家犬主动脉窦影像分析和主动脉瓣支架瓣膜的研制

目的:观察家犬主动脉窦造影特点,研制可经导管植入主动脉瓣支架瓣膜的可行性.方法:选用健康杂种犬10只,行左心室造影,对主动脉窦部造影影像分析.将新鲜的猪心包经脱细胞处理后给予0.6%戊二醛浸泡36 h,缝合在瓣膜环上,制成主动脉瓣支架瓣膜.并将瓣膜支架经动脉植入家犬心脏主动脉瓣位置.经胸超声评价瓣膜功能.结果:左室造影可清晰显示主动脉窦部宽度和高度;升主动脉直径(1.73±0.15)mm,主动脉窦部直径(2.15+0.24)mm,冠脉开口至窦部的距离(1.12+0.14)mm.经胸超声检查示人工瓣膜瓣叶功能正常,无返流.结论:主动脉瓣支架瓣膜设计合理,功能正常,可用于经导管主动脉瓣膜置换的实验研究.     

瓣膜高度对移植主动脉瓣开闭性能的影响

临床上治疗主动脉瓣膜关闭不全的的手术多采用瓣膜移植,但术后患者重建的主动脉根部存在扩张现象,因此瓣膜高度的不足会致使主动脉瓣膜再次关闭不全。本文研究不同主动脉瓣膜高度设计对瓣膜开闭性能的影响,通过体外数值模拟,获取最佳手术方案,提供技术支持和理论依据。本文以根部直径26.0 mm、瓣膜高度14.0 mm为参照,建立瓣膜高度增量为±0.5 mm的六组三维几何模型。通过对模型最大应力、瓣口面积和接触力等参数的结构力学计算和分析,获得合理的几何尺寸。研究发现,六组模型的最大应力值范围在640～690 kPa之间,与文献的结果相符合;瓣膜高度分别为13.5、14.0、14.5 mm的三组模型的瓣口面积在合理范围内;六组瓣叶接触力随瓣膜高度增加呈增大趋势。研究表明主动脉瓣膜的高度对主动脉瓣膜关闭性能存在影响,太小或太大的瓣膜高度会减小主动脉收缩期的瓣口面积,影响主动脉开闭功能。     

主动脉根部扩张情况下窦部直径对瓣膜开闭性能的影响

本研究旨在探讨在主动脉瓣及瓣环本身无明显病变、主动脉根部不断扩张的情况下,主动脉窦部直径对主动脉瓣开闭性能的影响。本研究参考临床手术指导尺寸,构建了不同主动脉窦部直径和根部直径的25组主动脉根部模型。窦部直径DS取值分别为32、36、40、44、48 mm,根部直径DA取值分别为26、27、28、29、30 mm。通过有限元软件进行结构力学计算,对模型最大应力、瓣口面积和接触力等参数进行分析,评估扩张状态下的瓣膜开闭性能。研究发现当DS=32 mm且DA=26,27 mm,以及DS=36 mm且DA=26 mm时瓣膜出现开放狭窄;DS=32,36,40 mm且DA=30 mm,以及DS=44,48 mm且DA=29,30 mm时,瓣膜出现关闭不全;其他15组瓣膜运动正常。结果表明,主动脉窦的尺寸对主动脉瓣膜关闭性能存在影响。较小的窦部直径适应较大的根部直径,较大的窦部直径适应较小的根部直径,窦部直径为40 mm时,瓣膜的各项力学表现良好,能适应相对较大范围的根部扩张。     

球扩式介入主动脉瓣膜支架的抗迁移力学行为

目的 研究球扩式主动脉瓣膜支架植入后的抗迁移力学行为。 方法 建立球扩式瓣膜支架介入主动脉瓣膜后的抗迁移力学模型,采用数值模拟方法研究不同瓣环椭圆率、摩擦因数、瓣膜支架材料及自体瓣叶钙化情况对瓣膜支架抗迁移力的影响规律。 结果 当主动脉瓣环椭圆率为 0. 2、0. 3、0. 4、0. 5 时,对应的最大抗迁移力分别为12. 37、10. 94、8. 50、4. 75 N;当摩擦因数为 0. 1、0. 2、0. 3 时,瓣膜支架的最大抗迁移力分别为 8. 98、11. 00、13. 10 N;L605 钴铬合金制成的瓣膜支架的锚定性要优于 316L 不锈钢制成瓣膜支架的锚定性,其对应的最大抗迁移力分别为 13. 10、9. 82 N;当自体瓣叶发生钙化时,最大抗迁移力为 13. 1 N,而未钙化时最大抗迁移力仅为 5. 51 N,相比而言降低了 57. 9% 。 结论 随着主动脉瓣瓣环椭圆率不断增大,瓣膜支架的锚定性逐渐降低;随着瓣膜支架与组织间的摩擦因数不断增大,最大抗迁移力也不断增大;L605 钴铬合金制成的瓣膜支架比 316L 不锈钢制成瓣膜支架的锚定性能优异;瓣膜发生钙化情况下瓣膜支架的锚定性要优于未发生钙化时的锚定性。 研究结果为抗迁移瓣膜支架的结构设计和临床选择提供重要的科学依据。     

自体心包补片修补主动脉瓣环辅助主动脉瓣置换

背景：在主动脉置换过程中常遇到瓣环钙化、瓣周囊肿等特殊情况,这时一般应用特殊技术辅助主动脉瓣置换。 目的：观察自体心包补片修补主动脉瓣环辅助主动脉瓣置换治疗钙化性主动脉瓣狭窄并瓣环钙化的临床可行性。 方法：回顾性分析2009年1月至 2012年1月郑州大学第一附属医院42例钙化性主动脉瓣狭窄并瓣环钙化患者的临床资料,并通过统计学软件处理自体心包补片修补主动脉瓣环技术辅助主动脉瓣置换前后的主动脉瓣有效瓣口面积指数、最大跨瓣压差、血流峰值速度、左室射血分数等数据,分析自体心包补片修补主动脉瓣环技术辅助主动脉瓣置换的应用效果。 结果与结论：无置换中死亡病例,置换中主动脉阻断时间为52-88(63.0±18.1) min,体外循环时间为78-122(102.6±25.1) min,置换后1例患者出现急性肾功能衰竭,经床旁血透治疗后治愈。余患者无严重置换并发症。置换后住院天数为7-20(13.6±5.5) d。置换后多普勒超声心动图示：瓣膜功能良好,均未发现主动脉瓣周漏。置换后6个月的主动脉瓣有效瓣口面积指数、最大跨瓣压差、血流峰值速度、左室射血分数均有显著改善,与置换前比较差异均有显著性意义(P < 0.05)。证实对置换适应证合适的特殊换瓣患者,自体心包补片修补主动脉瓣环辅助主动脉瓣置换可取得满意的外科治疗效果,且操作安全简单,是一项可行的技术。     

细主动脉根部植入无支架和有支架瓣膜的比较

由于替代物不配影响了主动脉瓣替换后的效果 ,特别是发生在细主动脉的根部的患者 ,其原因是手术后残余的压力阶差 ,影响了左室舒张而降低长期存活。外科医生往往根据瓣环参数试图植入最大的瓣膜。工艺标号给外科医生提供了这样的信息 ,他们用此来判定为患者植入足够大的瓣膜。有经验的医生可选择不同的替代品 ,或扩大瓣膜 ;或将瓣膜坐在瓣环上。近年的报告证实在标出的瓣膜大小与实际尺寸存在差异。因此我们认为根据不同的制造商标出的瓣膜的大小进行替代瓣膜的血液动力学比较毫无意义。本研究是基于测量瓣膜内径基础上进行替代瓣膜的血液动…     

主动脉瓣二叶、冠状动脉开口畸形合并夹层动脉瘤一例

死者成人男性。尸体解剖发现主动脉瓣二叶、冠状动脉开口畸形且合并夹层动脉瘤。现报告如下:心脏,重270克,室壁厚:左室0.8cm、右室0.3cm。主动脉瓣呈二叶,周径7cm,左瓣长3cm、右瓣和后瓣融合、二者间无瓣膜联合,瓣膜边缘增厚卷曲。左、右冠状动脉均开口于左主动脉窦内,相距1.5cm。主动脉根部有一向升主动脉延续的夹层动脉瘤,长6cm,环绕主动脉周径约1/2,内膜有一裂口位主动脉瓣膜上     

经导管主动脉瓣置换术研究现状及进展

经导管主动脉瓣置换(transcatheter aortic valve replacement,TAVR)是一项治疗严重主动脉瓣狭窄的新型微创技术,目前主要应用于存在高危、中危风险或手术禁忌证的患者。本文总结了目前TAVR的植入路径、围术期影像学检查、TAVR系统的研发和应用进展。植入路径主要包括经股动脉、经心尖路径、经主动脉等。超声和多层螺旋CT是围术期的主要影像学依据。34 mm Evolut R瓣膜和Sapien 3瓣膜的新型设计,明显减少了瓣周漏的发生,并为髂血管异常的患者实施TAVR提供了可能。JenaValve获准应用于治疗主动脉瓣关闭不全,拓宽了TAVR的适应证。最后对TAVR的发展进行了展望。     

经导管主动脉瓣及肺动脉瓣置换的应用解剖

目的为经导管瓣膜置换提供正常人主动脉瓣膜及肺动脉瓣膜的相关应用解剖.方法解剖测量40例(男28,女12)外形大小正常的成年人心标本.结果测得主动脉瓣、肺动脉瓣周径分别为(63.25±8.43)mm、(66.52±11.25)mm;瓣膜游离缘长度分别为(26.25±3.84)mm、(27.51±5.15)mm;瓣膜附着缘长度分别为(20.36±3.51)mm、(21.27±4.64)mm;游离缘距窦底的距离分别为(15.15±2.67)mm、(16.54±4.33)mm左、右冠状动脉开口距主动脉根部距离分别为(16.59±4.16)mm、(17.23±3.26)mm.主肺动脉长度(33.54±8.15)mm.结论带瓣膜支架的大小和形状的设计应根据主动脉以及主肺动脉开口的大小及与周边结构的关系来选择.     

主动脉瓣部分关闭和完全开放的有限元分析

目的探究不同的初始状态设置对瓣膜仿真计算的影响。方法创建初始状态分别为主动脉瓣部分关闭和完全开放的二维结构模型,对瓣膜和主动脉侧、心室侧的血管壁施加随时间变化的压力载荷,采用有限元法研究在两种不同初始状态设置下瓣膜关闭时的最大应力、对合长度和接触力。结果以完全开放为初始状态的模型在瓣膜关闭时的应力和接触力更大,瓣膜闭合程度较差,周期性循环中应力和闭合程度的变化较大;部分关闭为初始状态下瓣膜在关闭时的应力和接触力小,闭合程度较好,周期性循环中应力和闭合程度的变化小。结论在初始状态为部分关闭时,计算过程的稳定性和瓣膜的闭合程度较好,在进行数值模拟计算时可以给予更多的考虑。研究结果可为瓣膜和主动脉根部生物力学机制的研究提供参考。     

Patient-specific simulations of transcatheter aortic valve stent implantation

Transcatheter aortic valve implantation (TAVI) enables treatment of aortic stenosis with no need for open heart surgery. According to current guidelines, only patients considered at high surgical risk can be treated with TAVI. In this study, patient-specific analyses were performed to explore the feasibility of TAVI in morphologies, which are currently borderline cases for a percutaneous approach. Five patients were recruited: four patients with failed bioprosthetic aortic valves (stenosis) and one patient with an incompetent, native aortic valve. Three-dimensional models of the implantation sites were reconstructed from computed tomography images. Within these realistic geometries, TAVI with an Edwards Sapien stent was simulated using finite element (FE) modelling. Engineering and clinical outcomes were assessed. In all patients, FE analysis proved that TAVI was morphologically feasible. After the implantation, stress distribution showed no risks of immediate device failure and geometric orifice areas increased with low risk of obstruction of the coronary arteries. Maximum principal stresses in the arterial walls were higher in the model with native outflow tract. FE analyses can both refine patient selection and characterise device mechanical performance in TAVI, overall impacting on procedural safety in the early introduction of percutaneous heart valve devices in new patient populations.     

A European update on transcatheter aortic valve implantation (TAVI) in the COVID era

Minimally invasive approaches for aortic valve replacement are now at the forefront of pathological aortic valve treatment. New trials show comparability of these devices to existing therapies, not only in high-risk surgical cohorts but also in low-risk and intermediate-risk cohorts. This review provides vital clinical and anatomical background to aortic valvular disease treatment guidelines, while also providing an update on transcatheter aortic valve implantation (TAVI) devices in Europe, their interventional trials and associated complications.     

Relationship between the membranous septum and the virtual basal ring of the aortic root in candidates for transcatheter implantation of the aortic valve

Knowledge of the anatomy of the membranous septum, as a surrogate to the location of the atrioventricular conduction axis, is a prerequisite for those undertaking transcatheter implantation of the aortic valve (TAVI). Equally important is its relationship of the virtual basal ring. This feature, however, has yet to be adequately described in the living heart. We analyzed computed tomographic angiographic datasets from 107 candidates (84.1 ± 5.2 years, 68% women) for TAVI. Using multiplanar reconstructions, we measured the height and width of the membranous septum, and the distances of its superior and inferior margins from the virtual basal ring plane. We also assessed the extent of wedging of the aortic root between the mitral valve and the ventricular septum. Mean heights and widths of the membranous septum were 6.6 ± 2.0, and 10.2 ± 3.1 mm, respectively, with its size significantly associated with that of the aortic root (P < 0.05). Its superior and inferior margins were 4.5 ± 2.3 and 2.1 ± 2.1 mm, respectively, from the plane of the basal ring. The inferior distance, the surrogate for the adjacency of the atrioventricular conduction axis, was ≤ 5mm in 91% of the patients. Deeper wedging of the aortic root was independently correlated with a shorter inferior distance (β = 0.0569, P = 0.0258). The membranous septum is appreciably closer to the virtual basal ring than previously appreciated. These findings impact on estimations of the risk of damage to the atrioventricular conduction axis during TAVI. Clin. Anat. 31:525–534, 2018. © 2018 Wiley Periodicals, Inc.     

Assessment of the influence of the compliant aortic root on aortic valve mechanics by means of a geometrical model

In recent years several researchers have suggested that the changes in the geometry and angular dimensions of the aortic root which occur during the cardiac cycle are functional to the optimisation of aortic valve function, both in terms of diminishing leaflet stresses and of fluid-dynamic behaviour. The paper presents an analytical parametric model of the aortic valve which includes the aortic root movement. The indexes used to evaluate the valve behaviour are: the circumferential membrane stress and the stress at the free edge of the leaflet, the index of bending strain, the bending of the leaflet at the line attachment in the radial and circumferential directions and the shape of the conduit formed by the leaflets during systole. In order to evaluate the role of geometric changes in valve performance, two control cases were considered, with different reference geometric configuration, where the movement of the aortic root was ignored. The results obtained appear consistent with physiological data, especially with regard to the late diastolic phase and the early ejection phase, and put in evidence the role of the aortic root movement in the improvement of valve behaviour.     

6-Month aortic valve implantation of an off-the-shelf tissue-engineered valve in sheep

Diseased aortic valves often require replacement, with over 30% of the current aortic valve surgeries performed in patients who will outlive a bioprosthetic valve. While many promising tissue-engineered valves have been created in the lab using the cell-seeded polymeric scaffold paradigm, none have been successfully tested long-term in the aortic position of a pre-clinical model. The high pressure gradients and dynamic flow across the aortic valve leaflets require engineering a tissue that has the strength and compliance to withstand high mechanical demand without compromising normal hemodynamics. A long-term preclinical evaluation of an off-the-shelf tissue-engineered aortic valve in the sheep model is presented here. The valves were made from a tube of decellularized cell-produced matrix mounted on a frame. The engineered matrix is primarily composed of collagen, with strength and organization comparable to native valve leaflets. In vitro testing showed excellent hemodynamic performance with low regurgitation, low systolic pressure gradient, and large orifice area. The implanted valves showed large-scale leaflet motion and maintained effective orifice area throughout the duration of the 6-month implant, with no calcification. After 24 weeks implantation (over 17 million cycles), the valves showed no change in tensile mechanical properties. In addition, histology and DNA quantitation showed repopulation of the engineered matrix with interstitial-like cells and endothelialization. New extracellular matrix deposition, including elastin, further demonstrates positive tissue remodeling in addition to recellularization and valve function. Long-term implantation in the sheep model resulted in functionality, matrix remodeling, and recellularization, unprecedented results for a tissue-engineered aortic valve.     

Infective endocarditis in patients who have undergone transcatheter aortic valve implantation: a review

BackgroundTranscatheter aortic valve implantation (TAVI) has been approved for the treatment of severe aortic stenosis since 2008 and recent trials have shown that TAVI is at least non-inferior to surgical aortic valve replacement (SAVR) with regards to short-term efficacy and safety in patients across all surgical risk profiles. Prosthetic valve endocarditis of the transcatheter heart valve is a feared complication; data on the risk of infective endocarditis (IE) subsequent to TAVI are now gradually emerging.ObjectivesWe set forth to conduct a review of the incidence, diagnosis, microbial aetiologies, prevention, outcome and management of TAVI-IE.SourcesFrom the MEDLINE database we included a total of 12 observational studies and five studies of long-term results from randomized controlled trials.ContentThe incidence of TAVI-IE was reported to be between 0.7% and 3.0% per person-year. The most common microbes were reported to be enterococci, Staphylococcus aureus, streptococci and coagulase-negative staphylococci. International guidelines on prevention strategies of IE recommend good sanitary conditions including cutaneous care, good oral hygiene and good care of dialysis catheters. Antibiotic prophylaxis is recommended by guidelines prior to dental procedures in patients with TAVI; however, evidence is sparse. The majority of the patients included in this review with TAVI-IE had an indication for surgical intervention due to IE (50.0% or more); however, only a small subset of the patients underwent surgery (16.4% or less). The in-hospital mortality was around 25%, i.e. of the same order of magnitude as in prosthetic valve IE in general, but varied substantially between studies (from 11% to 64%).ImplicationsThe US Food and Drug Administration's approval of TAVI in patients at low surgical risk may change the characteristics of patients with TAVI, which may influence the incidence, management, and outcome of patients with TAVI-IE.     

In vivo behavior of epoxy-crosslinked porcine heart valve cusps and walls

Calcification limits the long-term durability of xenograft glutaraldehyde-crosslinked heart valves. In this study, epoxy-crosslinked porcine aortic valve tissue was evaluated after subcutaneous implantation in weanling rats. Non-crosslinked valves and valves crosslinked with glutaraldehyde or carbodiimide functioned as control. Epoxy-crosslinked valves had somewhat lower shrinkage temperatures than the crosslinked controls, and within the series also some macroscopic and microscopic differences were obvious. After 8 weeks implantation, cusps from non-crosslinked valves were not retrieved. The matching walls were more degraded than the epoxy- and control-crosslinked walls. This was observed from the higher cellular ingrowth with fibroblasts, macrophages, and giant cells. Furthermore, non-crosslinked walls showed highest numbers of lymphocytes, which were most obvious in the capsules. Epoxy- and control-crosslinked cusps and walls induced lower reactions. Calcification, measured by von Kossa-staining and by Ca-analysis, was always observed. Crosslinked cusps calcified more than walls. Of all wall samples, the non-crosslinked walls showed the highest calcification. It is concluded that epoxy-crosslinked valve tissue induced a foreign body and calcification reaction similar to the two crosslinked controls. Therefore, epoxy-crosslinking does not represent a solution for the calcification problem of heart valve bioprostheses.     

Large-displacement 3D structural analysis of an aortic valve model with nonlinear material properties

Grafts used in aortic valve-sparing procedures should ideally not only reproduce the geometry of the natural aortic root but also its material properties. Indeed, a number of studies using the finite element method have shown the importance of the natural sinus shape of the root in the functioning of the normal aortic valve, and the relative increase in stresses due to the replacement of the valve by a stiffer synthetic graft. Because of the wide range in experimentally measured values of aortic wall and leaflet material properties, studies by different research groups have incorporated very different material properties in their models. The aim of the present study was to investigate the influence of material properties on aortic wall displacements, and to determine which material properties would most closely match reported experimental data. Two geometrically accurate 3D models corresponding to the closed and open valve configurations were created in Pro/Engineer CAD software. Loads corresponding to systolic and diastolic pressures were specified and large-displacement structural analyses were carried out using the ANSYS package. Results have indicated that the closest match to experiments using isotropic material properties occurred for a Young's modulus of about 2000 KPa. Nonlinear models based on experimental stress-strain curves have shown similar displacements, but altered strain distribution patterns and significantly lower stresses. These results suggest that an accurate comparison of potential new graft models would have to be made with natural aortic valve models incorporating nonlinear material behavior.     

Simulation of Self Expanding Transcatheter Aortic Valve in a Realistic Aortic Root: Implications of Deployment Geometry on Leaflet Deformation

Self expanding Transcatheter Aortic Valve Replacements (TAVR) can conform to the geometry of the aortic annulus and the calcified leaflet complex, which may result in leaflet distortion and altered leaflet kinematics, but such changes have not yet been characterized. In this study we developed a computational model to investigate the deployment of a self expanding TAVR in a realistic aortic root model derived from multi-slice computed tomography (MSCT) images. We simulated TAVR crimping/deployment in realistic and idealized aortic root models, followed by diastolic loading of the TAVR leaflets in its final deployed configuration. The TAVR deployed in a realistic aortic root had increased peak loading in the commissural region of the leaflets compared to TAVRs under idealized circular deployment conditions (2.97 vs. 1.52 MPa). Furthermore, orientation of the TAVR in the asymmetric aortic annulus such that the commissures of the TAVR are aligned with the native valve commissures minimized the effect of TAVR stent distortion on peak stresses in the TAVR leaflets (2.97 vs. 2.35 MPa). We propose that preoperative planning of the orientation of the TAVR in the aortic root annulus might minimize the impact of potential stent distortion on leaflet function and may in turn increase long term leaflet durability.