Willis覆膜支架治疗犬颈内动脉虹吸段动脉瘤的影像学和组织病理学研究

Treatment of carotid-siphon aneurysms by using Willis stent-graft:an angiographic and histopathologic study in dogs

目的建立一种犬颈动脉虹吸段(CS)动脉瘤模型,并观察12个月以测试新型Willis颅内覆膜支架系统的机械性能;评价植入支架在弯曲段血管内的组织学反应。方法通过外科手术方法建立12只犬24枚颈动脉直段侧壁囊性动脉瘤(A组),和12只犬12枚CS动脉瘤(B组)。每枚动脉瘤行1枚覆膜支架植入治疗。以血管造影方法评价支架植入即刻,1、3、6和12个月随访动脉瘤闭塞、支架内漏、支架成角、载瘤动脉是否通畅及再狭窄率等情况。支架段血管行光镜和扫描电镜检查,评价动脉瘤腔内血栓形成,内膜增生和内皮化情况。结果B组中,支架植入即刻血管造影显示2枚动脉瘤存在轻度内漏,3枚支架存在轻度成角现象;12个月时随访,内漏均消失,1支载瘤动脉发生闭塞,3支载瘤动脉有轻度狭窄(<50%)。A组中,1支载瘤动脉闭塞,2支载瘤动脉轻度狭窄(<50%)。电镜检查所有支架内均有新生内膜形成,动脉瘤腔内均充满血栓。B组动物,12个月时才完成完全内皮化过程,内皮细胞排列与血流动力学方向具有很强的相关性。结论应用Willis覆膜支架治疗犬CS动脉瘤方法学上可行。与直段血管相比,弯曲段血管内覆膜支架植入后,支架内皮化时间延长。

Objective To establish a carotid siphon aneurysm model in dogs in order to test the mechanical features of a newly-designed Willis covered stent-graft and to investigate the histological reaction of the stent-implanted vessel during a follow-up period of 12 months. Methods Twenty-four saccular side- wall aneurysms were surgically created in twelve dogs （group A） and 12 carotid siphon aneurysms in another twelve dogs （group B）. A Willis stent-graft was implanted in each aneurysm. Angiography was performed immediately after the procedure and 1, 3, 6 and 12 months after the implantation to investigate the aneurysm isolation, endoleak, stent angulation, and the patency or restenosis of the parent artery. Light and scanning electronic microscopy were used to identify aneurysmal sac thrombi, intima hyperplasia and endothelial progress of the stent-loaded arterial segment. Results In group B, postoperative immediate angiography demonstrated that two aneurysms had mild endoleak and three stents became angulated. Follow-up exam 12 months after the procedure revealed that all previous endoleaks disappeared, one parent artery became occluded and three parent arteries developed mild stenosis （ 〈50%）. In group A, occlusion of parent artery was seen in one and mild stenosis （ 〈50%） in 2 cases. Electronic microscopy revealed new intima formation in all stents, and all aneurysmal sacs were filled with thrombi. In group B, the endothelialization process was not completed until 12 months after the stent implantation, and a marked correlation existed between endothelial cell arrangement and the hemodynamic orientation. Conclusion It is feasible to treat carotid-siphon aneurysm in dog with a Willis stent-graft. The complete endothelialization of the covered stent in tortuous vessel takes longer time than that in rather straight vessel.