| IntroductionStroke is the second leading cause of death worldwide, of which80percent is caused by focal ischemic stroke resulting from artery embolism.And in ischemic stroke patients, when the diameter of blood vessels greater than2millimeters became blocked, embolic encephalon infarction of which fatality rate is53%-92%formed. According to the statistics,3.25million cerebral thrombosis patients occur in our country every year, so it is important to look for a safe, effective, and feasible method in the treatment of patients with cerebral thrombosis in order to improve the cure rate of this disease.At present, thrombolysis with intravenous or arterial rt-PA for treatment of cerebral infarction is effective because it can improve prognosis of the nervous system. However, only4.5%-6.3%patients can receive thrombolytic therapy due to some reasons such as short window for thrombolytic therapy,long recanalization time,high incidence of cerebral hemorrhage and so on. Based on above phenomenon.how to gain higher recanalization and minimize risks in shorter time is the key to cure arterothrombtic cerebral infarction(ACI). Mechanical thrombectomy provides a newly valuable technology for treatment of embolic encephalon infarction. Now, it attracts more and more attention and is becoming the hot spot in the field of endovascular therapy for its higher rate of recanalization, lower complication rate and longer time windows.Most of the mechanical thrombectomy device is still under preclinical study phase,although some in Phase I or II Clinical Trial. At the moment, thrombectomy device for curing acute arterothrombtic cerebral infarction is very few in the world. As far as we know, there are only two systems, one is MERCI thrombectomy device passed authentication via U.S.A. FDA,and the other is penumbra negative pressure thrombectomy device applied to clinical use last year. Due to some shortcomings of present thrombectomy devices such as short application in Clinical Cases, high price, lack of distal protection device and high rate of again infarction,it seems to be particularly necessary to develop a safe and effective thrombectomy device. We have developed a new type of cerebral artery thrombectomy device which has many advantages of perfect structure, reasonable price and distal protection device, cooperated with Medical Apparatus&Instruments Company. Its effectiveness and safety as well as time windows were verified through experimental study. The study is to provide the theoretic foundation and security guarantees for cerebral artery thrombectomy device in clinical application, promote the application of homemade device and the development of cerebral artery thrombectomy technique so as to increase the cure rate and improve the prognosis of this diseaseThe study includs two parts,one is research of mechanical thrombectomy device in cerebral artery and establishment of acute embolic cerebral infarction animal model, the other is experimental study on the mechanical thrombectomy in the treatment of cerebral artery embolism. The first part is divided into two experiments.The first experiment is about research on the mechanical thrombectomy in the treatment of cerebral artery embolism and vitro experiment. The second experiment is about establishment and evaluation of acute embolic cerebral infarction animal model which is suit to mechanical thrombectomy. The third experiment comprise two parts.The first part is about Comparative efficacy evaluation experimental study of acute thromboembolic cerebral infarction using mechanical thrombectomy,the second is about Animal experiment study of magnetic resonance diffusion imaging and brain BDNF protein expression changes after acute embolic cerebral infarction embolectomy at different time windowsPart I Development of mechanical thrombectomy device and establishment of animal model for intracranial arterial mechanical thrombectomyExperiment1Development and experiment in vitro of mechanical thrombectomy device for intracranial arterial thrombusObjective:Design&Manufacture a device which not only removes thrombus but also protects distalend.Methods:We renewed design idea and overcame shortcomings of commercially produced import thrombectomy device at present, cooperating with Hunan putnam’s medical instrument Co. LTD. niti wire and platinoiridium was applied as materials and a thrombectomy bascket which can control the diameter size and has a cant was produced, by using precision braiding machine and laser welding machines basket. Meanwhile, matching fairlead、collecting pipe、wire-guide、Loader、controlling handle and other control system were manufactured by using HDPE、PTFE、ABS、 PC、PtW and other material. Do vitro tests. According to YY0450.1of national criteria, the appearance of mechanical thrombectomy、X-ray detectability, basket’s density、disruptive force、bend、fracture. Joint strength and other inspection of playsical properties were proceed; According to GB/T16886.1.2.4.11of Chinese medicine industry standards, hemolysis、toxicity、sensitization、fever reaction and other biological tests were performed.Results:It was confirmed by vitro tests that thrombectomy bascket can effectively remove intravascular thrombi, protect remote blood vessels from thrombosis fragments blocking and increase the safety of thrombectomy. The result of device mechanical property examination didn’t show twist、corrode、Creases and other unnatural bent. All Components can be detected in the X-ray. The disruptive force>5N, the diameter of wire-mesh basket less than0.4mm。 Bursting test hasn’t break trace, bend test is zero defect, Joint strength meet the industry standard; Biological tests showed that there were no hemolysis, toxicity,sensitization, fever reaction, and indicated it has good biocompatibility.Conclusion:The design idea of mechanical thrombectomy is advanced, rational construction. Technology have reached the technical level of the similar products at home and abroad. The device has advantages of incorporated thrombectomy, distal protection,safety, and provide reliability for its animal experiment and clinical test. Experiment2Establishment and evaluation of acute embolic infarction animal model for mechanical thrombectomyObjective:To Establish Animal models of acute arterial embolism which is suit to mechanical thrombectomy, similar to human acute embolic cerebral infarction, and evaluate the effectiveness of embolectomy to the model.Methods:Acute embolic cerebral infarction model was established by methods of carotid artery ligated on one side, temporary carotid artery occlusion and Injection of thrombin on the other side in New Zealand rabbits (n=30). evaluated the effectiveness of the model by Using DSA、DWI、TCD and pathological examination.20New Zealand rabbits which were successfully modeled were randomly assigned by random number table into non-treatment group and thrombectomy treatment group(10rabbits for each group), the non-treatment group did not get any treatment, thrombectomy treatment group received the intracranial arterial embolectomy by device6h later after embolism onset. Used the TCD examination respectively and record the average velocity of the right middle cerebral artery before the embolism and after embolism1h and6h; used DWI to record ADC value after embolism6h and24h. the non-treatment group were sacrificed after embolism24h,5brains were dyed with TTC stain, the rest of5brain with HE stain were observed the pathological changes light microscope, electron microscope and immunohistochemistry. the Vascular recanalization were detected under DSA after embolectomy of the treatment group. Comparing the ADC and Vmca changes between the two group in different time.Results:The DSA showed that the occlusion rate of the embolization side of the carotid artery is83%after the30New Zealand rabbits model establishment. The DWI showed infarcts after embolization6h,24h pathological checking (dyed with TTC stain) showed infarcted zone, Brain edema, nerve cell coagulation necrosis, Karyopyknosis and disappearance, nerve cell and glial cell obvious decrease or disappearance. It showed that the ultra-structure of the nerve cell was damaged, the organelle was obviously swelling, part of the mitochondria vacuolized, the foot board of the astrocytes vacuolized, endothelial nuclei degenerated.the blood vessel recanalization rates was80%after embolectomy, it is statistical significance (before and after embolization:P=0.000; before and after embolectomy: P=0.000)compared the Vmca before and after embolization,before and after the embolectomy. The Vmca of the thrombolysis after embolized6h group was42.28±1.92cm/s, the Vmca of the non-treatment group was29.02±1.72cm/s, comparison between the two groups was statistical significance(F=47.490P=0.000); the ADC of the embolectomy group after embolectomy was on the rise, the ADC of the non-treatment group was on the decline, the ADC of the thrombolysis after embolized24h group was0.81±0.08, the ADC of the non-treatment group was0.56±0.10, compared the ADC of the two group was statistical significance(P=0.000).Conclusion:The success rate is high,the stability of the model is satisfactory and it has a good repeatability to use the method of temporary carotid artery occlusion and Injection of thrombin to make animal models of acute arterial embolism which is suit to mechanical thrombectomy, this method is suit to experimental study and effect evaluation for intracranial arteries thrombectomy device. Part Ⅱ Animal experiment study of intracranial arterial mechanical embolectomy deviceExperiment1Comparative experimental study of efficacy evaluation of acute thromboembolic cerebral infarction mechanical thromboectomyObjective:To demonstrate the efficacy and safety of domestic intracranial arterial embolectomy device through the experimental study, to explore the advantages between mechanical thrombectomy and mtra-arterial thrombolysis. Providing a basic theory for intracranial arterial embolectomy using into clinically.Methods:The acute arterial thromboembolism animal model was established by injection thrombin into rabbit artery with blood flow temporary block, which is suitable to mechanical embolectomy in30rabbit. According to the random number table, the30rabbit are divided into non-treatment group, the thrombolysis group, mechanical thrombectomy group. After3hours of embolization, the thrombolysis group received intra-arterial recombinant human tissue-type plasminogen activator (Rt-PA) thrombolysis, mechanical thrombectomy of intracranial arterial embolectomy device was applied to mechanical thrombectomy group, the situation of vessel recanalization was observed under digital subtraction angiography (DSA), as well middle cerebral artery flow velocity (VMCA) changes were record through the transcranial Doppler (TCD), before and after treatment. Each group, after embolization,3h,6h,8h,12h,24h respectively received magnetic resonance diffusion imaging (MR-DWI). differences in apparent diffusion coefficient (ADC) were compared; brain CT scan was performed to check the intracranial complications after treatment in treatment group at24hours, the neurological deficits were scored24h later, pathological changes of vessel and brain tissue were observed by a light microscope and transmission electron microscope after examination of24h magnetic resonance and CT.Results:Embolectomy, thrombolysis group recanalization rate was80%,20%respectively, re-pass rate difference was statistically significant (P=0.025), the VMCA of the two groups after treatment was statistically significant (P=0.000).; the vascular pathology of embolectomy parts observed by light microscopy and electron microscopy demonstrated endothelial cells arranged in neat rows, without performance of the vascular endothelial damage; head CT examinations showed the thrombectomy group had no intracranial bleeding, the intracranial hemorrhage rate of the thrombolytic group was10%; The differences of ADC value after12h and24h MRI between the thrombectomy group and the thrombolysis group were statistically significant (P<0.05), the ADC value differences in other each time were not statistically significant (P>0.05); thrombectomy group ADC values showed an upward trend after the embolectomy. In thrombolysis group, non-treatment group, ADC values showed a downward trend; neurological deficit score of thrombectomy group was significantly higher than the thrombolysis group and the non-treatment group, had statistically significant difference compared with the thrombolysis group and non-treatment group (thrombolysis group:P=0.003non-treatment group: P=0.001); light and electron microscope examination revealed that the brain neuronal morphology of the thrombectomy group did not significantly abnormal, astrocytic foot plate mild vacuolization, neuronal damage is minor; thrombolysis group organelles degree in-re-swelling, compression of the vessel lumen, astrocytic foot plate vacuolization, edema of the astrocytes, and neuronal damage obvious; neurons form of non-treatment group, structural damage, chromatin margination, nuclear solid shrinkage, fragmentation, nuclear membrane dissolved and disappeared, was vacuolization of the astrocytic foot plate, compression narrowing of the vessel lumen, endothelial cell nucleus degeneration.Conclusion:The experiment confirmed that embolectomy of intracranial arterial embolectomy device can quickly restore the occluded artery blood flow to improve the occlusive vascular recanalization rate, early embolectomy can save ischemic brain, it is an effective and safe treatment for the acute thromboembolic cerebral infarction.It is better than the current application of endovascular treatment, has good prospect for clinical application. Experiment2Animal experiment study of magnetic resonance diffusion imaging and brain BDNF protein expression changes after acute embolic cerebral infarction embolectomy at different time windowsObjective:Mechanical embolectomy with the domestic intracranial arterial embolectomy device was performed in rabbit model of acute embolic cerebral infarction. To research and analyze the changes of magnetic resonance diffusion-weighted imaging, ADC value, infarct volume and brain-derived neurotrophic factor expression at different time windows after embolectomy, and to explore the effects and time window using mechanical thrombectomy treatment by intracranial arterial embolectomy deviceMethods:The acute arterial thromboembolism animal model was established by injection thrombin into rabbit artery with blood flow temporary block, which is suitable mechanical embolectomy in25rabbit. According to the random number table,25rabbits were divided into non-treatment group,3hours mechanical thrombectomy group,6hours mechanical thrombectomy group,8hours mechanical thrombectomy group,12hours mechanical thrombectomy group (n=5each group).(mechanical embolectomy was performed at3h,6h,8h,12h through the femoral artery undering DSA guide), magnetic resonance diffusion-weighted imaging, the calculation of each period of apparent diffusion coefficient (ADC) and infarct volume were observed at3h,6h,8h,12h,24h. The animals were sacrificed after MRI, brains were removed and observed BDNF protein expression changes with immunohistochemical method, as well pathology examination by light and electron microscopy,(the experiment of3hours thrombectomy group used the experimental data of second part of the experiment one, the total using experimental animals are20).Results:In the acute phase, ADC values of the non-treatment group and12h thrombectomy group gradually decreased, and infarct volume gradually expanded. In acute phase after embolectomy, ADC values of3h,6h,8h thrombectomy groups gradually increased, and infarct volume gradually reduced. From6h to24h, infarct volume gradually expanded in non-treatment group and12h thrombectomy group. Compared with non-treatment group, infarct volume of3h,6h,8h thrombectomy groups were reduced by10.4%,9.8%,5.1%and24.7%,23.9%,10.6%at the same time segment of12h and24h.24hours after infarction, compared with non-treatment group and12h thrombectomy group,3h,6h and8h thrombectomy groups were with higher ADC values and lower infarct volumes, the differences were statistically significant (P<0.05). Compared with8h thrombectomy group,3h,6h thrombectomy groups were with higher ADC values and lower infarct volumes. Differences of the ADC values were statistically significant (3h:P=0.000;6h:P=0.000); infarct volumes had no significant difference (3h:P=0.699;6h:P=1.000). Compared with6h thrombectomy group,3h thrombectomy group were with higher ADC values and lower infarct volumes, the difference between them wase not statistically significant (ADC values:P=0.235infarct volumes:P=1.000).24h BDNF protein expression results presented that BDNF expression of3h,6h and8h thrombectomy groups were significantly higher than12h thrombectomy group and non-treatment group, where differences were statistically significant (P<0.05). BDNF protein expression in3h thrombectomy group was higher than in6h,8h thrombectomy groups, Compared with6h and8h thrombectomy group, Differences of the BDNF protein expression were statistically significant (6h:P=0.00208h:P=0.000); Compared with8h thrombectomy group,6h thrombectomy group were with higher BDNF protein expression, the difference between them wase not statistically significant (P=0.580). Light and electron microscope examination revealed that there were no obvious morphological abnormalities of brain tissue neurons in3h thrombectomy group. Neuronal damage was minor with slight changes. There were obvious damage of neurons in6h and8h thrombectomy groups, with part of the neuronal degeneration and moderate changes. Morphous and structure of neurons were damaged in non-treatment group, there were extensive necrosis of neuronal cells with severe changes.Conclusion:Application of intracranial arterial embolectomy device to thrombectomy in the early stage of thromboembolic cerebral infarction can reduce cerebral ischemic injury. It’s an effective for acute embolic cerebral infarction.The characteristic that mechanical embolectomy could rapidly recovered the blood flow make it more appropriate to extend the therapeutic time window. The ultra-early treatment is the best occasion for mechanical embolectomy. Thrombectomy within eight hours has therapeutic significance; DWI is a sensitive imaging method for dynamic observing and evaluating the therapeutic effect of acute cerebral infarction. |
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