Long-term results of permanent and bioresorbable scaffolds in the treatment of coronary artery disease

Abstract

Since the performance of the first successful coronary balloon angioplasty procedure in 1977 by the German cardiologist Andreas Gruentzig, the interventional cardiology has overcome a lot of shortcomings within a relatively short period of three decades [1]. The switch from plain old balloon angioplasty into the implantation of bare-metal stents (BMS) was an inevitable development after angiographic and clinical outcomes of treated patients showed a significant improvement in favour of BMS-implantation [2-3]. Nevertheless, major shortcomings such as the possibility of an (sub)acute thrombotic closure of the coronary stent due to a balloon-induced dissection and the occurrence of in-stent neo-intimal hyperplasia remained present after performing percutaneous coronary intervention (PCI) with stent implantation. In-stent neointimal hyperplasia, often dubbed as the “Achilles heel” of coronary stents, is one of the major causes of in-stent restenosis. It is a clear end product of the exaggerated activation, production and stacking of several immunological proteins as a consequence of a “foreign body” in the coronaries disrupting the lipid core of the atherosclerotic plaque. These proteins cause migration and proliferation of vascular smooth muscle cells and eventually narrow the lumen of the implanted coronary stent. Although coronary restenosis rates decreased from 30-50% with balloon angioplasty down to 20-30% in the stent era, the possibility of implanting “ticking time bombs” was taken for granted. This became even more worrisome when it was shown that restenosis does not present itself as a clinical benign entity post-PCI but rather in a heavily aggressive manner requiring hospitalization or even leading to death [4-5]. The long-term follow-up data of BMS-implantations shows that coronary revascularizations mostly occur within the first year post-PCI [6-7]. Although these coronary events have been heavily reduced by the implantation of drug-eluting stents (DES), novel unpredictable consequences have emerged. Side-effects, such as arterial wall inflammation and impaired reendothelialization processes, showed to be closely related to higher rates of (very late) stent thrombosis. The main focus in the further development of stents is momentarily concentrated on stents with novel antiproliferative coatings, stents with bioabsorbable polymers, stents without a polymer layer and the fully bioresorbable scaffolds. Like all progress in medical interventions, it is essential to not harm the patient throughout this complex evolvement process of coronary stents.