Studies in the development of a novel side-branch stent

冠状动脉疾病很常见。它的发生是由于冠状动脉壁中脂肪沉积物的积累，冠状动脉为心肌供血。这会导致血液供应不足，从而导致心肌供氧不足，导致胸部出现痉挛样感觉-心绞痛。最常见的治疗方法是使用支架;保持动脉开放的小金属丝网装置。全世界每年有400万个支架植入患者体内。在约15%的患者中，支架折断发生在分支点，然后可能需要在该点部署2个支架-一个在主动脉中，另一个在侧分支中邻接它。如果主分支和侧分支之间的角度较窄（即小于90度），并且由于支架具有方形端部，则不可能调节主分支和侧分支之间的角度-存在间隙或重叠，这两种情况都可能导致问题。间隙会导致疾病的不完全覆盖，而支架的重叠会导致血管重新变窄，有时会导致此时形成凝块，这反过来会导致动脉阻塞，从而导致心脏病发作。本项目的目的是开发一种新型支架，该支架可放置在侧分支中（具有特殊设计的末端，可通过主分支中的球囊进行修改），但侧分支支架不会塌陷到侧分支动脉腔内并阻塞血流。然后可以在主动脉中放置第二个标准支架。我们与原型设计公司（Protomed，马赛）进行了广泛的合作，以生产这种支架。初步工作包括计算机建模、模拟实验和计算机评估，以了解拟议的支架设计在动脉中部署时的表现。使用该方法，优化了具有良好机械性能（虚拟径向强度、输送能力和回缩）的支架设计，并生产了2个早期原型，并在视频侧分支模型中进行了试验，以观察其性能。原型也被放置在2头猪和结果评估与特殊的X射线技术-微CT。这项工作表明，生产具有可修改端部的支架的概念是可行的，然而这些实验也表明，需要修改以生产具有良好机械性能的完全覆盖血管侧分支的支架。我们已经与Protomed Labs的合作者联系，以确定如何改变支架可修改端的初始设计，以克服初始原型中出现的一些问题。然后，我们将使用计算机建模虚拟地测试这些新设计，以观察支架在不同角度展开时的表现。这是一个重要的阶段，因为任何问题都需要进一步修改设计和重新测试。然后，我们将从钴铬合金上激光切割支架，并通过在分叉的硅胶模型（2个模型代表不同的角度）内展开支架进行试验。将对支架展开进行拍摄和分析，以观察支架的可修改端如何表现。我们将确保支架支柱不会撞击分叉模型的管腔。还将评估支架的机械性能。任何问题都可以通过进一步的设计修改来解决。一旦原型成功，我们将在猪身上再次测试它们，以观察它们在实际血管分支点上的表现，以及在28天的实验中的表现，这将提供关于支架周围愈合程度的重要信息，并确保这种支架不会出现早期并发症，例如支架周围形成血块。这项研究的目的是生产一种支架，可以安全，有效和容易地用于治疗冠状动脉疾病的这一困难方面。

Coronary artery disease is common. It occurs due to build-up of fatty deposits in the wall of the coronary arteries which supply blood to the heart muscle. This results in inadequate blood supply and therefore insufficient oxygen getting to the heart muscle causing cramp like sensation in the chest - angina. The commonest way of treating this is with stents; small wire mesh devices that keep the artery open. 4 million stents are placed in patients worldwide each year. In about 15% of patients the narrowings occur at a branch point which may then require the deployment of 2 stents at that point -one in the main artery and a second one abutting it in the side branch. If the angle between the main branch and the side branch is narrow (ie less than 90 degrees) and as stents have square ends, accommodating the angle between the main branch and the side branch is impossible - there is either a gap or an overlap, both of which can cause problems. A gap will result incomplete coverage of the disease while overlap of stents canresult in re-narrowing of the blood vessel and sometimes can lead to clot forming at this point, which can in turn lead to blocking of the artery and hence lead to a heart attack. The aim of this project is to develop a novel stent that can be placed in the side branch (with a specially designed end that can be modified by a balloon in the main branch) but without the side branch stent collapsing into the side branch artery lumen and obstructing blood flow. A second standard stent could then be placed in the main artery. We have worked extensively with a prototype design company (Protomed, Marseilles) to produce such a stent. Preliminary work involved computer modelling, simulation experiment, and computer assessment to see how a proposed stent design would behave when it is deployed in the artery. Using this method, stent designs with good mechanical properties (virtual radial strength, deliverability and recoil) were refined and 2 early prototypes were produced and tested in videoed side branch models to see how they performed. The prototypes were also placed in 2 pigs and the results assessed with a special X ray technique- micro CT. This work showed that the concept of producing a stent with a modifiable end was viable, however these experiments also showed that modifications are required to produce stents that completely cover the vessel side branch with good mechanical properties.The proposed research will take this preliminary work forward. We have liaised with our collaborators at Protomed Labs to determine how the initial designs to the modifiable end of the stent need to be changed to overcome some of the problems seen within the initial prototypes. We will then test these new designs virtually using computer modelling, to see how the stents would behave when they are deployed at various angles. This is an important stage, as any problems will require further modifications to the design and retesting. We will then laser-cut the stents from cobalt chromium and test these by deploying them within silicone models of bifurcations (2 models representing different angles). The deployment of the stent will be filmed and analysed to see how the modifiable end of the stent behaved. We will look to ensure that none of the stent struts impinge into the lumen of the bifurcation model. Mechanical properties of the stent will also be assessed. Any problems with be addressed with further design modification. Once the prototypes are successful, we will test them again in pigs to see how they perform in actual blood vessel branch points, and also in 28 day experiments which will give important information regarding the degree of healing around the stent, and to ensure no early complications of such a stent arise, such as formation of blood clot around the stent. The aim of this research is to produce a stent that can be used safely, effectively and with ease to treat this difficult aspect of coronary disease.