There is no risk of electric shock during an electrocardiogram. The sensors, called electrodes, do not make electricity.

Some people may get a slight rash where the patches were placed. Removing the patches may feel uncomfortable for some people. It's similar to taking off a bandage.

You don't need to do anything to prepare for an electrocardiogram (ECG or EKG). Tell your healthcare team about all the medicines you take, including those bought without a prescription. Some medicines and supplements may affect the test results.

An electrocardiogram (ECG or EKG) can be done in a medical office or hospital. The test also may be done in an ambulance or other emergency vehicle.

Before

Before getting an electrocardiogram, you may be asked to change into a hospital gown. A member of your healthcare team may shave any hair on the area where the electrode patches are placed. This helps the patches better stick to the skin.

Once you're ready, you usually lie down on an examining table or bed.

During

During an electrocardiogram, up to 12 sticky patches called electrodes are attached to the chest and sometimes to the arms or legs. Wires connect the patches to a computer. The computer prints or displays results. Results are shown in waves. The waves are the signals that travel through the heart with each heartbeat.

You can breathe during the test. But stay still and do not talk. Movement may interfere with the test results.

After

Unless you're having a heart problem that needs immediate treatment, you can usually return to your daily activities after having an electrocardiogram.

Your healthcare professional might talk to you about the electrocardiogram (ECG or EKG) results the same day as the test. Sometimes the results are shared with you at your next appointment.

A healthcare professional looks for heart signal patterns in the electrocardiogram results. Doing this gives information about the heart's health such as:

• Heart rate. The heart rate is the number of times the heart beats a minute. You can measure your heart rate by checking your pulse. But an ECG may be helpful if your pulse is difficult to feel or too irregular to count accurately. ECG results can help diagnose an unusually fast heart rate, called tachycardia, or an unusually slow heart rate, called bradycardia.
• Heart rhythm. The heart's rhythm is the time between each heartbeat. It's also the signal pattern between each beat. An ECG can show irregular heartbeats, called arrhythmias. Examples include atrial fibrillation (AFib) and atrial flutter.
• Heart attack. An ECG can diagnose a current or previous heart attack. The patterns on the ECG results can help a healthcare professional learn which part of the heart is damaged.
• Blood and oxygen supply to the heart. An ECG done while you're having chest pain symptoms can help your care team learn whether reduced blood flow to the heart is the cause.
• Heart structure changes. ECG results can provide clues about an enlarged heart, congenital heart defects and other heart conditions.

If results show a change in the heartbeat, you may need more testing. For example, you might have an ultrasound of the heart, called an echocardiogram.