Many family physicians are acquainted with the problem of choosing which method of cardiac stress testing to use when evaluating a patient with symptoms that suggest possible cardiac ischemia. Lee and Boucher present a vignette of a 58-year-old woman with chest pain during exercise and review the testing options available and the guidelines for their use.
Exercise electrocardiography (treadmill testing) is the most widely available method of cardiac stress testing and the least expensive option, and has been the most extensively researched. Certain subgroups of patients are not appropriate candidates for treadmill testing (see accompanying table). Use of beta blockers or other anti-ischemic medications by patients undergoing treadmill testing can lead to erroneous results related to blunting of normal exercise-induced blood pressure and pulse changes, or masking of underlying cardiac ischemia. Ideally, these medications should be stopped several days before testing, although this step may not always be prudent or possible.
|Complete left bundle branch block|
|Electronically paced ventricular rhythm|
|Pre-excitation (Wolff–Parkinson–White) syndrome or other, similar electrocardiographic conduction abnormalities|
|More than 1 mm of ST-segment depression at rest|
|Inability to exercise to a level high enough to give meaningful results on routine stress electrocardiography|
|Angina and a history of revascularization|
Radionuclide imaging is the next most commonly employed modality to screen for cardiac ischemia. While the sensitivity and specificity of this mode is only modestly better than that of treadmill testing, this technique has the added capability of defining ischemic versus already infarcted myocardial tissue (i.e., reversible versus fixed defects). When patients cannot exercise adequately to produce cardiac stress, pharmacologic agents, including adenosine, dipyridamole, and dobutamine may be used to provoke ischemia.
Stress echocardiography is a recent addition to the diagnostic-testing arena. Like nuclear medicine techniques, it can provide information about ischemic versus infarcted tissue and can also evaluate left ventricular function and valvular pathology.
No large trials have compared the various stress testing techniques in a randomized fashion. Moreover, the availability of and expertise levels for the various modalities vary widely in different regions. Cost-effectiveness analyses are available but have had conflicting results because of differing estimates of sensitivity and specificity for the different testing techniques. Published guidelines have consistently advocated treadmill testing as the initial diagnostic test for men and women with suspected stable angina.
The authors conclude by presenting their own summary recommendations. In patients who do not have any of the clinical factors mentioned in the accompanying table, they recommend proceeding with treadmill testing. If the patient can vigorously exercise and no abnormality is detected, they suggest no further testing in this low-risk category. In high-risk patients (previous revascularization, angina with mild exertion), they recommend proceeding directly to cardiac catheterization in most cases. Intermediate risk patients, such as those with atypical chest pain or moderate exercise capacity, are candidates for radionuclide imaging techniques.