| Objective : To explore the method of establishing animal model of acute aortic dissection(AAD)involving visceral arteries,and to evaluate the imaging and hemodynamic effects of AAD intracavitary stenting.Methods : The first part is the establishment of animal models: Firstly,12 local healthy mongrel dogs were selected and randomly assigned to the experimental group or the control group,with 6 in each group.Both groups underwent thoracotomy on the left side under general anesthesia.The thoracic aorta was freed and the diameter was measured.The left aortic wall of the aorta was longitudinally cut to the inner 1/3layer of the media,and the middle membrane were separated by nerve strippers.In the control group,the dissection cavity was injected with elastase for 30 min,and then the middle membrane separated by a stripper or a self-made endometrial separator.In the experimental group,the super-sliding super-hard guide wire was used to separate the middle layer from the distal end with a single-bend catheter,and then the balloon was dilated,and then the elastase was perfused through the balloon catheter and maintained for 30 min.After the middle layer was separated,the aortic intima was laterally resected after blocking the aorta in both groups.The distal endometrium was sutured and fixed to the side wall of the aorta,and then the aortic incision was sutured to confirm that there was no bleeding in both groups.Both groups were given a blood pressure of 0.04 mg/kg of adrenaline to increase the blood pressure to 200 mmHg or more.After 20 minutes,the chest cavity was closed.The chest was closed after observing no abnormality for 20 minutes.Immediately after surgery,intratraumatic ultrasound(IVUS),computed tomography angiography(CTA)or digital subtraction angiography(DSA)were performed.The number and length of AAD in the two groups,as well as the involvement of the visceral branch arteries,were compared.The two groups of dogs were sacrificed 3 days after surgery.The length of the dissection was measured by aortic vascular specimens,and the pathological changes of the dissection were analyzed by HE staining.The second part is the experimental research of stent implantation: According to the improved modeling method,6 experimental dogs with AAD model involving visceral branches were established.The diameters of the proximal and distal aorta and true and false lumens were measured after modeling.According to the measurement results,the ratio of 10%-20%Oversize was selected.The stent graft and the bare metal stent are separately adjusted and assembled into the stent delivery system.Intracavitary treatment was performed within 3 days after modeling,and the abdominal aorta was dissected by open laparotomy.The stent graft was implanted into the proximal aorta of the aorta through the stent delivery system,and the bare stent was implanted into the aortic visceral artery.DSA or CTA was performed after operation,and stent implantation,dissection changes,and visceral blood supply were observed.After the examination,the test animals were sacrificed,and the blood vessel specimens were taken to observe the stent implantation and the sandwich false lumen changes.The CTA images before and after treatment were converted and integrated by Computational Fluid Dynamics(CFD)software,and the 3D model was reconstructed.Then the computational software ANSYS and CFX were used to simulate the model.The shear stress of the AAD tumor wall and the blood flow field of the visceral branch artery were analyzed before and after the endovascular treatment.The effectiveness of the multi-layer bare stent(MOBS)technique in the treatment of AAD involving the visceral artery was evaluated.Results:The first part:1.There were no significant differences in the age,weight and other general conditions between the two groups(p>0.05).2.The survival rate after dissection modeling between the two groups were 83.3%,p=1.00;the perioperative complication rate was 66.7%and 33.3%,respectively,p=0.29;the perioperative survival rate was 50.0%and 83.3%,respectively,p=0.26.The difference in the above results was not statistically significant.3.The formation rate of AAD in two groups were 100.0%vs 66.7%,and the difference was not statistically significant(p=0.15).The visceral artery involvement rate were 66.7%and 0%,respectively,and the difference was statistically significant between the two groups(p=0.01).The length of AAD in two groups were 16.38±1.22cm vs 4.00±3.21 cm(p<0.001),and the difference was statistically significant.4.After endovascular treatment,the interstitial false lumen is closed and thrombosis is formed,and the blood supply to the visceral and distal branches is significantly improved,achieving a good aortic morphological remodeling.The second part:1.In this experiment,6 experimental dogs were selected,and the successful rate of intraoperative device release was 100%.There are 7 implanted stents and 14 bare metal stents.The anatomical results of the vascular specimens showed that the stent was implanted well,the interstitial false lumens became smaller and the intracavitary thrombosis was formed.2.After the endovascular treatment,the average diameter of the normal cavity of the celiac trunk artery was increased and the false lumen was decreased,the difference was statistically significant(p<0.05);and the mean diameter of the mesenteric artery and the left and right arteries was true.The difference was not statistically significant(p>0.05).3.The results of CFD analysis showed that the wall shear stress(WSS)was significantly reduced after intracavitary treatment.The blood pressure of the false lumen was significantly reduced at the distal end of the fracture,while the blood pressure of the true cavity was increased.Significant statistical significance(p<0.001);and visceral branch arterial blood flow increased after MOBS implantation,the difference between the two groups was statistically significant(p<0.001).Conclusion:1.The improved modeling method significantly improved the success rate of the AAD animal model involving the visceral artery compared to the traditional modeling method.2.After modeling,IVUS,CTA,and DSA were selected for examination,which can reflect the characteristics of the AAD model from multiple examination results and provide a stable animal model for further endovascular treatment.3.The animal model is similar to the human dissection in terms of morphology and extent,and can be used as an animal test platform for studying human aortic dissection.4.After endovascular treatment,the interstitial false lumen is closed and thrombosis is formed,and the blood supply to the visceral and distal branches is significantly improved,achieving a good aortic morphological remodeling.5.The results of CFD analysis showed that after MOBS treatment,the nature of blood flow field in visceral artery area was remodeled.MOBS can effectively improve the blood flow of visceral branch arteries,indicating that MOBS has the experimental basis for treating AAD involving visceral arteries.6.In this study,the use of MOBS in the treatment of AAD involving the visceral branch area yielded good results,but due to the small sample size,lack of comparison studies with other methods and the results of the middle and long-term studies,it may lead to biased results.Therefore,it is necessary to further increase the amount of experimental samples,design controlled trials and conduct long-term studies to provide a reliable theoretical basis for clinical practice. |
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