What Does An Abnormal ECG Mean?

What is an ECG?

An electrocardiogram (ECG) is a first-line test used by your Cardiologist to obtain valuable information about your heart health by measuring the electrical activity of the heart. The ECG allows your Cardiologist to detect heart attacks, heart rhythm problems, and other heart-related conditions.

An ECG involves the use of small electrodes attached to your chest, arms and legs. These electrodes detect electrical signals produced by the heart, which are then translated and recorded by a machine, showing your heart rate, heart rhythm and electrical waveforms.

What is considered a “normal” ECG result?

1. Heart rate: A normal resting heart rate for adults is between 60 and 100 beats per minute.

2. Rhythm: A normal ECG rhythm is described as sinus rhythm (regular) and without significant pauses or extra beats.

3. Waveform: A normal ECG waveform includes the:

    • P wave — the electrical activity that causes the atria to contract
    • QRS complex — the electrical activity that causes the ventricles to contract
    • T wave — this represents the ventricles returning to their resting state

4. Intervals: Intervals refer to the duration of time that includes one segment and one or more waves:

    • PR interval — the time it takes for the electrical signal to travel from the atria to the ventricles (generally between 120 and 200 milliseconds)
    • QT interval — the time it takes for the ventricles to contract and relax, should be within normal limits

What is an abnormal ECG result?

An abnormal ECG result could mean anything from an abnormal heart rate, irregular rhythm, abnormal waveforms or abnormal intervals:

1. Abnormal heart rate: A heart rate that is faster or slower than what is considered normal could be a sign of atrial fibrillation

2. Abnormal heart rhythm: An irregular heart rhythm refers to an ECG reading with long pauses or extra beats.

3. Abnormal waveform: Abnormalities in the waveforms of an ECG reading could mean that the electrical signals in the heart are not being transmitted or conducted properly.

4. Abnormal intervals: A prolonged PR interval can indicate a problem with the electrical conduction system of the heart (delayed conduction of the SA node), while a prolonged QT can indicate a problem with the lower chambers of the heart(ventricles).

What does an abnormal ECG mean?

There are many reasons why an ECG is abnormal, and it is important to note that not all of these indicate a serious heart problem. It does, however, mean that further testing should be done to rule out certain heart conditions. These include:

1. Arrhythmias: An ECG can detect abnormalities in the heart’s rate and rhythm, which could indicate heart rhythm problems such as atrial fibrillation.

2. Coronary Artery Disease (CAD): An abnormal ECG may also indicate the presence of coronary artery disease: plaque build-up causing blockage in the arteries that supply blood to the heart.

3. Electrolyte imbalances: An abnormal ECG may indicate potential electrolyte imbalances, such as abnormal potassium levels.

4. Structural heart problems: An abnormal ECG may suggest underlying structural abnormalities of the heart, such as enlarged heart muscles, abnormally functioning heart valves, or congenital heart defects.

An ECG result is not definitive, but it is a quick and non-invasive way of getting a baseline understanding of your heart health and helps your doctor decide whether further diagnostic tests are. These may include blood tests, exercise treadmill stress tests, an echocardiography and more.


An ECG is an essential part of your heart health assessment. Hopefully this article has provided you a basic understanding of what an ECG is. If you have an abnormal ECG, during your clinical evaluation, your Cardiologist will be able to explain to you your ECG findings and discuss its significance.

If you experience any symptoms such as heart palpitations, a radiating pain in your chest or would simply like to get your heart checked, please consult your Cardiologist for a proper analysis.

How can we help you?

We offer consultation for a comprehensive range of cardiac diagnostic tests and treatment plans.

Dr Joshua Loh

Senior Consultant Interventional Cardiologist

Medical Director at Capital Heart Centre, Dr Joshua Loh has more than 15 years of experience in the field of cardiology.

He has extensive experience in the treatment of complex coronary and interventional procedures.