Assessment of metabolism, sympathetic function, and viability in ischemic myocardium

为评价正常大鼠和缺血大鼠心脏的血流灌注、代谢和交感神经功能，应用心肌灌注示踪剂(TL-201和Tc-99m)、I-125-(-15-对碘苯基)-3-R、I-125-甲基十五烷酸和I-125-间十二烷基胍对正常大鼠和缺血大鼠心脏进行了心肌灌注、代谢和交感神经功能的显像。注射示踪剂后15min，I-125-BMIPP分布均匀，心外膜摄取比为0.98±0.23。I-125-MIBG在各节段分布均匀，但注射后15分钟心外膜摄取比值为0.95±0.01，注射后3小时降至0.80±0.04。在急性缺血模型中，冠状动脉左前降支结扎，5分钟和20分钟后注射替罗福明和BMIPP。缺血5min时，非缺血区心肌的示踪剂摄取量降至0.36±0.08，缺血区中央BMIPP摄取量与正常区相似，为0.34±0.07。然而，在缺血周围区，BMIPP摄取减少(0.63±0.08)与灌流异常(0.39±0.11)相比相对较轻，提示灌流代谢不匹配。结果表明，急性心肌缺血20min后，心肌对脂肪酸的摄取相对血流灌注异常有较大的保留，提示联合应用心肌灌注和代谢显像对急性心肌缺血的病理生理诊断有一定的参考价值。

To assess the cardiac perfusion, metabolism and sympathetic function in normal and ischemic rats' heart were imaged using perfusion tracers (Tl-201 and Tc-99m tetrofosmin), I-125-(-15-(p-iodophenyl)-3-R,S-metyl pentadecanoic acid (BMIPP), and I-125-metaiodobenzylguanidine (MIBG).In normal rats, both perfusion tracers distributed homogeneously among anterior, septal, lateral, inferior walls and endmyocardial and epicardial layers at 15 minutes after tracer injection. I-125-BMIPP also distributed homogeneously at 15 minutes after tracer injection and showed end to epicardial uptake ratio to be 0.98±0.23. I-125-MIBG distribute homogeneously among all segments but end to epicaldial uptake ratio was 0.95±0.01 at 15 minutes after injection and decreased to 0.80±0.04 at 3 hours after injection.In acute ischemic model, left anterior descending coronary artery was occluded and 5 and 20 minutes later, tetrofosmin and BMIPP were injected. In 5 minutes ischemia perfusion tracer uptake decreased to 0.36±0.08 of non-ischemic myocardium accompanied with similar reduction of BMIPP uptake of 0.34±0.07 of normal area in the center of the ischemic area. However, in peripheral zone of ischemia, BMIPP uptake reduction (0.63±0.08) was relatively mild compared with perfusion abnormality (0.39±0.11), suggesting perfusion metabolic mismatch. In 20 minutes ischemia, similar results were observed.These results suggested that 20 minutes after acute ischemia, myocardial fatty acid uptake was relatively preserved compared with perfusion abnormality, indicating that combined perfusion and metabolic imaging is useful for the evaluation of pathophysiologic diagnosis of acute myocardial ischemia.