Assessment of the injury and repair of cardiac myocyctes after reperfusion with stress 99mTc-MIBI dipyridamole myocardial imaging

doi:10.3321/j.issn:1673-8225.2003.18.004

Abstract：Aim To study the relationship of 99mTc-MIBI uptake to the morphology of injury and repair of cardiac myocytes in the injured area of old myocardial infarction (OMI) in dogs. Methods Twelve dogs were divided into 2 groups of 6 dogs to undergo ligation of left anterior descending coronary artery (LAD) by 85% or 95% respectively so as to create OMI models. Five months after, dipyridamole and 99mTc-MIBI were injected intravenously so as to obtain myocardial tomography. One day after, nitroglycerin was given sublingually and then 99mTc-MIBI of the same dose was injected intravenously to obtain nitroglycerin intervention myocardial tomography. The reversible defect area, necrosis area, and normal area were identified by comparison of the stress dipyridamole myocardial imaging and the nitroglycerin intervention myocardial imaging. Then the dogs were killed and their hearts were taken out to observe the cardiac myocyte ultrastructure of the different area by transmission electron microscope (TEM). Results The stress 99mTc-MIBI dipyridamole myocardial imaging and the nitroglycerin intervention 99mTc-MIBI myocardial imaging were very similar between the group of ligation by 85% and the group of ligation by 95% . The necrosis areas were bigger in the cardiac apex, anterior septum, anterior wall, and anteriolateral wall with thinner radioactivity. Parts of these areas where re-distribution of 99mTc-MIBI was observed after nitroglycerin intervention were reversible areas. TEM showed the basically identical morphology of mitochondria in cardiac myocytes.In nitroglycerin intervention 99mTc-MIBI distributed necrosis area,there were no intact cardiac myocytes. In the reversible defect area of stress 99mTc-MIBI dipyridamole myocardial imaging, mainly in the myocytes with low blood reperfusion, some of the mitochondria were swollen and deformed seriously, the matrix density was reduced obviously scattered with empty mitochondria a few of which were continuous, and the mitochondrial membrane and cristae were not intact. In the areas near the normal myocardium the majority of mitochondria in cardiac myocytes were almost oval in shape with basically intact membrane, slightly reduced matrix, and regularly arranged cristae, but few of the mitochondria were injured seriously. Conclusion The 99mTc-MIBI uptake is related to the injury degree of cardiac myocytes. After the blood flow is improved, the majority of injured cardiac myocytes may be repaired in the reversible defect area by using stress 99mTc-MIBI-dipyridamole myocardial imaging.