Exercise electrocardiography testing has been a valuable noninvasive tool for many decades in the evaluation of patients with suspected or known coronary artery disease (CAD) and remains widely utilized. The primary goals of noninvasive stress testing are to aid in the diagnosis of obstructive CAD and to provide risk stratification in an attempt to estimate the probability of myocardial infarction (MI) or death. Although cardiac stress imaging can improve the diagnostic yield and enhance risk stratification beyond exercise electrocardiogram (ECG) variables alone, the standard exercise ECG stress test should play a key role in the evaluation of patients with suspected CAD. The exercise ECG continues to be of great value, especially as the CAD paradigm has shifted from an emphasis on diagnosis to the importance of risk stratification.
It is beyond the scope of this chapter to review the instrumentation, patient preparation, technical considerations, detailed instructions, and interpretation of exercise ECG testing; much of this material is discussed in Chapter 8. Additional information is available for review in prior publications from the American Heart Association.1–4 As a general rule, exercise testing is most commonly performed on a treadmill using a standardized protocol that incrementally increases both the speed and grade of the treadmill in an attempt to achieve maximal cardiac stress. A variety of exercise protocols have been developed, with the Bruce protocol being the most commonly used. Despite the strong clinical validation of the Bruce protocol, the use of a singular protocol for all patients is not appropriate.
Exercise testing is generally a safe and well-tolerated procedure, yet clinical judgment and appropriate supervision should be employed. Death or MI may occur in up to 1 per 2500 tests.2,5 Absolute and relative contraindications to exercise testing and indications for the termination of exercise testing are summarized in Chapter 8.2
The standard criterion of an abnormal exercise ECG response is ST-segment depression (horizontal or down-sloping) ≥1 mm 80 ms after the J-junction. Using the standard 12-lead ECG, ST-segment depression in lead V5 has the greatest diagnostic value for CAD, whereas ST-segment depression confined only to the inferior leads is of little value. ST-segment depression does not localize areas of ischemia. ST-segment elevation in leads without Q waves occurs infrequently. This finding represents transmural ischemia and, as a result, localizes ischemia and the culprit vessel. Exercise-induced ST-segment elevation in lead aVR has been utilized to improve detection of left main or ostial left anterior descending artery disease.6
It is well recognized that certain drugs (beta-blockers and nitrates) reduce test sensitivity, and resting baseline ECG abnormalities (left ventricular hypertrophy with strain, digoxin effect, and ST-segment depression) reduce test specificity and should be taken into consideration for test interpretation. Bayes' theorem states that the greatest yield of testing for diagnostic purposes occurs in patients who have intermediate ...