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An electrocardiogram (ECG) is a test used to measure the rate and regularity of your heartbeat in order to see if it is functioning properly.

At The London Clinic, our cardiologists can perform several types of ECG to detect abnormal heartbeats. Which ECG you have will depend on your symptoms and your individual circumstances.

What does an ECG measure?

An ECG measures the electrical activity of your heart that causes it to beat. The test can be used to check whether your heart is functioning properly, or whether there may be damage to it as a result of drugs, devices such as pacemakers, an existing heart disorder such as an irregular heartbeat, or a past heart attack.

During an electrocardiogram, a machine called an electrocardiograph records the electrical activity of your heart muscle and translates this as a pattern on a computer screen or on paper. If your heart is functioning normally, the ECG will have a characteristic pattern, while any irregular heartbeat will change the shape of the pattern produced.

Why have an ECG?

There are several reasons why your doctor may recommend that you have an ECG:

  • If you’re about to have an operation that could affect your heart, we need to make sure that we know how well it is working beforehand.
  • After surgery, so your doctor can measure how active you can be as you recover.
  • If you’re experiencing symptoms that may indicate a problem with your heart, such as dizziness, heart palpitations or chest pain.
  • If you’re at an increased risk of heart disease due to family history or because of lifestyle factors such as smoking, being overweight, being diabetic, or having high cholesterol.

A standard ECG

A standard ECG, also called a resting ECG, is taken while you’re at rest. Your doctor will ask you to lie down and will put small sticky electrodes onto your legs, arms and chest. These electrodes contain wires attached to a recording machine.

When your heart beats, the electrical signal that is produced is picked up by the electrodes and transmitted to the recorder, which then produces a pattern on a screen or on paper.

Exercise ECG

If a resting ECG doesn’t give your doctor enough data, he or she may recommend that you have an exercise ECG, also known as a stress test, which is done while you’re exercising in order to see how your heart performs under stress.

As with a resting ECG, an exercise ECG also involves sticking patches on your chest that are connected to a recorder. However, rather than staying still, you’ll be asked to do some kind of exercise such as running on a treadmill or cycling on a stationary bike. Your doctor will start you off gradually and then increase the speed or intensity of the exercise, all while measuring your heartbeat every few minutes.

24-hour ambulatory ECG

Also known as a Holter monitor or an ambulatory ECG, a 24-hour ambulatory ECG involves monitoring your heartbeat over a 24-hour period. During this time, you’ll wear a portable receiver around your waist that is connected to electrodes on your chest. This allows your doctor to monitor your heart’s activity over an extended period as you go about your normal activity.

It is not uncommon for your heart specialist to recommend a longer period of ECG recording beyond 24 hours (36 hours or even 7 days) to increase the chance of detecting a heart rhythm disturbance.

In most cases, your doctor will fit the recorder at a hospital, and you’ll then be able to go home and continue normal activity while keeping a diary of any symptoms you experience.

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