| Research Abstract |
Mechanism of myocardial stunning was studied with radionuclide met hods. Canine coronary arteries were ligated for 30 min andreperfused for 2 hrs, when myocardial blood flow and myocardial Ca uptake (^<99m>Tc pyrophosphate (PYP) uptake) was examined. Bloodflow was normalized but echocardiography demonstrated reduced wall motion associated with in creased PYP. Administration of Ca antagonists fascilitated a recovery of wall motion and suppress the PYP uptake. In canine models, ^<123>I-metaiodo-benzyl-guanidine, which was closely correlated with myocardial cat echolamine con-tents, was not reduced in the stunned myocardium but was in the infarction. This suggests that depletion of catecholamine at thenerve endings may not present in the stunned myocardium but may in the extreme ischemia such as infarction. According to the analysis with ^<123>I-beta-methyliodophenyl pentadecanoic acid and ^<18>F- fluorodeoxy-glucose, lipid metabolism was suppressed and anaero-bic glucose metabolism was accelarated in spite of recovery of blood flow (metabolic stunning).
Clinically, increased myocardial PYP uptake are present in patients with nonQ-infarction, suggesting Ca are closely associ-ated with stunning. In the stunned, ^<11>C-acetate clearance was also low indicating reduced regional O_2 consumption and normali-zed with dobutamine infusion.
Thus, myocardial stunning with impaired wall motion seems tobe related with increased Ca uptake and reduced energy consumption.
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