An exercise stress test is a special type of test that is used to measure the heart’s tolerance for exercise and to detect various forms of heart disease. The most common type of exercise stress test combines some form of mild exercise with an electrocardiogram (EKG) to measure the heart’s activity both at rest and while working. This test is administered on an outpatient basis, often in a hospital, clinic or physician’s office. It is noninvasive, generally safe and painless. Exercise stress tests may also be performed with echocardiography or nuclear imaging techniques to gain additional diagnostic information.

During an EKG stress test, the EKG records the heart’s electrical activity as a graph on a moving strip of paper or video monitor. The highly sensitive electrocardiograph machine measures the heart’s rhythms and electrical impulses. The painless EKG is done while the patient is exercising in a controlled manner on a treadmill or stationary bicycle at varied speeds and elevations. This increases the heart's need for oxygenated blood, which makes it easier for physicians to provoke symptoms or signs that would indicate heart disease.

Many people with coronary artery disease will eventually have abnormal EKG readings. However, because a non-stress EKG is done while the patient is at rest, certain abnormalities that might occur during periods of exertion may not be detected. Because it is common to see this false-negative result (i.e., the EKG does not detect any damage or abnormality that is present), a non-stress EKG may not be adequate to rule out suspected heart disease, and an exercise stress test may be ordered.

During an exercise stress test, the physician will evaluate the patient’s general state of health and the heart’s reaction to exercise. As the intensity of the workout increases, the patient’s heart rate, blood pressure and general appearance are monitored both by the heart monitor (EKG) and the physician. The higher the level of exercise, the harder the heart has to work and the more blood flow is needed. This test allows the physician to evaluate whether the blood supply to the heart is sufficient during different levels of exercise intensity. Certain changes in the EKG pattern or in blood pressure will help the physician measure blood flow to the heart and evaluate the health of the coronary arteries.

EKG stress tests are noninvasive, generally quick, safe and painless. A physician may recommend an exercise stress test for a number of reasons:

• To screen for coronary artery disease in some patients who do not have symptoms. Although general screening is not usually recommended, several recent research studies indicate exercise stress tests can identify coronary problems in patients without symptoms.
  
  
• To gauge exercise capacity in heart failure patients who are being considered for a heart transplant.
  
  
• To diagnose heart-related causes of symptoms such as chest pain, shortness of breath or lightheadedness. Angina, a type of chest pain caused by lack of oxygen-rich blood in the heart, is a classic symptom of coronary artery disease. Stable angina occurs at predictable times, such as increased exertion. During a stress test, a physician might attempt to provoke a bout of stable angina to help determine if a patient is suffering from coronary artery disease.
  
  
• To determine a safe level of exercise in cardiac patients who wish to increase their level of physical activity.
  
  
• To check the effectiveness of a balloon angioplasty (a procedure in which plaque in the arteries is pushed back against the artery walls to make more room for blood flow), or other procedures that have been performed.
  
  
• To predict future risk of dangerous heart-related conditions, such as heart attack.
  
  
• To provide an objective assessment of functional capacity in patients whose symptoms do not match the severity of the underlying heart disease.

Although the exercise stress test is generally safe, it is not without a small risk to certain patients. According to a 2001 statement by the American Heart Association, an exercise stress test should not be ordered for patients who have: 

• Experienced a heart attack in the previous two days
  
  
• Unstable angina, or chest pain that occurs at unpredictable times and is considered a very serious warning sign of an impending heart attack
  
  
• Uncontrolled arrhythmias, or abnormal heart rhythms
  
  
• Severe aortic heart valve disease with symptoms
  
  
• Uncontrolled heart failure with symptoms
  
  
• Endocarditis, acute myocarditis or pericarditis
  
  
• Acute aortic dissection
  
  
• Acute pulmonary embolism
  
  
• Other non-cardiac disorders that may be aggravated by exercise