【作者】 姜海滨；

【导师】 秦永文；

【作者基本信息】 第二军医大学 ， 内科学， 2012， 博士

【摘要】 研究背景：随着人口老龄化进程的加速，主动脉瓣狭窄的发病率逐年升高，在美国，75岁以上人群主动脉瓣狭窄的发病率是4.6%，仅次于高血压和冠心病，80岁以上老年人中40%会出现瓣膜钙化和主动脉瓣退行性狭窄。对于主动脉瓣狭窄，传统的治疗方法是外科手术，然而，大约30-50%的患者存在严重合并症的患者无法接受外科治疗。2002年，Cribier等率先开展了经导管主动脉瓣膜置换术（Transcatheter Aortic Valve Replacement，TAVR）并获得成功，之后，经导管主动脉瓣膜置入的相关器械和技术的研究逐渐受到重视。目前进行动物实验和进入临床应用的瓣膜支架有数十种之多，而应用最多的主要有两种，即球囊扩张式的Edwards瓣膜支架系统和自膨式的CoreValve瓣膜支架系统。自经导管主动脉瓣膜置换装置投入临床使用以来，全球已完成近4万余例病例。Partner研究已经证明：经导管主动脉瓣膜的手术效果要明显优于标准治疗，对于那些不能耐受外科手术治疗的严重主动脉瓣病变的高危患者,经导管瓣膜植入术1年生存率与外科手术相似。此外，该技术也可应用于主动脉生物瓣衰败的患者，即“瓣中瓣”植入技术。从现有趋势看，经导管瓣膜支架置入技术逐渐成熟，有可能发展成为外科治疗的补充和替代方法。2010年伊始，上海中山医院、北京阜外医院、301医院和长海医院先后在国内率先应用Corevalve自膨式和Edwards球囊扩张式瓣膜支架成功地进行了人体主动脉瓣膜置换手术。因准入程序复杂、审批制度严格、进口器材价格昂贵，SFDA尚未批准该项技术在国内应用。我国人口老龄化发展趋势明显，根据国家统计局的报告，2009年我国60岁及65岁以上老年人口分别达到1.67亿人、1.13亿人，占总人口的12.5%、8.5%，而到2051年将达到4.37亿峰值。鉴于我国人口基数庞大，老龄患者对TAVR手术的需求将十分巨大，基于国情，为了降低医疗费用，减轻患者负担，研制具有自主知识产权的瓣膜支架的势在必行。自2006年起，国内多家医疗机构开展了经导管瓣膜支架置换的基础研究，但尚无国产器械在临床上得到应用。为填补国内空白，我科从2010年起与乐普医疗器械有限公司合作，研制了国产化经导管镍钛合金自膨式主动脉瓣膜支架置换系统，并开展了经导管主动脉瓣膜置换的实验研究。研究目的:研制国产化经导管自膨式主动脉瓣膜置换系统，并使用该系统对实验山羊进行主动脉瓣膜置换，评价国产经导管主动脉瓣置换装置的可靠性和安全性，观察瓣膜支架性能，为进一步的临床研究提供依据。研究方法：（1）经导管主动脉瓣置换的应用解剖和影像学研究分别解剖测量20例正常的成人心脏标本和20只健康山羊心脏标本。观察主动脉瓣膜区解剖位置及毗邻关系，应用游标卡尺分别测量主动脉瓣环的周径、主动脉瓣游离缘长度等距离，选取6头健康山羊行心脏彩超检查并在DSA下行造影。测量山羊股动脉、颈内动脉、腹主动脉下段的直径。（2）经导管镍钛合金自膨式主动脉瓣膜置换系统的研制以镍钛合金管为材料，激光雕刻加工成为菱形网眼直筒型支架，经热处理模具定型为“酒杯型”的支架。选用新鲜的猪心包，先给予0.01%胰蛋白酶中震荡脱细胞处理后24小时，后给予0.6%戊二醛液在4℃温度下浸泡36小时，再用2%L-谷氨酸浸泡24小时后，按照模具裁剪成瓣叶，使用无损伤线将瓣叶连续缝合在支架上组成瓣膜支架。输送装置由外鞘管、内芯、控制手柄组成。研制可将瓣膜支架收纳入鞘管的预载辅助装置。（3）体外实验和瓣膜支架测试以直径20mm的带金属标记环的硅胶管模拟的主动脉根部，在透视下将瓣膜支架插入硅胶管内，模拟经导管主动脉瓣膜置换手术过程。瓣膜支架释放后以硅胶管刻度线为基准，测量瓣膜支架瓣环线的偏差距离。再按时间顺序将30次释放分为A、B、C三组，以A组为对照组进行比较瓣膜支架瓣环线与基线的偏差范围。（4）右室起搏频率与主动脉瓣区压力变化的研究选取6只成年健康山羊，全麻下经股静脉将临时起搏电极送至右心室，连接临时起搏器，频率范围由150次/分递增至350次/分，以25次/分频率递增，测量在不同起搏频率下主动脉瓣上和瓣下的收缩压、舒张压和平均压，并计算压力阶差。（5）经导管主动脉瓣膜置换的实验研究：选择16只健康山羊，使用国产经导管主动脉瓣膜置换系统，分别经过颈内动脉和腹主动脉下段途径，在X线透视下经导管原位置换主动脉瓣。术后随访12个月，按术后即刻、3个月、6个月、12个月的时间节点，进行心电图、影像学、血流动力学随访。选择部分动物处死，进行大体解剖学和病理学检查。对于初次定位释放不准确的实验羊使用“瓣中瓣”技术进行补救。（6）新型可回收主动脉瓣膜支架系统的研制研制经导管可完全回收的镍钛合金自膨式主动脉瓣膜置换系统。可回收结构为铆钉连接，支架由主动脉部、底部、腰部、延伸段四个部分组成，瓣膜支架的输送和释放由输送索和鞘管配合控制。对该装置开展体外实验并进行初步的动物实验。统计学处理：使用SPSS18.0软件进行统计学处理。结果:（1）正常成人和实验山羊测得主动脉瓣周径分别为(69.56±3.48)mm、(59.43±7.51)mm；瓣膜游离缘长度分别为(29.17±2.21)mm、(21.33±2.75)mm；瓣膜附着缘长度分别为(23.45±2.66)mm、(18.20±2.36) mm；游离缘距窦底的距离分别为(17.58±3.22)mm、(12.90±1.85)mm；左室流出道长度分别为(22.30±2.49)mm、(17.82±3.37)mm；左冠开口到窦底的距离分别为(15.51±1.13)mm、(10.30±0.89) mm；右冠开口窦底的距离分别为(12.88±0.87)mm、(8.36±1.24) mm。实验羊股动脉、颈内动脉、腹主动脉下段的直径分别为(5.33±2.39) mm、(7.20±1.65) mm、(8.24±2.77) mm。影像学分析羊主动脉直径为(18.02±3.37) mm；瓣环直径为(18.25±1.59) mm。（2）瓣膜支架的分为主动脉部、腰部和左室流出道部三个部分，主动脉部膨大，腰部直径最细，左室流出道部略呈锥形，按腰部最径分为18、20、22、24mm四种规格。瓣膜支架整体通过16F的鞘管输送，通过操作手柄控制瓣膜支架的定位释放。体外实验表明，输送系统工作可靠，推送过程对人工瓣膜支架无影响；辅助预载装置可快速进行瓣膜支架的预载，而不损坏支架。（3）在瓣膜支架的体外释放实验中，成功释放30次（100%），准确释放23次（76.67%）。其中，支架瓣环线与基线重合4次，未及基线5次（平均值-2.00±1.00mm），超过基线21次（平均值2.84±2.56），30次释放偏离基线平均值2.03±3.05。A组平均值3.60±4.14，B组平均值1.90±2.60（P＞0.05），C组平均值0.6±1.07（P＜0.05）。（4）起搏频率与压力变化研究发现：收缩期主动脉跨瓣压力阶差随起搏频率的加快而升高，至250-300次/分时，由-25.00±3.90mmHg上升至11.17±10.85到13.50±3.89mmHg之间。舒张期跨瓣压力阶差随起搏频率的加快而降低，至250-300次/分时，稳定在47.00±3.03到43.83±2.93mmHg之间，压力阶差降幅达50.11%（P＜0.01,95%CI）。（5）16只实验羊中，初期2只羊因植入支架过大、定位释放位置过深导致大量反流死亡；2只羊支架被吸入心室；1只羊支架植入后右冠状动脉被堵塞，出现缓慢性心律失常，术后3小时突发室颤抢救无效死亡；1只羊死于血管并发症。2只羊瓣膜支架首次植入过高，行“瓣中瓣”技术补救，即时成功；1只羊因支架首次植入位置过高后，将首枚瓣膜支架退至降主动脉释放再植入第二枚瓣膜支架，即时成功。9只羊即时成功。术中造影测算主动脉瓣环直径(18.25±1.59)mm、瓣膜支架平均直径(22.60±0.97)mm手术时间（98.60±16.21）min。实验山羊术后即刻、3个月、6个月和12个月心脏彩超提示人工主动脉瓣膜工作正常，心功能与术前比较无明显变化；左室造影及人工主动脉瓣上造影证实支架的位置及瓣膜功能良好；心电图检查未见传到阻滞及其他心律失常。术后即刻解剖见瓣膜支架位置良好。术后12个月解剖见支架无移位，透明的内膜组织覆盖支架表面，扫描电镜下见支架上覆盖内皮细胞形态成熟，列致密有序。（6）新型可完全回收主动脉瓣膜支架分为主动脉部、腰部、左室流出道、延伸桁架四个部分，延伸桁架顶端的固定螺母可与输送索相连接。输送系统由鞘管、内芯、输送索、止血阀四个部分组成。鞘管直径为16F。体外实验和初步动物实验表明：新型瓣膜支架使用配套输送装置可顺利释放和回收，重复数十次，未见支架瓣膜损坏。结论：国产化自膨式主动脉瓣膜支架系统设计合理，性能稳定，植入方便，成功地应用于实验山羊的经导管主动脉瓣膜置换，植入体内后随访12个月血流动力学和生物相容性指标良好，可应用于经导管主动脉瓣膜置换的临床试验。更多还原

【Abstract】 Background: The incidence of aortic stenosis was increased significantly with thedevolopment of aging population. Valve calcification and degenerative stenosis of the aorticvalve are arised in more than40%of80-year-old elderly. The incidence of AS in thepeople over the age of75is4.6%, AS has been the major disease second only tohypertension and coronary heart disease in America. The traditional treatment methods foraortic stenosis is surgery valve replacement. However, about30-50%patients with severecomplications can not recieve surgical treatment.In2002, Cribier et al.launched transcatheter aortic valve replacement surgerysuccessfully. Following this, the equipment and technology of transcatheter aortic valvereplacement gained attention gradually, the concept of transcatheter valve replacement hadbeen accepted by the experts. At present, dozens of valve stented have been used in animalexperiments or clinical application, however only Edwards and CoreValve valved stentsystem have been used the most widely.Since the TAVR device was used into clinical, more than35,000cases has beencompleted in the world. The Partner studies have shown that: the1year survival rate ofTAVR is similar with surgery for those severe aortic valve disease patients at high risk whocan not recieve the surgical treatment. In addition, TAVR can also be treated the patients withaortic bioprosthesis failure. This technology is mature and develop ing complementary andalternative treatment for SAVR.Beginning in2010, some AS patients had been treated with the Corevalve and Edwardsprosthetic valved stents at Zhongshan Hospital and Changhai Hospital respectively in China.The TAVR procedures have been performed at some hospitals in Beijing later. However, thistechnology is still not carried out widely in our country on account of high cost and withoutratification by SFDA. In addition, few patients can afford the high medical costs to receivedTAVR treatment with the valved stents which imported abroad. Therefore, the research ofvalved stents localization is imperative. But the progress of localization is slow relatively, nohomemade devices for TAVR has been applied in clinical. We had developed aself-expandable pulmonary valved stent and aortic valved stent since2006. We havedeveloped a transcatheter nitinol self-expanding aortic valved stent system for TAVR with theLepu(Beijing) Medical Device Co., Ltd.since2010, and carried out the experimental study with this device.Objectives: To evaluate the feasibility and safety of transcatheter replacement of aorticvalve of goats with a new-type self-expanding valved stent, test the function of the stent, andprovide experimental data for further studies.Methods:(1)Applied anatomy and imaging of transcatheter aortic valve replacementTwenty adult human heart specimens and twenty fresh healthy hircine hearts weredissected and measured. Observe the anatomic position of aortic valves and the relationshipbetween the aortic valves and adjacent structure firstly. The perimeter of aortic valve annulus,the length of aortic valve free margin and attachment margin were measured respectively. Thearea of valve leaflet, the distance from coronary ostium to sinus bottom and the length ofascending aorta were also measured. Six healthy goats were also used for measurement ofheart anatomy in vivo; The diameter of aortic annulus, left ventricular myocardium thickness,left ventricular end-diastolic volume, left ventricular end-systolic volume, and left ventricularejection fraction were evaluated by transthoracic echocardiography; Left ventriculography wasperformed to determine the best projecting position for aortic sinus imaging; The catheterdelivery system of16F and18F was inserted through the femoral artery, the left iliac arteryand the infrarenal aorta respectively, the diameter of which was measured at baseline.(2) Development of the self-expanded valved stent and delivery systemA diamond-shape meshes stent was engraved from domestic straight nickel-titaniumalloy tubes by laser and been formed the valved stent with three parts those were aortic part,left ventricular outflow tract part and waist part by heat treatment. Fresh porcine pericardiumwas shaked continuously in a0.01%trypsin solution for24hours, then cross-linked with a0.6%glutaraldehyde solution at4°C for36hours, and then was immersed in2%L-glutamicacid solution for24hours to remove toxicity of glutaraldehyde. The processed porcinepericardium was trimmed into leafets and sutured by hand into the stent. The delivery systemconsists of an outer sheath，an inner dilator, control handle. The outside diameter of deliverysystem is14-French. The valved stent can be intaken into the sheath with preloading assistdevices.(3) Experiments of new TAVR device in vitroInsert the shealth loaded valved stent into a translucent silicone tube with a metal ring by DSA, release the vavled stent when the prosthetic annulus overlapped with the metal ring onthe tube. measure the distance from the prosthetic annulus to the metal ring after releasing.The data was been divided into3groups(Group A, Group B and Group C). Group B, Group Ccompared with Group A.(4) The effect of pacing frequency on transaortic valve pressure gradients in goatsSix healthy adult goats randomly chosen for the study were tested under generalanesthesia. A temporary pacing lead connected with a temporary pacemaker be sent to theright ventricle through the femoral vein. The pacing frequency range from150beats/min to350beats/min by increment of25beats/min. The aortic systolic, diastolic and meanpressure were measured at different pacing frequency and the pressure gradients in aortic werecalculated.(5) Experimental study of transcatheter aortic valved stent implantationSixteen healthy goats was selected to replace the aortic valve in situ through the internalcarotid artery or infrarenal aorta with the new TAVR device under DSA,and were followedup for12months after procedure. ECG, imaging and hemodynamic examination wereundergone at the time of immediate postoperative period,3months,6months and12months, and some goats were killed to for gross anatomy and pathology examination. The“valve-in-valve” technique was used to remedy goats which the first valved stent implantedincorrectly..(6) Development of retractable aortic valved stent systemDeveloping two kinds of transcatheter retractable nitinol self-expanding aortic valvestents and the supporting delivery devices. It’s structure was connected with rivet. The valvedstent was made up of four parts which were aorta, bottom, waist and extension part.Delivering and releasing of the valved stent were controlled by cable. Preliminary experimentsof the devices were test in both vitro and vivo.Results:(1) The perimeter of aortic valve annulus of adult and canines in vitro were (69.56±3.48)mm and (59.43±7.51) mm respectively, the length of aortic valve free margin were (29.17±2.21) mm and (21.33±2.75) mm respectively, the length of attachment margin were (23.45±2.66) mm and (18.20±2.36) mm respectively, the distance from lower edge of left coronaryartery to valve annulus (15.51±1.13) mm and (10.30±0.89) mm respectively, the distance from lower edge of right coronary artery to valve annulus (12.88±0.87) mm and (8.36±1.24) mmrespectively. The diameter of hircine aortic annulus and aorta in vivo by imaging was(19.24±2.67) mm and (18.02±3.37)mm respectively. The diameter of the femoral artery, theleft internal carotid artery and the infrarenal aorta was (5.33±2.39) mm，(7.20±1.65) mm and(8.24±2.77) mm respectively. The18F catheter delivery system could be easily insertedthrough the infrarenal aorta.(2) The valved stent consists of three parts: the aortic part, waist part and left ventricularoutflow tract part. The aortic part is inflate, the waist part is thin relatively and the leftventricular outflow tract is slightly cone-shape. The valved stents were been divided fourspecifications as18,20,22and24mm of four specifications in accordance with diameter of thewaist and the shape of valve is completely imitated native valve. The valved stent can beintaking into the16F sheath designed specially with the supporting device, and be implantedin vivo through the vessel. The releasing is controlled by the operating handle. Experiments invitro showed the delivery sheath worked reliably. The pre-loaded supporting device loadedvalve effectively. The repeated deployment was smoothly, and the valved stent appeared nodamage.(3) The valved stents had been released successfully30times by DSA(success ratio100%), of which23times are accurate(76.67%). the prosthetic annulus overlapped the metalring4times, no come up to the the metal ring5times(average value-2.00±1.00mm) andsurpassed the metal ring21times(average value2.84±2.56mm). The average value of inclinethe base overall is2.03±3.05, Group A is3.60±4.14, Group B is1.90±2.60（95%CI: P＞0.05）and Group C is0.6±1.07（95%CI: P＜0.05).(4) The transaortic valve systolic pressure gradient rised with the acceleration of thepacing rate. When the pacing rate accelerated to250-300beats/min, the pressure gradientrised from-25.00±3.90mmHg to11.17±10.85~13.50±3.89mmHg. Diastolic transvalvularsystolic pressure gradient declined with the acceleration of the pacing rate. When the pacingrate accelerated to250-300beats/min, the pressure gradient was in the43.83±2.93~47.00±3.03mmHg, showing a lower decline rate of50.11%(P <0.01,95%CI).(5) Of sixteen goats, two die of stents implanted were too large and improper position.One died of right coronary artery was blockaged by stent, and this goat lived for3hours afterprocedure. One died of vascular complications. The position of valved stents is too high in2 goats in first implantation, then they were remedied by "valve-in-valve " technique. Thevalved stent’position of first implantation is too high, then it was retracted and deployed in thedescending aorta, then another stent was implanted in situ successfully. Nine goats weresurvive. The mean aortic annulus diameter was (18.25±1.59) mm on fluoroscopymeasurements at baseline. The mean aortic stent diameter was (22.60±0.97) mm, theprocedure time was (98.60±16.21) min. Imaging inspection showed that the aortic prostheticvalves working properly and cardiac function of the goats were regular in postoperativeimmediacy,3months,6months and12months. The ECG showed no evidence of conductionblock and other arrhythmias. The tissue specimen of postoperative immediacy,3months and12months showed that the valve stents were in good position. A layer of transparentendometrial tissue covering the stent surface on the anatomical specimens after12months.The endothelial cells covered on the valve stents were mature and compact under scanningelectron microscope.(6) The new retractable valved stent consists of four parts: the aortic part, waist part, leftventricular outflow tract part and extension part. The nut on the top of extension part can beconnected with the cable which can push and deploy the valved stent. Delivery systemconsists of the sheath, the inner core, cable and hemostatic valve. The diameter of sheath is16French. Experiment showed that the new valve stent can be deployed and retractedsmoothly witn the supporting delivery devices, the valved stents had no damage afterdeployed repeatly.Conclusions: The self-designed aortic valved stent was implanted into the native aorticannulus of canines successfully, which has good structural stability and excellentbiocompatibility. The study shows that the new-type valved stent and delivery system weresafe, feasible and efficient. The results support the further investigation of the aortic valvedstent for possible use in clinical.更多还原