Drug-eluting stents in vascular intervention.
CONTEXT: Restenosis is the most important long-term limitation of stent implantation for coronary artery disease, occurring in 15-60% of patients. In-stent restenosis, a refractory coronary lesion resulting from neointimal hyperplasia, challenges both vascular biologist and interventional cardiologist. Various drugs and devices have been used tried to overcome restenosis but are not particularly successful. Over 1500000 percutaneous coronary interventions are done annually. Restenosis is not only important clinically but also for its impact on health-care costs. STARTING POINT: Growth and migration of vascular smooth-muscle cells result in neointimal proliferation after vascular injury and are the key mechanism of in-stent restenosis. The rationale of the most recent approaches to restenosis (eg, brachytherapy and immunosuppressive agents) arises from the similarity between tumour-cell growth and the benign tissue proliferation which characterises intimal hyperplasia. Several immunosuppressants have been tested for their potential to inhibit restenosis, with the novel strategy of administering the drug via a coated stent platform. Local drug delivery achieves higher tissue concentrations of drug without systemic effects, at a precise site and time. The first multicentre trial with stents coated with sirolimus was by Marie-Claude Morice and colleagues (N Engl J Med 2002; 346: 1773-80). In a trial of 238 patients, restenosis of 50% or more at 6 months was 0% and 27% with sirolimus or normal stents (p<0.001), respectively, after percutaneous revascularisation. Muzaffer Degertekin and colleagues (Circulation 2002; 106: 1610-13) present data on 2-year follow-up of 15 patients who had been implanted with the sirolimus stent in another study, and confirm persistent inhibition of restenosis and an absence of unexpected adverse events. WHERE NEXT? Local application of antiproliferative agents is a promising technique and research is developing. Other agents with potential benefits (eg, statins, local gene-therapy, adenovirus-mediated arterial gene-transfer, L-arginine, abciximab, angiopeptin, recombinant pegylated hirudin, and hiloprost) as well as improvements in polymer technology (biodegradable smart polymers, coatings for multiple-drug release) are under evaluation. The clinical impact of the elimination of restenosis may influence the approach to coronary artery disease, the future of cardiac surgery, and health-care economics in cardiology.