A new stent is riddled with 100-micrometer-wide depressions that hold drugs. (Courtesy of Conor Medsystems)

Coronary stents that secrete drugs to prevent scarring are a standard medical treatment, with more than one million implanted in U.S. patients every year. But some studies indicate that these stents--coated with a polymer that holds the drugs--may present their own problems. In March, for example, a study released by University Hospital in Basel, Switzerland, found that some patients who received them suffered higher rates of blood clotting than those using bare-metal stents.

Select from the choices above to read the entire article.