What is it?
An electrocardiogram — abbreviated as EKG or ECG — is a test that measures the electrical activity of the heartbeat. With each beat, an electrical impulse (or “wave”) travels through the heart. This wave causes the muscle to squeeze and pump blood from the heart. A normal heartbeat on ECG will show the timing of the top and lower chambers.
The right and left atria or upper chambers make the first wave called a “P wave” — following a flat line when the electrical impulse goes to the bottom chambers. The right and left bottom chambers or ventricles make the next wave called a “QRS complex.” The final wave or “T wave” represents electrical recovery or return to a resting state for the ventricles.
Why is it done?
An ECG gives two major kinds of information. First, by measuring time intervals on the ECG, a doctor can determine how long the electrical wave takes to pass through the heart. Finding out how long a wave takes to travel from one part of the heart to the next shows if the electrical activity is normal or slow, fast or irregular. Second, by measuring the amount of electrical activity passing through the heart muscle, a cardiologist may be able to find out if parts of the heart are too large or are overworked.
Why would I have this test?
An ECG is one of the most common heart tests. It is the only way of uncovering certain problems with the heart’s electrical impulses. There are a number of reasons why someone may have an ECG, including an irregular heartbeat, shortness of breath when they exert themselves, significantly high blood pressure, palpitations or a suspected heart valve problem. It can also be a useful way of ruling out problems. If your doctor recommends an ECG, think of it as a basic investigation.
What does the test involve?
The ECG is a simple test, with 10 electrodes used to record 12 different views of your heart’s electrical activity. You don’t need to do anything to prepare for it. An electrode is attached to each ankle and wrist with sticky pads and six more are attached to the chest. The patient lies almost flat with the head and chest raised a little. Relaxing for a few minutes before the recording is made is important, as this allows the electrode connections to stabilise and means the ECG will be more reliable. During this time, your details can be recorded on the ECG machine.
Will it hurt?
No. There’s no pain or risk associated with having an electrocardiogram. When the ECG stickers are removed, there may be some minor discomfort.
Are there any after effects?
Very rarely someone may have a slight skin reaction to the electrodes, but normally there are no after effects.
What will it tell my doctor?
An abnormal ECG can tell your doctor if you have any of these issues:
- irregular heartbeat (an arrhythmia)
- problems with the spread of electrical activity within the heart
- an enlarged heart
- areas of the heart with reduced blood supply
- a ‘silent’ heart attack (an interruption to blood flow in the coronary arteries without usual heart attack symptoms).
In an acute emergency, the ECG can help your doctor treat you. For example, the electrical source of a high heart rate may be located, which will determine appropriate treatment.