Mechanolytic management of transcatheter aortic valve thrombosis

Data on the incidence, characteristics, and treatment of thrombosis of a transcatheter aortic valve implantation (TAVI) implant are scarce. We report a challenging case of a TAVI thrombosis occurring 6 months after the procedure. Initial anticoagulation using low-molecular-weight heparin followed by thrombolytic therapy failed to both relieve symptoms and alleviate thrombosis. However, the condition of the patient deteriorated rapidly, necessitating the use of balloon valvuloplasty followed by low-dose thrombolysis. The uniqueness of the case can be summarized as follows: (1) first report of balloon valvuloplasty to manage a case of TAVI thrombosis; (2) thrombolytic therapy after balloon valvuloplasty was successful to further reduce gradient from valve thrombosis.     

生物瓣膜:多年轻是年轻

A favorite question in Doctors and Patients is, ＂What valve would you use for patient ？ And what kind of valve suits me better in my life ？ Would you use a mechanical prosthesis, a bioprosthesis .9 Numerous studies show that there are many safe choices and that the operation has to be individualized to the patient.     

复合鞣制方法处理生物瓣膜生物材料性能评估

目的：对复合鞣制方法处理的生物材料性能及生物瓣膜临床应用效果进行评估。方法：对比用戊二醛、阳离子油、三氧化二铬及甘油等复合鞣制的生物材料和单纯戊二醛鞣制生物材料的组织钙含量。对生物材料进行组织学、超微结构和机械抗张强度测试，用傅立叶红外光谱仪测定羧基含量。生物瓣膜经体外模拟疲劳寿命实验台加速检测。结果：复合鞣制生物材料组织钙含量低，组织胶原纤维结构排列致密、整齐，细胞结构完整，收缩温度在86～90℃时生物材料最柔软，抗张强度19．9～25．9N／mm^2，延伸率43．4％～46．0％；红外光谱图显示羧基(COOH^-1)峰明显降低；体外模拟加速疲劳实验台测试，猪主动脉瓣膜能经受3．892亿次循环，牛心包瓣膜为3．888亿次，从受力疲劳方面看将能经受住大约10年的寿命。结论：用复合鞣制方法处理生物材料，可提高生物瓣膜的柔软性和强度，对生物瓣膜的防钙化起重要作用。     

冷冻速率对猪主动脉冷冻保存效果的影响

目的比较不同冷冻速率对大口径猪动脉功能及内皮的影响.方法 16头乳猪切取胸主动脉,每根主动脉分3段,作为对照、-1℃/min冷冻和-5℃/min冷冻处理.分别测定内皮细胞死亡率和血管活性药物引起的收缩、舒张程度.结果 -5℃/min冷冻组内皮细胞死亡率明显高于-1℃/min冷冻组和对照组,P＜0.01.冷冻组由去甲肾上腺素引起的收缩张力值明显低于未冷冻对照组P＜0.01.-5℃/min组明显低于-1℃/min组,P＜0.01.冷冻组由乙酰胆碱引起的张力下降绝对值与对照组差异无显著性,P＞0.05;舒张程度与对照组有明显差异,P＜0.01.-5℃/min组舒张程度明显低于-1℃/min组,P＜0.01.内皮细胞死亡率与乙酰胆碱舒张作用呈负相关,P＜0.05.结论冷冻对猪主动脉的结构和功能造成损伤.慢速冷冻对内皮细胞破坏小,对血管平滑肌的收缩和内皮依赖性舒张的损害小.     

The susceptibility of bioprosthetic heart valve leaflets to oxidation

The clinical use of bioprosthetic heart valves (BHV) is limited due to device failure caused by structural degeneration of BHV leaflets. In this study we investigated the hypothesis that oxidative stress contributes to this process. Fifteen clinical BHV that had been removed for device failure were analyzed for oxidized amino acids using mass spectrometry. Significantly increased levels of ortho-tyrosine, meta-tyrosine and dityrosine were present in clinical BHV explants as compared to the non-implanted BHV material glutaraldehyde treated bovine pericardium (BP). BP was exposed in vitro to oxidizing conditions (FeSO₄/H₂O₂) to assess the effects of oxidation on structural degeneration. Exposure to oxidizing conditions resulted in significant collagen deterioration, loss of glutaraldehyde cross-links, and increased susceptibility to collagenase degradation. BP modified through covalent attachment of the oxidant scavenger 3-(4-hydroxy-3,5-di-tert-butylphenyl) propyl amine (DBP) was resistant to all of the monitored parameters of structural damage induced by oxidation. These results indicate that oxidative stress, particularly via hydroxyl radical and tyrosyl radical mediated pathways, may be involved in the structural degeneration of BHV, and that this mechanism may be attenuated through local delivery of antioxidants such as DBP.     

Removal of Alpha-Gal Epitopes from Porcine Aortic Valve and Pericardium using Recombinant Human Alpha Galactosidase A

It has been reported that the immune response due to α-Gal epitopes is an important factor in tissue valve failure. The elimination of the interaction between the natural anti-Gal antibodies and α-gal epitopes on the xenografts is a prerequisite to the success of xenografts in humans. Previously, we reported that the green coffee bean α-galactosidase could remove all α-Gal epitopes from cell surface of porcine aortic valve and pericardial tissue, but it has limitations on cost effectiveness. In this study we wanted to know whether the recently produced recombinant human α-galactosidase A has the same effective enzymatic activity as green coffee bean α-galactosidase in removing α-Gal epitopes from the same tissues. After treating fresh porcine aortic valve and pericardial tissue with recombinant α-galactosidase A, each sample was stained with Griffonia simplicifolia type I isolectin B4 indirect immunoperoxidase avidin-biotin technique. We then examined whether the α-Gal epitopes were reduced or abolished in each consecutive concentration of recombinant α-galactosidase A by comparing the degree of the Griffonia simplicifolia isolectin B4 staining. As a result, the recombinant α-galactosidase A could remove cell surface α-Gals on porcine aortic valve and pericardial tissue as effectively as green coffee bean α-galactosidase.     

牛心包纤维支架宿主细胞重建后体内移植实验

目的 初步探讨牛心包纤维支架宿主细胞重建后体内移植后内皮细胞抗切应力和抗钙化能力以及肌成纤维细胞迁移和自身修复能力。方法 （1）新鲜牛心包片经脱细胞、鞣制、改性后制成试片。（2）A组试片上依序种植宿主肌成纤维细胞和内皮细胞（EC），B组试片上不种植细胞，随后将两组试片分别移植于猪腹主动脉壁上。（3）2个月后对试片进行厚度、钙含量、扫描电镜及组织学检查。结果 （1）A组试片表面覆盖白色光滑组织；B组试片呈灰黄色。A组试片钙含量显著低于B组（P〈0．05），但仍显著高于新鲜牛心包（P〈0．05）。（2）A组试片显著厚于B组试片（P〈0．05）。（3）A组试片60％～70％的表面覆盖EC，裸露的胶原纤维间隙已消失，肌成纤维细胞已迁移至表层下支架的1／2～2／3；B组试片表面无细胞，浅层有少量的肌成纤维细胞生长，大部分胶原纤维间隙消失。结论 通过组织工程技术在体外实现完全内皮化、部分间质细胞化的牛心包纤维支架材料，有可能成为构建组织工程新型生物瓣膜的材料。     

Experimental bioprosthetic reconstruction of the trachea

Summary We removed the tracheas from sacrificed laboratory animals and subjected this tissue to multistep chemical processing. This method allowed us to preserve the cartilage and reduce its antigenicity, thus creating a bioprosthesis very similar to the host tissue. By using allogeneic and xenogeneic prostheses so prepared, no signs of immune rejections were seen following heterotopic or orthotopic implantations. The transplanted cartilage remained stable for periods ranging up to 21 weeks in recipient rats, while partial morphologic integrity of the cartilage was seen up to 1 year in pigs. Reepithelialization of the transplant with ciliated epithelium was completed in all specimens 12–24 weeks following surgery. Segmental replacement of up to one third of the whole trachea was possible in rats, whereas similar segmental replacements failed in pigs. We also found that successful reconstruction of window-shaped defects was possible. We consider our tracheal bioprosthesis to be superior to cialit-preserved grafts and also to most other biological reconstruction procedures.