Fernando Boccalandro, MD, FACC, FSCAI

1. What is the purpose of exercise stress testing (EST) and how can a patient exercise during stress testing?

    EST using electrocardiography (ECG) is routinely performed to diagnose myocardial ischemia, estimate prognosis, evaluate the outcome of therapy, and assess cardiopulmonary reserve. Exercise is used as a physiological stress to detect cardiac abnormalities that are not present at rest. They are accomplished with a treadmill, bicycle ergometer, or, rarely, with an arm ergometer, and may involve ventilatory gas analysis (the latter is called a cardiopulmonary stress test). Different protocols of progressive cardiovascular workload have been developed specifically for EST (e.g., Bruce, Cornell, Balke-Ware, ACIP, mAICP, Naughton, Weber). Bicycle ergometers are less expensive and smaller than treadmills and produce less motion of the upper body, but early fatigue of the lower extremities is a common problem that limits reaching maximal exercise capacity. As a result, treadmills are more commonly used in the United States for EST. Much of the reported data are based on the multistage Bruce Protocol, which is performed on a treadmill and has become the most commonly used protocol in clinical practice. ESTs may involve only ECG monitoring or may be combined with other imaging modalities (i.e., nuclear imaging, echocardiography).

2. What is the difference between a maximal and submaximal EST?

3. How helpful is an EST in the diagnosis of coronary artery disease?

    Multiple studies have been reported comparing the accuracy of EST with coronary angiography. However, different criteria have been used to define a significant coronary stenosis, and this lack of standardization, in addition to a variable prevalence of coronary artery disease in different populations, complicates the interpretation of the available data. A meta-analysis of 24,074 patients reported a mean sensitivity of 68% and a mean specificity of 77%. The sensitivity increases to 81% and the specificity decreases to 66% for multivessel disease, and to 86% and 53%, respectively, for left main disease or three-vessel coronary artery disease. The diagnostic accuracy of EST can be improved by combining other imaging techniques with EST such as echocardiography or myocardial perfusion imaging.

4. What are the risks associated with EST?

    When supervised by an adequately trained physician, the risks are very low. In the general population, the morbidity is less than 0.05% and the mortality is less than 0.01%. A survey of 151,944 patients 4 weeks after a myocardial infarction showed slight increased mortality and morbidity of 0.03% and 0.09%, respectively. According to the national survey of EST facilities, myocardial infarction and death can be expected in 1 per 2,500 tests.

5. What are the indications for EST?

    The most common indications for EST, according to the current American College of Cardiology (ACC) and American Heart Association (AHA) guidelines, are summarized in Box 6-1. When considering ordering an EST, three fundamental factors need to be considered to have an optimal diagnostic test: a normal baseline ECG, a patient who is able to exercise to complete the exercise protocol planned, and an appropriate indication for EST.

6. Should asymptomatic patients undergo ESTs?

    In general, asymptomatic patients should be discouraged from undergoing EST because the pretest probability of coronary artery disease in this population is low, leading to a significant number of false-positive results, requiring unnecessary follow-up tests and expenses without a well-documented benefit. There are no data from randomized studies that support the use of routine screening EST in asymptomatic patients to reduce the risk of cardiovascular events. Nevertheless, selected asymptomatic patients may be considered for EST under specific clinical circumstances if clinically appropriate (e.g., diabetic patients planning to enroll in a vigorous exercise program, certain high-risk occupations, positive calcium score, family history).

7. What are contraindications for EST?

    The contraindications for EST according to the current ACC/AHA guidelines are summarized in Box 6-2.