What is electrocardiogram (ECG)? Understanding the Basics

Table of contents

  • Introduction
  • What is an electrocardiogram (ECG)?
  • Why might I need an electrocardiogram?
  • How do I get ready for an electrocardiogram?
  • What types of ECG tests are done?
  • How to read ECG?
  • What are the risks of an ECG?
  • Abnormalities on ECG
  • Conclusion
Key Takeaways

1. ECG is a key tool that reveals your heart's rhythm, rate, and overall health.

2. If you face symptoms like chest pain, palpitations, dizziness, or breathlessness, your doctor may suggest an ECG for a clearer understanding.

3. ECG helps spot heart issues early, enabling timely action and effective management.


Heart diseases are a global threat, and early diagnosis is the key to their effective management. ECG is a crucial tool in uncovering heart conditions. Read on for insights into the significance of timely detection and empower yourself for a heart-healthy life.

So let us begin with understanding what is an electrocardiogram.

What is an electrocardiogram?

Our heart is a pump that circulates blood throughout the body. It works by responding to electric signals that are generated in the sinoatrial (SA) node-a small, specialised group of cells located in the right upper chamber of the heart. These electric signals control the heart's rhythm, speed, and the strength of contractions (how hard the heart squeezes).

 SA node of the heart

An electrocardiogram test, also known as an ECG or EKG records these signals. It helps to understand your heart's performance by recording its rate (how often it beats) and rhythm (how regularly it beats). 

ECGs are painless. It is a quick way to check your heart's performance at the hospital, doctor’s clinic or even with personal devices like smartwatches.

In traditional ECGs, small patches called electrodes are attached to the skin on your chest, arms, and legs and connected to the ECG machine. It records the heart's electrical activity which is then printed out as a report.

ECG examination of the heart

Why might I need an electrocardiogram?

Your doctor might order an ECG check-up to determine

  • Irregular heartbeats (arrhythmias) 
  • Blocked or narrow arteries in the heart 
  • A previous heart attack
  • Treatment effectiveness of implanted devices or medicines in managing heart diseases
  • Structural changes in the heart such as an enlarged heart or heart defects.
  • Cause for symptoms such as chest pain, breathlessness, fatigue, difficulty while exercising, palpitations, rapid pulse, dizziness, etc

How do I get ready for an electrocardiogram?

Getting ready for an ECG is simple. Your doctor or technician will explain the test and answer any questions you have. Follow the below steps 

How do I get ready for an electrocardiogram

What types of electrocardiogram tests are done?

The three types of ECG tests include:

  • Resting ECG: It measures the heart's electrical activity at rest. You need to remain still and avoid movements, coughing, or shaking to avoid faulty results. 
  • Exercise ECG (Stress Test): This measures the heart activity during physical activity, usually on an exercise bike. Blood pressure is also monitored during this test. It helps identify issues that may only appear during exercise. The test is stopped if any irregularities in the ECG occur. 
  • Holter Monitor: This records heart activity over 24 hours. Small electrodes on the chest are connected to a portable device worn on a belt or around the neck. The recorded data, along with information about your daily activities, like physical activity and sleep, are then analysed by a computer at the doctor's office. It is useful for capturing occasional irregular heartbeats that do not show up in regular ECG.

How to read an electrocardiogram test?

 ECG interpretation
 ECG interpretation

When your heart beats normally, the ECG shows a specific pattern. 

  • The P wave represents the electrical signal spreading across the upper chambers of your heart, making it squeeze and pump blood into the lower chambers.
  • PR Segment: It represents a brief pause, allowing the electrical signal to travel from the upper to the lower chambers of the heart.
  • PR Interval: It shows how long the electrical signal takes to move through the upper chambers to the lower chambers of the heart.
  • The bigger waves (Q, R, and S) called the QRS complex, show the lower chambers of the heart squeezing.
  • The T wave indicates the electrical signal has stopped, and the lower part relaxes. 
  • The ST segment shows a pause after the heart squeezes and before it relaxes. 
  • QT Interval: It is the time from the start of the QRS complex to the end of the T wave. It represents the entire time it takes for the heart to squeeze and then relax.

This cycle keeps your heart working steadily, pumping blood as it should. Changes in these ECG waves may indicate potential issues with the heart’s electrical system. 

What are the risks of an electrocardiogram test?

An ECG or EKG is a generally safe and non-invasive procedure. In some patients it might cause:

  • Skin irritation 
  • Faulty results especially in pregnancy, obesity, certain medications, electrolyte imbalance, smoking and exercising before the test, etc.

Abnormalities on ECG

These may include

  • Unusual Heart Rate: If your heart beats too fast or too slow, it might suggest a condition known as arrhythmia. 
  • Abnormal Heart Rhythm: If your ECG shows irregularities, like long pauses or extra beats, it could mean your heart rhythm is not regular.
  • Unusual Wave Patterns: If the waves on your ECG look different, it might suggest that the electrical signals in your heart are not flowing correctly.
  • Irregular Time Gaps: A longer PR interval could mean an issue with the upper part of your heart's electrical system, while a prolonged QT interval might indicate a problem with the lower chambers. 
Abnormalities on ECG


ECG is a simple, painless test for diagnosing various heart issues. It helps to understand defects in the heart’s electrical system. Understanding the basics of ECG interpretation, from heart rate, and rhythm to electrocardiography wave patterns, empowers you to take charge of your health. 

For ongoing heart care, we recommend downloading our Aware app- a reliable companion on your path to a healthy heart. By staying informed and proactive, you can actively contribute to your heart's vitality. Don't forget, that a heart-healthy lifestyle and regular check-ups can pave the way for a longer, healthier life. 

About the Author
Dr. Satish Madiraju, a renowned cardiologist is passionate about consumer heart health and is on a mission to prevent a million heart attacks. He shares his expertise not only on heart health but also on leadership, digital health, and improving patient experience.
Share this post
Aware App Icon
Download Aware: The #1 health app for a strong and healthy heart.

Related Articles

Heart Attack Prevention

Your Ultimate Guide to Dark Chocolate Side Effects and Benefits.

Explore dark chocolate’s side effects, benefits, and eating tips. If you're a fan of intense dark chocolates, this blog is for you!
Lucky Mehtani, B. Pharm.
February 9, 2024
Heart Attack Prevention

Living well with Congestive Heart Failure (CHF)

Your guide to understanding and conquering Congestive Heart Failure (CHF) causes, diagnosis, and current management options.
Dr. Satish Madiraju, MD, FACC, FACP, FSVM
February 2, 2024
Heart Attack Prevention

What is electrocardiogram (ECG)? Understanding the Basics

What is electrocardiogram (ECG), and how to interpret it for better heart health? Understand ECG testing in diagnosing different heart conditions.
Dr. Satish Madiraju, MD, FACC, FACP, FSVM
January 22, 2024