Electrocardiogram

What is an electrocardiogram (EKG) test?

An electrocardiogram (EKG) test is a simple, painless, and quick test that records the electrical signals your heart makes when it beats. These signals tell your heart’s four chambers to contract (squeeze) in a specific rhythm that your heart needs to pump blood to your body.

An EKG recording of your heart’s electrical signals looks like wavy lines with sharp spikes in them. These lines can be broken down into three main parts. These parts are:

• The P wave. This is the first part of the signal, and it shows how well the upper chambers of your heart work.
• The QRS complex. This is the second part of the signal. It’s the sharp spike on the wavy line, and it shows how well the lower chambers of your heart work.
• The T wave. This is the third and final part of the signal, and it shows how well your heart recovers after its chambers contract.

With an EKG recording, your health care provider can see:

• How fast your heart is beating
• Whether the rhythm of your heartbeat is steady or irregular
• The strength and timing of the electrical signals passing through each part of your heart

Sometimes information from an EKG can help measure the size and position of your heart's chambers.

Other names: ECG test, Holter monitor, ambulatory electrocardiography, continuous electrocardiograms, transtelephonic event monitors

What is it used for?

Your provider can use an EKG test to look for abnormal heart activity that may be a sign of heart disease or damage. The results of this test can’t diagnose a heart condition on their own, but with the results of other tests and your medical history, your provider can diagnose and monitor conditions such as:

• Arrhythmia
• Cardiomyopathy
• Coronary artery disease
• Heart attack
• Heart failure
• Heart valve diseases
• Congenital heart defects

Your provider may also use an EKG to:

• See if your heart is healthy enough for an upcoming surgery.
• Find out how well a new medicine for heart disease is working.
• Monitor your heart health after you get a pacemaker. This is a device that maintains your heart’s rhythm when the heart isn’t able to do so on its own.
• Find out if you had a heart attack in the past but didn’t know it.

EKG tests are mainly used for people who have symptoms of a heart condition or have already been diagnosed with a heart condition. They are not generally used to screen people who don't have symptoms unless they have an increased risk of developing heart disease. Your provider can explain your risk for heart disease and let you know if need to have an EKG test. In certain cases, your provider may have you see a cardiologist, a doctor who specializes in heart diseases.

Why do I need an EKG test?

You may need an EKG test if you have symptoms of a heart condition, including:

• Chest pain
• Rapid or irregular heartbeat
• Shortness of breath
• Dizziness
• Fatigue
• A decrease in your ability to exercise

An EKG is often the first test you’ll have if you have signs of a heart condition or if you have a heart condition that your provider wants to monitor. It may be done in your provider’s office, an outpatient clinic, in a hospital before surgery, or as part of another heart test called a stress test.

You may also need an EKG if you:

• Are about to have surgery and your provider is concerned about your heart health.
• Have started treatment for a heart condition. This can include taking heart medicine and getting a pacemaker.
• Have an increased risk for developing heart disease. You may have an increased risk if heart disease runs in your family or if you have another condition, such as diabetes, that makes your risk higher than normal.

What happens during an EKG test?

An EKG test only takes a few minutes. It generally includes these steps:

• You will lie on an exam table.
• A provider will place several electrodes (small sensors that stick to your skin) on your arms, legs, and chest. The provider may need to shave body hair to make sure the electrodes stay on.
• The electrodes are attached by wires to a computer or a special EKG machine
• You will lie very still while your heart's electrical activity is recorded on a computer or printed on paper by an EKG machine.

Will I need to do anything to prepare for the test?

Some medicines can affect the accuracy of your results. You may need to stop taking certain medicines or supplements before this test, so tell your provider about everything you take. But don’t stop taking any medicines unless your provider tells you to.

You don't need any other special preparations for an EKG test.

Are there any risks to the test?

There is very little risk to having an EKG. You may feel a little discomfort or skin irritation after the electrodes are removed. The EKG doesn't send any electricity to your body. It only records electrical signals from your heart.

What do the results mean?

Your provider will check your EKG results for a steady heartbeat and rhythm. If your results are not normal, it may be a sign of a heart condition. The specific condition depends on which part of your EKG wasn't normal.

You may need to have other heart health tests before your provider can make a diagnosis. Your provider can explain what your test results mean for your heart health and treatment.

Learn more about laboratory tests, reference ranges, and understanding results.

Is there anything else I need to know about an EKG?

An EKG is a "snapshot" of your heart's activity over a very short time. If you have heart symptoms that come and go, a regular EKG may not catch the problem. In that case, your provider may recommend that you wear a small portable EKG monitor that can record your heart for days or longer while you do your normal activities. You may also need a longer EKG recording if your provider wants to check how well your heart is working after a heart attack or to see if treatment is helping you.

There are many types of long-term EKG monitors. The two main groups are Holter monitors, which can be worn for up to two days, and event monitors, which may record your heart activity for weeks to years depending on the type.

A Holter monitor is about the size of a small camera. You usually wear it on a belt or strap around your neck for a day or two. Wires under your clothes attach to electrodes that stick to your chest. The monitor records your heart's electrical signals the whole time you're wearing it. You may be asked to keep a diary of your symptoms during the test period. After the test period, you remove the monitor and return it according to the instructions. A provider will review the recording of your heart's electrical activity from the monitor.

An event monitor records your heart's electrical activity when you press a button or when the device detects abnormal heart activity. There two main types of event monitors:

• Event monitors that you wear or carry with you. You wear some monitors on your chest or wrist. Other monitors are designed for you to carry. If you have symptoms and are carrying a monitor, you will have to hold the monitor to your chest. These event monitors may be used for weeks to months. Some of them wirelessly transmit information about your heart to a provider. Others must be returned so a provider can examine the recorded information.
• Event monitors that are inserted under the skin of your chest. These are called implantable event monitors. They are put under your skin during minor surgery that’s often done in a doctor’s office. These monitors can track your heart’s electrical activity for years. You may need this type of EKG monitor if you had a stroke or frequently faint, and your provider hasn’t found the cause. Implantable monitors wirelessly transmit the information they record so your provider can regularly check it.