Abnormalities or damage to the heart's structure are the most common cause of atrial fibrillation (AF). Possible causes of AF include:
- High blood pressure
- Heart attacks
- Coronary artery disease
- Abnormal heart valves
- Heart defects you're born with (congenital)
- An overactive thyroid gland or other metabolic imbalance
- Exposure to stimulants, such as medications, caffeine, tobacco or alcohol
- Sick sinus syndrome — improper functioning of the heart's natural pacemaker
- Lung diseases
- Previous heart surgery
- Viral infections
- Stress due to pneumonia, surgery or other illnesses
- Sleep apnea
However, some people who have AF don't have any heart defects or damage, a condition called lone AF. In lone AF, the cause is often unclear, and serious complications are rare.
Source: Mayo Clinic