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Diagnosing Atrial Fibrillation

Initially, you’ll talk with your health care provider about your medical history. You will also have a physical exam. After that, you might need to undergo one or more diagnostic tests, outlined below.

Often one test doesn’t offer your health care team enough insight into why you’re having symptoms. You might have a number of tests, each one providing more information.

Medical History

Your health care provider will first ask about your medical history and medications. There will be questions about your family’s medical history, your eating and exercise habits, and how well you sleep. As a result, your provider can rule out some causes for your symptoms.

Physical Exam

Your health care provider will listen carefully to your heartbeat. When checking your lungs, the provider will ask you to inhale and exhale. It’s likely the health care provider will palpate (touch) your abdomen and chest area to see if everything feels normal.

Blood Test

A blood test cannot confirm if your heart rhythm is normal. But it can reveal if:

  • Your symptoms are due to another health problem
  • You might have thyroid or kidney problems
  • You have an infection or anemia (anemia is a decreased number of red blood cells)

Some of these conditions can lead to atrial fibrillation. The blood test can also check for evidence of a heart attack.

Electrocardiogram (ECG / EKG)

An electrocardiogram reveals how your heart’s electrical system is working. The ECG senses and records each electrical impulse that moves through the heart. It is this impulse that causes the heart muscle to contract and pump blood to your entire body. The ECG shows the graph pattern of electrical impulses. It looks like a series of peaks and valleys, which represent your heart rhythms. An ECG allows your health care provider to see if your heart rhythm is normal. Or it can reveal if you have an abnormal rhythm such as atrial fibrillation.

What It’s Like to Have an Electrocardiogram
Small sensors called electrodes, with gel or adhesive on the back, are put on your chest, and sometimes on your arms and legs. The electrodes connect to wires on the ECG machine in order to record the heart's electrical signals. The ECG, which takes about 10 minutes, is done while you are lying flat.

Stress Test

A stress test is meant to “stress” your heart with exercise, in order to increase your heart rate. It is done while you have a blood pressure cuff on your arm, and your blood pressure is checked regularly. You are also connected to the ECG machine. The ECG can reveal if you may have an abnormal heart rhythm while you are exercising.

What It’s Like to Have a Stress Test
Instead of lying flat as you would if you are having only an ECG test, the stress test is done while you exercise. You might be walking or running on a treadmill. Or you might be on a stationary bicycle. The stress test itself may last only 15 minutes, but expect to be there for about an hour. Sometimes people cannot exercise as much as is needed for the stress test. In those cases  patients take medication that increases their heart rate.

Holter Monitor

A Holter monitor is like a small, portable electrocardiogram (ECG). But an ECG records your heart rhythm for only about 15 minutes. A Holter monitor records your ECG nonstop for a full 24 to 48 hours while you are at home. You will also need to keep a diary of your daily activities. Then, in case atrial fibrillation is found on the recording, you and your health care provider know what you were doing at the time. (For instance, exercise can possibly cause abnormal heart rhythms.)

What It’s Like to Wear a Holter Monitor
Having a Holter monitor test is similar to having an ECG. Small sensors (electrodes) are attached to your chest. Wires from the electrodes connect to the battery-operated Holter device. The device is worn around the neck, or kept in a pocket or on a belt. While wearing the Holter monitor, you can perform all of your regular daily activities.

Event Monitor

While an ECG records heart rhythms for 15 minutes and a Holter monitor records for 1-2 days, an event monitor records ECGs of your heart rhythms over an even longer period of time. While it doesn’t record nonstop, it records when you feel symptoms, for a few minutes at a time. You would usually use this battery-powered monitor for up to 30 days.

Different Types of Event Monitors

An event monitor, or event recorder, is a good choice if your symptoms don't occur often. Keep a diary of your daily activities, and when any symptoms occur. Together, your diary and the ECG help your health care provider see when your symptoms occur.

There are two types of event monitors:

  • Symptom event monitor
  • Looping memory monitor

For either type, your health care provider will explain to you how you can send the recordings to the clinic office through your phone. Your provider will check the ECG recordings for any sign of abnormal rhythms.

What It’s Like to Wear Symptom Event Monitor
With this type of monitor, there is no need to put electrodes on your chest. The monitor is a small device you hold, put in your pocket, or wear on your wrist. When you feel symptoms, you put the device against your chest and press the recording button. The back of the device has small metal pieces that function as the electrodes, to record your ECG.

What It's Like to Wear a Looping Memory Monitor
With this type of monitor, the health care provider puts electrodes on your chest in the clinic. Although you can wear the electrodes in the shower and during daily activities, you will have to change them occasionally. Your health care provider will tell you exactly where to place the electrodes and how often to change them. Wires connect the electrodes to a small monitor. When you feel symptoms, you press the recording button. The monitor stores your ECG for a few minutes before and during your symptoms.

Note: If you have paroxysmal atrial fibrillation—which stops on its own—longer monitoring may be helpful. For instance, studies have looked at patients who have had a stroke, including whether atrial fibrillation might be the cause. Data showed that 30-day monitors were more than 6 times as likely to allow doctors to make a correct diagnosis, compared to a 24-hour Holter monitor.1

Implantable Loop Recorder

This implantable recorder captures your ECG, nonstop, over a period of about 3 years. It is implanted in your chest during a minor procedure. The loop recorder is a good choice if your symptoms occur only rarely, or if you pass out during symptoms. Its advantage is that it offers long-term monitoring of your heart. 

How the Loop Recorder Sends Data to Your Health Care Provider

As with the other monitors, your health care provider may ask that you keep a diary of your daily activities, and when any symptoms occur. Together, your diary and the ECG help your provider see if atrial fibrillation causes your symptoms. A small companion device, which you’ll place next to your bed, wirelessly connects to the recorder. While you sleep, that second device sends the ECG recordings to your provider’s office.

What It’s Like to Have an Implantable Loop Recorder
The implantable loop recorder, smaller than a key, is implanted in your chest while you’re in the provider's office. The area where it is inserted is numbed with a local anesthetic. Your health care provider makes a tiny incision, positions the device, and then closes the incision. Health risks after the procedure include infection at the implant site, or skin redness from a reaction to the device.

EP Study

An electrophysiology (EP) study provides the most in-depth look at your heart's electrical system. The test offers details about any abnormal heart rhythms you may have. During the test, catheters (long, thin, flexible tubes) are gently inserted into your heart. The catheters have electrodes at the tips. The electrodes can both:

  • Send electrical impulses to your heart
  • Record your heart's electrical activity

The EP study can reveal:

  • If you have an abnormal heart rhythm, such as atrial fibrillation
  • Where the atrial fibrillation begins in the heart
  • Whether medication could treat your atrial fibrillation
  • Whether a procedure—for instance, an ablation—might be helpful for your atrial fibrillation


What It’s Like to Have an EP Study

Your health care provider will advise you about what you can eat or drink before the procedure. You might also be asked to stop taking certain medications before the test. When you get to the hospital, the health care team will put an intravenous (IV) line into your forearm or hand. You will receive a sedative, to help make you relaxed and drowsy, through the IV.

The EP study is done in your hospital’s EP lab. The doctor makes a very small incision in the groin area, near the top of the thigh. That area will be numbed so you shouldn't feel pain. However you may feel some pressure as the catheters are advanced through your vein and into your heart.

Through the catheter, your doctor sends small electric pulses to the heart. These pulses will cause your heart to beat at different speeds. You may feel your heart beating faster.

An EP study takes 1-4 hours. Afterwards the health care team puts pressure on the puncture site to stop any bleeding. You will be told how long you need to keep your leg still. After the sedative has worn off, your doctor will talk to you about your test results.

Usually people go home the same day. However you’ll have to have someone drive you home. You’ll also need to take it easy for the rest of the day. Risks of the procedure include infection, bruising, or bleeding where the catheter was inserted. More rarely, risks include a blood clot where the catheter was inserted, or abnormal heart rhythms.


An echocardiogram uses sound waves to create moving images of your heart. (Sometimes this term is shortened to “echo.”) As the sound waves reach your heart, the sound echoes off your heart. A computer uses these echo patterns to create images that can be seen on a monitor. The images are saved so your doctor can examine them.

The moving images allow the doctor to see:

  • How your heart is beating
  • How well it is pumping blood
  • If your heart valves are working properly
  • The size of your atria (the heart’s top chambers)
  • The size of your left ventricle (1 of your heart’s 2 lower chambers)

There are 2 types of echocardiograms.

Transthoracic echocardiogram (TTE): Transthoracic means through the thoracic (chest) wall. The TTE is more common than the TEE.

Transesophageal echocardiogram (TEE): Transesophageal means through the esophagus. The esophagus connects the throat with the stomach. A TEE might be needed if standard echocardiogram (TTE) images don’t provide enough detail. Because the esophagus is so close to the atria, the heart’s upper chambers, a TEE can provide very clear images of the atria and heart valves.

What It’s Like to Have a Transthoracic Echocardiogram

Small sensors, called electrodes, are placed on your chest. The electrodes connect to wires on the ECG machine to check your heart rhythm. The technician puts gel on a wand, called a transducer. The wand moves repeatedly over your heart. You may feel pressure because the wand is held very firmly against the chest while the technician moves it. The technician needs to press the wand on your skin, however, to produce the best images of your heart. The TTE should take less than an hour.

What It’s Like to Have a Transesophageal Echocardiogram

Your health care provider will ask you to not have anything to eat or drink for several hours before the test. This test is usually performed in a hospital. When you arrive, the health care team will put an intravenous (IV) line into your forearm or hand. You will receive a sedative, to help make you relaxed and drowsy, through the IV. In addition, your throat will be numbed.

A long, thin, flexible tube, with a transducer on the end, is guided down your throat. You may feel some discomfort as the probe is guided into your esophagus. The transducer records the sound wave echoes from your heart.

The TEE takes less than an hour. But because you had a sedative, you’ll stay in the hospital for a few hours. Your throat may be sore for several hours afterward. You will need someone to drive you home. And you can usually return to your normal activities the next day.


Magnetic resonance imaging (MRI) provides 3D images of your heart. This test uses magnets, radio waves, and a computer to create the images. The images allow the doctor to see:

  • Your heart’s chambers and valves
  • The larger blood vessels in your heart
  • How well blood flows through your heart

What to Avoid Taking into an MRI

MRI is both safe and painless for most people. But because strong magnets are used in the test, people with any type of metal, or metal device, inside the body should not have an MRI. The exception is when a metal device is certified as MRI safe. Be sure to tell the doctor if you have any of these in your body:

  • Metal fragments
  • Pacemakers or implantable cardioverter defibrillators (ICDs)
  • Inner ear (cochlear) implants
  • Intrauterine devices (IUDs)
  • Implanted drug infusion pumps
  • Neuro-muscular stimulators, to help manage pain
  • Certain dental implants (ask your dentist if they are MRI safe)

Before the test, it’s very important to remove all objects from your body that may contain metal or electronics. This includes jewelry—rings, earrings, piercings—as well as watches, hairpins, dentures, and hearing aids.

Also, be sure not to take your credit or debit cards into the MRI room. It’s possible that the machine could erase or damage the magnetic strip on the back of the cards.

What It’s Like to Have an MRI

You can usually eat normally and take your daily medicines beforehand, unless your health care provider tells you not to. This test is usually done in a hospital. Because the MRI machine is noisy, the technician may offer you earplugs, or headphones to listen to music.

You lie on a table that slides inside a tunnel-shaped structure. A technician will watch you from another room; you can speak to him/her by microphone. The MRI machine uses a magnetic field and radio waves, but you won’t feel them. You will notice how the machine makes tapping or thumping sounds, which is normal.

The scan can last for 30 or up to 90 minutes. It’s very important to stay still so the images aren’t blurred. You can usually return to your normal activities right after the MRI.

CT Scan

A computed tomography (CT) scan takes multiple images of the heart from different angles. The machine uses X-ray beams that rotate around you to create the images. With the images, a computer creates 3D models of the heart. The images allow the doctor to see your heart’s chambers, valves, and blood vessels.

Sometimes the health care team will give you a certain type of dye, which is called contrast material. This contrast dye can help highlight certain areas of your heart, such as your heart’s blood vessels.

What It’s Like to Have a CT Scan

You can usually eat normally and take your daily medicines beforehand, unless your health care provider tells you not to. This test is usually done in a hospital. If you’re having a contrast CT, the dye will be injected through a vein in your arm. You may feel your body warming during the injection. Or you might notice a metallic taste in your mouth.

You lie on a table that slides into the large open center of the CT scanner. The CT scanner will be over your chest.

During the test you will hear soft buzzing, clicking, or whirring sounds while the CT scanner is taking pictures. A technician will watch you from another room; you can speak to him/her by microphone. The technician may ask you to hold your breath for a few seconds during the test.

The CT lasts only about 10 minutes, and it’s painless. It’s very important to stay still so the images aren’t blurred. You can usually return to your normal activities right after the CT.

The main risk from a CT scan is that it exposes you to the same amount of X-rays that you would naturally be exposed to in 2 years. So patients should not have more CT scans than guidelines recommend. Doctors also use the lowest dose of radiation possible to take the images. Talk to your health care provider if you have any concerns.

If you find out that you have atrial fibrillation, be sure to talk to your health care team about the best treatments for you. Read why early and effective treatment for your atrial fibrillation is so important.


Page References

1. Rosenfeld L.E.,  Amin, A.N., Hsu, J.C., Oxner, A., Hills, M.T., Frankel, D.S. (2019).The Heart Rhythm Society/American College of Physicians Atrial Fibrillation Screening and Education Initiative. Heart rhythm, 16(8), e59-e65. doi: 10.1016/j.hrthm.2019.04.007