EXERCISE STRESS TESTING IN THE APPARENTLY HEALTHY ADULT
(ANY PERSON CONSIDERING A CONDITIONING PROGRAM OR ANY OTHER CHANGE IN HIS OR HER USUAL LEVEL OF PHYSICAL ACTIVITY SHOULD DETERMINE WHAT HEALTH RISKS ARE INVOLVED. THIS IS AN INDIVIDUAL MATTER, AND CAN ONLY BE DETERMINED AFTER CONSULTATION WITH A PERSONAL PHYSICIAN. IN SOME CASES CERTAIN TESTS MAY BE NECESSARY TO ASSESS THE RISKS OF EXERCISE, AND SUCH RISKS MAY MAKE EXERCISE DANGEROUS OR EVEN FATAL FOR A FEW INDIVIDUALS. CHECK WITH YOUR DOCTOR BEFORE EMBARKING ON ANY EXERCISE PROGRAM).
Exercise stress testing refers to the controlled monitoring of various vital signs, electrocardiogram, and physical findings of an individual while he or she undergoes a pre-defined and carefully monitored amount of graded exercise. As a rule, the form of exercise given involves either a treadmill or a stationary bicycle. The details of performing the test from the patient's perspective are discussed in the Surgery and Procedures section of HealthNet. This discssion will deal with the indications for and implications of such testing in individuals who have no apparent disease of the heart.
The common indication of such testing is either prior to initiation of an exercise program, or as a "screening" maneuver. Occasionally, an individual at very high risk for coronary disease will undergo the procedure to look for occult disease in the absence of symptoms.
Several factors are important in understanding the limitations of exercise testing. First, it is important that the test be properly performed, and that the patient exert sufficient effort to reach 85% of the maximum predicted heart rate. Technical aspects of the EKG and blood pressure recording must be satisfactory. All symptoms must be recorded, and certain drugs such as diuretics and many other blood pressure medications can interfere with the results. There are numerous other factors which must be taken into account, but usually an adequate exercise test can ultimately be achieved if all these factors are understood.
The goal of testing is to determine that it is safe and reasonable for an individual to exercise vigorously. Two major dangers are felt to potentially increase the risk of sudden death during vigorous exercise: sudden disturbances in heart rhythm such as ventricular fibrillation, and a heart attack brought about by the sudden demands of exercise in the face of plugged up coronary arteries. The theory is that by detecting the early signs of such problems during an exercise test, the severe problems can be identified and possibly corrected.
Unfortunately, there are many uncertainties about the ability of exercise testing to meet these goals. In asymptomatic individuals with proven significant coronary artery blockage (detected with catheterization) only 65% have an abnormal exercise test; i.e. 35% or so will be missed by the test. Furthermore, especially in younger patients, and more in women, there is a 10% incidence of falsely positive results, i.e. detected abnormalities on exercise EKG in patients who are then catheterized and found to have essentially normal coronary arteries.
It is imperative to point out that in patients with symptoms or some other reason to suspect that coronary disease may be present even before the test is done, the implications of the results may be totally different. In this setting, various techniques involving radioactive isotopes injected into a vein while the test is performed can enhance the accuracy of the study. At present, few if any authorities are proposing that such radioactive techniques be applied to the asymptomatic patient simply wondering whether he or she can safely exercise.
Certain benefits can be derived from a stress test. First of all, there are a number of patients with marked coronary disease with no symptoms during their sedentary lives, who first come to light during a routine stress test, and are then advised to avoid rigorous exercise or undertake further tests and treatments. Critics point out that most of these patients can be identified with a careful history, risk factor assessment, cholesterol level, and resting EKG. Nonetheless, a few will be found only upon stress testing.
Countering this aspect is the fact that sudden death during exercise may occur despite a recently normal exercise test, with or without the finding of coronary disease at autopsy. Thus, a negative exercise test can be falsely reassuring.
A final unpleasant but real aspect of exercise testing is the medicolegal atmosphere prevailing in many areas of the country, which may lead some physicians to advise stress tests for fear that if something untoward should happen to a patient during exercise, a normal test would provide retrospective support for any litigation which may ensue. This is clearly not a sound medical indication for ordering a test, but must be addressed in any discussion of the topic.
Lastly, the cost of exercise testing ranges from $60.00 to $200.00 or more. Multiplied by tens of thousands annually, this factor cannot be ignored in today's cost-conscious environment.
In the face of such ambiguity, it is difficult to determine whether an exercise stress test should be performed prior to beginning a vigorous exercise program. Only the personal physician who knows the patient individually can give sound advice, and this remains the only proper source of information. Many doctors will suggest that such testing be limited to those people who, by reason of age and risk factors, are more likely to be harboring unsuspected problems. These might include patients with a strong family history of heart disease, diabetes, elevated cholesterol levels, cigarette smoking, or those first exercising over the age of 50 (some authorities would use a lower age limit).
Conclusions
There is insufficient knowledge to determine what benefit, if any, is gained from the performance of a standard exercise stress test in asymptomatic individuals about to embark on a vigorous exercise program. The test has definite limitations, and many authorities advise limiting such testing to those individuals whose risk for coronary disease based on epidemiologic factors is considerably above the average risk. The proper source and only proper source for such advice for any individual is his or her personal physician.
Remember that 50% of men and 67% of women’s first symptom of heart disease is a heart attack or stroke, therefore symptoms are a poor guide for the presence or absence of heart disease. See your doctor, establish your risk and be proactive!
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