Electrocardiogram (EKG)
Key points
- An electrocardiogram (EKG) is a painless recording of the heart's electrical activity.
- An EKG can be used to evaluate patients with chest pain, patients thought to be having a heart attack, and patients suspected of having coronary artery disease or a cardiac arrhythmia.
- In most cases, no special preparation is necessary.
- You will need to expose the skin above your ankles, wrists and chest.
What Is It?
An electrocardiogram (EKG) is a painless recording of the heart's electrical activity. This electrical activity is detected by small metal electrodes, which are placed on the patient's wrists, ankles and chest. Then the electrical signals are carried from the electrodes through wires to the EKG machine, which transforms the signals into standard patterns or waves. Different waves represent different areas of your heart through which tiny electrical currents flow, causing the heart muscles to contract and relax. Briefly, the P wave represents the current in the atria, or the upper chambers of the heart; the QRS complex, the current in the ventricles (the lower heart chambers); and the T wave, the heart's brief "rest period" as it repolarizes (recharges electrically) between heartbeats.
The paper tracing of EKG waves shows the heart rate and heart rhythm, and can give important clues about damage to the heart muscle or irritation of the membrane around the heart (pericardium).
In most cases, a basic EKG takes about five to 10 minutes. It can be performed in a doctor's office, in a laboratory or in a hospital bed.
What It's Used For
An EKG can be used to evaluate patients with chest pain, patients thought to be having a heart attack, and patients suspected of having coronary artery disease or a cardiac arrhythmia. It also can help to diagnose pericarditis (an inflammation of the membrane around the heart), pulmonary embolism (a blood clot blocking blood flow in a lung), abnormal blood levels of potassium or calcium, or overdoses of certain medications.
An EKG sometimes is performed as part of a regular physical examination or as a screening test in people at high risk of heart problems, including people with high blood pressure (hypertension), high cholesterol, diabetes, a strong family history of heart problems, and people who smoke. The EKG sometimes will show the patient has coronary artery disease even if there are no symptoms.
During surgery, a continuous EKG tracing helps to monitor the functioning of the patient's heart.
Preparation
In most cases, no special preparation is necessary. However, if you are taking any medications, be sure to tell the EKG technician about these drugs beforehand. This is because certain medicines have effects on the heart that can influence the appearance of an EKG tracing.
Since you will be asked to remove any bracelets and long necklaces during your EKG, you may wish to leave these items at home. Also, it would be helpful to wear a shirt that can be unbuttoned easily.
How It's Done
Written and revised by
Andrey Nailor, M.D.
Our doctors write and review articles for accuracy and keep them up to date.
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