COMPARATIVE-STUDY OF REST TC-99M SESTAMIBI SPET AND LOW-DOSE DOBUTAMINE STRESS ECHOCARDIOGRAPHY FOR THE EARLY ASSESSMENT OF MYOCARDIAL VIABILITY AFTER ACUTE MYOCARDIAL-INFARCTION - IMPORTANCE OF THE SEVERITY OF THE INFARCT-RELATED STENOSIS

Rest technetium-99m sestamibi single-photon emission tomography (SPET) has been shown to underestimate viability in some patients with chron ic ischaemic myocardial dysfunction. The present study was designed to appraise the value of Tc-99m-sestamibi as a viability tracer in patie nts with a recent myocardial infarction and to determine factors that might influence its accuracy in assessing infarct size, Therefore, res t Tc-99m-sestamibi SPET, low-dose dobutamines stress echocardiography and quantitative coronary angiography were performed in 51 patients wi th a recent myocardial infarction. Perfusion activity and regional wal l motion were scored semi-quantitatively using the same segmental divi sion of tile left ventricle, Assessment of Tc-99m-sestamibi uptake as a marker of viability was performed by comparing a binary uptake score (viable=>50% vs necrotic =less than or equal to 50% of the maximal tr acer activity) with a binary wall motion classification during low-dos e dobutamine infusion (viable=normal/hypokinetic vs necrotic=akinetic/ dyskinetic). Infarct size, expressed as the number of segments With ev idence of necrotic tissue, was significantly greater in the scintigrap hic study than in the echocardiographic study (2.8+/-1.5 vs 2.2+/-1.3, P=0.006), This overestimation of infarct size by by Tc-99m-sestamibi was present only in patients with a severe infarct-related stenosis (% diameter stenosis greater than or equal to 65%-100%) and particularly those with ''late'' reperfusion therapy (time delay greater than or e qual to 180 min), in patients without a severe infarct-related stenosi s. Tc-99m-sestamibi was able to accurately distinguish viable from nec rotic segments. Thus, rest Tc-99m-sestamibi scintigraphy early after a cute myocardial infarction may underestimate residual viability within the infarct region, particularly in patients with low flow state coro nary anatomy, as a result of a severe infarct-related stenosis and/or late reperfusion therapy.