[Drug and instrumental therapeutic approaches for prevention of restenosis]

In recent years, several of the shortcomings of coronary angioplasty have been successfully countered. With more effective measures of treating acute complications, better equipment and more experienced operators, there has been a subsequent expansion of the indications and the type of lesions suitable for angioplasty. In the long-term, however, the restenosis rate remains the limiting factor for the success of the procedure. To date, clinical studies using systemic therapy or alternative instrumental devices have not convincingly demonstrated a benefit in preventing restenosis. New devices have mostly been used to manage complications at angioplasty or to increase the type of lesions that can be tackled transluminally. This article will describe recent findings relating to the pathology of restenosis and then discuss a new therapeutic concept, local drug delivery to suppress restenosis. The aim of this method of drug application is to achieve a high local concentration of agents that inhibit restenosis, while avoiding systemic side-effects. Possible substances which could be utilized in this manner include conventional therapies such as platelet or calcium antagonists, or anti-thrombotic, anti-inflammatory or anti-proliferative treatments, and also novel agents such as gene therapy. The latter strategy might include inhibition of certain stimulatory factors that control restenosis, for example, through antisense oligonucleotides, or alternatively, augmentation of naturally occurring inhibitory factors, perhaps with expression vector plasmids and virus-mediated gene integration. The various ways in which these substances can be locally delivered to the arterial wall, together with results from initial experimental studies will be summarized. It is possible that eventually the combination of effective treatments with local drug delivery (LDD) may at last resolve the restenosis problem in patients.