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NIH MedlinePlus the Magazine, Trusted Health Information from the National Institutes of Health

Atrial Fibrillation

Atrial Fibrillation: Diagnosis

Physical Exam

Your doctor will do a complete cardiac exam. He or she will record the rate and rhythm of your heartbeat and take your pulse and blood pressure reading. Your doctor will likely check for any signs of heart muscle or heart valve problems. He or she will listen to your lungs to check for signs of heart failure.

Your doctor also will check for swelling in your legs or feet and may look for an enlarged thyroid gland or other signs of hyperthyroidism (too much thyroid hormone).

Tests and Procedures


An EKG is a simple, painless test that records the heart's electrical activity. It's the most useful test for diagnosing AFib.

An EKG shows how fast different regions of your heart are beating and the heart's rhythm (steady or irregular). It also records the strength and timing of electrical signals as they pass through your heart.

The two most common types of portable EKGs for long-term recording are Holter and event monitors.

Holter and Event Monitors

A Holter monitor records the heart's electrical activity for a full 24-or 48-hour period. You wear small patches called electrodes on your chest. Wires connect these patches to a small, portable recorder. The recorder can be clipped to a belt, kept in a pocket, or hung around your neck.

An event monitor is similar to a Holter monitor. You wear an event monitor while doing your normal activities. However, an event monitor only records your heart's electrical activity at certain times while you're wearing it.

Stress Test

Some heart problems are easier to diagnose when your heart is working hard and beating fast. During stress testing, you exercise to make your heart work hard and beat faster while heart tests are done. If you can't exercise, you may instead be given medicine to make your heart work hard and beat fast.


Echocardiography (echo) uses sound waves to create a moving picture of your heart. The test shows the size and shape of your heart and how well your heart chambers and valves are working together to pump blood to your lungs and body.

Transesophageal Echocardiography

Transesophageal echo, or TEE, uses sound waves to take pictures of your heart through your esophagus (the passage leading from your mouth to your stomach). Your heart's upper chambers, the atria, are deep in your chest. They often can't be seen very well using transthoracic echo. Your doctor can see the atria better using TEE. TEE is used to detect blood clots that may be forming in the atria because of AFib.

Chest X-Ray

A chest X-ray is a painless test that creates pictures of the structures in your chest, such as your heart and lungs. This test can show fluid buildup in the lungs and signs of other AFib complications.

Blood Tests

Blood tests check the level of thyroid hormone in your body and the balance of your body's electrolytes. Electrolytes are minerals that help maintain fluid levels and acid-base balance in the body. They're essential for normal health and functioning of your body's cells and organs.

Winter 2015 Issue: Volume 9 Number 4 Page 24