An electrocardiogram (ECG / EKG) is a recording of the small electric waves being generated during heart activity.

The waves are registered by electrodes placed on certain parts of the body.

The electrocardiogram is painless and is usually done when the patient is resting. However, if there is any concern that a patient's symptoms may be caused by coronary artery disease the test is done while the patient is on an exercise bike or treadmill.

An ECG can be used to assess if the patient has had a heart attack or evidence of a previous heart attack.

An ECG can be used to monitor the effect of medicines used for coronary artery disease.

An ECG reveals rhythm problems such as the cause of a slow or fast heart beat.