Structural design of a stent for a percutaneous aortic heart valve

[摘要] Elderly patients suffering from aortic valvular dysfunction are often deniedaortic valve replacement due to the fact that they are classified astoo old and fragile to handle the physical stress of open-heart surgeryand cardio-pulmonary bypass. There exists a need for an alternative solutionwhich places less physical stress on the body. The developmentof a percutaneous aortic heart valve (PAHV), which may be implantedthrough a minimally invasive procedure, will provide a solution to oldand fragile patients who otherwise have a very limited life expectancy.The development of such a device entails a costly and time-consumingprocess which involves a number of phases, including a prototype developmentphase, an in-vitro testing phase, an animal trial phase and ahuman trial phase.This thesis focuses on the design and analysis of the stent componentfor a PAHV, suitable for implantation in sheep (animal trial phase). Theprocess of developing a first prototype, involved an analysis of the stent design requirements. This analysis was followed by a concept generationphase as well as comprehensive finite element (FE) analyses of the mostpromising concepts. The objective of the FE analyses was to determinethe effects of a variation in strut width on the performance characteristicsof the concepts. Based on the results of the FE analyses, final geometrieswere selected for each of the two most promising concepts. Subsequentto the selection of the final geometries, a number of prototypes were manufactured.The prototypes were subjected to an electro-polishing process.An experimental analysis was also conducted on the prototypes to evaluatethe accuracy of the (FE) simulations as well as the actual performanceof the stent prototypes.The results of the FE analyses and experimental analyses indicatedthat strut width had a substantial influence on the parameters that weredefined to characterise stent performance. The results of the analyses alsohighlighted the advantages and disadvantages of each concept and aidedin identifying the concept that would be most suitable for the requiredapplication.Limitations of the study were identified and recommendations weremade to assist the continued research and development of the device.

[发布机构] Stellenbosch University