Initially described in 1977, the procedure involved placement of a balloon-tipped catheter across a subtotal stenosis followed by balloon inflation and deflation to improve coronary flow. Although the initial patient treated was fortunate to have an early and long-lasting excellent result, many early patients did not – with initial success rates of only 60%, and a relatively high rate of acute occlusion from the arterial trauma of balloon inflation that resulted in myocardial infarction and need for emergency coronary bypass surgery and culminated in increased mortality rates. In those patients fortunate enough to have a good initial angiographic result, restenosis with recurrent blockage of the segment initially treated occurred in up to 40% to 50% of patients within six or seven months of the initial index procedure.

Having recognized these problems, investigators and industry developed, tested, and implemented a variety of devices to make the procedure safer, more effective, and able to be applied in an ever-broadening group of patients and coronary lesions. Although some of the new technology never reached a sustaining application, other specific devices did – the foremost of these was the application of intracoronary stenting. This approach was initially tested and then approved for treatment of acute closure occurring as a result of percutaneous coronary intervention. By acting as a mechanical scaffold, stenting was very effective in preventing and treating coronary dissection and occlusion. Early problems with stenting, however, included the requirement for intense anticoagulation and antiplatelet therapy, which led to long hospitalization times and high bleeding rates. Newer approaches substantially ameliorated these problems and led to widespread use. By the late 1990s, stents had become the dominant revascularization strategy and had been found to improve early as well as late outcomes compared with conventional percutaneous transluminal coronary angioplasty (PTCA). Although restenosis rates were improved and reduced by approximately 30% compared with conventional PTCA, the problem was not eliminated. In the setting of stent placement, restenosis was found to be related to excessive neointimal hyperplasia. Stents worked by preventing recoil of the arterial segment compared with conventional PTCA, which showed that neointimal hyperplasia was even increased. Grading schemes for in-stent restenosis were developed. In some patients, this in-stent restenosis was very resistant to therapy and many patients eventually required surgery for the treatment of it. Given the magnitude of the problem, new approaches were developed to treat the in-stent restenosis, including the development of the entire field of vascular brachy therapy.

Recognizing that in-stent restenosis was the result of neointimal hyperplasia, research focused on means to prevent it. These efforts culminated in the current generation of devices which have now become predicate devices – namely, drug-eluting stents.

Current drug-eluting stents have three components:

1. The bare metal backbone, which serves as the mechanical scaffold – this element affects deliverability, access to side branch and surface area over which the drug is delivered.

2. A polymer or combination of polymers – this is a critical component. It varies from manufacturer to manufacturer. Concerns have been expressed over the eventual degradation of the polymer and whether that will lead to inflammation. The specific polymer affects distribution kinetics of drug delivery.

3. The specific drug – at the present time, there are two approved drugs – Sirolimus and paclitaxel. The release kinetics depend upon the specific drug chosen and the polymer. Both fast- and slow-release formulations have been tested. Multiple other drugs and drugs classes are being tested.