How Atrial Fibrillation Is Diagnosed

An irregular heartbeat may or may not cause symptoms. If your doctor thinks you have it, the first thing he’ll do is listen to your heart. He may be able to hear your irregular heartbeat with a stethoscope. If not, 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 your doctor may also refer you to a:

  • Cardiologist, a doctor who specializes in heart diseases and conditions
  • Electrophysiologist, a doctor who specializes in arrhythmias

First, the doctor will ask detailed questions about your:

  • Symptoms
  • Health habits
  • Health problems
  • Family medical history

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


Does AFib Show Up on an Electrocardiogram (EKG)?

Yes. This simple, painless test is the most helpful to diagnose AFib. 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 heart rhythm monitor to keep tabs on your ticker over a longer time.

Holter Monitor

You keep this device 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, usually for a 30-day period. 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 month or so -- as long as it takes to catch and record the trouble.

Mobile Cardiac Telemetry (MCT)

You might hear this called mobile cardiac monitoring. You wear this small device 24/7, and it monitors your heart as you go about your daily life. Most send a Bluetooth signal to a data center, which analyzes the info and gives your doctor a report.

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 best faster 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 that poor blood flow has caused

Transthoracic echocardiogram (TTE). This imaging test gives your doctor a picture of your beating heart. The doctor uses a device called a transducer to give off and read sound waves that bounce off the walls and valves in your heart. A computer uses the data to create a video of your heart. Your doctor can see the size of your heart, how well it’s working, if your heart valves are working, and if you have any blood clots.

Transesophageal echocardiogram (TEE). This imaging test gives the doctor a picture of your heart. He’ll place a probe down your esophagus (the tube that connects your mouth to your stomach). It goes right behind your heart. Once the probe is in place, it works the same way as a TTE.


Chest X-Ray

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

Cardiac Computerized Tomography (CT) or Magnetic Resonance Imaging (MRI)

This imaging test uses an X-ray machine and a computer to take pictures of the inside of your heart and your chest. The resulting 3D image can help doctors spot problems in your atria and other heat structures that could signal AFib.

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.

Portable Electrocardiogram

You might hear this called a handheld EKG or a symptom event monitor. Or it could look like a wristwatch. It has electrodes on back that take your pulse at your chest or your wrist. You can get one from a discount store, drugstore, or online. The doctor may suggest you do it so you can take a quick reading when you feel something. It’ll store your EKG data in its memory for your doctor to read.

Fitness Trackers

It looks like popular smartwatches outfitted with special sensors called photoplethysmographic sensors (or PPGs) can, in fact, detect AFib. Also, at least three fitness trackers can also detect a type arrhythmia called paroxysmal supraventricular tachycardia.

Tilt-Table Test

If you’ve fainted (the doctor will call this syncope), he may suspect a problem with the part of your nervous system that controls heart rate and blood pressure. When they both drop, less blood goes to your head, and you faint. This test checks for that. You’ll lie flat on a table with straps around your body to hold you in place. After about 15 minutes, the table will be raised quickly so you’re straight up, as if you were standing. The doctor will keep the table upright for 45 minutes and track your heart rate and blood pressure.

WebMD Medical Reference Reviewed by James Beckerman, MD, FACC on May 17, 2018



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American Heart Association: “Cardiac Event Recorder,” "Common Tests for Arrhythmia."

Northwestern Memorial Hospital: "Atrial Fibrillation Express Test."

Medscape: "Atrial Fibrillation Workup: Lab Studies."

Medical Devices: Evidence and Research.

Heart Rhythm Society: “Artificial Intelligence Automatically Detects Atrial Fibrillation Using Apple Watch’s Heart Rate Sensor,” “Benefits of monitoring patients with mobile cardiac telemetry (MCT) compared with the Event or Holter monitors,” “Diagnosing Atrial Fibrillation (AFib),” “New Study Show Popular Smart Watches Accurately Measure Rapid Heart Beat.”

Current Treatment Options in Cardiovascular Medicine: “Role of Magnetic Resonance Imaging in Atrial Fibrillation Ablation.”

Heart Rhythm: “2017 ISHNE-HRS expert consensus statement on ambulatory ECG and external cardiac monitoring/telemetry.”

Mayo Clinic: “Tilt table test.”

iproc: “Screening of Atrial Fibrillation Using Wrist Photoplethysmography from a Fitbit Tracker.”

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