What Are the Common Causes of an Abnormal ECG?

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  • Written By: M. DePietro
  • Edited By: W. Everett
  • Last Modified Date: 15 January 2019
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An electrocardiogram (ECG) is a medical test done to record the electrical activity of the heart. It is a non-invasive procedure that can be done quickly. An abnormal ECG may be caused by a variety of factors, including an arrhythmia, or a faster or slower than normal heartbeat. Other causes may include a defect in the heart muscle, heart failure, and coronary artery disease.

Within the heart, an electrical signal travels from the upper chamber to the lower chamber, making the heart contract, or beat. Several conditions may change the electrical signal in the heart. An electrocardiogram is one of the first steps to determine problems with the heart. ECG results are available immediately after the procedure, which may help the doctor make a quick diagnosis and begin treatment.

Additional reasons for an abnormal ECG include a current, impending, or past heart attack. Myocardits, which is inflammation of the heart, can also cause ECG abnormalities. Enlargement of the heart and heart valve disease may also lead to abnormal results.

Chemical imbalances in the blood may also cause an ECG to be abnormal. Chemicals in the blood, such as potassium and sodium, are known as electrolytes. The electrolytes are needed for proper heart function. If the levels of certain electrolytes change and become either abnormally high or abnormally low, the heart’s electrical activity may be affected. These changes in electrical activity can lead to an abnormal ECG.


An abnormal electrocardiogram may also be caused by some type of congenital defect in the heart. This type of heart problem is present from birth. Several heart defects may result in an abnormal ECG, such as narrowed valves, holes in the heart, and right ventricular hypertrophy. In some cases, symptoms may not be present, and a person is not aware of the situation until he has an abnormal electrocardiogram.

It is important to understand that although an ECG can detect an abnormal heart rhythm, it may not identify the cause. For instance, an ECG may show tachycardia, which is a fast heart rate, but there are many causes of this abnormal rhythm. After an abnormal ECG, additional tests may be needed determine the cause of the abnormality. Other tests, such as an echocardiogram, stress test, blood work, or a cardiac catheterization, may be needed to determine the cause of an abnormal electrocardiogram.


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Post 3

@Nefertini - ECGs are painless tests and there are no known side effects associated with having one aside from an occasional reaction to the sticky electrode patches used to attach the wires of the ECG machine to your skin. These allergic reactions, though, are typically mild skin rashes that soon go away. The ECG doesn't send any electricity into your body. It just measures your heart's electrical activity and is a very safe test.

Post 2

@Ceptorbi, I agree that ECGs are an important first step in diagnosing and treating heart disease. However, I wonder if there are any possible side effects that could occur when having one of these tests.

Post 1

Most people I know who had an abnormal ECG had to have a stress test soon afterward. Surgery may also result since abnormalities in these tests can indicate blood vessel blockages or other vascular or coronary problems that need treatment. Your heart is a vital organ, so if your doctor wants you to have an ECG get it promptly so any problems can be diagnosed and treated as soon as possible.

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