| No-reflow phenomenon following reperfusion after acute myocardial ischemia has attracted much attention of the investigators due to its higher incidence and worse prognosis. Introduction of MCE into the clinical use brings with the effective measures to reveal the appearance of no reflow. However the mechanism of no-reflow remains unclear at present and no available therapeutic method could effectively prevent or eliminate no reflow phenomenon in clinical management of ischemia-reperfusion. So we design the experimental study with main purposes as follows: (1) making of canine model of myocardial no reflow mimic the in vivo condition of human acute myocardial ischemia-reperfusion. (2) to explore the characteristics of myocardial metabolic changes in no reflow sites. (3) comparing the pathologic damages of myocardium and microvascularure in ischemic region with that in reperfused no reflow region. (4) investigating platelet activation at presence of myocardial no reflow by assessing of activated platelet glycoprotein Ilb/IIIa receptors. By analyzing the changes mentioned above we will search for the exact mechanism of myocardial no reflow so as to supply instructions to the clinical treatment of myocardial no reflow.Materials and methods:1.Making of canine model of myocardial no reflow:Eighteen adult mongrel dogs routinely anesthetized are used to elicit the myocardial no reflow, which are cannulated in femoral artery and vein. The animals are ventilated by breathing apparatus. LAD of the animals are separated 1 cm through left thoracic cavity and installed with the Dopplerflow probe to survey the CBF. Artery clamp is located onto the separated LAD at the proximal site for occluding CBF. No reflow is judged with MCE by the criteria that no flow or narrow flow can be measured after reperfusion. BP, HR and heart electrical activity are monitored simultaneously.2. Assessing of myocardial metabolism by PET:The animals are injected through cannulated femoral vein 18F-FDG by the dosage of 1 mCi/kg ?w. PET imaging of normally perfused, no reflow, low reflow and completely reperfused myocardium are scanned by the Adventive PET imaging scanner.3. Morphological and pathological investigating of myocardium and cardiomierovasculature by microscope and electronic microscope:Myocardium of normally perfused, ischemic and no reflow spot are punctured , sliced and stained respectively for biopsies. The Slices are observed with microscope and electronic microscope for the pathologic and morphologic changes of myocardium and microvasculature.4. Assay of GPIIb/IIIa recepors, a marker of platelet activating by ELISA method:PVB and SVB are extracted respectively from the animals of myocardial ischenia, no reflow and total reperfusion and conveied with siliconed glass test tube. Platelet GPIIb/IIIa receptors from samples are mearsured by the method of ELISA.Results:1. Ideal model of ischemia-reperfusion-no reflow is successfully madeOf 18 dogs 14 finish the experiments undergoing 3h ischemia and 3h reperfusion. No reflow phenomenon occurrs in 4 of the 14 animals. Low reflow occurrs in one of the 14 animals. Incidence of no reflow and low reflowe is respectively 28.57% and 7.14%.2. Changes of myocardial metabolismAll myocardium located within the areas of ischemia, no reflow, low reflow and well reperfusion has metabolic changes in PET imaging. The scales of metabolically changed myocardium in PET imaging is much less than the perfusion defect region measured by MCE.3.Pathologic alteration of myocardium andcardiomicrovascu latu re:Under microscope we find the main ischemic changes of myocardium and microvessels include myocardial degeneration, confluence, No apparent changes among the microvasculatures. But the reperfused no reflow myocardium and litte arterioles exhibit myocytoswelling, colliquation and infiltration of the cells within the vessels into the interstitial tissue.Under electronic microscope we observe that ischemic my...
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