| ObjectivesDifferent drugs were used to damage blood vessels to induce inflammation.By coarctation of abdominal aortic outflow tract,the blood flow is blocked,thus increasing the stress of the blood vessel wall.The high risk factors of AAA rupture are comprehensively analyzed from the changes of tube wall pressure and vascular pathology to provide theoretical basis for clinical AAA rupture risk assessment.MethodThirty healthy New Zealand white rabbits were selected and weighed 2 ? 3 kg.They were randomly divided into 5 groups of 6 animals each: calcium chloride infiltration group,calcium chloride infiltration combined with abdominal aorta outflow tract constriction group,and low concentration trypsin infiltration group,low concentration trypsin infiltration combined with abdominal aorta outflow tract constriction group,high concentration trypsin infiltration combined with abdominal aorta outflow tract constriction group.The infiltrating blood vessels were wrapped with different drugs for 30 min respectively.After drug injury in the outflow tract constriction group,different types of cat urinary catheters were selected according to the diameter of the blood vessels to ligate the distal end of the infiltrating section in parallel with the abdominal aorta,and then the catheter was withdrawn to form a constriction of about 50-60%.Abdominal aorta ultrasound examination was performed on the experimental rabbits every week after operation to observe and measure the diameter change of abdominal aorta in the infiltrating section.Routine blood changes were detected on fasting blood samples in the early morning before surgery,2 days after surgery,1week after surgery,and 2 weeks after surgery;fasting blood samples were collected in the morning and 1 week after surgery in normal blood vessels After standing,takethe upper serum to detect the changes of IL-6 and MMP-9 content in blood;The changes of blood pressure in rabbits were monitored by electronic blood pressure monitor at 1 week and 2 weeks after operation,and the peak wall stress(Peak wall stress,PWS)of abdominal aortic wall was calculated by ANSYS 15.0 software;Two weeks later,the test rabbits were euthanized,and the abdominal aortic injury segment was fixed,embedded,and sectioned.HE staining was used to observe the changes in tissue structure and cell composition of the aortic wall,and EVG staining was used to observe the extent of elastic fiber damage to the aneurysm tube wall,And the image analysis software was used to measure the vascular intima,media thickness,and elastic fiber area percentage.The test data were statistically processed using Excel and SPSS 19.0 software.The comparison between groups was tested by Duncan's method.P <0.05 was considered statistically significant.ResultThe vasodilatation of the calcium chloride infiltration group and the trypsin infiltration group did not reach 1.5 times,no abdominal aortic aneurysm formed.In calcium chloride+stenosis group,the tumor formation rate was 66.67%,the average vessel dilatation was 1.61 times and no ruptured aneurysm.The tumor formation rate in the low concentration pancreatin+stenosis group was 83.33%,the average vascular dilatation was 1.89 times and no ruptured aneurysm.The tumor formation rate in the high concentration pancreatin+stenosis group was 100.00%,the average vascular expansion was 2.43 times and three experimental rabbits(3/6)died due to ruptured aneurysm.The results of blood routine examination showed that the total number of leukocytes in each group increased within 2 days after operation,and the number of lymphocytes remained unchanged within 2 days after operation.The neu of calcium chloride group,calcium chloride + stenosis group and low concentration pancreatin group increased significantly(P < 0.05)and that of high concentration pancreatin +stenosis group was 2 days after operation,respectively D showed that mononuclearcells(Mon)increased significantly(P < 0.05).All the indexes recovered to the preoperative level 1-2 weeks after operation.Two weeks after the operation,the content of IL-6 in each group was increased by 2-5 pg/m L compared with 1 week after the operation,and the high concentration pancreatin+stenosis group was significantly higher than other groups(P < 0.05).The content of MMP-9 in each group decreased by 3-4 ng/m L compared with 1week after operation.the high concentration pancreatin+stenosis group was still significantly higher than other groups(P < 0.05).The pre-operative cuff measurement of the test rabbit was about 70 mm Hg.At1 w after operation,the MAP of the narrowed outflow tract increased by about 10 mm Hg compared with that before operation,which was significantly higher than that of the non-narrowed outflow tract(P <0.05).At 2w after operation,the MAP of each group was not compared with 1w obvious change.Computer numerical simulation found that the narrowing of the outflow tract increased the stress on the vessel wall.The results of sectioning showed that the thickness of the normal abdominal aorta intima was about 3.2 ?m,the vascular intima of each group was significantly thickened by drug damage(P <0.05),and the vascular intima thickness after calcium chloride injury was significantly larger than that after trypsin injury The thickness of the intima of the blood vessel(P <0.05),and the thickness of the intima of the blood vessel after low concentration of trypsin injury was significantly larger than that of the blood vessel after high concentration trypsin injury(P <0.05);The thickness of the middle membrane of the normal abdominal aorta was about 134.83 ? M.the middle membrane of the calcium chloride infiltrated group was 33.65% thicker than that of the normal abdominal aorta.EVG staining showed that the curvature of the elastic fibers of the middle membrane was straightened,and there were fractures and fragments.The middle membrane of the calcium chloride + stenosis group was split,form a cavity with a diameter larger than the thickness of the membrane in other groups.The thickness of the membrane in the low concentration trypsin infiltration group and the low concentration trypsin + stenosis group increased by 10.68%-13.55% compared with the normal abdominal aorta.EVG staining showed that the elastic fibers were partially broken and changed.Thin,but the whole still has integrity and continuity.In the high-concentration pancreatin + stenosis group,the membrane thickness was 89.93% lower than that of the normal abdominal aorta.EVG staining showed that the wall structure was loose,and the elastic fibers were significantly reduced compared to the normal abdominal aorta.Conclusion1.Due to the difference in aorta diameter between different individuals,the AAA expansion multiple can better assess the risk of rupture than AAA diameter,When the AAA expansion multiple is greater than or equal to 2.43 times,it is easy to break;2.Narrowing the abdominal aortic outflow tract will increase the MAP of experimental rabbit by about 10 mm Hg,and increase the wall stress of AAA,thereby accelerating the expansion of the AAA and increasing the risk of AAA rupture;3.A large amount of elastin and collagen hydrolysis by High levels trypsin that will cause the blood vessel wall to become thinner and loose,and it is easier to rupture the AAA due to local elastic fiber fracture and collagen fiber collapse when the wall stress increases... |
PDF Full Text Request