What is ECG (Electrocardiogram) ?

ECG – Electrocardiogram

ECG stands for electrocardiograms. It’s a simple test that measures the electrical activity of the heartbeat. It is the most commonly used medical study in the assessment of cardiovascular disease. With every beat, an electrical impulse travels through the heart. The waves cause the muscle to squeeze and pump blood from the heart. The process of producing an Electrocardiogram is Electrocardiography, which is a graph of voltage versus time. It’s a recording of the electrical activity of the heart by using electrodes placed on the skin. The heart is a two-stage electrical pump and the electrical activity of it can be measured by electrodes placed on the skin.

The electrodes then will detect the small electrical changes that are the consequences of cardiac muscle depolarization followed by repolarization during the cardiac cycle.

The ECG contains three important components which are :

  • The P wave, which represents the depolarization of atria
  • The QRS complex represents depolarization of ventricles
  • The T wave, which represents the repolarization of ventricles


The overall use of an ECG is to obtain information about the electrical function of the heart. There are many reasons why someone may have ECG, such as

  • Irregular heartbeat
  • Symptoms such as shortness of breath, fainting, seizures
  • High blood pressure
  • Heart valve problem
  • Medication monitoring
  • Cardiac stress testing

The ECG is a test, which includes 10 electrodes used to record 12 different views of the heart’s electrical activity. An electrode is attached to ankles and wrist with sticky pads and six more are attached to the chest.

Electrocardiographs are recorded by machines which consist of a set of electrodes connected to a central unit. Earlier, the ECG machines were constructed with analog electronics, in which the signal drove a motor to print out the signal onto paper. And nowadays, electrocardiographs use analog to digital converters to convert the electrical activity of the heart to a digital signal.

Many of the ECG machines are now portable and commonly include a screen, keyboard, and printer on a small wheeled cart.

ECGs are normally printed on a grid where the horizontal axis represents time and the vertical axis represents voltage.

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Mayuri Bhoyar

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