【作者】 苏存华；

【导师】 徐志云； 韩林； 王军； 宋智钢；

【作者基本信息】 第二军医大学 ， 外科学（专业学位）， 2013， 博士

【摘要】 背景与目的：急性A型主动脉夹层一种严重危及病人生命的灾难性疾病。其特点是起病突然，病情进展迅速，死亡率高，如不及时诊治，急性A型主动脉夹层发病后最初的48小时内，每小时病死率达1％～4％，48小时内自然死亡率可达50%。及时的外科手术治疗能够有效防止夹层破裂、心包填塞、心力衰竭等致命性并发症的发生。目前的治疗方法主要有传统手术治疗以及在此基础上发展的传统手术结合冰冻象鼻干技术和血管腔内隔绝手术治疗。然而传统手术操作复杂，吻合困难；需要长时间的体外循环（CPB）和深低温停循环（DHCA），手术创伤大，且极易发生术后出血，术后需要大量输血。即使近几年来经过手术技术和围手术期处理技术的提高，手术死亡率和术后并发症发生率仍然居高不下。腔内隔绝治疗由于主动脉解剖因素以及支架本身制作因素的影响限制了其目前在临床的广泛应用。为此，近年有学者尝试应用杂交手术技术治疗急性A型主动脉夹层，并取得了一定的发展，其结果令人鼓舞。然而由于主动脉弓部解剖结构的特殊性和血流动力学的复杂性，目前世界上还没有专门针对杂交手术中治疗主动脉弓部疾病的血管支架。本课题的目的在于研制一种全新结构的人造主动脉弓血管覆膜支架,覆膜支架经过体外测试合格后应用于动物实验，通过动物实验验证其临床应用的可行性和安全性。我们期望这种人造主动脉弓覆膜支架在应用过程中能在保证手术质量的同时大大简化手术过程，缩短手术时间，降低手术并发症，改善生存率，提高治疗效果，从而应用于临床时能更加有效的解除主动脉弓部疾病患者的痛苦，造福于该类患者。方法：1.人造主动脉弓覆膜支架的设计及体外性能测试1）人造主动脉弓覆膜支架的基本构架。主动脉术中覆膜支架系统由术中覆膜支架（简称术中支架）和输送系统组成，术中支架由裸支架、ePTFE覆膜和涤纶布组成。裸支架在ePTFE覆膜内外层的中间，涤纶布固定在术中支架的近端，并被ePTFE覆膜包覆在内层。支架为自膨胀式支架。血管支架整体结构设计成与主动脉弓部形态相符合的结构，由1个主体和多个（1-3）分支构成，主体对应主动脉弓部位的大动脉，分支分别对应主动脉弓上头臂干、左颈总动和、左锁骨下动脉分支血管。输送系统由手柄、固定杆和鞘芯、主体包膜和拉线、Tip和鞘芯、分支包膜和分支拉线、导丝等部件组成。固定杆和手柄固定在一起，鞘芯从手柄中间穿过；拉线和固定块连接在一起，通过固定块可以将拉线抽掉；导丝从Tip和鞘芯中间穿过。术中支架的主体会固定在固定杆上并被主体包膜包覆，支架的分支部分会装入分支包膜中。2）人造主动脉弓覆膜支架的体外性能测试。A.人造主动脉弓覆膜支架外观和主要尺寸测试：通过目测和电子显微镜下放大2.5倍检查支架和输送系统：检查支架是否有断裂、有灰尘、污垢、松动等；覆膜材料的表面是否光滑整洁，有无破洞、裂缝、伤痕。检查输送系统的外表面是否清洁光滑，有无折痕、硬弯、污渍、裂纹、毛刺等加工缺陷。用游标卡尺和直尺检测主动脉术中覆膜支架系统的尺寸。B.人造主动脉弓覆膜支架物理性能测试：a、通过拉力机及相应的夹具分别进行覆膜支架系统的支架连接强度、支架和覆膜间连接强度、支架的径向支撑力以及覆膜破裂力的物理力学方面的检测； b、通过压力泵向覆膜支架内腔注入常温蒸馏水，进行覆膜渗透量的测试； c、将对应的小于支架直径10-20%的血管模型放在水浴锅中用输送系统将支架释放到的血管模型中，目测支架金属部分与血管模型的柔顺性和贴壁性；d、用输送系统将支架释放到30-37℃水浴锅中用正常视力或矫正视力在放大5倍的条件下检查支架外表面，进行回弹性的测试；e、将装好支架的硅胶管安装到疲劳机中，启动试验机开关，按照调好的频率、振幅、零位点进行疲劳强度的测试；f、将主动脉术中覆膜支架直接放置在X射线成像设备上，进行成像观察及射线可探测性测试。C.人造主动脉弓覆膜支架化学性能测试：将包装灭菌好的主动脉术中覆膜支架与输送系统分开分别取样制作检验液，进行还原物质、酸碱度、发残渣、重金属总含量、紫外吸光度、环氧乙烷残留量的测定。D.人造主动脉弓覆膜支架输送系统物理性能测试：a、将固定杆和手柄分别固定在拉力机上的上下夹具上，以一定的移动速度进行拉伸，进行固定杆和手柄连接力的测试；b、同样的方法进行鞘芯与固定杆连接力、鞘芯与Tip头连接力以及拉线和固定块连接力的测试；c、将支架试样预先脱脂清洗干净后全部浸入（全浸法）温度为20℃±5℃的0.5mol/L氯化钠溶液中，保持168h。用10倍显微镜放大观察试件表面的腐蚀痕迹。进行输送系统金属部分耐腐蚀性能测试。E.人造主动脉弓覆膜支架输送系统显微结构测试:将试样经仔细抛光后,不进行腐蚀，观察夹杂物的形态和数量，用专业金相分析软件Image Plus Pro6.0定量分析夹杂物的面积百分比；将抛光后的试样经腐蚀剂（4%硝酸）腐蚀后，放在镜相显微镜下观察其微观组织，并定量统计晶粒度。3．人造主动脉弓覆膜支架的动物实验研究1）以犬为实验对象，挑选了20条杂种德国牧羊犬深低温停循环条件下切开升主动脉远端，植入导丝并将人造主动脉弓覆膜支架沿导丝分别引导进入远端降主动脉、左锁骨下动脉、右侧头臂动脉，待支架位于恰当位置后释放支架，缝合支架与主动脉远端，并与主动脉近端做端端吻合。术后均予围手术期的临床观察。观测手术时间、主动脉阻断时间、手术出血量、术后输血量、术后死亡率、并发症发生率等指标。2）观察术后中期（6个月内）实验动物的恢复情况，有无严重并发症的发生；并在6个月后行主动脉CT血管造影术及数字减影血管造影（DSA）检查，进一步明确支架情况。3）影像学检查后处死动物并取出标本。标本固定后分别行苏木精－伊红（HE）染色、维多利亚蓝（VB）染色观察覆膜支架在体内的组织结构。结果：1．通过体外实验得到主动脉术中覆膜支架系统外观和主要尺寸满足产品设计要求。实验组所有支架支架连接强度测试均远大于5N；支架径向支撑力>4N；ePTFE膜与支架间连接强度、包裹针织涤纶布区域覆膜与支架间连接强度均远大于15N；覆膜渗透量均≤100ml/cm2/min；覆膜破裂力≥10N；所有支架柔顺性良好，无绞结现象、无折弯、贴壁性、回弹性较好，均能恢复原来形状；经疲劳实验后所有支架覆膜与支架连接完好，覆膜无破洞，裂缝，缝线无脱落，金属丝无断裂，金属丝连接点无松脱；X射线影像观察显示支架可探测性良好。所有检测均证实主动脉术中覆膜支架物理性能满足产品设计要求。覆膜支架与输送系统制样检验液还原物质<2ml、酸碱度<1.5、发残渣<2mg、重金属总含量<1μ g/ml、紫外吸光度<0.1、未测及环氧乙烷残留。所有检测均证实主动脉术中覆膜支架化学性能满足产品设计要求。固定杆和手柄连接力、鞘芯与固定杆连接力和鞘芯与Tip头连接力的测试、拉线和固定块连接力均远大于15N；所有样品金属部分表面无锈蚀，为a级。所有检测均证实主动脉术中覆膜支架输送系统物理连接力性能满足产品设计要求。所有样品的NiTi丝及钢套中晶粒度不粗于4级；所有样品的NiTi丝及钢套中疏松和非金属夹杂物的颗粒不超过39μ m，面积百分比不超过2.8%，符合要求。2．动物实验20例，手术死亡2例（死亡率10%），手术平均体外循环时间和停循环时间分别为80.2±7.54和10.7±1.94min，存活的动物均恢复良好，术后无明显并发症。术后6个月CT增强造影及血管造影检查示：支架主体和两个分支形态正常，未见血栓堵塞和狭窄。未见支架的移位、内漏。覆膜支架腔内面光滑，完整覆盖白色的膜状物，未见血栓形成。覆膜支架标本HE染色：对比未植入支架覆膜支架主动脉壁，植入覆膜支架后组织标本切片提示主动脉壁中膜和内膜无明显改变，腔内有均有内膜组织增生，组织结构一致，伴大量新生血管形成。VB染色：对比未植入支架覆膜支架主动脉壁，植入覆膜支架后组织标本切片提示实验组中膜弹力纤维完整，内膜弹力纤维排列轻度紊乱。结论：1.我们设计的新型人造主动脉弓覆膜支架具备合格的外观和尺寸。并且覆膜支架以及其输送系统物理性能、化学性能、以及显微镜检测均合符要求。2.动物实验证明新型人造主动脉弓覆膜支架符合人造血管代用品的基本要求，安全性可靠，具有一定的临床价值。3.实验研究表明应用新型人造主动脉弓覆膜支架的杂交手术技术与传统开放手术和腔内隔绝技术相比，在简化手术操作、减少手术时间和手术创伤、减少手术死亡率和术后并发症发生率等方面具有较明显的优势。4.本动物实验仅是小样本的动物实验，本产品的临床效果还需要大样本远期随访以及临床试验进一步证实。更多还原

【Abstract】 Background:Acute type A aortic dissection(ATAAD) remains a life threatening disease. It ischaracterized by sudden onset, rapid progression and high mortality. Without timelydiagnosis and treatment, the fatality rate was from1%to4%per hour within the first48hours after the onset of Stanford type A aortic dissection, and the natural mortality up to50%within48hours.Timely surgical treatment can prevent fatal complications such as cardiac tamponade,heart failure, and aortic rupture. The current treatment methods include the traditionalsurgical treatment, the treatment combining traditional surgery frozen elephant trunktechnology and endovascular repair. However, the traditional surgery accompaniescomplex surgical techniques, slow anastomosis, a long period of cardiopulmonary bypass(CPB) and deep hypothermic circulatory arrest (DHCA), and postoperative anastomoticbleeding. The overall in-hospital mortality and complications following conventionalsurgical treatment of acute Stanford type A dissection remains high, despite theimprovements in surgical techniques and perioperative care. Endovascular therapy islimited by many anatomic factors when it was applied in patients with Stanford Adissection. Recently, several studies have been performed and reported the initialencouraging results of hybrid aortic arch repair in small series. But because of theparticularity of the anatomical structure of the aortic arch and the complexity ofhemodynamic, we couldn’t find a kind of specifically stent targeted hybrid surgicaltreatment of aortic arch disease at home and abroad.The purpose of this topic is to develop an artificial aortic arch stent-graft with newstructures. After passing the in vitro testing, the stent grafts were used in experimentalresearchs to test the feasibility and safety of clinical application in animal experiments. Wehope that the artificial aortic arch grafts could greatly simplify the surgical process, shortenthe operation time, reduce complications and improve patient survival, and moreeffectively relieve the pain of the patients with aortic arch diseases, while the quality of thesurgery must be guaranteed.Methods:1. Design and ex vivo test of the artificial aortic arch prosthesis 1) Basic structure of the artificial aortic arch prosthesis.The main part of the device consists of a stent-graft and a delivery system, thestent-graft consists of bare Nitinol stent, ePTFE membrane and the polyester suture portion.The ePTFE membrane covers on the two sides of the metal skeleton and the polyestersuture portion located in the proximal end of the stent-grafts. The stent-grafts enabledself-expansion. The overall structure of the stent is designed to be consistent with aorticarch morphology structure, including a main body, and1to3branches. The main bodycorresponds to the aortic arch, the branches correspond to the left subclavian artery, leftcommon carotid artery and brachiocephalic trunk, respectively. The delivery systemconsists of the handle member, the fixed rod and the sheath core member, the mainenvelope and the wire member, Tip and the sheath core member, branch envelope and thebranch pull member and guidewire. Fixed rod and handle are fixed together, the core of thesheath passes through from the handle middle. The pull member and fixed blocks areconnected together, and the pull member could be deprived through a fixed block. Theguide wire passes through the middle of Tip and sheath core. The main body of stent-graftis fixed with the fixed rod and covered with the main envelope, and the branches areloaded into the branch envelopes.2) Ex vivo test of the artificial aortic arch prosthesisA. The appearance and size testing of the artificial aortic arch stent-graft: thestent-grafts and delivery system are check through visual and electronic microscope (2.5times zoom): check if the bracket is broken, dust, dirt, loose; if the graft surface is smoothand clean, if there are holes, cracks and scratches. Check if the outer surface of the deliverysystem is clean and smooth, no creases, no hard bends, no stains, no cracks, no glitches, noprocessing defects. The size of the artificial aortic arch prosthesis is detect by verniercaliper and ruler.B. Physical performance testing of artificial aortic arch graft: a) The detection ofphysical mechanics including the strength of the stent-graft connection, the connectionstrength between the tectorial membrane and the metal stent, the stent radial force and thelamination rupturing force was tested by the tensile machine and the mold; b) Injecting intothe stent lumen with room temperature distilled water via pressure pump, to test thepermeation amount of the stent graft; c) The vessel model whose diameter is10-20%smaller than the stent is on the water bath, releasing the stent into the vessel model with the delivery system, checking the flexibility and adherent of the stent-graft underdirect vision; d) Release the stent-graft into water bath under the conditions of30-37℃bythe delivery system to check the outer surface of the stent, for testing the reboundresilience; e) The silicone tube fixed with the stent-graft is installed into fatigue machine,opening test switch, to test fatigue strength in accordance with a good tune frequency,amplitude, and zero points; f) The stent-graft is placed directly on the X-ray imagingapparatus, for rays detect testing.C. Chemical properties testing of the artificial aortic arch graft: the sterilizedstent-graft and stent system were sampled to product testing liquids separately, check thereducing substances, pH, fat residue, the total content of heavy metals, ultravioletabsorbance, ethylene oxide residues.D. Physical performance testing of delivery system: a) The fixed rod and the handleare respectively fixed to the upper and lower jig in the tensile machine, setting the tensilemachine to be stretched under a certain speed, testing connecting force between the fixedrod and the handle. b) The connecting force between the sheath core and the fixed rod, thecore of the sheath and the Tip head as well as the cable and fixed block were tested in thesame way; c) Cable and fixed block are fixed to the upper and lower jig in the tensilemachine respectively, testing connecting force between; d) The sample was pre-degreasingcleaned, and then was immersed into20℃±5℃0.5mol/L sodium chloride solution,keeping168h. Signs of corrosion of the specimen surface were enlarged and observed witha microscope (10times), to test the corrosion resistance of the metal transported system.E. Microstructure testing of the delivery system: a sample after carefully polished, nocorroded was performed to observe the morphology and quantity of inclusions, quantitativeanalysis of the percentage of the area of the inclusions was performing using professionalmetallographic analysis software Image Plus Pro6.0; a sample after polished andcorroded(4%nitric acid), on the mirror phase under the microscope to observe themicrostructure, and quantitative statistics crystallite size.2.Animal Experiments of the artificial aortic arch prosthesis1)20adult German sheepdogs were used as surgical objects in our experiments.Incising distal ascending aorta under deep hypothermic circulatory arrest, introducing theguide wires of the stent system, advancing the main body and the branches carefully intothe proximal descending aorta, left subclavian artery, and brachiocephalic artery along individual guide wires, deploying the stent-graft when the main body and branches of thisstent graft system were satisfactorily positioned, suturing the suturing portion to thetransected distal stump of the ascending aorta, and proximal ascending aorta in end-to-endanastomosis fashion. Clinical observation of peroperative period and the short and mediumterm (6months) was performed. We observed operation time, circulatory arrest time,operative bleeding, postoperative drainage, postoperative mortality, complications rate andso on.2) CTA and DSA were performed on the animals6months after the surgery.3)Animals were sacrificed after imaging test and the specimen were removed.Hematoxylin-eosin (HE) staining and Victoria Blue (VB) were performed to observe theorganizational structure of the body.Results:1. Appearance and size of the stent graft system is qualified. The connection strength of allthe stents were much larger than5N; stent radial force was greater than4N; the connectionstrength between the ePTFE tectorial membrane and the metal stent is much greater than15N; permeation amount of the tectorial membrane coating penetration volume is far lessthan100ml/cm2/min; membrane rupture force is much greater than10N. All stent-graftswere described with good flexibility, without kinking phenomenon, no bending, with goodadherence, good rebound resilience, being able to restore the original shape; the connectionbetween all stents and tectorial membrane was intact after fatigue test, tectorial membranewith no holes or cracks, the suture without shedding, wire without fracture, wireconnection point with no loose; observation of X-ray images confirmed good stentdetectability. All tests were confirmed stent physical properties to meet product designrequirements. Sample test solution of the stent-graft and the delivery system showedreducing substances <2ml, pH <1.5, fat residue <2mg, total content of heavy metals<1μg/ml, ultraviolet absorbance <0.1, and unmeasured ethylene oxide residues. All testswere confirmed chemical properties of the stent to meet product design requirements. Theconnection force between the fixed rod and the handle, the core of the sheath and the fixedrod, the core of the sheath and the Tip head was much larger than15N; there was nocorrosion on the surface of all the metal part, as a class. All tests were confirmed physicalconnection force properties of the delivery system to meet product design requirements.The crystallite size of the NiTi wire and the steel sleeve is not thicker than4; inclusions particles in NiTi wire and steel sets in all samples does not exceed39μm; area percentagedoes not exceed2.8%, to meet the requirements.2. Two cases died in experiemental group (mortality of10%), the mean cardiopulmonarybypass time, circulatory arrest time were80.2±7.54and10.7±1.94min, respectively.The surviving animals recovered well with no significant complications.Aortic imaging including CTA and DSA6months after surgery indicated that the mainbody and branches of the stent grafts were of normal morphology, no thrombus and narrow,no stent displacement, no internal leakage was observed. The luminal surface of theendoprosthesis had a thin but full coverage layer of uniform white neointima, without anyloosely attached mural thrombus. Histologic sections with H&E stain displayed a normalarrangement of the media and adventitia and exuberant circumferential intimalproliferation with or without neo-microvessels, compared with the control sections.Histologic sections with VB stain showed a normal distribution pattern and density of theelastic fibers and collagen bundles in the medial and adventitial layer, and the integrity ofinternal elastic lamina in the experiment group was moderately destoried by the extrusionof proliferated intima.Conclusions:1. The new type of artificial aortic arch stent-grafts we designed have qualified appearanceand size. And physical properties, chemical properties, and microscopic examination of thegrafts as well as their delivery system complied with requirements.2. The animal experiments show that the new artificial aortic arch grafts meet the basicrequirements of artificial vascular substitutes. It is safe and reliable and has real clinicalvalue.3. Compared with traditional open surgery and endovascular exclusion technology, thestudy shows that our new artificial aortic arch stent-grafts combining hybrid surgicaltechnique simplifies the surgical procedure, reduces the surgical time and surgical trauma,and brings down surgical mortality and incidence of postoperative complications.4. This experiment is only a small sample of the animal experiment, the clinical effects ofthe products requires a large sample, long-term follow-up and clinical trials to confirm.更多还原