Detection of myocardial viability in ischemic-reperfused rat hearts by Tc-99m sestamibi kinetics

Background. The purpose of this study was to evaluate technetium 99m sestamibi (MIBI) kinetics in assessing myocardial viability in hearts subjected to different ischemia-reperfusion treatments, resulting in graded severity of injury. Methods and Results. Sixteen isolated Krebs-Henseleit-perfused rat hearts were divided into 3 groups: control (flow, 12 mL/min; n = 5), ischemic-reperfused with glucose (IR+G, n = 6), and ischemic-reperfused without glucose (IR-G, n = 5). MIBI (11.1 mBq [300 μCi]) was infused for 60 minutes (uptake), followed by a 60-minute clearance. MIBI uptake (percent injected dose per gram) was significantly decreased in the IR+G (2.07 ± 0.31) and IR-G groups (2.03 ± 0.23; P = not significant with IR+G) compared with the control group (3.06 ± 0.25, P < .05). Fractional washout of MIBI was more rapid in the IR-G group (72.7% ± 3.9%, P < .05) than in the control (21.9% ± 1.9%) and IR+G groups (20.3% ± 1.7%). End retention (percent injected dose per gram) of MIBI in the IR-G (0.60 ± 0.12) and IR+G groups (1.60 ± 0.18) was significantly less than in the control group (2.30 ± 0.11, P < .05), respectively. The retention in the IR-G group was less than in the IR+G group (P < .05). Creatine kinase assay, triphenyltetrazolium chloride staining, and transmission electron microscopy analysis demonstrated more serious myocardial damage in the IR-G group than in the IR+G group. End MIBI activity was highly correlated with myocardial viability determined by triphenyltetrazolium chloride staining (r = 0.94; P < .05) and creatine kinase assay (r = -0.86; P < .05). Conclusions. Clearance of Tc-99m sestamibi is sensitive to metabolic states and may be used for assessment of ongoing myocardial damage.