Comparative localization of myocardial ischemia by exercise electrocardiography and myocardial perfusion SPECT

Background. Prior angiographic study has shown that the patterns of ST-segm ent depression during exercise do not provide localizing information of the responsible coronary lesion. However, little is known regarding the abilit y of exercise-induced ST-segment displacement to localize myocardial perfus ion defects. Methods and Results, We studied 552 consecutive patients without prior myoc ardial infarction who had reversible perfusion defect in one vascular terri tory on rest Tl-201/exercise Tc-99m-labeled sestamibi dual-isotope myocardi al perfusion single photon emission computed tomography (SPECT) and ischemi c ST depression or elevation during exercise, Of these, 192 patients had an giographically documented coronary artery disease (CAD), Two hundred thirty -two patients had maximal ST depression in anterior leads, 247 patients had maximal ST depression in inferior leads, and 45 patients had similar maxim al ST depression in both anterior and inferior leads. Twenty-eight (5%) pat ients had ST elevation with absent Q waves. In patients with maximal ST dep ression in anterior leads, perfusion defects were found in the territory of the left anterior descending coronary artery (LAD) in 30%, in the territor y of the right coronary artery (RCA) in 52%, and in the territory of the le ft circumflex coronary artery (LCX) in 18%, Tn patients with maximal ST dep ression in inferior leads, perfusion defects were found in RCA territory in 44%, in the LAD territory in 42%, and in the LCX territory in 14%, Compare d with exercise ST depression, the less common finding of ST elevation did provide accurate Localization of perfusion defects. When ST elevation was g reatest in the anterior leads, 96% of patients had LAD territory defects. W hen ST elevation was most prominent in the inferior leads, 100% patients ha d RCA territory defects. Data of coronary angiograms demonstrated that myoc ardial perfusion SPECT correctly identified the most stenotic coronary dise ase for LAD (94%), LCX (72%), and RCA (75%). Conclusions. The findings of this study indicate that the site of maximal S T-segment depression does not identify the localization of myocardial perfu sion defects. However, the less common finding of exercise-induced ST-segme nt elevation does predict localization of myocardial ischemia.