介入式主動脈二次曲面人工心臟瓣膜的設計與開發

Design and Development of Interventional Aortic Quadric-surfaced Prosthetic Heart Valve

郭騰文(Teng-Wen Kuo)

指導教授 ： 蕭浩明

國立臺灣大學/工學院/機械工程學研究所/碩士(2020年)

https://doi.org/10.6342/NTU202001364

摘要

主動脈瓣膜疾病的盛行隨著全球人口平均預期壽命的增長而又再次的浮出檯面，其造成之退化性主動脈瓣膜疾病可能會引發兩種不同的情況，分別是使瓣膜無法順利關閉之主動脈瓣閉鎖不全，以及使瓣膜無法順利開啟之主動脈瓣狹窄，治療方式依嚴重性分為早期藥物治療及晚期瓣膜置換，而嚴重性的診斷標準通常是使用心臟超音波來量測流速以及跨瓣壓力差，倘若因瓣膜硬化程度逐漸嚴重，卻無執行適當的處理，可能會進一步衍生出其他心臟相關疾病。有鑑於此，本研究提出針對主動脈瓣膜置換的「介入性二次曲面人工心臟瓣膜」，透過簡化及優化瓣膜曲率的設計及製造方式，開發出一款新型且仍維持良好的臨床特性之人工心臟瓣膜。
本研究著眼於介入性人工心臟瓣膜的開發，從設計最佳化到製程的有限元素分析及部署後的血液動力學分析，並實際製造出雛型品。首先是設計方面，藉由電腦輔助設計軟體，訂定出設計參數並依序繪製出經導管血管支架以及圓柱面、圓球面、圓拋物面和橢球面之人工心臟瓣膜；接著是有限元素分析方面，透過分析施加週期性心率負載的延展性聚四氟乙烯二次曲面人工心臟瓣膜的機械性質，以及鎳鈦合金血管經導管血管支架之製造及臨床上的機械性質，以確認雛型品在製造及臨床上不會造成材料的破壞，最後以Goodman疲勞安全係數分析再次評估經導管血管支架的抗疲勞強度；再來為血液動力學分析方面，設定一理想胸主動脈控制體積系統，並於胸主動脈入口施加週期性的流速場，模擬結果顯示部署二次曲面瓣過後之血液流速場及跨瓣壓力差，綜合有限元素分析以及血液動力學分析，可以發現瓣膜開啟後之形狀越為規律，其機械性質以及血液動力學的結果較具有臨床上的優勢；最後是製造方面，透過設計二維的公母壓克力模具，並裁出相對應的人工心臟瓣膜之模型，最後縫合於經導管血管支架上，即可完成本論文提出之介入式主動脈二次曲面人工心臟瓣膜雛型品。

關鍵字

有限元素法 ； 血液動力學 ； 鎳鈦合金 ； 延展性聚四氟乙烯 ； 人工心臟瓣膜 ； 血管支架 ； 主動脈瓣膜疾病

並列摘要

With the increase in the average life expectancy of the global population, the prevalence of the aorta heart valve disease promotes significantly. Degenerative aortic valve disease may lead to two different conditions; namely, "Aortic Insufficiency or Aortic Regurgitation" prevents the aortic valve from closing perfectly. In contrast, "Aortic Stenosis" prevents the valve from opening entirely. The aortic valve diseases are divided into two different treatments, drug treatment and prosthetic valve replacement, according to their severity. By using cardiac ultrasound, the speed and trans-valvular pressure gradient can be determined to identify its severity level. Once the hardened heart valve has become severe and without proper treatment, it may result in other heart-related diseases. In this research, a simply constructed interventional prosthetic heart valve for the aortic heart valve replacement surgery, called "quadric-surfaced prosthetic heart valve", is proposed. The design purpose is to simplify and optimize the complex curvature into easily manufacture but still retain well clinical characteristics.
Development of a quadric-surfaced prosthetic heart valve is proposed in this research, including optimal design, finite element analysis of manufacturing, hemodynamic analysis after deployment, and manufacturing processes. In the design process, the design parameters are defined with the help of computer-aided design software. The cardiovascular stents and prosthetic heart valves with the cylindrical surface, spherical surface, circular parabolic surface and ellipsoidal surface are designed respectively. In the simulation process, the aim is to analyze the manufacturing and clinical mechanical properties. This research constructs not only the expanded-Polytetrafluoroethylene quadric-surfaced prosthetic heart valve with cyclic pressure due to the heartbeat but also the nitinol cardiovascular stent as well. Besides, Goodman life analysis is used to evaluate the fatigue resistance of cardiovascular stent. In the hemodynamic analysis process, the system of control volume for an ideal thoracic aorta is introduced into the computational fluid dynamics model. The periodic inlet velocity boundary condition is applied also due to the heartbeat. The simulation result indicates that the velocity field and the trans-valvular pressure gradient after the deployment of the quadric-surfaced prosthetic heart valve. According to finite element analysis and hemodynamic analysis, the more regular shape of the heart valve opens, the better the result of the mechanical properties and hemodynamic performance. In the manufacturing process, by designing male and female acrylic dies to cut out the expanded-Polytetrafluoroethylene model of the corresponding quadric-surfaced prosthetic heart valve. Finally, sewing it inside the cardiovascular stent and the prototype of the interventional aortic quadric-surfaced prosthetic heart valve can be completed.

並列關鍵字

Finite element analysis ； Hemodynamics ； Nitinol ； expanded-Polytetrafluoroethylene ； Prosthetic heart valve ； Cardiovascular stent ； Aortic valve disease

參考文獻

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