Myocardial perfusion imaging and gated cardiac blood pool scanning: clinical application

Myocardial perfusion imaging with thallium-201 and gated cardiac blood pool scanning are finding increasing use in clinical cardiology. These noninvasive techniques have been found useful in detecting myocardial infarction independent of the electrocardiogram and determining the site and extent of the infarct as well as its effect on left ventricular function. These studies provide important prognostic data and are proving to be of value in evaluating patients with cardiogenic shock. Neither the thallium-201 myocardial perfusion image nor the gated cardiac blood pool scan can distinguish between acute and chronic myocardial damage. In clinical situations where this is important, infarct avid imaging with technetium-99m pyrophosphate allows determination of whether a given perfusion defect or wall motion abnormality is acute. Myocardial perfusion imaging with thallium-201 at rest and after exercise is also proving to be of value in evaluating patients with suspected ischemic heart disease. Initial studies suggest that the technique may be more sensitive than exercise electrocardiography and is of special value in minimizing the occurrence of false positive exercise tests for the diagnosis of ischemic heart disease. The combined tracers technique is also of value in the evaluation of patients undergoing coronary bypass graft surgery and those with cardiomyopathy.