Thallium-201 Myocardial Imaging in Unstable Agina and Variant Angina

Abstract

Scintigraphic myocardial perfusion defects with 201T1 may represent either myocardial infarction or a region of transient ischemia. The results of repeated imaging in patients with acute myocardial infarction suggested that during the initial acute phase, in addition to necrotic tissue, surrounding transient ischemic tissue may be visualized [1]. Moreover, scintigraphic defects, indistinguishable from those seen in (acute) myocardial infarction can be obtained following exercise induced ischemia [2–6] or ischemia resulting from coronary spasm in variant angina [19]. An important portion of coronary care unit admissions includes patients who have repeated episodes of myocardial ischemia, i.e., patients with unstable angina. Therefore, it is of clinical relevance in the coronary care unit to evaluate the potential role of 201T1 scintigraphy in patients with unstable angina. In the present chapter we will discuss 1) the pattern of 201T1 scintigraphy in patients with unstable angina; and 2) the potential predictive value of 201T1 scintigraphy in identifying patients with unstable angina who have a poorer prognosis or greater tendency to subsequently develop acute myocardial infarction. All patients with unstable angina pectoris were purposely studied during the pain free period. It seemed conceivable that injecting 201T1 during an anginal attack would result in a high percentage of scintigraphic defects and probably diminish a potential discriminative value of the method. Moreover, in clinical practice the majority of patients arrive at the coronary care unit some time after the last anginal attack. If a diagnostic test performed at this time could distinguish high and low risk patients, important therapeutic decisions might be made at the earliest possible times.KeywordsUnstable AnginaPerfusion DefectCoronary Care UnitNormal Coronary ArteryCoronary SpasmThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.