123I-labeled 15-(p-iodophenyl)-3R,S-methyl pentadecanoic acid (BMIPP) is a branched-chain free fatty acid that is used to evaluate various cardiac diseases. The aim of the present study was to investigate the relationship between myocardial perfusion (99mTc-sestamibi) and BMIPP uptake, and to correlate perfusion and metabolic alterations with regional left ventricular dysfunction in patients with myocardial infarction (MI). ECG-gated dual-isotope myocardial SPECT was performed on 130 patients with MI with sestamibi (555 MBq) and BMIPP (148 MBq). The patients were classified into 3 groups according to PTCA therapy and the interval between the onset of infarction and RI injection (OR time). Group A (n-56) included patients whose OR time was less than one month and who had undergone successful PTCA, Group B (n=36) had OR times of less than one month and had conservative medical therapy, and Group C (n=38) had OR times of over one month. The severity scores of the dual-isotope images were calculated from the defect scores in 9 segments. From the ECG-gated SPECT data with sestamibi, the left ventricular ejection fraction (LVEF; %) and regional wall motion were determined automatically using the QGS programTM. LVEF obtained from gated SPECT correlated well with the severity scores for sestamibi and BMIPP (r=−0.68 and −0.76, respectively). The Δ severity scores (BMIPP scores — sestamibi scores) of Group A were significantly higher than those of the other two groups (3.6±3.0 vs. 1.5±1.7 and 1.0±1.4, p<0.001). The rate of dysfunctional segments with normal sestamibi distribution was significantly higher in Group A than in Group C (20.7% vs. 6.7%, p<0.001). ECG-gated dual-isotope SPECT is useful since myocardial perfusion, fatty acid metabolism and left ventricular function can be analyzed during a single examination, so that this procedure has the potential to provide comprehensive information when evaluating patients with ischemic heart disease.