A-fib is commonly caused by changes or damage to the heart's structure. Possible causes of A-fib include:

  • heart attacks
  • viral infections
  • high blood pressure
  • aging
  • lung diseases
  • coronary artery disease
  • abnormal heart valves
  • heart defects
  • overactive thyroid gland
  • certain medications
  • caffeine, tobacco, or alcohol
  • the heart's natural pacemaker not working properly
  • stress
  • previous heart surgery
  • sleep apnea

Though these are common causes of A-fib, some people have A-fib without any heart defects or damage. This condition is called lone atrial fibrillation. The cause of lone atrial fibrillation is not always clear. However, serious complications for this condition are rare.