This records the electrical activity of the heart. The test takes about ten minutes and is painless. You lay on an examination couch during the test. A technician places several plastic tabs (electrodes) your arms, legs and chest. These electrodes detect the minute electrical signals that are produced by the heart muscle. A wire connects each electrode to a machine that records the signals and prints them out on paper. The ECG record shows if there has been any previous damage to the heart muscle such as that caused by a heart attack. It does not detect the presence of narrowing’s in the coronary arteries. In some patients the ECG can show evidence of a tendency to heart rhythm disturbances. Occasionally the ECG shows an actual heart rhythm change especially if this has been present for some time.