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Electrocardiogram (ECG)

What is Electrocardiogram (ECG)?

An electrocardiogram (ECG) is a graphic record produced by an electrocardiograph that provides details about one’s heart rate and rhythm and any other related abnormalities; it depicts if the heart has enlarged due to hypertension (high blood pressure) or evidence of a myocardial infarction previously (heart attack if any). Electrocardiogram (ECG) is one of the most common and effective tests for all drugs. It is easy to perform, non-invasive, yields outcomes instantly and is useful to identify hundreds of heart conditions.

ECGs from healthy hearts have a distinct, characteristic shape. Any inconsistency in the rhythm of the heart or damage to the heart muscle can alter the heart’s electrical activity thereby changing the shape on the ECG.

Table of Content:

ECG Test

ECG test can be used to check the rhythm of the heart and the electrical movement. The electrical signals are detected due to the attachment of the sensors to the skin which are generated as and when the heart beats. These signals are recorded by the machine and examined by a medical practitioner for an unusual signs.

Who is recommended an ECG test?

ECG test is a common measure in monitoring the health of those diagnosed with heart ailments to aid in assessing the artificial cardiac pacemakers or in detecting the effects of some medications on the vital organ – the heart.

Doctor suggests ECG for those who are at a risk of heart diseases (family history of heart disorders), those who smoke, are obese, have diabetes, high blood pressure or cholesterol. ECG test could also be suggested to those that show the following signs and symptoms –

  • Shortness of breath
  • Dizziness
  • Chest pain
  • Palpitations

Why ECG is done?

Two main forms of data are given by an ECG –

  • Determining time taken for electromagnetic pulse to travel through the heart
  • To find if areas of heart are overworked or too large

First, a surgeon will determine how long it takes for the electromagnetic pulse to travel through the heart by calculating time intervals on the ECG. Whether the electrical activity is natural or sluggish, fast or erratic, figuring out how long a pulse takes to travel from one part of the heart to the next.

Second, a cardiologist may be able to find out if areas of the heart are too large or overworked by measuring the amount of electrical activity that flows through the heart muscle. Ten electrodes are mounted on the arms of the patient and on the top of the heart in a traditional 12-lead ECG. The average strength of the electrical potential of the heart is then calculated from 12 different angles (“leads”) and reported over a period of time (usually 10 seconds). Throughout the cardiac phase, the total intensity and trajectory of the electrical depolarization of the heart are observed at each moment.

Evidence does not support the use of ECGs as an attempt for prevention among those without symptoms or at low risk of cardiovascular disease. This is because an ECG may incorrectly suggest a concern, leading to misdiagnosis, initiation for invasive procedures, and overtreatment. Individuals working in certain sensitive professions, such as aeroplane pilots, may need to have an ECG as part of their routine safety evaluations.

Objective of ECG 

The overall objective of an ECG is to obtain information about the heart’s electrical function. For this material, clinical needs are diverse and often need to be paired with knowledge of the heart anatomy and symptoms of physical examination to be understood. Some signs for an ECG are as follows:

An ECG is used to measure:

  • Any heart damage and weaknesses in various parts of the heart muscle
  • How quickly your heart beats and whether it normally beats
  • The effects of drugs or devices used to control your heart (such as a pacemaker)
  • The size and position of your heart chambers
  • To diagnose abnormal heart rhythms

Also Check: Systole and Diastole 

How is an ECG carried out? – ECG Test Procedure

An ECG is a safe and painless test that usually takes only a few minutes.

Using adhesive patches to bind leads from an electrocardiograph system to the skin on your hands, legs, and chest. This leads to your heart reading signals and sending this information to the electrocardiograph. On a paper strip or on a monitor, the computer then prints the text.

Before the patches are attached, one is usually asked to remove the upper clothing, the chest needs to be cleaned or shaved. Once the patches are placed, hospital staff offers a gown to cover self. The ECG test takes about only a few minutes.

There are three primary ECG types:

Resting ECG If your doctor is interested in how your heart works while you’re in rest, you’ll be asked to lie down and relax while recording your heartbeat.
Exercise ECG The doctor may be interested in how the heart responds to movement and you may be asked to walk or run on a treadmill or cycle on an exercise bike when monitoring your pulse.
24-hour ECG Often checking your rhythm throughout the day may be useful, so you’ll be asked to wear a portable electrocardiographic unit. A doctor will read the notes from the device when you access the machine.

The Electrocardiogram Wave

An ECG has three main components: the P wave, which denotes depolarising atria; the QRS complex, denotes the depolarization of the ventricles; and the T wave represents repolarising ventricles.

During each pulse, a healthy heart has an ordered process of depolarization that starts with pacemaker cells in the sinoatrial node, extends throughout the atrium, and moves through the atrioventricular node into its bundle and into the fibres of Purkinje, spreading throughout the ventricles and to the left.

The electrical activity occurs in a small patch of pacemaker cells called the sinus node during a regular heartbeat. This produces a small blip called the P wave when the impulse stimulates the atria. It then activates the main pumping chambers, the ventricles, and produces the large up-and-down in the middle, the QRS complex. The last T wave is a time of regeneration as the impulse reverses over the ventricles and travels back.

If the heart is beating normally, it takes about a second (approximately 60 heartbeats per minute) for the entire cycle.

Electrocardiogram Wave



In the normal ECG pattern, there is a regular pattern of The P wave, QRS complex, and T wave. They occur in a sequence.



When the heart muscle doesn’t get enough blood with oxygen, it causes discomfort, that feels like putting pressure on the chest. This condition is termed as Angina pain. It can sometimes be misunderstood as indigestion. As you can see in the figure above (see arrow), the ST-segment dips, which normally is flat.

Serious heart attack

Serious heart attack

The elevated ST segment of the ECG is an indication of a serious heart attack. In the medical terminology, it is referred to as “STEMI”, which needs immediate attention. Generally, the ST segment remains flat.

Atrial fibrillation

Atrial fibrillation

Atrial fibrillation is the state when the atria and the ventricles show a lack of coordination of movement. It results in rapid heartbeat, weakness and shortness of breath. On ECG, it is represented by jumpy baseline and the P wave disappears.

Difference between ECG and EKG test

An ECG and an EKG have no difference. Hence, if an ECG is similar to an EKG, then why the difference in abbreviations? The answer is—when translated into the German language, the word electrocardiogram is spelt Elektro-kardiographie. EKG is just the way few prefer to say ECG based on this translation.

Also Read:

Frequently Asked Questions


What is an electrocardiogram (ECG) test?

Electrocardiogram (ECG) is defined as a recording of the heart’s electrical activity. It is simple test, a graphic record produced by an electrocardiograph provides details about one’s heart rate and rhythm and depicts if the heart has enlarged due to hypertension or evidence of myocardial infarction (if any).


What are the three components of ECG?

An ECG has three main components – the P wave denotes the depolarization of the atria; the QRS complex denotes depolarization of the ventricles, and the T wave represents repolarising ventricles.


What does an abnormal ECG mean?

An abnormal ECG mainly denotes a variation in the heart rate or heart rhythm. For example, an irregular QRS complex without a P wave denotes atrial fibrillation. Likewise, an elevated ST segment in an ECG is an indication of a serious heart attack.

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