An electrocardiogram is a simple, painless test that measures your heart’s electrical activity. It’s also known as an ECG or EKG. Every heartbeat is triggered by an electrical signal that starts at the top of your heart and travels to the bottom. Heart problems often affect the heart’s electrical activity.

Your doctor may recommend an EKG if you’re experiencing symptoms or signs that may suggest a heart problem, including:

  • pain in your chest
  • trouble breathing
  • feeling tired or weak
  • pounding, racing, or fluttering of your heart
  • a feeling that your heart is beating unevenly
  • detection of unusual sounds when your doctor listens to your heart

Measuring the electrical activity of the heart may help your doctor determine if chambers of the heart are possibly too large or overworked. In other cases, an EKG can help determine the cause of your symptoms along with what type of treatment might be necessary.

If you have a family history of heart disease, your doctor may also order an EKG to look for early signs of heart disease. No matter your age, it’s important to be aware of any symptoms that may indicate a heart problem and talk with a doctor about possibly scheduling an EKG.

An EKG records a picture of your heart’s electrical activity for the time that you’re being monitored. However, some heart problems come and go. In these cases, you may need longer or more specialized monitoring.

Stress test

Some heart problems only appear during exercise. During stress testing, you’ll have a continuous EKG while you’re exercising. Typically, this test is done while you’re on a treadmill or stationary bicycle.

Holter monitor

Also known as an ambulatory ECG or EKG monitor, a Holter monitor records your heart’s activity over 24 to 48 hours or up to 2 weeks while you maintain a diary of your activity to help your doctor identify the cause of your symptoms. Electrodes attached to your chest record information on a portable, battery-operated monitor that you can carry in your pocket, on your belt, or on a shoulder strap.

Event recorder

Symptoms that don’t happen very often may require an event recorder. It’s like a Holter monitor, but it records your heart’s electrical activity just when symptoms occur. Some event recorders activate automatically when they detect arrhythmia. Other event recorders require you to push a button when you feel symptoms. You can send the information directly to your doctor over a phone line.

Loop recorder

A loop recorder is a device that is implanted in your body, under the skin of your chest. It functions as an electrocardiogram would but allows for continuous remote monitoring of your heart’s electrical signals. It’s looking for irregularities that can cause fainting or palpitations.

There are few, if any, risks related to an EKG. Some people may experience a skin rash where electrodes were placed, but this usually goes away without treatment.

People undergoing a stress test may be at risk for a heart attack, but this is related to the exercise, not the EKG.

An EKG only monitors the electrical activity of your heart. It does not emit any electricity and is completely safe, even during pregnancy.

The Holter monitors can sometimes cause an allergy or rash on the areas of the skin where the EKG electrode pads are placed. This is more likely when they’re worn for many consecutive days.

Loop recorders are often used without any negative effects and have gotten smaller and more efficient over time. As with any procedure like this one, there is the possibility of mild pain, slight bruising, or infection at the implantation location.

There are a few things to consider when preparing for an EKG, including:

  • removing any metallic objects such as jewelry
  • possibly shaving chest hair
  • avoiding drinking cold water right before test
  • no exercising, or increasing your heart rate, before the test
  • keeping the room at a moderate temperature to avoid shivering

Drinking cold water can cause changes in the electrical patterns that the test records, while exercising can increase your heart rate and affect the test results. Removing jewelry and shaving helps attach the electrodes more securely.

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Illustration by Jason Hoffman

An EKG is quick, painless, and harmless. When going through an EKG, here are a few steps to expect during the test:

  • After changing into a gown, a technician attaches about 10 soft electrodes (about the size of a quarter) with a gel to your chest, arms, and legs. These electrodes are attached to wires that are attached to the EKG machine.
  • If these areas where the electrodes are attached are not shaved, the technician may shave them for you.
  • During the test, lie still on the table and breathe normally.
  • Do not talk during the test.
  • The machine will record your heart’s electrical activity and show results on a graph.
  • Once the test is complete, the electrodes are removed and discarded. The entire procedure should take about 10 minutes.

Typically, there is no immediate aftercare following an EKG test or immediate changes to diet or activities unless your doctor recommends otherwise. Results of the test are usually available immediately, and your doctor may go over them with you right away.

In some cases, the doctor may consult a cardiologist to review the results as well.

If your EKG shows normal results, your doctor will likely go over them with you that same day during your visit or at a follow-up visit.

If results appear abnormal, or show signs of any health problems, your doctor should contact you immediately to go over options to improve your heart’s condition. Signs of abnormalities that may show up in an EKG could include:

  • irregular heartbeat
  • heart defects, including an enlarged heart, a lack of blood flow, or birth defects
  • electrolyte problems, chamber dilation, chamber hypertrophy, or how electricity is moving through the heart
  • blocked arteries, or coronary artery disease

If the test shows signs of these abnormalities, your doctor will go over options to improve your heart’s condition. This may include prescribing medication or suggesting lifestyle changes such as modifying your diet or exercising more.