How an EKG/ECG Works

The electrocardiogram — universally abbreviated as ECG or EKG (from the German Elektrokardiogramm) — is one of the most important diagnostic tools in medicine. It is a simple, painless, non-invasive test that records the electrical activity of the heart over a brief period. Despite its simplicity, the ECG can detect heart attacks, arrhythmias, conduction abnormalities, electrolyte imbalances, drug effects, and structural heart disease findings — making it indispensable in emergency medicine, cardiology, and primary care.

The Electrical Basis Of The Ecg

The heart's pumping action is triggered by electrical impulses. Each cardiac cell has the capacity for electrical depolarization — a rapid shift in the charge across the cell membrane from negative (resting) to positive (activated), followed by repolarization back to the resting state. When cardiac cells depolarize, they contract. When they repolarize, they relax.

These electrical events generate small electrical currents that spread through the body's conductive tissues (blood and body fluids are good conductors) and can be detected at the skin surface. The ECG electrodes placed on the skin detect these tiny voltage differences and amplify them, producing the characteristic waveform tracing.