Coronary stenting: Difference between revisions

In the early years of percutaneous coronary intervention (PCI) the only available method to treat coronary stenoses was balloon angioplasty. However, balloon angioplasty alone, also known as plain old balloon angioplasty (POBA) was hampered by a few important technical limitations. For example, an important early complication of POBA was acute vessel closure,  which could only be treated with emergency coronary artery bypass graft surgery (CABG).(1) Moreover, acute vessel recoil at the site of balloon inflation led to suboptimal early results of POBA, and restenosis rates were frequently reported to be >20%.  The introduction of coronary artery stents, pioneered by Julio Palmaz, Richard Schatz, Cesare Gianturco and Gary Roubin,  led to important advances in PCI.(2) By virtually eliminating acute vessel closure, hospitals were PCIs were performed no longer needed a surgical backup team, and for many years now PCIs are performed in hospitals without cardiothoracic surgery departments. Moreover, restenosis rates were reduced by as much as 50% with the use of bare metal stents (BMS) compared with POBA.(3, 4) However, the introduction of the BMS also introduced the complication of stent thrombosis which occurs in 2-5% of patients depending on lesion and patient characteristics. More recently, at the beginning of the current millennium drug-eluting stents (DES) caused another revolution in PCI. Again, restenosis rates were cut in half compared with BMS and the latest generation of DES with bio-compatible polymers have been shown to reduce stent thrombosis compared with BMS. This section provides an overview about technical specifications, and data on safety and efficacy of different types of coronary artery stents.

Bare-metal stents are made of different types of metals, for example stainless steel, nitinol, cobalt-chromium or platinum-chromium. Stents can be either self-expanding, or balloon-expandable, and exert a scaffolding force to prevent acute recoil of the treated coronary artery stenosis. Bare-metal stents were introduced in the 1980s in an effort to prevent acute vessel occlusion and restenosis, two common complications after POBA. An early report on the use of BMS in coronary arteries was cause for optimism, in 19 patients who received stainless-steel BMS in the mid-1980s (before the era of dual antiplatelet therapy, DAPT) two acute stent occlusions occurred, and one patient died (without suspicion for a thrombotic occlusion), and no further restenosis or occlusions were observed up to nine-month follow-up.(2) <br />

However, a study published in 1991 in the New England Journal of Medicine reported sobering outcomes in a series of 105 patients undergoing BMS implantation.(5) Complete occlusion of the coronary artery stent was observed in 24% of patients at follow-up coronary  angiography after one month. Out of the 27 occlusions, 21 occurred within the first 14 days after stent implantation. Moreover, restenosis (defined as >50% diameter stenosis at follow-up) was observed in 14% of patients with patent stents. An excerpt from the accompanying editorial reflects the disappointment that ensued “I believe that the introduction of most these new devices will be of passing interest only. The development of mechanical interventions (such as stents) that attempt to overcome the response to injury caused by intravascular therapeutic interventions (such as balloon angioplasty) is probably futile.”(6) <br />