Intra-coronary stents are metal mesh tubes that are inserted into coronary arteries to open a blocked artery. They were first used in the mid-1990s and were shown to be superior to balloon angioplasty alone. The original generation of stents, called "bare metal stents" (BMS), worked very well and were widely used. However, they had problems with a process called in-stent restenosis, or recurrence of the blockage within the stent. To solve this problem, "drug-eluting stents" (DES) were developed. Drug-eluting stents are coated with a medication to prevent restenosis, and have largely solved the problem of in-stent restenosis. Drug-eluting stent use expanded rapidly because of the multiple large-scale randomized trials that showed better outcomes with DES compared to bare metal stents. Drug-eluting stents are now used in approximately 85 percent of cases in the U.S.
Because a stent is a foreign body that is exposed to the bloodstream, anti-platelet drugs (aspirin, and Plavix® or Ticlid®) are required to prevent platelets from sticking to the stent and forming a blood clot, a process known as stent thrombosis (ST). As the arterial wall heals, new tissue grows over the stent, and with time the stent is no longer at risk for clotting. This was recognized with the initial bare metal stents, and patients were required to take anti-platelet medication for one month after the procedure. However, the medication on a drug-eluting stent delays the healing process, and therefore patients with a drug-eluting stent need to take anti-platelet medication for a longer period of time. The current recommendation is that patients who receive a drug-eluting stent take anti-platelet medication for one year.
Recent media reports have highlighted stent thrombosis in drug-eluting stents and led to some concerns from patients who have these stents. Despite the attention paid to this by the lay press, the fact is that this is a very rare complication. Stent thrombosis occurs with both bare metal stents and drug-eluting stents, but the question is whether it happens more frequently with drug-eluting stents than bare metal stents. The answer to that question is not known at this time. There is currently no conclusive evidence that stent thrombosis occurs more frequently in drug-eluting stents compared to bare metal stents. A few small studies have shown a trend toward a higher incidence of stent thrombosis in drug-eluting stents, but none of the trials were large enough or designed properly to definitively answer this question.