Drug-eluting stent: a review and update

Abstract

The development of stent has been a major advance in the treatment of obstructive coronary artery disease since the introduction of balloon angioplasty. However, neointimal hyperplasia occurring within the stent leading to in-stent restenosis is a main obstacle in the long-term success of percutaneous coronary intervention (PCI). The recent introduction of drug-eluting stents (DES) contributes a major breakthrough to interventional cardiology. Many large randomized clinical trials using DES have shown a remarkable reduction in angiographic restenosis and target vessel revascularization when compared with bare metal stents. The results of these trials also appear to be supported by evidence from everyday practice and non-controlled clinical trials. However, the expanded applications of DES, especially in treating complex lesions such as left main trunk, bifurcation, saphenous vein graft lesions, or in-stent restenosis, are still under evaluation with ongoing studies. With the availability of different types of DES in the market, the issue of cost should not be a deterrent and DES will eventually be an economically viable option for all patients. The adoption of DES in all percutaneous coronary intervention may become a reality in the near future. In this review article, we summarize the recent development and progress of DES as well as compare and update the results of clinical trials.

Figure 1

Pathophysiology of in-stent restenosis and the mechanisms of action of different therapeutic agents. Abbreviations: ECM, extracellular matrix; SMC, smooth muscle cells.

Figure 2

Cross-section of a stent strut with a drug-loaded polymeric coating.

Figure 3

Uniform vs nonuniform drug distribution in closed cell vs open cell stents was shown in the longitudinal sections of the vessel wall after a deployment of a drug-eluting stent. Drug concentration was shown in the color intensity in the column. Upper red-brown color is the highest and lower blue color is the lowest drug concentration. (Upper panel). A cross-section of vessel after a deployment of a drug-eluting stent depicts nonuniform strut spacing resulting in uneven drug distribution (Lower panel).

Figure 4

Different types of stent-based drug delivery system: (A) Drug released by diffusion from polymer, (B) Drug released by diffusion through ratelimiting coating, (C) Drug released by swelling of coating, (D) Drug release directly from coating, (E) Drug loaded in pore or reservoir in stent, (F) Drug release by erosion of polymer coating, (G) Drug loaded in nanoporous reservoir in coating, (H) Drug loaded between coating layers, (I) Drug released by hydrolysis or enzymatic action from polymer, (J) Bioerodable polymer coating stent.