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Electrocardiogram (ECG)

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Our bodies are primarily made of fluids. Body fluids are crucial for the normal operation of our tissues and perform the crucial tasks of supplying nutrients to live cells and removing toxic toxins created by our systems. Other systems that facilitate these activities have been evolved by other organisms. However, complex creatures like humans need fluids like blood and lymph to carry out the mentioned functions.

What is an Electrocardiogram?

An electrocardiogram is referred to as ECG. It provides a graphic representation of the electrical activity of the heart during a cardiac cycle, allowing us to visualize any anomalies and assess the heart’s functionality. Three electrical leads, one to each wrist and the left ankle, are inserted into the patient to create a conventional ECG graph, which continuously tracks the heart’s activity. Passing through our hearts, the human heart creates an electrical impulse that it then produces on its own.


The research of cardiac disorders was transformed 120 years ago with the invention of electrocardiography equipment. Using a mercury capillary electrometer, Augustus Waller made the first attempts to record heartbeats in 1887. The father of cardiac electrocardiography and its founder is regarded to be Willem Einthoven. To record an accurate portrayal of the ECG, he began his research using a mercury capillary electrometer and analytically reduced its distortion. With the addition of a string galvanometer that he created; he further altered the ECG recordings.

Electrocardiograph Process

The ECG test is painless and relatively easy to do. It examines the electrical changes that occur in a person’s heart during each cardiac cycle, including depolarization and repolarization. The actions that must be taken to do an ECG test are as follows: First, several tiny, adhesive electrodes are placed on the patient’s arms, legs, and chest. These electrodes are then wired to the ECG equipment to record the minute variations in the heart’s electrical activity throughout each cardiac cycle.

Types of ECG Tests

ECG testing comes in three primary categories:

  • Resting ECG: This kind of ECG is used to examine the electrical activity of the heart while it is at rest. During this examination, the patient is instructed to relax; after which, their heart rate is recorded.
  • Exercise ECG: With this type of ECG, the electrical activity of the heart during stress or exercise is examined. The patient is asked to cycle or run on a treadmill during this test while their heart rate is being tracked.
  • 24-hour ECG: As implied by the name, this type of ECG lasts for 24 hours. The heart’s electrical impulses are measured using a device called a Holter Monitor.


Different Waves an Electrocardiogram Produces


It stands for the atria’s electrical excitation (or depolarization), which causes both atria to constrict. P-wave characteristics duration of P 0.12 seconds 2.5 mm for P amplitude horizontal front Axis of the P wave: 0 to 750 P waves with notch may be seen in the frontal plane.

QRS Complex 

It symbolizes the ventricles’ repolarization, which sets off their contraction. Complex QRS with a duration of a little longer than ten seconds Different leads and individuals have different QRS amplitudes. QRS voltages are affected by two factors: Dimensions of the ventricular chambers (i.e., the larger the chamber, the larger the voltage) and ventricular chamber proximity to the chest electrodes.


The end of the T-wave indicates the conclusion of systole, and it symbolizes the ventricles returning from their agitated to normal condition (repolarization). Except in the right precordial leads, the T wave typically peaks in the same direction as the QRS wave. The T wave is usually upright in a typical ECG. The heart rate of a person can be calculated by counting the number of QRS complexes that take place in a specific amount of time.

Electrodes and Leads

The ability to record electrical currents is made possible via electrodes, which are conductive pads fastened to the skin. By examining numerous electrodes, an ECG lead—a graphical representation of the electrical activity of the heart—is produced. In other words, the electrical currents detected by various electrodes are analyzed to determine the value of each ECG lead. The 12-lead ECG, often known as a conventional ECG, is created by utilizing 10 electrodes and is known as a 10-lead ECG. The limb leads and chest leads make up the two sets of ECG leads that make up these 12 leads.

Interpretation of ECG

It includes various steps that are mentioned below:

  1. Patient details
  2. Situation details
  3. Rate
  4. Rhythm
  5. Axis
  6. P-wave and P-R interval
  7. Q-wave and QRS complex
  8. ST segment
  9. QT interval
  10. T-wave

Electrocardiograph Importance

  • Diagnosing cardiac arrhythmias (abnormal heartbeats) and identifying coronary artery disorders so that treatment can be started right once.
  • It is used to check on individuals with heart conditions such as diabetes, high blood pressure, or high cholesterol.
  • It is also capable of identifying myocardial infarctions that have already occurred.
  • It can be used to keep an eye on any medication’s side effects.
  • It can be used to examine the functionality of mechanical implants made into a patient’s heart.
  • It can be used to identify non-cardiac illnesses including hypothermia or pulmonary embolism.

ECG’s Uses in Medicine

The main goal of electrocardiography is to gather data regarding the electrical impulses of the heart. This means that it may be able to identify symptoms of earlier heart attacks or even any undiagnosed cardiac ailment. The medical applications of such data are particularly beneficial and provide a greater understanding of illnesses like:

  1. Seizures
  2. Fainting
  3. Ventricular hypertrophy
  4. Arrhythmia
  5. Myocardial infarction or heart attack
  6. Deep vein thrombosis
  7. Pulmonary embolism
  8. Cardiac dysrhythmias

It also shows potential in several other applications, including: 

  1. CTA (computed tomography angiography) and MRA (magnetic resonance angiography of the heart).
  2. Examining adolescents for hypertrophic cardiomyopathy as a part of sports-related deaths such as sudden cardiac death
  3. Identifying structural cardiac disorders
  4. Cardiac stress examinations
  5. Evaluating the severity of the electrolyte abnormalities
  6. Keeping track of heart medication effects
  7. The patient’s biotelemetry
  8. Monitoring the type of anesthesia used is important.

Why is an ECG performed?

  • If you have any blocked or narrowed arteries in your heart (coronary artery disease), it can be used to determine or detect arrhythmias, which can cause chest pain or a heart attack.
  • To determine whether you’ve already experienced a heart attack or not.
  • To check to see whether the medications are having any negative impacts on our biological systems.

Diagnosed by ECG

The following are a few of the numerous heart conditions that an ECG can identify:
Prior heart attacks damage to the heart, such as when one of the heart’s arteries is blocked (coronary occlusion), abnormal position of the heart, abnormal rhythm (arrhythmia) – rapid, slow, or irregular heartbeats, abnormal size of the heart, disturbances of the heart’s conducting system, abnormal rhythm (arrhythmia) – pericarditis or myocarditis, abnormal position of the heart, heart inflammation.

FAQs on Electrocardiogram (ECG)

Question 1: Define ECG.


The ECG abbreviation stands for electrocardiogram. We can visualize any anomalies and evaluate the heart’s functionality thanks to the graphic representation of the electrical activity of the heart during a cardiac cycle that is provided.

Question 2: Explain the waves of the electrocardiograph.


There are three waves of the electrocardiograph:

  • P-wave: depolarization of the atria
  • QRS- complex: depolarization of the ventricles
  • T-wave: repolarization of the ventricles. 

Question 3: Explain the process of the electrocardiograph.


The process of electrocardiograph includes: First, several tiny, adhesive electrodes are placed on the patient’s arms, legs, and chest. These electrodes are then wired to the ECG equipment to record the minute variations in the heart’s electrical activity throughout each cardiac cycle.

Question 4: Write the medical uses of the electrocardiograph.


Medical uses of electrocardiograph:

  1. Chest discomfort or suspicion of a myocardial infarction (heart attack), such as an ST elevated myocardial infarction (STEMI) or a non-ST elevated myocardial infarction (NSTEMI).
  2. Shortness of breath, murmurs, fainting, seizures, strange twists, or arrhythmias, such as palpitations that have just started, as well as monitoring of known cardiac arrhythmias
  3. Drug monitoring (e.g., Digoxin toxicity, drug-induced QT prolongation) and overdose management (e.g., tricyclic overdose).
  4. Test for cardiac stress.

Question 5: Mention the types of ECG tests.


  1. Resting ECG
  2. Exercise ECG
  3. 24-Hour ECG

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Last Updated : 04 Dec, 2022
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