What is an Electrocardiogram?
An electrocardiogram — abbreviated as EKG or ECG — is a test that measures the electrical activity of the heartbeat. With each beat, an electrical impulse (or “wave”) travels through the heart. This wave causes the muscle to squeeze and pump blood from the heart. A normal heartbeat on ECG will show the timing of the top and lower chambers.

The right and left atria or upper chambers make the first wave called a “P wave” — following a flat line when the electrical impulse goes to the bottom chambers. The right and left bottom chambers or ventricles make the next wave called a “QRS complex.” The final wave or “T wave” represents electrical recovery or return to a resting state for the ventricles.

Why is it done?
An ECG gives two major kinds of information. First, by measuring time intervals on the ECG, a doctor can determine how long the electrical wave takes to pass through the heart. Finding out how long a wave takes to travel from one part of the heart to the next shows if the electrical activity is normal or slow, fast or irregular. Second, by measuring the amount of electrical activity passing through the heart muscle, a cardiologist may be able to find out if parts of the heart are too large or are overworked.

Does it hurt?
No. There’s no pain or risk associated with having an electrocardiogram. When the ECG stickers are removed, there may be some minor discomfort.

Is it harmful?
No. The machine only records the ECG. It doesn’t send electricity into the body.

An EKG shows:

  • How fast your heart is beating
  • Whether the rhythm of your heartbeat is steady or irregular
  • The strength and timing of electrical signals as they pass through each part of your heart
  • Doctors use EKGs to detect and study many heart problems, such as heart attacks, arrhythmias (ah-RITH-me-ahs), and heart failure. The test’s results also can suggest other disorders that affect heart function.

Who Needs an Electrocardiogram?

Your doctor may recommend an electrocardiogram (EKG) if you have signs or symptoms that suggest a heart problem. Examples of such signs and symptoms include:

  • Chest pain
  • Heart pounding, racing, or fluttering, or the sense that your heart is beating unevenly
  • Breathing problems
  • Tiredness and weakness
  • Unusual heart sounds when your doctor listens to your heartbeat
  • You may need to have more than one EKG so your doctor can diagnose certain heart conditions.

An EKG also may be done as part of a routine health exam. The test can screen for early heart disease that has no symptoms. Your doctor is more likely to look for early heart disease if your mother, father, brother, or sister had heart disease—especially early in life. You may have an EKG so your doctor can check how well heart medicine or a medical device, such as a pacemaker, is working. The test also may be used for routine screening before major surgery. Your doctor also may use EKG results to help plan your treatment for a heart condition.

What To Expect Before an Electrocardiogram

You don’t need to take any special steps before having an electrocardiogram (EKG). However, tell your doctor or his or her staff about the medicines you’re taking. Some medicines can affect EKG results.

What To Expect During an Electrocardiogram

An electrocardiogram (EKG) is painless and harmless. A nurse or technician will attach soft, sticky patches called electrodes to the skin of your chest, arms, and legs. The patches are about the size of a quarter. Often, 12 patches are attached to your body. This helps detect your heart’s electrical activity from many areas at the same time. The nurse may have to shave areas of your skin to help the patches stick. After the patches are placed on your skin, you’ll lie still on a table while the patches detect your heart’s electrical signals. A machine will record these signals on graph paper or display them on a screen. The entire test will take about 10 minutes.