Electrocardiography (ECG or EKG) is a valuable technique for discovering information about the heart. Basically, it is a recording of the electrical activity of your heart, taken from electrodes attached to the chest and often shown on paper or on a monitor in the form of “waves.” Health care providers can interpret these waves to learn a great deal about the presence of heart damage as well as about the blood and oxygen supplied to the heart. Specific ECG patterns provide clues to heart muscle damage and heart chamber enlargement. However, resting ECG results may be normal even in the presence of heart disease, requiring further testing to clarify the actual conditions of the heart.

For patients suspected of having coronary artery disease, the ECG may reveal more information during exercise. This is called stress testing. Graded exercise is performed on a motorized treadmill or stationary bicycle, and the ECG and blood pressure are monitored continuously by a physician. If coronary disease is present, the ECG may become abnormal with increasing grade and speed. The degree and type of ECG abnormality correlate with the presence and severity of coronary disease, and may serve as a guide for treatment and further testing.