What is an Electrocardiogram (ECG)?

Electrocardiogram (ECG) is a medical test that measures and records the electrical activity of the heart.

The heart is a muscular organ that beats rhythmically to pump blood throughout the body delivering oxygen to organs and tissues.

The sinoatrial node, SA node, is the natural pacemaker of the heart. It sends signals to the muscle fibres of the heart telling them when to contract. Each contraction is one heartbeat.

In an ECG test, the electrical impulses made while the heart is beating are recorded and documented on a strip of paper.

Why is an ECG done?

An electrocardiogram (ECG) is done to:

  • Assess the heart's electrical activity for any abnormalities.
  • Find the cause of unexplained chest pain, such as from a heart attack, inflammation of the sac surrounding the heart (pericarditis), or angina.
  • Assess the cause of symptoms of heart disease, such as shortness of breath, dizziness, fainting, or rapid, irregular heartbeats (palpitations).
  • Find out if the walls of the heart chambers are too thick (hypertrophied).
  • Assess the health of the heart when other diseases or conditions are present, such as high blood pressure, high cholesterol, cigarette smoking, diabetes, or a family history of early heart disease.

ECG Procedure

An electrocardiogram (ECG) is usually done by a health professional and the results are interpreted by a doctor, such as an internist, family medicine doctor, electrophysiologist, cardiologist, anesthesiologist, or surgeon.

During an ECG, the patient will lie on his/ her back on a bed or table. Small metal discs called electrodes will be taped to the arms and legs to record the heart rate during the test.

Small pads soaked in alcohol may be placed between the electrodes and your skin to improve the conduction of the electrical impulses.

The electrodes may be moved at different times during the test to measure the heart's electrical activity from different locations on the chest.


An ECG is a completely safe test with no adverse risks or side effects.

The electrodes that are placed on the body are used to transfer an image of the electrical activity of your heart to a strip of paper. No electricity passes through your body from the machine, so there is no danger of getting an electrical shock.

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