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Diagnostic Tests – Stress (Exercise Tolerance) Testing
What Is Stress (Exercise Tolerance) Testing?
Stress testing, also known as exercise tolerance testing, is a noninvasive method used to detect myocardial ischemia without immediately resorting to coronary angiography. It is performed in patients whose chest pain does not provide a definite diagnosis of ischemic heart disease. By increasing the heart’s workload, the test helps determine whether the coronary arteries can supply enough blood to meet the myocardial oxygen demand. If blood flow is inadequate, electrical or symptomatic signs of ischemia will appear.
How Is the Test Performed?
During the test, the patient exercises—usually on a treadmill or stationary bicycle—until they reach greater than 80% of their maximum predicted heart rate, calculated as 220 minus age. Throughout the exercise, clinicians closely monitor the EKG for changes suggestive of ischemia, most notably ST-segment depression. In addition to EKG changes, development of hypotension, light-headedness, shortness of breath, or typical chest pain during the test is also considered evidence of ischemia. The test continues until symptoms appear, the target heart rate is achieved, or the patient cannot continue safely.
When Should Stress Testing Be Used?
Stress testing is the correct choice in several clinical scenarios where ischemia is suspected but not definitively established:
- When the patient’s chest pain is atypical and the clinical story is equivocal for ischemic heart disease.
- After a myocardial infarction, to determine whether there is a need for coronary angiography or further intervention.
- In patients already taking anti-ischemic medications, to assess whether the dosages are sufficient to prevent ischemia during exertion.
In cases like these, stress testing provides valuable diagnostic and prognostic information without immediately requiring invasive procedures.
What Is the Most Accurate Test After a Positive Stress Test?
If a stress test is abnormal, the next step—the most accurate confirmatory test—is coronary angiography. Angiography provides direct visualization of the coronary arteries, allowing identification of the exact location and severity of any obstructive lesions. It is the gold standard test when a stress test suggests ischemia and further evaluation is required.
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