Electrodes pass impulses to a machine that records wave forms on graph paper.
They show the speed and strength of the impulses as they travel through the heart. The test is done in 10 minutes in a doctor's office. Some patients, especially with sporadic symptoms, may be asked to wear a portable monitor for a continuous recording. A stress test is an EKG taken during exercise, usually on a treadmill or stationary bike, sometimes until symptoms occur. Stress tests diagnose the cause of chest pain, assess abnormal heartbeats, monitor the effectiveness of drugs and evaluate the safety of beginning an exercise program, especially after a heart attack or surgery.