The Value of Exercise Thallium Imaging

Physicians can choose from among many diagnostic techniques to evaluate patients with known or suspected ischemic heart disease. The physician wishing to determine whether a patient who has symptoms consistent with angina has significant coronary artery stenosis can order a stress electrocardiogram, stress echocardiogram, radionuclide ventriculogram, coronary angiogram, or nuclear perfusion imaging test. Within this last category alone are dozens of variations, including isotope (thallium or sestamibi or teboroxime), acquisition method (planar or tomographic [single-photon emission computed tomography]), stressor (exercise or dobutamine or dipyridamole or adenosine), analysis technique (qualitative or quantitative), and many other technical variables (for example, the time to reimaging after exercise and at-rest reinjection of the imaging agent). Each of these methods varies in cost, complexity, reproducibility, safety, patient comfort, and ability to answer specific questions. The challenge for the physician, therefore, is to choose the best technique for a given patient at a given time for a given question of clinical interest. The most appropriate choice depends on the characteristics of the patient being studied, the local institutional expertise, and, even more importantly, the question being addressed.

Although there are many reasons for performing the diagnostic techniques mentioned above, most fall into the following categories: 1) to determine the presence or absence of significant coronary artery obstructions in a patient with signs or symptoms consistent with this disease; 2) to determine the severity and extent of coronary stenosis; 3) to assess prognosis in patients with known or suspected coronary disease; 4) to assess the physiologic significance of coronary stenoses visualized by angiography; 5) to assess the “viability” of a region of the myocardium before revascularization; 6) to gather information that can guide treatment options; and 7) to assess response to a treatment strategy. Physicians must understand the specific clinical questions to be addressed before choosing specific …