Thrombosis after implantation of drug-eluting stents.

S tent thrombosis is the sudden occlusion of a stented coronary artery due to thrombus formation. Despite major improvements in antiplatelet therapy, thrombotic events remain the primary cause of death after percutaneous coronary interventions. The clinical consequences of stent thrombosis are frequently catastrophic and include death in 20% to 48% of cases or major myocardial infarction in 60% to 70%. When bare metal stents (BMS) were first introduced, stent thrombosis was a common complication. Most episodes occurred within 2 weeks of stent implantation and often resulted in myocardial infarction and, not infrequently, death. Technical improvements, such as the use of adequately sized balloons and high-pressure deployment, helped to substantially decrease thrombosis rates. In addition, a regimen of dual antiplatelet therapy (aspirin plus a thienopyridine) was found to reduce the incidence of stent thrombosis even further. Dual antiplatelet therapy is prescribed for 2-4 weeks after BMS implantation, the time required for stent endothelialization to take place. Thrombosis that occurs more than 30 days after the implantation of a BMS is extremely rare. This complication first appeared when intracoronary radiation (brachytherapy) was introduced as a treatment for in-stent restenosis. Intracoronary radiation was found to delay reendothelialization in animals, thus predisThrombosis After Implantation of Drug-Eluting Stents