Stress Tests

Background

Cardiac stress tests are common procedures that are performed to evaluate patients for evidence of coronary artery disease (CAD). The gold standard for the diagnosis of CAD is cardiac catheterization and angiography; however, this is an invasive procedure that is not indicated for all patients. Therefore, many patients with a low to intermediate risk for CAD will undergo stress testing first to ascertain whether a subsequent cardiac catheterization is needed. There are two components to a stress test. The first is the method in which the patient’s heart will be stressed. The options are exercise (on a treadmill or stationary bike) or pharmacologic (several agents are available), as tolerated, typically to achieve at least 85% of the age-adjusted maximum predicted heart rate (220 beats per minute – the patient’s age = maximum predicted heart rate). The second component is the method by which the heart is assessed for evidence of ischemia to the coronary arteries. The typical options are electrocardiogram (EKG) monitoring, nuclear imaging to evaluate coronary blood flow, or echocardiography to evaluate left ventricular systolic function. Which components are optimal for a given individual is based on multiple variables. For example, a patient with severe arthritis who cannot exercise on a treadmill will typically undergo a pharmacologic stress test.

The most common stress tests (in no particular order) are treadmill exercise EKG stress test, treadmill exercise or pharmacologic nuclear stress test, and exercise (treadmill or stationary bike) or pharmacologic (e.g., dobutamine) stress echocardiography.

How to Use It

A stress test is performed to evaluate a patient for evidence of CAD. Typically, a patient will report chest discomfort or symptoms with exertion that are suggestive of heart disease, prompting the test. A stress test may also be performed in patients with established CAD to evaluate the progression of disease. A patient with a positive stress test will undergo further testing, usually with cardiac catheterization. A patient with a negative stress test will typically be reassured that his or her symptoms are not from CAD. Stress testing may have false-negative results; however, if a patient continues to have symptoms concerning for CAD, he or she may still undergo cardiac catheterization. ^, Any of the stress tests can be performed in the inpatient or outpatient settings.

An exercise EKG stress test will evaluate a patient for evidence of EKG changes while undergoing exercise. A test is considered abnormal (positive) if characteristic ST-segment depressions or ST-segment elevations (suggesting ischemia) are noted on the EKG during the test. See Chapter 26: Electrocardiography for more information about the EKG.

A nuclear stress test may be done with either exercise on a treadmill or by administering a pharmacologic agent. A cardiologist will compare the rest and stress nuclear images, and a study will be deemed abnormal (positive) if there is worse flow on the stress images. ^, Patients who are actively wheezing should not undergo a pharmacologic nuclear stress test.

Stress echocardiography can also be done with exercise or by administering a pharmacologic agent. The cardiologist will compare the function of the left ventricle at rest compared with stress. If there are parts of the ventricle that are not contracting properly, the test will be considered abnormal (positive). See Chapter 25: Echocardiography for more information about this test.

How It Is Done