| Background:Ascending aortic dissection is a critical cardiovascular disease with a high incidence rate,accounting for 66% of acute aortic dissections.As the population ages,its incidence is expected to significantly increase.Currently,open surgery is the main treatment method,but approximately 30% of patients are unable to undergo this treatment due to surgical risks.Although endovascular repair has been widely applied in Stanford Type B dissections,its application in ascending aortic dissections still faces challenges.Issues such as mismatch between stent performance and anatomical characteristics remain unresolved.This study aims to optimize the stent structure and manufacturing process to address the unique challenges of treating ascending aortic dissections,ensuring stent stability throughout the cardiac cycle,reducing the risk of complications,and achieving a better integration between the stent and the aortic wall,thus improving the safety and effectiveness of endovascular treatment.Methods:1.A retrospective review was conducted on patients admitted to the emergency department with ascending aortic dissection and those with a normal ascending aorta from October 2022 to October 2023.All subjects underwent total aortic electrocardiogram-gated computed tomography angiography.Exclusion criteria included patients with a tear at the sinotubular junction or those with dissection affecting the aortic root and the sinotubular junction.During the examination,the entire thoracic aorta was reconstructed in images to measure the morphological changes of the ascending aorta across different cardiac cycle phases.The length,diameter,and curvature radius of the ascending aorta during various cardiac cycles were measured.Paired t-test heatmaps were used to evaluate the variability of parameters at different phases of the cardiac cycle in the same participant,considering a p-value of less than 0.05 as statistically significant.The trend of average changes in parameters at different phases of the cardiac cycle was represented in line graphs.Statistical analysis was performed using SPSS and R software to analyze changes in morphological parameters of the ascending aorta at different stages of the cardiac cycle,providing data support for the design of endovascular implants for ascending aortic dissection.2.Stent graft design optimizations were performed,including adjustments to the geometric structure and manufacturing processes,to enhance adaptability and stability in complex vascular environments.Adjustments were made to the stent graft body and bare stent design to optimize the design,incorporating advanced manufacturing processes and introducing a new sealing ring design.To verify the performance of the optimized stent graft,tests were conducted referencing the dynamic measurement results of the electrocardiogramgated computed tomography angiography of ascending aortic dissection,including radial support force tests,compliance tests,bending performance tests,and fixation capabilities tests,to theoretically validate the optimization effects of the stent graft.3.Swine were employed as the animal model for the establishment of ascending aortic dissection,followed by the implantation of ascending aortic stent grafts.The swine were divided into two cohorts: one group served as the control,receiving no stent graft implantation post-dissection creation,while the other group underwent immediate stent graft implantation after the dissection was established.Postoperative evaluation included total aortic computed tomography angiography and transesophageal echocardiographic assessment to determine the placement accuracy,compliance,and impact on the ascending aorta structure of the stent grafts.Immediate postoperative assessments,along with further evaluations at three months,encompassing imaging studies,autopsies,and histopathological examinations,were conducted to discern the short-to medium-term effects of endovascular treatment on the swine models of ascending aortic dissection.Result:1.Measurements and analyses were conducted on 13 patients with ascending aortic dissection and 18 individuals from a normal control group.The results revealed that the average diameter at the sinotubular junction during systole for patients with ascending aortic dissection was 34.86±4.45 mm,and during diastole,it was 33.13±4.37 mm,with an average diameter change rate of 5.28%±0.83%.The mid-section of the ascending aorta had an average diameter of 32.40±3.77 mm during systole and 31.67±3.81 mm during diastole,with an average diameter change rate of 2.36%±1.24%.The distal section of the ascending aorta had an average diameter of 32.74±4.77 mm during systole and 32.04±4.81 mm during diastole,with an average diameter change rate of 2.26%±0.82%.The central axis length of the ascending aorta was 74.23±14.69 mm during systole and 73.00±15.06 mm during diastole,with a change rate of 1.86%±2.59%.The average curvature radius of the ascending aorta was 47.19±12.41 mm during systole and 48.76±12.72 mm during diastole,with an average change rate of 7.37%±4.25%.Notably,the diameters at the sinotubular junction,mid-section,and distal section of the ascending aorta exhibited significant trends of variation throughout the cardiac cycle,while the central axis length and curvature radius did not show notable differences.Compared to the normal ascending aorta,the sinotubular junction in patients with ascending aortic dissection exhibits significant dilation.Furthermore,the diameter change rate of the sinotubular junction throughout the cardiac cycle in patients with ascending aortic dissection is significantly greater than that of the normal ascending aorta.2.A comparison of stent graft samples before and after optimization,focusing on radial support force,compliance,bending performance,and fixation capabilities,revealed improvements in the performance of the optimized stent grafts.Radial support force testing indicated that the optimized stent grafts exhibited a significant increase in radial support force when expanded to 85%,90%,and 95% of their diameters,with the average radial support force decreasing from 0.50N/mm,0.31N/mm,and 0.10N/mm before optimization to 0.15N/mm,0.11N/mm,and 0.05N/mm,respectively.In compliance testing,the optimized stent grafts showed better adaptability to deformation,with lower fluctuations in radial support force.Regarding bending performance,the optimized stent grafts required less force to bend and demonstrated a smaller rebound force once the bending force was removed.Finally,in in vitro tests simulating blood circulation,the stent grafts displayed stable fixation performance.3.Three swine successfully established ascending aortic dissection models and had stent grafts implanted.Postoperative computed tomography angiography evaluations indicated that the stent grafts were effectively deployed in the ascending aorta and achieved acceptable apposition with the surrounding aortic wall.No contrast agent was observed entering the false lumen of the dissection,and complications such as endoleaks were not detected.However,the bare stent region of the grafts interfered with aortic valve movement.Transesophageal echocardiography showed that the average diameter of the ascending aorta underwent minor changes at different stages of the cardiac cycle post-implantation,suggesting that the stent grafts did not significantly affect the compliance of the ascending aorta.Pathological examinations of the "burb" area and the main body of the optimized stent grafts revealed fewer adverse reactions.Compared to the animal dissection models without stent graft implantation,models with implanted stent grafts showed media thickening and formation of neointimal tissue.Conclusion:1.Throughout the cardiac cycle,the diameter of the ascending aorta in patients with ascending aortic dissection and healthy individuals is significantly larger during systole than in diastole.Compared to other parts of the ascending aorta,the diameter change rate of the sinotubular junction in both groups of patients is the most pronounced throughout the cardiac cycle.Additionally,the diameter change rate of the sinotubular junction within the cardiac cycle in patients with ascending aortic dissection is significantly greater than that of the normal ascending aorta.2.With the optimization of the stent graft,while ensuring fixation capabilities,there is a reduction in radial support force,an enhancement in compliance,and an enhancement in bending performance.Theoretically,the optimized stent graft reduces damage to the ascending aorta wall and lessens the impact on the pumping function of the ascending aorta.3.The optimized stent graft can effectively repair the ascending aortic dissection and has a certain promotive effect on the healing process of the ascending aortic dissection.The misalignment between the stent graft deployment system and the central axis of the ascending aorta can lead to one side of the stent graft protruding forward,affecting aortic valve movement. |
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