Electrocardiogram (ECG, EKG)

Electrocardiogram is a quick, painless test that records the electrical activity of the heart. It might be taken at rest or during exercise.

It is the standard clinical tool for diagnosing arrhythmias (abnormal rhythms), and to check if the heart is getting enough blood or if areas of the heart are abnormally thick.

Small patches called electrodes are placed on different parts of the body. Then different tracings of the heart's electrical activity are made and permanently recorded on paper or in a computer.

Three major waves of electric signals appear on the ECG. Each one shows a different part of the heartbeat.

• The P wave records the electrical activity of the atria.
• The QRS wave records the electrical activity of the ventricles.
• The T wave records the heart's return to the resting state.

Doctors study the shape and size of the waves, the time between waves, and the rate and regularity of beating. The waves tell a lot about the heart and its rhythm.