冠狀動脈疾病之血管與支架交互作用模型

Abstract

動脈粥狀硬化是造成心血管疾病最主要的原因之一，以往是透過外科手術來進行治療。然而隨著醫療科技的進步，血管支架逐漸成為治療的黃金準則。儘管血管支架手術的治療成效表現亮眼，但手術後仍有血管再狹窄的風險。因此本研究透過有限元素軟體建立氣球擴張式血管支架與理想血管之交互作用模型，模擬血管支架於血管中的部署情形，並觀察部署過程中血管支架與血管壁之間的接觸關係；文中首先探討施加的壓力對血管壁以及血管支架的機械性質所造成的影響，接著選用兩款血管支架(VYW-shaped Stent與V-shaped Stent)於含有硬化斑塊的血管中進行部署模擬，觀察兩款血管支架對硬化斑塊的影響。建立的血管模型中包含了血管內膜、中膜、外膜及硬化斑塊，並賦予其高彈性之材料性質；而在氣球擴張式血管支架部分則是使用鈷鉻合金作為其材料。由血管支架部署在純血管的模擬結果顯示，當所施加的壓力不斷增大，血管壁的高應力分布區域就愈廣，而量測到的血管支架徑向支撐強度也隨之增加。由血管支架部署在含有硬化斑塊的血管之模擬結果顯示，硬化斑塊的種類與其所承受的應力大小有著很密切的關係，Calcified硬化斑塊將承受較多較大的應力，而Cellular硬化斑塊則是呈現較小的應力分布；若以血管支架款式來探討，V-shaped Stent支撐血管壁的能力較VYW-shaped Stent差，因此以術後長時間來看，V-shaped Stent比VYW-shaped Stent可能擁有更高的機率發生血管再狹窄的現象。本研究可提供血管支架的設計者做為新一代支架設計的參考與醫師施行手術前的風險評估以達到最佳療效。

Atherosclerosis is one of main factors of cardiovascular diseases which were usually performed by surgeries in the past. However, with the advancement of medical technology, intravascular stents have become a gold standard to treat such disorders. Despite the excellent performance of stent treatment, potential risks associated with restenosis may occur after stenting. In this study, finite element models were developed to investigate the influence of both stent inflation pressures and different stent designs (VYW-shaped Stent and V-shaped Stent) on the artery wall along with the mechanical properties of stents during the deployment of a balloon expandable stent into an idealized coronary artery. The constructed artery geometries contained intima, media, adventitia and plaque with hyperelastic material; balloon expandable stent was used of Cobalt-Chromium alloy. In the stent-artery interaction simulation without plaque, the results showed that the high-stress area of the artery wall was wider when the inflation pressure became larger, and the radial strength of stent was also increased. In the stent-artery interaction simulation with plaque, the plaque type was found to have a significant influence on the stresses induced within the plaque. The stresses on the stiffer calcified plaques were higher compared to those on the softer cellular plaques. By the comparison between two stent designs, V-shaped stent had less support to artery wall than VYW-shaped stent. Therefore, regarding a long-term clinical outcome, V-shaped stent may have a higher possibility to occur restenosis than VYW-shaped stent. This study provides great insight for the future optimized design and physician practice to achieve a best possible clinical outcome.