Atrial fibrillation (AFib) is a heart condition marked by an irregular heartbeat, also known as an arrhythmia. To see if you have AFib, your doctor may run several tests, including an electrocardiogram (ECG). By reviewing your symptoms, test results, and risk factors, healthcare professionals can diagnose AFib and provide the right treatment.

ECG is a key test for diagnosing AFib. This article will cover what to expect during an ECG procedure and help you understand the results.

AFib Symptoms and Risk Factors

Symptoms of atrial fibrillation can vary from person to person. Some people may experience chest pain or palpitations, which are rapid, fluttering, or pounding sensations in the chest. Others may feel lightheaded, fatigued, or short of breath. In some cases, AFib may not have noticeable symptoms and can only be detected through a medical evaluation.

Certain risk factors increase a person’s likelihood of developing AFib. These can include:

• Older age
• Current or past smoking
• Sedentary lifestyle
• A history of extreme exercise or excessive physical activity
• Obesity
• Being tall
• Hypertension (high blood pressure)
• Diabetes
• Excessive alcohol or drug use
• Medical history of heart disease or heart attacks
• Thyroid problems
• Sleep apnea (a sleep disorder where your breathing starts and stops)
• A family history of AFib

If you have any of these risk factors or experience symptoms that suggest an abnormal heart rhythm, talk to your healthcare provider.

What Is an Electrocardiogram?

An electrocardiogram — which you may see abbreviated as either ECG or EKG — is a medical test that measures the heart’s electrophysiology (electrical activity). An ECG detects the heart’s rhythm, how regularly it pumps, and how its different parts work together. It can also help identify blocked blood vessels and heart attacks — whether old or recent.

There is a group of cells in the right upper chamber of the heart known as the sinoatrial node. This node releases electrical activity, causing a rapid sequence of events that enable the heart to contract and pump blood to the rest of the body.

The four heart chambers are divided into two upper chambers — the atria — and two lower chambers, called ventricles.

During atrial fibrillation, the normal heart rhythm is disrupted. The atria do not contract properly and send too many electrical signals to the ventricles, causing a rapid and irregular heartbeat. This chaotic activity leads to blood pooling inside the atria, increasing the risk of clots.

An ECG device picks up this activity. It uses small electrodes placed on various body parts (usually the chest, arms, and legs) to measure both the rate and rhythm of your heartbeats. Using up to 12 electrodes, the ECG can look at your heart from 12 different views, also known as leads. The leads provide information on heart function from one part of the heart to the next.

The measurements from an ECG show up as complex waveforms from each lead on gridded paper, which a cardiologist can interpret to see how well your heart is pumping.

Getting an ECG: What To Expect

Electrocardiograms are safe, painless procedures that can help your cardiologist determine whether you have AFib or another type of arrhythmia. Minor side effects may include a rash where the adhesive patches are attached to your skin. If you’re scheduled to have an ECG, you may wonder what is involved.

When you arrive at a medical office for your ECG, you may have to change into a medical gown. A medical professional will place up to 12 small adhesive patches with electrodes on your chest, arms, and/or legs. If you have hair where the electrodes should go, this may be shaved before the placement of the electrodes, as hair can make it harder to detect electrical signals.

The ECG procedure is relatively short — only a couple of minutes. You will be lying down the whole time. It’s important to be quiet and try to relax as much as possible. Movement from shivering or stress can make the ECG harder to interpret. Preliminary results are often immediately available directly from the ECG device. However, a medical professional should follow up with you to confirm the results.

The ECG procedure is relatively short — only a couple of minutes. You will be lying down the whole time.

What Do Doctors See on an ECG?

The waves on the ECG measure different parts of the heart and how they are functioning.

Looking at the distance between the highest waves on an ECG graph — known as R waves — is the most accurate way to determine heart rate. In AFib, the R-R ratio — the time between R waves on the ECG — will be irregular throughout the recording. This means the distance between these peaks may be shorter or it may be longer. Overall, an AFib heart rate will be higher than normal.

Irregularity in the R-R ratio is one sign doctors use to tell the difference between AFib and other conditions, such as atrial flutter. In atrial flutter, while the heart rate may be faster, there will be more regularity in the R-R ratio on an ECG. This means the time between each R wave will be the same length, but shorter than the time it would be for someone with a normal heart rate.

Another portion of the ECG doctors look at to determine whether you have AFib is called the P wave. The P wave is present if there is normal activity of the sinoatrial node. While the P wave can vary in size, when there is no P wave on an ECG, this indicates problems with atrium functioning.

Other Tests for Diagnosing AFib

An ECG is the main method of diagnosing AFib. Sometimes an ECG will not catch AFib because it’s only a quick snapshot of what’s going on in your heart. If your doctor still has reason to suspect AFib, it’s important to continue with additional testing.

If left untreated, AFib can cause stroke and heart failure.

An ECG is the main method of diagnosing AFib. Sometimes an ECG will not catch AFib because it’s only a quick snapshot of what’s going on in your heart.

Additional testing for AFib may include:

• Advanced electrical monitoring — This can be performed with a device called a Holter monitor to measure the heart’s electrical activity continuously for 24 hours. An event monitor can record unusual heart rhythms for up to 30 days, and an implantable loop recorder can record it for up to three years.
• Echocardiogram — This test uses sound waves to create an image of your heart and blood vessels.
• Blood tests — These can measure thyroid, kidney, and liver function. They also can assess electrolytes and total blood counts.
• Sleep studies — These can reveal sleep apnea, which can increase the risk of developing AFib.
• A chest X-ray or MRI scan — These can look at the heart’s size and overall structure.
• Exercise stress tests — These involve assessing how your heart is functioning while you’re exercising (usually on a treadmill or stationary bike).

Consult Your Doctor

If you’re experiencing symptoms of AFib or have a higher risk for it, talk with your doctor. You may also require further care from a heart rhythm specialist called an electrophysiologist. AFib can be managed with medication, procedures, and medical devices. Lifestyle changes may also help. Many MyHeartDiseaseTeam members have echoed the same message when it comes to getting AFib diagnosed: “Don’t wait.”

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