Nuclear cardiology. II. The role of myocardial perfusion imaging using thallium-201 in diagnosis of coronary heart disease.

Since its introduction, thallium-201 has become the agent of choice in the clinical assessment of relative myocardial perfusion. Extensive evaluation has shown that it is of particular value in the diagnosis of coronary heart disease in patients with baseline S-T segment abnormalities or an inadequate heart rate response resulting in an inconclusive exercise electrocardiographic response. In addition, thallium-201 imaging is of value in the patient with a suspected false positive stress test; however, the definite incidence of false negative studies in patients with coronary heart disease tempers complete reliance on this approach. In the patient with a diagnostic exercise electrocardiographic stress test, thallium-201 provides limited additional information. Moreover, current techniques of analysis do not permit assessment of the number of coronary arteries with obstructive lesions. In the setting of acute myocardial ischemia, the role of thallium-201 is less clear. In acute myocardial infarction, the significant incidence of false negative responses combined with a multiplicity of potential causes of resting defects including severe but chronic coronary disease or unstable angina limits its diagnostic value.