An electrocardiogram — also referred to as EKG or ECG — is a test that measures the electrical signals that control the rhythm of your heartbeat. Your doctor can look for patterns among these heartbeats and rhythms to diagnose various heart conditions.

An electrocardiogram may show:
• Evidence of heart enlargement.
• Signs of insufficient blood flow to the heart.
• Signs of a new or previous injury to the heart (heart attack).
• Heart rhythm problems (arrhythmias).
• Changes in the electrical activity of the heart caused by an electrolyte imbalance in the body.
• Signs of inflammation of the sac surrounding the heart (pericarditis).

• Who needs an EKG?
• What's the difference between an EKG and a regular cardiac stress test?
• Understanding Your Test Results

Who needs an EKG?

Your doctor may use this painless, noninvasive test to detect irregularities in your heart rhythm, structural abnormalities in your heart or problems with the supply of blood and oxygen to your heart. An EKG can also confirm if you're having a heart attack or if you've had a heart attack in the past — but it cannot predict whether you will have a heart attack in the future.

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What's the difference between an EKG and a regular cardiac stress test?

During an electrocardiogram, various electrodes — often 12 to 15 — are attached to your arms, legs and chest. Electrodes are sticky patches applied with a gel to help detect and conduct the electrical currents of your heart. The test normally takes just a few minutes and is performed while you are lying down.

However, if your heart problems occur most often during exercise, your doctor may ask you to walk on a treadmill or ride a stationary bike during your EKG. This is called a stress test. If you have a medical condition that makes it difficult for you to walk, medication may be injected to stimulate your heart.

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Understanding Your Test Results

During your EKG, the doctor will look for a consistent, even heart rhythm and a heart rate between 60 and 100 beats a minute. Variations provide a wealth of clues about your heart health, including:
• Heart rate. Normally, heart rate can be measured by simply checking your pulse. But an EKG may be helpful if your pulse is difficult to feel or too fast or too irregular to count accurately.
• Heart rhythm. An EKG can help your doctor identify an unusually fast heartbeat (tachycardia), unusually slow heartbeat (bradycardia) or other heart rhythm irregularities (arrhythmias). These conditions may occur when any part of the heart's electrical system malfunctions. In other cases, medication can trigger arrhythmias.
• Heart attack. An EKG can often show evidence of a previous heart attack or one that's in progress. The patterns on the ECG may indicate which part of your heart has been damaged, as well as the general extent of the damage.
• Inadequate blood and oxygen supply to the heart. An EKG can often help your doctor determine whether chest pain is caused by reduced blood flow to the heart muscle, a prime characteristic of coronary artery disease.
• Structural abnormalities. An EKG can provide clues about enlargement or inflammation of the heart, congenital heart abnormalities and other heart problems.

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