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Atrial Fibrillation (AFib)

About Atrial Fibrillation

A heart that beats in regular intervals is said to be in normal sinus rhythm. Atrial fibrillation (AFib) is an abnormal heart rhythm that causes the two upper chambers of the heart, the atria, to quiver instead of contracting.

This happens because the electrical signals that regulate the atria become erratic and start firing at 300 to 400 times per minute, resulting in a fast, irregular rate in the lower chambers that can in turn lead to severe symptoms. The triggers for atrial fibrillation are usually found in the pulmonary veins, which drain oxygenated blood from the lungs into the left atrium.

Why is AFib a problem?

When the upper chambers of the heart beat too fast or uncontrollably, blood may pool in the left atrial appendage and form clots, increasing the risk for stroke. About 15 percent of strokes occur in people with AFib. In addition, if you have a-fib, you may not feel well because your heart is unable to pump effectively.

How is AFib diagnosed?

  • electrocardiogram (EKG or ECG)
  • monitoring (Holter or mobile cardiac monitor or event recorder)

What additional tests may be ordered after AFib is diagnosed?

  • echocardiogram (an ultrasound of the heart)
  • CT
  • MRI

What are the symptoms of AFib?

  • shortness of breath
  • weakness
  • fatigue
  • palpitations (the feeling of a rapid, fluttering or pounding heartbeat)
  • low blood pressure (hypotension)
  • dizziness
  • fainting

What are the risk factors for AFib?

  • existing heart disease
  • heart surgery
  • family history (genetics)
  • obstructive sleep apnea
  • lung disease
  • diabetes
  • high blood pressure (hypertension)
  • thyroid problems
  • excessive alcohol consumption

What are the different types of atrial fibrillation?

Paroxysmal AFib (intermittent) - Paroxysmal AFib refers to AFib that occurs sometimes and then stops. The AFib stops by itself and the heart returns to normal rhythm. As the heart goes in and out of AFib, the pulse rate may change from slow to fast and back again in short periods of time.

Persistent AFib (continuous) - Persistent AFib is when the AFib does not stop by itself. Medications or a special type of electrical shock (called a cardioversion) is used to help the heart return to normal rhythm. If no treatment is given, the heart will stay out of rhythm. 

Longstanding persistent AFib - Persistent AFib that lasts longer than a year

Permanent AFib - Permanent AFib is when the patient or doctor decides not to restore normal rhythm. Usually medications and controlled electrical shock cannot help return the heart to normal rhythm.

When do you seek help from a doctor?

If you have any symptoms of atrial fibrillation, an appointment with your doctor should be scheduled.

AFib Guide

A free guide to help you understand causes, symptoms, diagnosis and treatment of atrial fibrillation.


AFib Video Series

Access videos from our heart experts and learn more about the symptoms, risks and treatments for AFib.

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