Atrial Fibrillation
Atrial Fibrillation

Atrial Fibrillation Diagnosis


A healthcare provider will diagnose atrial fibrillation based on your medical and family history, a physical exam, the results from an electrocardiogram (EKG), and possibly other tests and procedures. If you have atrial fibrillation, your provider will also look for any disease that may be causing it and assess your risk of developing dangerous blood clots. This will help them plan the best way to treat you.

Medical history

To help diagnose atrial fibrillation, your provider will ask about your eating and physical activity habits, family history, and other risk factors for atrial fibrillation and heart disease. You may be asked whether you have any other symptoms. This information can help your provider determine whether you have other conditions that may be causing you to have atrial fibrillation.

Physical examination

Your provider will do a complete examination of your heart and lungs, including:

  • Checking for signs of too much thyroid hormone, such as a thyroid gland that is larger than normal
  • Checking for swelling in your legs or feet, which could be a sign of heart failure or a heart that is larger than normal
  • Checking your pulse to find out how fast your heart is beating
  • Listening to the rhythm of your heartbeat
  • Listening to your lungs to check for signs of heart failure or infection
  • Measuring your blood pressure

Diagnostic tests

To diagnose atrial fibrillation, your provider will likely do an EKG first to record your heart’s electrical activity. If you have one, data from your pacemaker or implanted defibrillator may also be helpful. If the diagnosis is unclear from the EKG or if more information is needed, your provider may order additional testing:

  • Blood tests check the level of substances in the blood, such as potassium and thyroid hormone. This can help find the cause of your atrial fibrillation and show how well your liver and kidneys are working, which can help your doctor decide which medicines are most appropriate.
  • Echocardiography shows areas of poor blood flow to the heart, areas of heart muscle that are not contracting normally, and previous injury to the heart muscle caused by poor blood flow. It may also identify harmful blood clots in the heart’s chambers.

Other tests

Your provider may order other tests to record abnormal heart rhythms that happen under specific conditions or outside of the clinic, confirm whether you have atrial fibrillation or another arrhythmia, and find the best treatment.

  • Chest X-rays look for signs of complications from atrial fibrillation, such as fluid buildup in the lungs or a heart that is larger than normal.
  • An electrophysiology study records your heart’s electrical signals if your doctor wants more detail about what is causing a particular EKG reading or to distinguish among possible types of arrhythmias.
  • Holter and event monitors record your heart’s electrical activity over long periods of time while you do normal, day-to-day activities. These portable EKG monitors can help assess the cause of symptoms, like palpitations or feeling dizzy, that happen outside the doctor’s office. Most portable monitors will send data directly to your doctor.
  • A loop recorder records the heart’s electrical activity. Some loop recorder models are worn outside the body, and some require minor surgery to place the device under the skin in the chest area. Implanted devices can record data for months and are used to detect patterns in abnormal heart rhythms that do not happen very often.
  • A sleep study can determine whether sleep apnea might be causing your symptoms.
  • A stress test or exercise stress test studies changes in your heart’s activity that occur with increase in heart rate and recovery after exercise. If you cannot exercise, you may be given medicine to make your heart work hard and beat fast.
  • Transesophageal echocardiography detects blood clots that may be forming in the heart’s upper chambers because of atrial fibrillation. It uses sound waves to take pictures of your heart through the esophagus.
  • A walking test measures your heart activity while you walk for 6 minutes. This can help determine how well your body can control your heart rate under normal circumstances.


Healthcare providers usually screen for atrial fibrillation only when you have risk factors. However, your provider may check for symptoms of atrial fibrillation as part of your regular medical care. Your provider may also recommend healthy lifestyle changes to help you lower your risk of developing atrial fibrillation. Screening steps may be part of your regular care if you are 65 or older or if you have other risk factors.

  • A pulse check may help your provider detect an irregular speed or unusual heart rhythm even without symptoms.
  • If you had a stroke and there is no clear cause, your doctor may recommend screening for atrial fibrillation with a Holter or event monitor or a loop recorder.
  • Several devices are now available to detect and record your heart’s rhythm similar to an EKG. These devices may also email the data to your doctor.
Fact Sheet

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