Dual-isotope myocardial SPECT in patients with redefined myocardial infarction

Background: According to the redefinition of myocardial infarction (MI) by the ESC/ACC Committee, patients with unstable angina (UA) without significant elevation of creatine kinase (CK) but with elevation of troponin T should be diagnosed as MI. Methods: One hundred and forty-six consecutive patients formerly diagnosed as UA, with peak CK levels < twice upper normal level, who underwent myocardial Thallium-201 (TI; perfusion tracer) and I-123-15-iodophenyl 3-methyl pentadecanoic acid (BMIPP; metabolism tracer) dual isotope single-photon emission computed tomography (SPECT), were retrospectively reclassified into redefined MI and UA groups according to the redefinition (troponin T: rapid bedside assay positive or quantitative level > 0.10 ng/ml). Dual SPECT findings were analyzed qualitatively and quantitatively in blinded manner. Results: Forty-seven patients (32%) were redefined as MI and 99 patients (68%) were redefined as UA. On admission, there were small but statistically significant elevations in laboratory parameters such as white blood cell count, C-reactive protein, CK and CK-MB in the redefined MI group compared with the redefined UA group. The proportion of patients with perfusion and metabolic abnormalities was significantly higher in the redefined MI group (TI defect 36% vs. 4%, odds ratio: 13.5, p < 0.001; BMIPP defect 64% vs. 23%, odds ratio: 5.8, p < 0.001). Semi-quantitative evaluation revealed that the total TI and BMIPP scores were significantly higher in the redefined MI patients (p < 0.001). Conclusions: In the redefined MI patients, perfusion and metabolic abnormalities occurred frequently and more extensively. However, TV BMIPP dual SPECT had limited ability to detect minor myocardial infarcts classified as redefined MI. A more sensitive stratification combined with troponin T directed assignment should be established to incorporate the ongoing minor infarcts which could not be assessed by serial dual-scintigraphic evaluations. (c) 2005 Elsevier Ireland Ltd. All rights reserved.