组织损伤和钙化可能是生物人工心脏瓣膜失效的独立机制。

Tissue damage and calcification may be independent mechanisms of bioprosthetic heart valve failure.

作者信息

Vesely I, Barber J E, Ratliff N B

机构信息

The Department of Biomedical Engineering, The Lerner Research Institute, The Cleveland Clinic Foundation, Ohio 44195, USA.

出版信息

J Heart Valve Dis. 2001 Jul;10(4):471-7.

PMID:11499593

Abstract

BACKGROUND AND AIM OF THE STUDY

Porcine bioprosthetic valves have excellent hemodynamics and do not require anticoagulation, but have limited durability. Cusp tearing is a major cause of bioprosthetic valve failure. It has been suggested that the mechanism of bioprosthetic valve failure is stiffening by calcification, which leads to elevated stresses and secondary collagen fiber damage and leaflet tearing. This thesis was tested in explanted porcine bioprostheses.

METHODS

A total of 60 explanted porcine bioprosthetic valves was tested mechanically, and 15 explanted valves were examined grossly and histologically. Circumferentially and radially oriented samples of cusp tissue were tested uniaxially in a materials testing machine and compared with five controls.

RESULTS

Mean (+/-SD) duration of implantation was 10.9+/-5.6 years. Circumferential specimens from explants were less extensible than controls (11.0+/-5.5% versus 24.5+/-2.8% strain, p <0.001), and failed at lower tensions (973+/-733 versus 3075+/-911 N/m, p = 0.001) and at lower strains (21.2+/-8.1% versus 47.3+/-7.1% strain, p <0.001). Radial specimens from explants were less extensible (28.7+/-6.8% versus 39.2+/-5.9% strain, p = 0.002) and failed at lower strains (60.3+/-17.3% versus 112.2+/-24.9% strain, p <0.001) than the controls. The stiffness of the explants was unchanged from controls in both circumferential and radial samples. There were no differences between explants and controls in radial and circumferential stiffness, and in radial failure strength. Calcification was mild and diffuse in most of the tested samples. Tears were found in areas without calcific deposits, along with breaks in collagen fiber bundles.

CONCLUSION

These results do not support the thesis that calcification stiffens glutaraldehyde-fixed porcine bioprostheses, except when the entire cusp is transformed into a solid mass of mineral. Rather, leaflet tears may develop as a result of accumulated mechanical damage that is independent of calcification.

摘要

研究背景与目的

猪生物瓣膜具有优异的血流动力学性能，且无需抗凝，但耐久性有限。瓣叶撕裂是生物瓣膜失效的主要原因。有人提出生物瓣膜失效的机制是钙化导致硬化，进而引起应力升高、继发胶原纤维损伤和瓣叶撕裂。本研究在取出的猪生物瓣膜上验证这一论点。

方法

对60个取出的猪生物瓣膜进行力学测试，对15个取出的瓣膜进行大体和组织学检查。将瓣叶组织的周向和径向样本在材料试验机上进行单轴测试，并与5个对照样本进行比较。

结果

植入的平均（±标准差）持续时间为10.9±5.6年。取出样本的周向标本比对照样本伸展性更差（应变分别为11.0±5.5%和24.5±2.8%，p<0.001），在较低张力下失效（分别为973±733和3075±911N/m，p = 0.001），且在较低应变下失效（应变分别为21.2±8.1%和47.3±7.1%，p<0.001）。取出样本的径向标本比对照样本伸展性更差（应变分别为28.7±6.8%和39.2±5.9%，p = 0.002），在较低应变下失效（应变分别为60.3±17.3%和112.2±24.9%，p<0.001）。在周向和径向样本中，取出样本的硬度与对照样本相比没有变化。取出样本与对照样本在径向和周向硬度以及径向失效强度方面没有差异。在大多数测试样本中，钙化轻微且呈弥漫性。在没有钙化沉积的区域发现了撕裂，同时伴有胶原纤维束的断裂。