An EKG, also called an ECG or electrocardiogram, is a test that records the electrical activity of the heart. It is commonly used to evaluate heart rhythm, heart rate, and certain signs of heart strain or injury. An EKG can be very helpful, but it does not tell everything about the heart. What does an EKG show? An EKG can show: Heart rate Whether the rhythm is regular or irregular Electrical signal patterns Certain rhythm abnormalities Possible signs of a current or prior hea