What is an Electrocardiography test?

Heart is a vital organ of the body, which is located in the chest cavity, between lungs, in a space behind the breastbone. The heart constantly contracts and relaxes to so as to supply fresh oxygenated blood to various parts of the body. During this process, the heart creates electrical signals, which can be measured to check for any abnormality in heart functioning or the presence of heart diseases.

Electrocardiography is a simple and painless procedure that records electrical signals of the heart while at rest and provides results in the form of an electrocardiogram (ECG/EKG). Occasionally, an ECG is recorded while exercising or performing some activity, which is known as ‘stress testing’.

Electrocardiography is an office- or clinic-based procedure and does not require extensive preparation. It is very commonly used by physicians in clinical practice for the diagnosis of some specific heart diseases. It provides information about the heart rate, rhythm, and whether the heartbeat is regular or irregular. Size and position of heart chambers can also be determined using an ECG.

  1. Why is an ECG test performed?
  2. How do you prepare for ECG test?
  3. How is an ECG test performed?
  4. What do ECG test results indicate?

An ECG test is performed to diagnose various heart diseases. It is usually part of routine check-ups and is done before hospitalisation. A doctor or cardiologist may suggest an ECG if an individual is having one or more of the following symptoms:

These symptoms sometimes indicate a possible problem in the heart. The doctor will use an ECG test to precisely diagnose the issue and its cause or origin.

Besides, an ECG test may be required if someone has a history of heart diseases, such as heart attack or rhythm problems. An ECG is performed before undergoing any surgical procedure or a major operation to check for any pre-existing heart illness that may be affected by the surgery. ECG monitoring is routinely performed in heart disease patients and to check the effectiveness of the ongoing medications for particular heart disease. An ECG is also used to monitor the working of an artificial pacemaker.

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ECG test usually takes about 5-10 minutes. It is commonly performed in an outpatient clinic or office. The doctor, ECG technician, or health care provider who is experienced in ECG testing will instruct the patient to lie down on an examination table.

The technician may trim or shave the hairs at the sites where electrodes are being placed.

No other specific time or preparation, such as fasting, is required. It can be performed before or after a meal. It is important to inform the doctor about any history of heart diseases or any family members with heart disease. In addition, it is also important to notify the doctor about ongoing medications for any condition or disease.

To perform an ECG test:

  • Multiple electrodes are placed on various regions of the chest and limbs (arms and legs).
  • These electrodes are attached to an ECG machine with a monitor through different coloured wires.
  • The electrical activity of heart will be displayed on the monitor screen of the ECG machine.
  • A doctor/technician will then take prints of this recording to check for any abnormality.

Your healthcare professional will analyse ECG records to check for the pattern of electrical activity, which is reflected on the ECG paper in the form of waves.

Normal results:

A normal pattern of waves in the ECG, which is confirmed by the doctor, indicates that the rate and rhythm of the heartbeat are within the normal range and there are no any irregularities or damage to the electrical system of the heart.

There are several heart diseases in which an ECG will show normal results. Hence, only an abnormality that affects the conduction of electrical signals specific to heart diseases can be detected in an ECG.

Abnormal results:

Abnormal results, as confirmed by the doctor, indicate that there may be some underlying problem that is ongoing or has occurred in the past. Sometimes, an instrumental error also leads to an abnormal ECG. Also, athletes may show some abnormal patterns in an ECG, which may not be indicative of any heart disease.

Few heart diseases that show specific ECG patterns and can be diagnosed on the basis of ECG findings with other supportive investigations include:

  • Arrhythmia (problems in the rhythm of heartbeats)
  • Very rapid or slow heartbeats
  • Irregular heartbeats
  • Heart attacks (heart stops functioning suddenly probably due to blocks in the blood vessels that supply blood to the heart)
  • Past episodes of heart attacks
  • Imbalance in some minerals, such as sodium or potassium, in the blood
  • Toxicity of certain medications, such as digitalis
  • Cardiomyopathies (thickening or enlargement of the heart walls due to various causes)
  • Problems in the heart valves

The doctor may suggest further investigations to confirm the diagnosis and to appropriately manage the underlying problem. In case of any doubts or concerns regarding the ECG or the results of an ECG, a discussion with the doctor will substantially help understand the problem and identify the method to manage it.

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. This information is purely from an educational perspective and is in no way a substitute for medical advice from a qualified doctor.


  1. Rehman I, Rehman A. Anatomy, Thorax, Heart. [Updated 2019 Feb 10]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2019 Jan
  2. National Heart, Lung, and Blood Institute: US Department of Health and Human Services; Electrocardiogram, May 2019.
  3. American Heart Association; Electrocardiogram (ECG or EKG), May 2019.
  4. National Health Service [internet]. UK; Electrocardiogram (ECG)
  5. Medline plus [internet]: US National Library of Medicine; Electrocardiogram
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