electrocardiogram

An electrocardiogram is a recording of the tiny electrical signals the heart makes each time it beats, picked up by sticky pads (electrodes) placed on the skin. Think of it like a microphone listening not to sound but to the electrical wave that sweeps through the heart muscle and tells it to squeeze. The machine turns that wave into a familiar tracing of bumps and dips on paper or a screen.

Every heartbeat begins as an electrical impulse in the heart's natural pacemaker, then spreads in an orderly path through the upper chambers (atria) and lower chambers (ventricles). Each part of that journey produces a characteristic deflection on the tracing — the small P wave, the tall QRS complex, and the rounded T wave. By reading the shape, size, and timing of these features, a clinician can judge the rhythm, the conduction, and whether the muscle is healthy or strained.

The ECG is quick, painless, cheap, and widely available, which makes it one of the most useful first tests in cardiology. It is important to remember, though, that it is a snapshot of electrical activity, not of the heart's pumping strength or its plumbing. A normal ECG does not rule out heart disease, and an abnormal one often needs other tests, such as blood work or imaging, to be understood fully.