Exercise stress tests

An exercise stress test is a common test that doctors use to see how the heart performs during exercise. In adults, it is also used to diagnose coronary artery disease. Exercise stress tests are also called exercise tolerance tests, stress tests, exercise electrocardiograms and treadmill tests. If pulmonary function is also monitored during exercise, it is called a cardiopulmonary exercise test (CPET or CPX). This can be combined with myocardial scintigraphy (nuclear stress test), or other measurements.

How does it work?

During an exercise stress test, the patient will wear small metal disks called electrodes. The electrodes are connected to wires called leads, which are connected to a monitor that records the electrical activity of the heart (ECG). This screen can also show pictures from a stress ECG and a nuclear stress test. By watching this screen, doctors can record the heartbeat while the patient exercises. Usually exercise is performed on a bike or a treadmill. However, if movement hampers the investigation (echocardiography, magnetic resonance imaging etc) exercise can be simulated by drugs.

Different types of exercise stress tests

An exercise stress test might also use echocardiography (called a stress echocardiogram) or radioisotope dyes that are injected into the bloodstream (called nuclear stress tests). When these tests are done, doctors can establish more about the structure, function and blood flow of the heart during exercise.

Procedure

The patient must avoid heavy meals and caffeine 4 hours before the test. (Caffeine can be found in some coffees, teas, fizzy drinks, chocolates, and over-the-counter pain relievers.) He should have soft drinks only. In addition, the patient should ask his or her doctor if any medication being taken should be stopped before the test. All patients, if they smoke at all, should refrain from smoking at least 12 hours before an exercise test.
A technician will use an alcohol swab, which might feel a little cold, to clean the areas of the skin where the electrodes will be placed. Next, electrodes will be placed on the chest and back. The electrodes are attached to an electrocardiograph machine, which records the heart's electrical activity. The ECG of a healthy person has a specific pattern, and changes in that pattern will tell doctors whether the patient has a problem with his or her heart. The patient will also wear a blood pressure cuff around the arm, which will be used to monitor blood pressure during the test.
Before the test, doctors will record blood pressure and pulse. They will also record the heart's electrical activity before the patient starts exercising (called a resting ECG). The patient will wear the electrodes during the exercise and for about 10 minutes afterwards.
During the test, the patient will be asked to walk on a treadmill or to ride a stationary bike. Every 2–3 minutes, the doctor or technician will increase the speed and slope of the treadmill or stationary bike, which will make the patient feel as though they are walking or pedalling uphill. The doctor or technician will look for changes in the ECG patterns and blood pressure levels, which will indicate that the patient’s heart is not getting enough oxygen. Other signs of coronary artery disease include chest pain or unusual shortness of breath while the patient is exercising.
It is vitally important that the patient tells the doctor or technician of any symptoms that occur during this exercise. The doctor or technician will then decide whether to stop or continue with the test.
At the end of the test, the doctor will give the patient a cool-down period where he or she might be asked to continue cycling less strenuously, lie down or sit quietly (all under full monitoring), depending on the hospital’s preference. After the test is over, the patient can eat, drink, and return to his or her normal activities.

Recommendations

An exercise stress test is recommended for children with congenital heart disease, in the following cases:

• to assess exercise capacity as a global marker for heart failure,
• to assess deterioration of valvular function during exercise in case of stenosis or regurge,
• to find exercise-induced arrhythmias,
• to assess progression or improvement of atrioventricular heart block,
• to assess peak heart rate in patients with congenital atrioventricular heart block, in patients with ß-blocker treatment, sinus node dysfunction, or in patients with ICD,
• to check pacer function during exercise and correct pacer programming,
• to assess blood pressure reaction on exercise especially in patients with coarctation,
• to find coronary stenosis after coronary surgery (Ross operation, arterial switch operation, aortic root surgery) or after Kawasaki disease,
• to find atherosclerotic coronary artery disease (extremely rare in children, adolescents, or young adults),
• to evaluate unclear exercise-inducible symptoms, and
• to exclude pulmonary disease in patients with unspecific symptoms.
  
  

Value and limitations of the test

The exercise stress test is a safe procedure, presenting only one case of death for every 10 000 tests (data obtained in laboratories with older patients after myocardial infarction) and complications are extremely rare. There are, however, some limitations. The test can not be performed if the patient has had a heart attack recently (less than 3 days prior), or has an unstable angina that is not medically stabilised, or has uncontrolled cardiac arrhythmia which causes haemodynamic deterioration. Furthermore, the test cannot be performed if the patient has severe symptomatic aortic stenosis, unstabilised heart failure, pulmonary embolism, acute pericarditis or myocarditis, aortic dissection, or physical, mental or psychological inability to undergo the test. The test is only of very limited value, if the patient is not willing to really exert himself.  

However, if the patient is motivated and able to get close to his cardiac exercise limit, exercise testing is an excellent procedure for diagnosis, for assessing cardiac function and for predicting the risk of cardiac events. Also, for managing therapy and giving patients advice on how much sport and physical activity they can safely enjoy.