How Atrial Fibrillation Is Diagnosed

An irregular heartbeat may or may not cause symptoms. So if your doctor suspects you have atrial fibrillation (AFib), he may ask for tests to confirm the diagnosis, find out what's causing it, and figure out the best way to treat it.

Doctor Exam

Sometimes your primary care or family doctor will be the one who diagnoses AFib. But in many cases, you see a heart doctor, called a cardiologist. Cardiologists who specialize in irregular heartbeats are called electrophysiologists.

First, the doctor will ask detailed questions about your symptoms, health habits, and health problems you or another family member have had.

During the physical exam, he's likely to:

  • Listen to your heartbeat's rate and rhythm
  • Take your pulse and blood pressure
  • Listen to your lungs
  • Check for signs of heart muscle or valve problems

Electrocardiogram (EKG)

This simple, painless test is the most helpful. It records your heart's electrical activity. It can show the:

  • Speed of your heartbeat
  • Rhythm of your heartbeat
  • Strength and timing of electrical signals passing through your heart

A doctor or technician places small patches, called electrodes, on different areas of your body, including several on your chest. These pick up signals that make wave patterns on the EKG results. It gives your doctor a picture of your heart's overall electrical activity.

But because the test is a quick snapshot, a standard EKG won't always catch AFib. Sometimes you'll need a portable EKG machine to keep tabs on your heart over a longer time.

Holter monitor. You keep this with you for 24 to 48 hours while it continuously records your heart's electrical activity. The extra time gives a better chance of picking up an abnormal heart rhythm, what doctors call an arrhythmia.

Just as with a regular EKG, you'll have small electrodes attached to your chest. Wires connect these electrodes to a small recorder you can clip on a belt, keep in a pocket, or hang around your neck.

Then you just go about doing what you usually do. Your doctor will check the recorded results later.

Event monitor. This works like a Holter monitor, but it only records your heart's activity at certain times. It might automatically start recording when it senses something is off. Or you might have to push a button when you feel:

  • Dizzy
  • Weak
  • Lightheaded
  • A racing or fluttering heart

You may need to wear it for a couple of months -- as long as it takes to catch and record the trouble.


Stress Test

It's just what it sounds like: A test that puts extra stress on your heart to see how it responds to working hard and beating fast. You'll be hooked up to an EKG during the test, and the technician will watch your heart rate and blood pressure, too.

Exercise is an easy way to get your heart pumping. You might ride a stationary bicycle or walk or run on a treadmill. That's why this is sometimes called a treadmill test.

If your body can't handle intense activity, you can take a special medicine that makes your heart work harder instead.


This test uses sound waves and a computer to create a moving picture of your heart. An "echo" gives your doctor information about:

  • The size and shape of your heart
  • How well the heart chambers and valves are working
  • Where the heart muscle isn't contracting the right way
  • Areas of poor blood flow
  • Previous injuries poor blood flow has caused

The same device makes the sound waves and picks them up bouncing back. When your doctor puts it on your chest, this procedure is called a transthoracic echocardiogram (TTE). To get closer to your heart so it's easier to make clear pictures and see blood clots, he can feed the device through your mouth and down your throat while you're sedated and won't feel it. That's called a transesophageal echocardiogram (TEE).

Chest X-ray

It can't show AFib, but it can show complications including fluid buildup and an enlarged heart.

Blood Tests

These can point your doctor to what might be causing your AFib. Blood tests may check for infection, thyroid, and kidney problems, signs of a heart attack, and more.

WebMD Medical Reference Reviewed by Suzanne R. Steinbaum, MD on August 24, 2017



National Heart Lung and Blood Institute: "How is Atrial Fibrillation Diagnosed?"

American Heart Association: "Common Tests for Arrhythmia."

Northwestern Memorial Hospital: "Atrial Fibrillation Express Test."

Heart Rhythm Society: "Diagnosing Atrial Fibrillation (AFib)."

Medscape: "Atrial Fibrillation Workup: Lab Studies."

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