ADENOSINE TC-99M SESTAMIBI SINGLE-PHOTON EMISSION TOMOGRAPHY FOR THE ASSESSMENT OF JEOPARDIZED MYOCARDIUM EARLY AFTER ACUTE MYOCARDIAL-INFARCTION - PARADOXICAL SCINTIGRAPHIC UNDERESTIMATION OF JEOPARDIZED MYOCARDIUM IN PATIENTS WITH A SEVERE INFARCT-RELATED STENOSIS

This study investigated the value of technetium-99m sestamibi scintigr aphy in identifying patients at risk for post-infarct ischaemia (=jeop ardized myocardium), especially within the reperfused infarct region. In 51 patients with a recent (<1 month) myocardial infarction, adenosi ne Tc-99m-sestamibi single-photon emission tomography (SPET) and dobut amine stress echocardiography (DSE) were performed and correlated with the presence of significant coronary artery stenosis [% diameter sten osis (DS) >50%] on quantitative coronary angiography. Regional perfusi on activity was analysed semiquantitatively (score 0-4) on a 13-segmen t left ventricular model. DSE was used for the estimation of the infar ct size (low-dose DSE) and for concomitant evaluation of ischaemia (hi gh-dose DSE). A reversible perfusion defect within the infarct region was observed in 20 of the 37 patients with a significant infarct-relat ed lesion (sensitivity of 54%) and only in one patient without a signi ficant infarct-related lesion (specificity of 93%). Further analysis r evealed that the scintigraphic assessment of jeopardized myocardium wa s fairly good in patients with a moderate (DS 51%-64%) infarct-related stenosis but was inadequate in patients with a severe (DS greater tha n or equal to 65%) infarct-related stenosis (sensitivity of 80% vs 36% , P<0.01), while the echocardiographic detection of ischaemia was not influenced by stenosis severity (sensitivity of 73% in both subgroups) . This scintigraphic underestimation of jeopardized myocardium was mai nly related to a severely impaired myocardial perfusion under baseline conditions, as was evidenced by a significantly more severe rest perf usion score in the infarct region in patients with a severe stenosis a s compared to those with a moderate stenosis (average score: 1.5+/-0.7 vs 2.1+/-0.6, P<0.01), while infarct size on echocardiography was sim ilar for both subgroups. It may be concluded that early after an acute myocardial infarction, adenosine Tc-99m-sestamibi SPET may underestim ate reperfused but still jeopardized myocardium, particularly in patie nts with a severe infarct-related stenosis. In these patients the eval uation of the ischaemic burden on rest-stress scintigraphy is hampered by the presence of a severely impaired myocardial perfusion in restin g conditions.