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ECG Testing

What is an ECG Test?

An electrocardiogram (ECG) is a medical test that detects cardiac (heart) abnormalities by measuring the electrical activity generated by the heart as it contracts.

The ECG machine that records the patient’s ECG is called an Electrocardiograph.

What are the Benefits of an ECG Test?

Your doctor may use an electrocardiogram to detect:

Irregularities in your heart rhythm (arrhythmias)
Detect blocked or narrowed arteries in your heart (coronary artery disease) that may cause chest pain or heart attacks,
Show structural problems with your heart's chambers
Help manage your heart health after a previous heart attack
Manage the effectiveness of ongoing heart disease treatments, (eg: pacemaker functioning)

How does an Electrocardiograph Work?

The electrocardiograph records the electrical activity of the heart muscle as it's various muscles and values open and shut.

These impulses are displayed as a data trace on a screen or paper. This data is then interpreted by a medical practitioner.

ECGs from healthy hearts have a characteristic shape. Any irregularity in the heart rhythm or damage to the heart muscle can change the electrical activity of the heart so that the shape of the ECG is changed.

Why is an ECG Diagnostic Test Performed?

A doctor may recommend an ECG for people who could be at risk of heart disease. Some reasons a doctor would request this test are:

family history of heart disease,
smoking
overweight,
diabetes,
high cholesterol, or
high blood pressure.

ECGs are often performed to monitor the health of people who have been diagnosed with heart problems, to help assess artificial cardiac pacemakers or to monitor the effects of certain medications on the heart.

Heart Disease Symptoms

If a patient is experiencing symptoms such as:

chest pain
shortness of breath
dizziness
fainting, or
fast or irregular heartbeats (palpitations).

an ECG may also recommend.

What can an ECG Test Help Diagnose?

The results of your ECG will determine what treatment you need if any.

Some heart problems that can be diagnosed by ECG include:

enlargement of the heart
congenital heart defects involving the conducting (electrical) system
abnormal rhythm (arrhythmia) – rapid, slow or irregular heartbeats
damage to the heart such as when one of the heart’s arteries is blocked (coronary occlusion)
poor blood supply to the heart
abnormal position of the heart
heart inflammation – pericarditis or myocarditis
cardiac arrest during the emergency room or intensive care monitoring
disturbances of the heart’s conducting system
imbalances in the blood chemicals (electrolytes) that control heart activity
previous heart attacks.

A person with heart disease may have a normal ECG result if the condition does not cause a disturbance in the electrical activity of the heart. Other diagnostic methods may be recommended if heart disease is suspected.

What Other Diagnostic Information can an ECG Show?

Your doctor will look for a consistent, even heart rhythm and a heart rate between 50 and 100 beats a minute.

Having a faster, slower or irregular heartbeat provides clues about your heart health, including:

Heart rate. Normally, the heart rate can be measured by checking your pulse. An ECG may be helpful if your pulse is difficult to feel or too fast or too irregular to count accurately. An ECG can help your doctor identify an unusually fast heart rate (tachycardia) or an unusually slow heart rate (bradycardia).
Heart rhythm. An ECG can show heart rhythm irregularities (arrhythmias). These conditions may occur when any part of the heart's electrical system malfunctions. In other cases, medications, such as beta-blockers, cocaine, amphetamines, and over-the-counter cold and allergy drugs, can trigger arrhythmias.
Heart attack. An ECG can show evidence of a previous heart attack or one that's in progress. The patterns on the ECG may indicate which part of your heart has been damaged, as well as the extent of the damage.
Inadequate blood and oxygen supply to the heart. An ECG done while you're having symptoms can help your doctor determine whether chest pain is caused by reduced blood flow to the heart muscle, such as with the chest pain of unstable angina.
Structural abnormalities. An ECG can provide clues about enlargement of the chambers or walls of the heart, heart defects and other heart problems.

Preparation for an ECG Test

Preparing for an ECG Test you will:

No need to restrict food or drink.
Ensure the doctor is aware of your regular medications,
Communicate any allergies to adhesive tapes or latex.
Wear suitable clothing (separate top and bottom) to allow easy access to the chest

During an ECG Test

During an ECG Test will:

Where necessary the selected electrode sites may be shaved.
Electrodes (sensors) are attached to the chest, arms and legs with suction cups or sticky gel.
The electrodes detect electrical currents generated by the heart – these are measured and recorded by the electrocardiograph.
Last a few minutes, and you should be able to go home soon afterwards

Results

An ECG recording machine will usually show your heart rhythm and electrical activity as a graph displayed electronically or printed on paper.

For an ambulatory ECG, the ECG machine will store the information about your heart electronically, which can be accessed by a doctor when the test is complete.

You may not be able to get the results of your ECG immediately. The recordings may need to be looked at by a specialist doctor to see if there are signs of a potential problem.

Other tests may also be needed before it's possible to tell you whether there's a problem.

You may need to visit the hospital, clinic or your GP a few days later to discuss your results with a doctor.