Noninvasive assessment of myocardial salvage after coronary reperfusion: A perpetual quest of nuclear cardiology

Abstract

There is a pressing need to develop reliable noninvasive approaches for determination of the initial extent of myocardium at risk during acute myocardial infarction and for early assessment of the degree of salvage after reperfusion therapy. To be clinically useful, the method employed should not delay the institution of thrombolytic drug administration, should be easy to perform with conventional imaging technology available in the community hospital setting and should be able to provide information relevant to myocardial viability in addition to flow enhancement. Thallium-201 imaging to assess coronary reperfusion. Myocardial perfusion imaging with thallium-201 has been utilized as a method for evaluating the efficacy of coronary reperfusion in acute myocardial infarction (1). When thallium-201 is injected intravenously during the occlusion phase (pretreatment), the degree of delayed redistribution after thrombolysis is proportional to the degree of flow restoration and, presumably, myocardial viability (2,3). Patients demonstrating successful thrombolysis had more thallium-201 redistribution and a smaller final thallium defect size in relation to prethrombolysis images than were observed in patients with a persistently occluded infarct-related vessel, who showed little change in defect size (4-6). Reduto et al. (4) found that the improvement in thallium-201 uptake on redistribution images correlated well with subsequent improvement in left ventricular ejection fraction. There are some important limitations to the use of thallium-201 rest redistribution imaging in evaluating patients receiving thrombolytic therapy. First, the time that it takes to obtain pretreatment images may delay the institution of therapy up to 20 or 30 min. This delay is not feasible because