Atrial fibrillation (AFib) is a heart condition characterized by an irregular heartbeat, also known as an arrhythmia. To see if you have AFib, your doctor may conduct several tests, including an electrocardiogram (ECG). By reviewing your symptoms and risk factors, health care professionals can diagnose AFib and provide appropriate 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 individuals may experience 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 be detected only through a medical evaluation.

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

• Older age
• Hypertension (high blood pressure)
• Diabetes
• A history of heart disease or heart attacks
• Thyroid problems
• Sleep apnea (a sleep disorder in which your breathing starts and stops)
• Excessive alcohol or drug use
• A family history of AFib

If you have any of these risk factors or experience symptoms that suggest irregular heartbeats, talk to your health care 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). ECGs can measure how fast the heart is pumping, the regularity of pumping, and how different parts of the heart are working together. They can also help detect blocked blood vessels and heart attacks — whether old or recent.

The heart has a group of cells in its upper portion 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 chambers of the heart are divided into two upper chambers — the atria — and two lower chambers, called ventricles. Additionally, the left and right sides of these chambers are split. The right atrium and right ventricle work together to pump blood in a healthy heart.

During atrial fibrillation, the normal heart rhythm is disrupted. The atria pump at different times than the ventricles, causing a rapid and irregular heart beat. This chaotic activity leads to pooling of blood inside the heart and not enough blood being pumped to the body.

An ECG device picks up this activity. It uses small electrodes placed on various body parts to measure both the rate and rhythm of your heart beats. Using 10 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 very safe procedures that can give you and your cardiologist good insight into whether you have AFib or another type of arrhythmia. 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’ll have to change into a medical gown for the procedure. A medical professional will place 10 small adhesive patches with the electrodes on your body. Of these electrodes, four will go on the limbs — one on each arm and leg — and the other six will be placed on the chest to capture different heart readings. If you have hair growing 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 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 them.

What Do Doctors See on an ECG?

The waves on the ECG measure different parts of the heart and how they’re 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 — between 100 and 175 beats per minute.

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 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 measures a type of activity that happens in the atria. 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 primary method of diagnosing AFib. Sometimes an ECG will not catch AFib because it’s only a short snapshot of what’s going on in your heart. It’s important to continue with additional testing if your doctor still has reason to suspect AFib.

If left untreated, AFib can result in the heart pumping out too little blood. This can lead to low blood pressure, as well as blood clots and stroke.

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 recorder can record unusual heart rhythms for up to 30 days.
• 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.

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.”

Talk With Others Who Understand

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Are you or a loved one living with atrial fibrillation? Did you have an ECG during your diagnosis? Share your experience in the comments below, or start a conversation by posting on your Activities page.