EKG, also called EKG or ECG, is a simple, painless test that records the heart's electrical activity. An EKG shows: How fast your heart is beating. Whether the rhythm of your heartbeat is normal. The strength and timing of electrical signals as they pass through each part of your heart. Doctors use EKGs to detect and study many heart problems such as heart attacks, arrhythmia and other disorders that affect heart function.