Diagnosis

Some people are unaware that they have atrial fibrillation (A-fib). A-fib may be detected when a doctor is listening to the heart with a stethoscope during a physical exam for other reasons.

A doctor may order several tests to diagnose A-fib or exclude other conditions that can cause similar symptoms. Tests may include:

• Electrocardiogram (ECG or EKG). This quick and painless test measures the electrical activity of the heart. Sticky patches (electrodes) are placed on the chest and sometimes the arms and legs. Wires connect the electrodes to a computer, which displays the test results. An ECG can show if the heart is beating too fast, too slow or not at all. An ECG is the main test for diagnosing atrial fibrillation.
• Blood tests. These help a doctor rule out thyroid problems or detect other substances in the blood that may lead to A-fib.
• Holter monitor. This small, portable ECG device is carried in a pocket or worn on a belt or shoulder strap during regular daily activities. It records the heart's activity continuously for 24 hours or longer.
• Event recorder. This device is similar to a Holter monitor, but it records only at certain times for a few minutes at a time. It's worn longer than a Holter monitor, typically 30 days. You generally push a button when you feel symptoms. Some devices automatically record when an irregular heart rhythm is detected.
• Echocardiogram. This noninvasive test uses sound waves to create images of the heart's size, structure and motion.
• Stress test. Also called exercise testing, stress testing involves running tests on the heart while exercising on a treadmill or stationary bike.
• Chest X-ray. X-ray images help a doctor see the condition of the lungs and heart.