to the rest of the heart. In atrial fibrillation, the electrical signals from the atria are fast and irregular. The atria shake instead of contract. Some signals do not reach the ventricles and the ventricles continue pumping. This pumping is usually irregular and sometimes rapid. This rhythm can reduce the heart’s ability to pump blood out to the body. Blood left in the heart chambers can form clots. These clots may sometimes break away and travel to the brain. This can cause stroke .
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CausesIn most cases, atrial fibrillation is due to an existing heart condition. Atrial fibrillation can also occur in people who do not have structural heart problems. A thyroid disorder or other condition may cause the abnormal rhythm. The cause of atrial fibrillation is sometimes unknown.
Risk FactorsAtrial fibrillation is more common in men and in people aged 55 years and older. Other factors that may increase your chance of atrial fibrillation include:
- Family history of atrial fibrillation
- Cardiovascular diseases, such as high blood pressure , coronary artery disease , heart failure , heart attack , heart valve disease, endocarditis , cardiomyopathy , congenital heart disease, prior episode of atrial fibrillation
- Lung diseases, such as emphysema , asthma , blood clots in the lungs
- Chronic conditions, such as overactive thyroid , diabetes
- Receiving general anesthesia
- Lifestyle factors:
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