Most coronary stents are made out of either bare or drug-coated metal that is intended to be a permanent structural support for coronary arteries, according to WebMD. There are alternative stents that are absorbed by the body or dissolve to form an organic coating within the artery but these are not yet widely available in the United States, as of 2015.
The FDA approved stents for use in human subjects in 1994. The earliest stents were made out of uncoated metal and were successfully able to prevent the collapse of the artery but were ineffective in preventing restenosis 25 percent of the time. Restenosis is the renarrowing of the artery after surgery, sometimes due to damage incurred by the lining of the artery during the stenting procedure, notes WebMD.
To reduce the need for additional surgeries, drug-eluting stents were introduced that were coated with medications to prevent restenosis from occurring, states WebMD. Drug-eluting stents were able to reduce the occurrence of restenosis to less than 10 percent in clinical trials, as well as providing improved patient outcomes for people with diabetes. After drug-eluting or bare-metal stents are introduced to an artery through surgery, they remain in the body unless further complications arise that require their removal.