Biodegradable Stents

Abstract

Percutaneous coronary intervention (PCI) is indispensable in the treatment of ischemic heart disease. In the early days of conventional balloon angioplasty, acute coronary occlusion as a result of coronary dissection or vessel recoil was observed immediately after PCI, and initial results were not satisfactory. Moreover, the long-term restenosis rate was 30–40%, and the recurrence of angina was a problem. In order to solve these problems, Sigwart et al. (1) developed a metallic stent, which was used clinically for the first time in 1986. As this pioneering work, the use of stents has become routine in the practice of PCI. Metallic stents are very effective in the prevention of acute coronary occlusion by coronary dissection or recoil of a vessel. Furthermore, the results of large clinical trials, such as STRESS and BENESTENT, suggested that metallic stents are also effective in the prevention of chronic restenosis (2,3). Despite the success that has been achieved with metallic stents, there are also some important limitations. There is a risk of subacute thrombosis (SAT) until endothelial cells cover the surface of the metallic stent. Although the frequency of SAT has been lowered by the use of antiplatelet agents, such as ticlopidine, for at least 1 mo after stent implantation, SAT has not been completely eliminated. Moreover, in-stent restenosis in a complicated coronary lesion poses a significant clinical problem especially with the expanding use of PCI to treat ischemic heart disease. Stents are thought to be required for about 12 mo to prevent lumen narrowing in response to chronic vessel remodeling. As metallic stents remain permanently implanted, there is concern about the deleterious effects of stents on the coronary vessels that may take several years to develop. Furthermore, metallic stents may serve as an obstacle for the treatment of instent restenosis.