Cause

Atrial fibrillation is caused by a problem with the electrical activity of the heart.

Conditions that damage the heart muscle or strain the heart may cause atrial fibrillation. These include:

• High blood pressure, a condition in which the force of blood against artery walls is too strong. Normal blood pressure is 119 millimeters of mercury (mm Hg) systolic over 79 mm Hg diastolic or below.
• Coronary artery disease and heart attack. Coronary artery disease is caused by the buildup of plaque on the inside of the coronary arteries. These blood vessels supply oxygen-rich blood to the heart muscle.
• Heart failure. Heart failure occurs when the heart is not able to pump blood effectively.
• Heart valve disease, most often mitral valve disease. Heart valve disease occurs when a heart valve is damaged or narrowed and does not properly control the flow of blood through and out of the heart.
• Cardiomyopathy. Cardiomyopathy damages the heart muscle and decreases the amount of blood it can pump.
• Myocarditis, which is inflammation of the heart muscle. Myocarditis may occur after a viral, fungal, or bacterial infection or another illness, such as diphtheria, rheumatic fever, or tuberculosis.
• Rheumatic heart disease. Rheumatic heart disease is damage to the heart muscle and heart valves that results from rheumatic fever.
• Congenital heart disease. Congenital heart defects are structural heart problems or abnormalities that have been present since birth.
• Endocarditis. Endocarditis can damage the heart muscle and heart valves.
• Wolff-Parkinson-White syndrome, which causes rapid or irregular rhythms (arrhythmias) in the heart.

Heart surgery, such as coronary artery bypass or valve surgery, can trigger atrial fibrillation. In people older than 65, any surgery can trigger atrial fibrillation and raise the risk of complications, such as a stroke. In these cases, atrial fibrillation may be short-lasting. Treatment can return the heart to a normal rhythm.

Other conditions that cause atrial fibrillation include:

• Chronic obstructive pulmonary disease (COPD), a group of diseases that make it difficult to breathe because air does not flow easily out of the lungs.
• Pneumonia, which is an inflammation of the lungs that is most often caused by infection with bacteria or a virus.
• Pulmonary embolism. Pulmonary embolism is the sudden blockage of blood flow in an artery in the lungs.
• Hyperthyroidism, a condition in which the thyroid gland produces too much thyroid hormone.
• Use of alcohol. Long-term, heavy alcohol use seems to be linked to atrial fibrillation. Besides long-term use, drinking a large amount of alcohol at one time (binge drinking) may also cause an episode of atrial fibrillation.
• Use of stimulants. These include medicines, such as theophylline, amphetamines, and decongestants that contain stimulants (such as pseudoephedrine); illegal drugs, such as cocaine, methamphetamines, or crank; and excessive nicotine or caffeine.
• Use of some prescription medicines, such as albuterol or theophylline.
• Pericarditis, which is an inflammation of the sac around the heart. Pericarditis can temporarily irritate the heart muscle.

Atrial fibrillation caused by a condition that is treatable, such as pneumonia or hyperthyroidism, often goes away when that condition is treated.

Atrial fibrillation can sometimes develop in people who do not have heart disease or other health conditions. This is called lone atrial fibrillation.