Electrocardiogram (ECG / EKG)

An electrocardiogram, abbreviated ECG or EKG, is a recording of the electrical activity of the heart taken from the surface of the body. Each heartbeat begins with an electrical impulse that spreads through the heart muscle and triggers it to contract, pumping blood. As this wave of electrical activity travels through the heart, it produces tiny voltage changes at the skin that electrodes can detect.

To record an ECG, electrodes are placed on the skin of the limbs and chest. The instrument measures voltage differences between pairs of electrodes, each pair giving a view, or lead, of the heart's activity from a particular angle. A standard clinical ECG combines several such leads to build a picture of the heart from multiple directions. The output is a trace showing repeating waves that correspond to the stages of each heartbeat: the spread of the impulse through the upper chambers, its passage through the lower chambers, and the recovery of the heart muscle between beats.

The ECG is a key tool for examining the cardiovascular system because the shape, timing, and regularity of these waves reveal how the heart's electrical system is working. A normal trace shows a steady rhythm with consistent intervals, while irregular or abnormal patterns can indicate arrhythmias, in which the heart beats too fast, too slowly, or unevenly, as well as problems with the conduction of the impulse. The test is painless and non-invasive, recording only the heart's own signals without applying current to the body.

Frequently asked questions

What does an ECG measure?

It records the electrical activity that drives each heartbeat, detected as small voltage changes at the skin by electrodes placed on the limbs and chest.

Are ECG and EKG the same thing?

Yes. They are two abbreviations for electrocardiogram and refer to the same test. EKG comes from the German spelling of the word.

What is an arrhythmia?

An arrhythmia is an abnormal heart rhythm, such as beating too quickly, too slowly, or irregularly. ECG patterns help identify these disturbances.