Stenting Development

In order to better understand the challenges of biodegradable stent development, it is useful to first think about what a stent must endure during its lifetime. Thus an engineering point of view is outhned in this section to distil some of the key material requirements of biodegradable stents. 

Nonionic contrast agents have been reported to cause adverse reactions such as confusion, seizures, ophthalmoplegia and memory loss. A 70-year-old female patient who xmderwent left carotid artery stenting develops mild... 

Synthetic materials used in the stents development such as PET or PTFE have failed in coronary revascularization [128]. Dacron grafts lead to thrombosis and neointimal thickening in low blood flow. The PTFE grafts also fail owing to surface thrombogenicity... 

Figure 21.40 Generations of DES. Reprinted from Khan, W., Farah, S., Domb, A. J., Drug eluting stents Developments and current status, / Control Release, 161, 703-712. Copyright (2012), with permission from Elsevier [73].

Lung volume reduction surgery is a rarely performed treatment option for heterogeneous emphysema patients with high hyperinflation. Novel semi-invasive and invasive alternatives are being developed, such as bronchial valves for heterogeneous emphysema treatment, and bronchial stents for homogeneous emphysema to reduce counteiproductive collateral ventilation. 

Self-expanding stents with a higher radial force (e.g., WingSpan, Boston Scientific Corp.) will probably play a key role in acute stroke cases related to intracranial atherosclerotic disease. Antegrade flow is essential for the maintenance of vascular patency, as particularly evident in patients with severe proximal stenoses who commonly develop rethrombosis after vessel recanalization. Furthermore, stenting of the proximal vessels may be required in order to gain access to the intracranial thrombus with other mechanical devices or catheters. In a recent series, 23 of 25 patients (92%) with acute n = 15) or subacute n = 10) ICA occlusions were successfully revascularized with this technique. " ... 

Initial tests in the rat revealed a high degree of tissue compatibility of Dat-Tyr-Hex derived polymers. More detailed tests are now in progress. In addition, tyrosine derived polymers are currently being evaluated in the formulation of an intracranial controlled release device for the release of dopamine, in the design of an intraarterial stent (to prevent the restenosis of coronary arteries after balloon angioplasty), and in the development of orthopedic implants. The use of tyrosine derived polymers in these applications will provide additional data on the biocompatibility of these polymers. 

Many readers, who are not in a position to set up a specied development project, or who do not wish to do so, will be using this book simply as an aid to learning from their experience of everyday management tasks. You should nevertheless find this chapter relevant to developing your creative ability to stent up any new venture - a normal part of the management process if you are not to remain trapped in routine. 

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