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Electrocardiogram (ECG): Why and How is it Done?

Electrocardiogram (ECG): Why and How is it Done?

Electrocardiogram or ECG or EKG is a test that measures the electrical activity of the heartbeat.

This test is one of the simplest and fastest tests to understand your heart and its functioning, particularly if you are experiencing heart palpitations. In this test, the doctor sticks small, plastic patches also called electrodes at certain spots on the chest, legs, and arms. These electrodes are connected to the ECG machine by lead wires.

This electrical activity measures your heartbeat, interprets it, and produces graphs for analysis. However, you should know, no actual electricity is passed into your body.

Natural electrical impulses help the blood flow properly by coordinating with the contraction of the different parts of the heart. An electrocardiogram records these impulses to show the rhythm of the heartbeats like how fast your heart is beating, and the strength and timing of the electrical impulses as they move to different parts of the heart.

Changes in an EKG can be a sign of many cardiovascular conditions.

Below are the types of ECG that your doctor may recommend undergoing.


Holter monitor Electrocardiogram (ECG)

Typically, the electrical activity of the heart is recorded over a period of 24 hours. In this test, your doctor attaches 3 or 4 electrodes on your chest along with a small recording device that is hung around your neck or worn as a belt.

The data collected by an EKG is then transferred to the doctor’s computer for analysis. For this test, your doctor needs to know your daily schedule and other factors like unusual events, sleep patterns, and physical activity.

An ECG is done only when you have an irregular heartbeat for quite some time.

Exercise Electrocardiogram (ECG)

In this test, the electrical activity of your heart is measured while you are performing any physical activity. Usually, the physical activity is riding an exercise bike or walking on a treadmill.

Each time the amount of exertion is increased by increasing the levels of the exercise bike. This makes it difficult to pedal. The test stops immediately if any irregularity in the electrocardiogram occurs. This test provides results on the power that was generated in Watts. Your blood pressure is also checked.

Resting ECG

In this test, you are instructed to lie down on your back with a bare chest. In resting ECG, it is essential to lie comfortably and calmly because moving, shaking, coughing, or tensing your muscles might affect your results.

A resting ECG takes hardly about a minute to five minutes at most.

Why is ECG done?

Your doctor will recommend an ECG to detect:

  • Arrhythmias (abnormal heart rhythms)
  • Pericarditis (inflammation of the sac surrounding the heart)
  • Coronary artery blockage
  • Enlargement of the heart
  • Areas of the damaged heart muscle (prior heart attack)
  • Heart valve disease
  • Bradycardia or tachycardia
  • Non-heart conditions like lung diseases or electrolyte imbalances
  • Congenital defects
  • To rule out heart disease
  • To monitor recovery from a heart attack, progression of heart disease, or the effectiveness of medicines to administer future treatments

Preparing for an ECG

You are not required to do any specific preparation for a standard electrocardiogram. However, it is essential that your doctor is aware of all the medications and supplements that you are taking. Your doctor may advise you to discontinue any medicine, if appropriate, to prevent any negative effects on the test.

Before an ECG, your doctor will give complete information about the electrocardiogram and how it is performed.

Unlike many other tests, fasting is not required in an electrocardiogram. However, your doctor may recommend special preparations if you have any underlying health conditions.

Ensure you tell your doctor if you have a pacemaker.


Understanding ECG Results

A healthy heart has a regular heartbeat pattern, but any damage or abnormalities in the heart will display differently.

Alphabetic letters P, Q, R, S, T identify different spikes of the printout and these are then studied by your doctor to indicate any cardiovascular problem. Doctors are given special training to read ECG readings as it is quite complex to understand. Some electrocardiogram machines have special software that helps to interpret the test.

If your test shows an abnormality, your doctor may suggest another ECG or an echocardiogram. Your doctor will study the information recorded by the ECG machine and look for any problems in your heart, including:

Structural abnormalities

An ECG can provide evidence of enlargements of the chambers or walls of the heart, heart defects, and other conditions.

Heart rate

Typically, your heart rate is measured by checking your pulse. An electrocardiogram may be helpful to count your pulse accurately especially when your pulse is too fast or too irregular to count.

This test helps your doctor to identify a usual slow heart rate (bradycardia) or unusually fast heart rate (tachycardia).

Heart attack

An electrocardiogram can show evidence of a previous heart attack as well as one that’s in progress. The patterns on the ECG may indicate which part of the body is damaged and up to what extent.

Inadequate oxygen and blood supply to the heart

An ECG is recommended while you have symptoms that can help your doctor to understand whether chest pain is caused due to reduced blood circulation to the heart, such as with the chest pain of unstable angina.

Heart rhythm

An ECG can show arrhythmias or heart rhythm irregularities. These conditions may occur when a part of your heart’s electrical system functions abnormally.

When should ECG be repeated?

Your doctor might ask you to undergo an ECG again if the previous electrocardiogram results show abnormality or negative. An ECG is asked to repeat to confirm the previous ECG test. If you are being treated for a condition, your doctor may ask you to repeat an ECG at regular intervals to check the effectiveness of the treatment.

What happens during an ECG procedure?

An ECG is done on an outpatient basis, but for certain cases, the patient has to stay in the hospital. Below are the steps that your doctor may follow for an ECG. However, you should know that steps may vary depending on your condition and your doctor’s practices.

Generally, steps that are followed to perform an ECG are:

  • You are asked to remove the jewelry and other accessories to prevent any interference with the test.
  • You will be asked to remove your clothes from the waist up. Your technician will ensure your privacy and help you cover your body with a sheet or gown and expose only necessary skin.
  • You will be asked to lie on the table and suggested not to move or talk during the test.
  • If the necessary spots are hairy, the technician will shave or clip small patches of hair, allowing the electrodes to stick on your skin closely.
  • Electrodes are the small, plastic patches that will be stuck on your legs, chest, and arms.
  • The lead wires are attached to these electrodes.
  • Once all attachment is done, your technician may enter identifying information about you in his/her machine computer.
  • It is then the test is started and may hardly take 1 to 5 minutes for the tracing to be completed.
  • Once done, the technician will disconnect the leads and remove electrodes from our skin.

After this procedure, you will either be asked to wait to meet the doctor or asked to continue your daily activities.

Learn more about heart arrhythmias and other conditions diagnosed by ECGs, here.

Hello Health Group does not provide medical advice, diagnosis or treatment.


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Written by Nikita Bhalla Updated Jun 27, 2021
Fact Checked by Hello Doctor Medical Panel