How to distinguish between normal and abnormal ECG signals

normal vs abnormal ecg signals

An electrocardiogram (ECG) is a test that measures the heart’s electrical activity. It is a non-invasive test involving electrodes on the skin to detect and record the electrical impulses that cause the heart to beat. The ECG is an essential diagnostic tool for identifying various heart conditions, including abnormal heart rhythms, heart attacks, and heart disease.

The electrocardiogram (ECG) tool is a crucial diagnostic and treatment tool for identifying and managing various cardiac-related diseases. It provides vital information about the status of a disease and a patient’s condition by analyzing the ECG signals generated by the heart. The ECG signal comprises segments, intervals, and waves, evaluated based on size and duration. These components help determine the cardiac rhythm type, and any deviation from the expected norm may indicate an abnormal heart rhythm called arrhythmia or dysrhythmia.    

One of the critical steps in analyzing ECG signals is the extraction of the QRS complex, which represents the depolarization of the ventricles. As per an article published in Research Gate, the Pan-Tompkins algorithm, a well-known method, is often used for this purpose. This algorithm involves several stages, including passing the ECG signal through a low-pass filter and a high-pass filter to remove noise from the signal. The filtered signal is then processed through derivative, squaring, integration, and decision-making circuits, extracting the QRS complex from the ECG signal.    

Accurate extraction of the QRS complex is crucial for identifying abnormal cardiac rhythms and assisting in diagnosing and treating various cardiac conditions. In this paper, we will discuss the importance of the ECG tool in diagnosing and treating cardiac diseases, the role of different components in evaluating ECG signals, and the significance of the Pan-Tompkins algorithm in extracting the QRS complex from the ECG signal. This blog will discuss how to distinguish between normal and abnormal ECG signals.    

Normal ECG Signal    

A standard ECG signal consists of several waveforms representing the heart’s electrical activity. These waveforms include the P wave, QRS complex, and T wave. The P wave represents the electrical activity that causes the atria to contract. The QRS complex represents the electrical activity that causes the ventricles to contract. The T wave represents the electrical activity that occurs during the recovery period of the ventricles.    

In an average ECG signal, the following criteria are met:  

  • The heart rate is between 60 and 100 beats per minute.  
  • The P wave precedes the QRS complex and follows the T wave.  
  • The PR interval is between 0.12 and 0.20 seconds.  
  • The QRS complex duration is between 0.06 and 0.10 seconds.  
  • The ST segment is flat and is not elevated or depressed.  

Abnormal ECG Signal    

An abnormal ECG signal can indicate various heart conditions, including arrhythmias, heart attacks, and heart disease. Some common abnormalities that can be seen on an ECG include the following:  

  • Atrial fibrillation: Irregular and rapid heartbeats that originate in the atria. 
  • Bradycardia: A slow heart rate, typically less than 60 beats per minute. 
  • Tachycardia: A fast heart rate, usually exceeding 100 beats per minute. 
  • Myocardial infarction: Occurs when blood flow to the heart muscle is blocked, resulting in a heart attack. 
  • QT prolongation: A lengthening of the QT interval can cause an irregular heart rhythm known as Torsades de Pointes.   

It is important to note that some medications and electrolyte imbalances can also cause abnormal ECG signals.    



Distinguishing between Normal and Abnormal ECG Signals    

A healthcare professional will evaluate the various waveforms and intervals on the ECG tracing to distinguish between normal and abnormal ECG signals. They will look for any deviations from the standard criteria mentioned above. They may also compare the ECG to previous ECGs to look for changes over time.

In addition to the ECG, other diagnostic tests may be ordered, such as a stress test, echocardiogram, or cardiac catheterization, to confirm a diagnosis. In conclusion, an ECG is essential for identifying various heart conditions. Understanding how to distinguish between normal and abnormal ECG signals is crucial in diagnosing and treating these conditions. If you have any concerns about your heart health, speak with your healthcare provider.  

One Response

Leave a Reply


Free CME credits

Both our subscription plans include Free CME/CPD AMA PRA Category 1 credits.

Digital Certificate PDF

On course completion, you will receive a full-sized presentation quality digital certificate.

medtigo Simulation

A dynamic medical simulation platform designed to train healthcare professionals and students to effectively run code situations through an immersive hands-on experience in a live, interactive 3D environment.

medtigo Points

medtigo points is our unique point redemption system created to award users for interacting on our site. These points can be redeemed for special discounts on the medtigo marketplace as well as towards the membership cost itself.
  • Registration with medtigo = 10 points
  • 1 visit to medtigo’s website = 1 point
  • Interacting with medtigo posts (through comments/clinical cases etc.) = 5 points
  • Attempting a game = 1 point
  • Community Forum post/reply = 5 points

    *Redemption of points can occur only through the medtigo marketplace, courses, or simulation system. Money will not be credited to your bank account. 10 points = $1.

All Your Certificates in One Place

When you have your licenses, certificates and CMEs in one place, it's easier to track your career growth. You can easily share these with hospitals as well, using your medtigo app.

Our Certificate Courses