Electrocardiogram (ECG / EKG)

Clinical definition of the ECG test
An electrocardiogram (ECG) is a test that records the electrical activity of the heart. It records any problems with the heart's rhythm and hence is used in the investigation and diagnosis of heart disease such as heart enlargement, heart inflammation and coronary heart disease.
ECGs from normal, healthy hearts have a characteristic shape. Any irregularity in the heart rhythm or damage to the heart muscle can change the electrical activity of the heart and thus change the shape of the ECG. 

Why is the ECG test done?
An ECG may be done in the following conditions:

  • For patients showing symptoms of a heart disease
  • To assess if the patient has had a heart attack or evidence of a previous heart attack
  • To monitor the effect of medicines used for coronary artery disease
  • To assess the function of artificial pacemakers
  • To measure the size and position of the chambers of the heart
  • Persons who may be at risk of heart disease due to
  • Family history of heart disease
  • Smoking habits
  • Overweight
  • Diabetes
  • High cholesterol
  • High blood pressure

What are the common signs/symptoms when the ECG test is done?
A doctor may recommend an ECG if a patient is experiencing symptoms such as:

  • Chest pain
  • Discomfort in other areas of the upper body
  • Shortness of breath or difficulty in breathing
  • Dizziness
  • Fainting
  • Irregular heartbeats
  • Breaking out in a ‘Cold Sweat’

Who should do the ECG test (Target population)?

Persons showing the above signs & symptoms.

What should I do before the ECG test?

Diagnostic procedure

Preparatory instructions before the test *

Small patches called electrodes are stuck to the skin at different areas of the body such as the arms, legs, and chest.

Typically the chest area may be cleaned i.e. some hair might be clipped or shaved to ensure that the patches stick to the skin easily.

The patches are connected by wires to a machine that converts the electrical signals of the heart into wavy lines, which may be printed on paper to show a typical graphical pattern.

Usually, the ECG is taken while the patient is resting. However sometimes, while investigating the cause of a heart disease, the ECG may be done when the patient is exercising or under minimal stress, to monitor changes in the heart. This type of ECG is often called a stress test.

The stress test may be done while the patient is on an exercise bike or treadmill.

Some medications like a few beta-blockers may interfere with the test results. Hence it is advised to check with the doctor before the test.

Also avoid exercising or drinking cold water immediately before the ECG test since it may cause false results.


*Subjects suffering from any illness or on oral or injectable medications are advised to consult their physician prior to requesting any tests or procedures.

How do I interpret my ECG test results?

Reference Range*


Heart rate

60 to 100 beats per minute

Heart rhythm

consistent and even

‘*A Reference range is a set of values which helps the healthcare professional to interpret a medical test. It may vary with age, gender, and other factors. Reference ranges may also vary between labs, in value & units depending on instruments used and method of establishment of reference ranges’

Diseases/conditions related to the ECG test

  • Enlargement of the heart
  • Congenital heart defects
  • Coronary occlusion
  • Poor blood supply to the heart
  • Abnormal position of the heart
  • Pericarditis or Myocarditis
  • Cardiac arrest during emergency room or intensive care monitoring
  • Electrical conduction disturbances
  • Imbalances in the blood chemicals (electrolytes) that control heart activity
  • Arrhythmias 
  • Coronary heart disease
  • Heart attack 
  • High blood pressure 

Other tests related to the ECG test

  • Physical examination
  • Chest X-rays
  • Echocardiogram (ultrasound of the heart)
  • Magnetic resonance imaging (MRI): scan of the chest
  • Blood tests
  • Cardiac catheterization
  • Stress Test

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