What is an ECG?
An ECG (EKG in North America) is also called an electrocardiogram. This test records the electrical activity of the heart. Classically this graphic representation of electrical current flowing through the heart is recorded on a moving paper, but nowadays it can be digitally recorded and archived in a computer.
An electrical impulse (or “wave”) travels through the heart with each heartbeat. This impulse starts in the right atrium (right upper chamber of the heart), generated by heart’s own independent “Pacemaker” and then travels throughout the heart tissue through a specialized highly sophisticated system of cells – just like “electrical wires”. This electrical current causes the heart muscle to contract, squeeze and pump blood through the heart.
A normal heartbeat on ECG will show a number of “waves” as described below:
The current flowing through the right and left atria (the upper chambers) make the first wave called a “P wave” — following a flat line when the electrical impulse goes to the bottom chambers (ventricles). There is usually a delay at this stage for the upper chambers to contract and force blood into the lower chambers before they start contracting and pumping blood out of their respective chambers. The electrical current passing through the right and left 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, after which the whole process starts again.
A normal average person will have close to 100,000 heartbeats in 24 hrs.
Why is it done?
An ECG gives a range of important information about heart’s health. It can tell doctors about heart rate, rhythm, conduction health of tissues, thickening of heart muscle, size of chambers, inflammation, ischemia (state of oxygen deprivation), heart attack (sudden blockage of blood supply to part of heart muscle), and a host of other important parameters.
There’s no pain or risk associated with having an electrocardiogram. When the ECG stickers are removed, there may be some minor discomfort. There are no harmful effects. The machine only records the ECG. It does not send electricity into the body.